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ACI 318-19 Presentation - changes to the concrete design standard

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ACI 318-19 Presentation

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WWW.CONCRETE.ORG/ACI318 1 Changes to the Concrete Design Standard ACI 318-19
WWW.CONCRETE.ORG/ACI318 2 American Concrete Institute is a RegisteredProvider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completionof this program will be reported to AIA/CES for AIA members. Certificates of Completionfor both AIA members and non-AIA members will be emailed to you soon after the seminar. This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any methodor manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials,methods, and services will be addressed at the conclusionof this presentation. The American Institute of Architects has approved this session for 7.5 AIA/CES LU/HSW Learning Units.
WWW.CONCRETE.ORG/ACI318 3 Learning Objectives 1. Understand where higher grades of reinforcement are accepted and changes to the requirements for structural concrete to allow the higher reinforcement grades, including development lengths and phi- factors. 2. Identify the added requirements to address shotcrete as a concrete placement method. 3. Explain the expanded scope of deep foundation provisions, including seismic requirements.
WWW.CONCRETE.ORG/ACI318 4 Learning Objectives 4. Learn the new requirements for post- installed screw type anchors and shear lug design for anchoring to concrete. 5. Describe the changes to shear design provisions and equations. 6. Identify new tension longitudinal reinforcement requirements in special structural walls
WWW.CONCRETE.ORG/ACI318 5 Speakers Speaker bios are included in your handouts for the presentation
WWW.CONCRETE.ORG/ACI318 6 Changes to the Concrete Design Standard ACI 318-19 Introduction
WWW.CONCRETE.ORG/ACI318 7 Today’s Seminar • Major changes • Grouped by topic • Organization • Existing structures • Loads & analysis • Slabs • Post-tensioning • Precast/Prestressed • Circular sections • Walls • Foundations • Anchorage to concrete • Seismic
WWW.CONCRETE.ORG/ACI318 8 Today’s Seminar • Major changes • Grouped by topic • High-strength reinforcement • Development length • Shear modifications • Durability and materials • Strut-and-tie method • Shotcrete • Appendix A
WWW.CONCRETE.ORG/ACI318 9 • Changes from ACI 318-14 to ACI 318-19 318-14 318-19 Today’s Seminar
WWW.CONCRETE.ORG/ACI318 10 Why Do We Change ACI 318? • Reflects new research • Construction practices change • Sometimes tragic events provide introspect – Earthquakes or other natural disasters – Collapses or construction accidents – Observed in-service performance • New materials – Or better ways of making established materials • More powerful analytical tools
WWW.CONCRETE.ORG/ACI318 11 Resources • ACI 318 • Speaker notes • ACI Reinforced Concrete Design Handbook • ACI 318 Building Code Portal
WWW.CONCRETE.ORG/ACI318 12 ACI 318-19 Variety of formats, including: • Printed copy – Softcover and hardcover • Enhanced PDF Versions • English • Spanish • In.-lb units • SI units
WWW.CONCRETE.ORG/ACI318 13 Speaker Notes Today’s presentation
WWW.CONCRETE.ORG/ACI318 14 ACI Design Handbook • 15 chapters • Explanatory text • Design aids • 2019 version expected early next year
WWW.CONCRETE.ORG/ACI318 15 ACI Design Handbook • 1: Building Systems • 2: Structural Systems • 3: Structural Analysis • 4: Durability • 5: One-Way Slabs • 6: Two-Way Slabs • 7: Beams • 8: Diaphragms • 9: Columns • 10: Walls • 11: Foundations • 12: Retaining Walls • 13: Serviceability • 14: Strut-and-Tie • 15: Anchorage
WWW.CONCRETE.ORG/ACI318 16 ACI 318 Building Code Portal
WWW.CONCRETE.ORG/ACI318 17 Changes to the Concrete Design Standard ACI 318-19 Organization
WWW.CONCRETE.ORG/ACI318 18 Major goals of ACI 318 organization • Ease of use • Find the information you need quickly – Consistent organization – Organized in the order of design • Increase certainty that a design fully meets the Code – A chapter for each member type – All member design provisions in one chapter
WWW.CONCRETE.ORG/ACI318 19 Navigation 10 Parts • General
WWW.CONCRETE.ORG/ACI318 20 Navigation 10 Parts • General • Loads & Analysis
WWW.CONCRETE.ORG/ACI318 21 ACI 318 Style
WWW.CONCRETE.ORG/ACI318 22 Navigation 10 Parts • General • Loads & Analysis • Members • Joints/Connections/ Anchors • Seismic • Materials & Durability • Strength & Serviceability • Reinforcement • Construction • Evaluation
WWW.CONCRETE.ORG/ACI318 23 Part 1: General • 1: General • 2: Notation and Terminology – dagg = nominal maximum size of coarse aggregate, in. – aggregate—granular material, such as sand, gravel, crushed stone, iron blast-furnace slag, or recycled aggregates including crushed hydraulic cement concrete, used with a cementing medium to form concrete or mortar.
WWW.CONCRETE.ORG/ACI318 24 Part 1: General • 3: Referenced Standards • 4: Structural System Requirements Materials Design loads Load paths Structural analysis Strength Serviceability Durability Sustainability Structural integrity Fire Safety Precast/ Prestressed Inspection
WWW.CONCRETE.ORG/ACI318 25 Part 2: Loads & Analysis • 5: Loads • 6: Structural Analysis – Simplified, first-order, second-order – Linear, nonlinear – Slenderness – Materials and section properties
WWW.CONCRETE.ORG/ACI318 26 Part 3: Members • 7: One-Way Slabs • 8: Two-Way Slabs • 9: Beams • 10: Columns • 11: Walls • 12: Diaphragms • 13: Foundations • 14: Plain Concrete
WWW.CONCRETE.ORG/ACI318 27 Typical member chapter sections • X.1 Scope • X.2 General • X.3 Design Limits • X.4 Required Strength • X.5 Design Strength • X.6 Reinforcement Limits • X.7 Reinforcement Detailing • X.? ?
WWW.CONCRETE.ORG/ACI318 28 ACI 318-19 Organization Δ Anchorage, Flexure, Shear, Deflection, Ch. 9 Ch. 11 Ch. 10 Ch. 12 Ch. 9 Ch. 9 Ch. 9 Ch. 9
WWW.CONCRETE.ORG/ACI318 29 Part 4: Joints / Connections / Anchors • 15: Beam-column and slab-column joints • 16: Connections between members • 17: Anchoring to concrete
WWW.CONCRETE.ORG/ACI318 30 Part 5: Seismic • 18: Earthquake Resistant Structures
WWW.CONCRETE.ORG/ACI318 31 Part 6: Materials & Durability • 19: Concrete: Design and Durability Properties • 20: Steel Reinforcement Properties, Durability, and Embedments (Credit: PCA)
WWW.CONCRETE.ORG/ACI318 32 Part 7: Strength & Serviceability • 21: Strength Reduction Factors • 22: Sectional Strength
WWW.CONCRETE.ORG/ACI318 33 Organization Member Chapter 9.5 — Design strength 9.5.2 — Moment 9.5.2.1 — If Pu < 0.10f’cAg, Mn shall be calculated in accordance with 22.3. 9.5.2.2 — If Pu ≥ 0.10f’cAg, Mn shall be calculated in accordance with 22.4. Toolbox Chapter 22.3 —Flexural strength… 22.3.3.4 … 22.4 — Axial strength or combined flexural and axial strength… 22.4.3.1 …
WWW.CONCRETE.ORG/ACI318 34 Part 7: Strength & Serviceability • 23: Strut-and-Tie Method • 24: Serviceability ,
WWW.CONCRETE.ORG/ACI318 35 Part 8: Reinforcement • 25: Reinforcement Details
WWW.CONCRETE.ORG/ACI318 36 Part 9: Construction • 26: Construction Documents and Inspection – 318 is written to the engineer, not the contractor. – Construction requirements must be communicated on the construction documents. – All construction requirements are gathered together in Chapter 26. – Design information – job specific – Compliance requirements – general quality – Inspection requirements
WWW.CONCRETE.ORG/ACI318 37 Part 10: Evaluation • 27: Strength Evaluation of Existing Structures – Applies when strength is in doubt – Well understood – analytical evaluation – Not well understood – load test
WWW.CONCRETE.ORG/ACI318 38 Benefits of ACI 318 organization • Organized from a designer’s perspective • Easier to find specific requirements • Intuitive location of information • Clarified cross references • Tables improve speed of understanding • Consistent language in text • Single idea for each requirement
WWW.CONCRETE.ORG/ACI318 39 Changes to the Concrete Design Standard ACI 318-19 Existing Structures
WWW.CONCRETE.ORG/ACI318 40 1.4—Applicability 1.4.1 This Code shall apply to concrete structures designed and constructed under the requirements of the general building code. … 1.4.3 Applicable provisions of this Code shall be permitted to be used for structures not governed by the general building code.
WWW.CONCRETE.ORG/ACI318 41 307 - Chimneys 562 - Repair 216 - Fire 313 - Silos 359 – Nuclear Contain. 349 – Nuclear Facilities 350 – Environmental 369 – Seismic Retrofit 376 – RLG Containment 332 – Residential 437 – Strength Evaluation Concrete designs governed by other ACI codes
WWW.CONCRETE.ORG/ACI318 42 Design recommendations provided in guides • Slabs-on-ground (ACI 360R) • Blast-resistant structures (ACI 370R) • Wire Wrapped Tanks (ACI 372R)
WWW.CONCRETE.ORG/ACI318 43 1.4.2—Repair 1.4.2 Provisions of this Code shall be permitted to be used for the assessment, repair, and rehabilitation of existing structures. R1.4.2 Specific provisions for assessment, repair, and rehabilitation of existing concrete structures are provided in ACI 562-19. Existing structures in ACI 562 are defined as structures that are complete and permitted for use.
WWW.CONCRETE.ORG/ACI318 44 Chapter 27 – Strength Evaluation of Existing Structures Applies when strength is in doubt • Well understood – analytical evaluation • Not well understood – load test – Monotonic procedure, ACI 318 – Cyclic procedure, ACI 437.2
WWW.CONCRETE.ORG/ACI318 45 27.4.6.2—Total test load, Tt Greatest of: (a) Tt = 1.15D + 1.5L + 0.4(Lr or S or R) →Tt = 1.0Dw + 1.1Ds + 1.6L + 0.5(Lr or S or R) (b) Tt = 1.15D + 0.9L + 1.5(Lr or S or R) → Tt = 1.0Dw + 1.1Ds + 1.0L + 1.6(Lr or S or R) (c) Tt = 1.3D →Tt = 1.3(Dw + Ds)
WWW.CONCRETE.ORG/ACI318 46 Changes to the Concrete Design Standard ACI 318-19 Loads & Analysis
WWW.CONCRETE.ORG/ACI318 47 Superposition of loads (R5.3.1) • Added commentary – If the load effects such as internal forces and moments are linearly related to the loads, the required strength U may be expressed in terms of load effects with the identical result. If the load effects are nonlinearly related to the loads, such as frame P-delta effects (Rogowsky et al. 2010), the loads are factored prior to determining the load effects. Typical practice for foundation design is discussed in R13.2.6.1. Nonlinear finite element analysis using factored load cases is discussed in R6.9.3.
WWW.CONCRETE.ORG/ACI318 48 Superposition of loads (R5.3.1) In other words: • First order, linear analysis M1.2D+1.6L = 1.2 MD + 1.6 ML • Second order or nonlinear analysis M1.2D+1.6L ≠ 1.2 MD + 1.6 ML
WWW.CONCRETE.ORG/ACI318 49 Wind Loads (R5.3.5) • Added commentary – ASCE 7-05 • Wind = service-levelwind • Use 1.6 load factor – ASCE 7-10 & ASCE 7-16 • Wind = strength-level wind • Use 1.0 load factor
WWW.CONCRETE.ORG/ACI318 50 Inelastic First-Order Analysis (Chapter 6) • Not mentioned in ACI 318-14 • Nonlinear material properties • Equilibrium satisfied in undeformed shape • Several revisions – Must consider column slenderness – No further redistribution – Clarifies requirements for each type of analysis Moment Curvature
WWW.CONCRETE.ORG/ACI318 51 Consistent Stiffness Assumptions (6.3.1.1) • ACI 318-14 dropped “consistent throughout the analysis” language No top steel required No bottom steel required No steel required
WWW.CONCRETE.ORG/ACI318 52 Torsional Stiffness (R6.3.1.1) • Clarification in commentary • Two factors – Torsional vs. flexural stiffnesses – Equilibrium requirements GJ vs. EI
WWW.CONCRETE.ORG/ACI318 53 Torsional Stiffness Equilibriumtorsion • Torsion in beam required to maintain equilibrium • Torsion and torsional stiffness of the beam must be considered Beam Cantilever slab
WWW.CONCRETE.ORG/ACI318 54 Torsional Stiffness Compatibilitytorsion • Torsion in girder not required to maintain equilibrium • Torsion and torsional stiffness of the beam may be neglected Beam Interior girder
WWW.CONCRETE.ORG/ACI318 55 Torsional Stiffness Compatibilitytorsion • Torsion in girder not required to maintain equilibrium • Torsion and torsional stiffness of the girder should be included Beam Exterior girder
WWW.CONCRETE.ORG/ACI318 56 Shear Area (6.6.3.1) Member and condition Moment of inertia Cross-sectional area for axial deformations Cross-sectional area for shear deformations Columns 0.70Ig 1.0Ag bwh Walls Uncracked 0.70Ig Cracked 0.35Ig Beams 0.35Ig Flat plates and flat slabs 0.25Ig Table 6.6.3.1.1(a)— Moments of Inertia and cross-sectionalareaspermitted for elastic analysisat factoredload level • No previous guidance
WWW.CONCRETE.ORG/ACI318 57 Floor Vibrations (R24.1) • Typical floors – Good performance • Areas of concern – Long/open spans – High-performance (precision machinery) – Rhythmic loading or vibrating machinery – Precast • Commentary references
WWW.CONCRETE.ORG/ACI318 58 Floor Vibrations • Resources – ATC Design Guide 1, “Minimizing Floor Vibration,” – Fanella, D.A., and Mota, M., “Design Guide for Vibrations of Reinforced Concrete Floor Systems,” – Wilford, M.R., and Young, P., “A Design Guide for Footfall Induced Vibration of Structures,” – PCI Design Handbook – Mast, R.F., “Vibration of Precast Prestressed Concrete Floors – West, J.S.; Innocenzi, M.J.; Ulloa, F.V.; and Poston, R.W., “Assessing Vibrations” • No specific requirements CIP Precast P-T
WWW.CONCRETE.ORG/ACI318 59 Concerns about deflection calculations • Service level deflections based on Branson’s equation underpredicted deflections for ρ below ≈ 0.8% • Reports of excessive slab deflections (Kopczynski, Stivaros) • High-strength reinforcement may result in lower reinforcement ratios
WWW.CONCRETE.ORG/ACI318 60 Heavily reinforced Midspan deflection Midspan moment Experimental Branson’s Eq. Bischoff’s Eq.
WWW.CONCRETE.ORG/ACI318 61 Lightly reinforced Midspan deflection Midspan moment Experimental Branson’s Eq. Bischoff’s Eq.
WWW.CONCRETE.ORG/ACI318 62 Ie should be the average of flexibilities
WWW.CONCRETE.ORG/ACI318 63 • Branson • Bischoff Branson combines stiffnesses. Bischoff combines flexibilities. Comparison of Branson’s and Bischoff’s Ie
WWW.CONCRETE.ORG/ACI318 64 • Table 24.2.3.5 ~ Inverse of Bischoff Eqn. • 2/3 factor added to account for: – restraint that reduces effective cracking moment – reduced concrete tensile strength during construction • Prestressed concrete Effective Moment of Inertia 𝑀𝑎 > Τ 2 3 𝑀𝑐𝑟, 𝐼𝑒 = 𝐼𝑐𝑟 1 − Τ 2 3 𝑀𝑐𝑟 𝑀𝑎 2 1 − 𝐼𝑐𝑟 𝐼𝑔 𝑀𝑎 ≤ Τ 2 3 𝑀𝑐𝑟, 𝐼𝑒 = 𝐼𝑔
WWW.CONCRETE.ORG/ACI318 65 Changes to the Concrete Design Standard ACI 318-19 One-Way Slabs
WWW.CONCRETE.ORG/ACI318 66 Structural Integrity Reinforcement Structural integrity provisions have been added • To improve structural integrity – To ensure that failure of a portion of a slab does not lead to disproportional collapse • To be similar to that for beams – bring one-way cast-in-place slab structural integrity in line with beam structural integrity provisions
WWW.CONCRETE.ORG/ACI318 67 Structural Integrity Reinforcement • 7.7.7 Structural integrity reinforcement in cast-in-place one-way slabs – 7.7.7.1 Longitudinal reinf. consists of at least ¼ of max. positive moment to be continuous Beam 1/4 M+ continuous
WWW.CONCRETE.ORG/ACI318 68 Structural Integrity Reinforcement – 7.7.7.2 Longitudinal reinf. at noncontinuous supports to be anchored to develop fy at the face of the support Beam
WWW.CONCRETE.ORG/ACI318 69 Structural Integrity Reinforcement – 7.7.7.3 Splices • Splice near supports • mechanical or welded in accordance with25.5.2 or 25.5.7 • or Class B tension lap splices in accordance with 25.5.2 Beam Splice
WWW.CONCRETE.ORG/ACI318 70 Shrinkage and Temperature Reinforcement 7.6.4.1 → 24.4 Shrinkage and temperature reinforcement 24.4.3.2 : Ratio of deformed shrinkage and temperature reinforcement area to gross concrete area • 318-14: as per Table 24.4.3.2 • 318-19: Ratio ≥ 0.0018 0
WWW.CONCRETE.ORG/ACI318 71 Minimum Flexural Reinforcement in Nonprestressed Slabs – One way 7.6.1.1: • 318-14: As,min as per Table 7.6.1.1 • 318-19: As,min = 0.0018Ag 1
WWW.CONCRETE.ORG/ACI318 72 Changes to the Concrete Design Standard ACI 318-19 Two-Way Slabs
WWW.CONCRETE.ORG/ACI318 73 The Direct Design Method and The Equivalent Frame Method – Removed: The direct design method (8.10) and the equivalent frame method (8.11) – Provisions in 318-14 – 8.2.1 … The direct design method or the equivalent frame method is permitted. – 6.2.4.1 Two-way slabs shall be permitted to be analyzed for gravity loads in accordance with (a) or (b): (a) Direct design method for nonprestressed slabs (b) Equivalent frame method for nonprestressed and prestressed slabs
WWW.CONCRETE.ORG/ACI318 74 Shearheads • Removed Shearhead provisions in 318-14 – 8.4.4.1.3 Slabs reinforced with shearheads shall be evaluated for two-way shear at critical sections in accordance with 22.6.9.8.
WWW.CONCRETE.ORG/ACI318 75 Opening in Slab Systems Without Beams Fig. R22.6.4.3—Effect of openings and free edges (effective perimeter shown with dashed lines) Note: Openings shown are located within 10h of the column periphery ACI 318 -14: 8.5.4.2(d) • within a column strip or closer than 10h from a concentrated load or reaction area satisfy – 22.6.4.3 for slabs without shearheads – or 22.6.9.9 for slabs with shearheads • 22.6.4.3: Reduced perimeter of critical section (bo) – Fig. R22.6.4.3 • 22.6.9.9: Reduction to bo is ½ of that given in 22.6.4.3
WWW.CONCRETE.ORG/ACI318 76 Opening in Slab Systems Without Beams Fig. R22.6.4.3—Effect of openings and free edges (effective perimeter shown with dashed lines). ACI 318 -19: 8.5.4.2(d) • closer than 4h from the periphery of a column, concentrated load or reaction area satisfying 22.6.4.3 • 22.6.4.3: Reduced perimeter of critical section (bo) – Fig. R22.6.4.3
WWW.CONCRETE.ORG/ACI318 77 Minimum Flexural Reinforcement in Nonprestressed Slabs – Two way 8.6.1.1 • 318-14 : As,min as per Table 8.6.1.1. • 318-19: As,min of 0.0018Ag, or as defined in 8.6.1.2 (discussed under two-way shear) 7
WWW.CONCRETE.ORG/ACI318 78 Reinforcement Extensions for Slabs without Beams ACI 318-14: 8.7.4.1.3 - Column strip top bars • Extend to at least 0.3ℓn • May not be sufficient for thick slabs – may not intercept critical punching shear crack – Reduce punching shear strength Punchingshear cracks in slabs with reinforcementextensions
WWW.CONCRETE.ORG/ACI318 79 Punching shear failure - Podium Slab • The failure crack did not intercept the top reinforcement.
WWW.CONCRETE.ORG/ACI318 80 Reinforcement Extensions for Two-Way Slabs without Beams ACI 318-19: 8.7.4.1.3 - Column strip top bars • Extend to at least 0.3ℓn but, not less than 5d Fig. R8.7.4.1.3- Punching shear cracks in ordinary and thick slabs d d
WWW.CONCRETE.ORG/ACI318 81 Reinforcement Extensions for Two-Way Slabs without Beams
WWW.CONCRETE.ORG/ACI318 82 Changes to the Concrete Design Standard ACI 318-19 Post-tensioning
WWW.CONCRETE.ORG/ACI318 83 Residential P-T Slabs (1.4.6) • Past confusion about P-T slab foundation design on expansive soils – Intent was for residential, but not mentioned with residential design provisions • Commentary clarifies use of PTI DC10.5-12 for P-T residential slabs and foundations on expansive soils
WWW.CONCRETE.ORG/ACI318 84 Residential P-T Slabs (1.4.6) • Coordinates with 2015 IBC requirements • Adds reference to ACI 360 if not on expansive soil
WWW.CONCRETE.ORG/ACI318 85 Max. Spacing of Deformed Reinf. (7.7.2.3) • Class C (Cracked) and T (Transition) one- way slabs with unbonded tendons rely on bonded reinforcement for crack control • Previously no limits for spacing of deformed reinforcement for Class C and T prestressed slabs • Industry feedback provided
WWW.CONCRETE.ORG/ACI318 86 Max. Spacing of Deformed Reinf. (7.7.2.3) • New limit is s ≤ 3h and 18 in. • Same as non-prestressed slabs Unbonded P-T Deformed reinforcement Slab Section s ≤ 3h and 18 in.
WWW.CONCRETE.ORG/ACI318 87 P-T Anchorage Zone Reinforcement (25.9.4.4.6) • Referenced from slab and beam chapters • Applies for groups of 6 or more anchors in thick slabs • Anchorage zone requires backup bars for bearing and hairpins for bursting • Hairpins must be anchored at the corners Backup bars Anchor bars Hairpins
WWW.CONCRETE.ORG/ACI318 88
WWW.CONCRETE.ORG/ACI318 89 P-T Anchorage Zone Reinforcement (25.9.4.4.6) • Thin slabs ≤ 8 in. → Anchor bars serve as backup bars • Thick slabs > 8 in. → Both backup bars and anchor bars required Backup bars Anchor bars Hairpins
WWW.CONCRETE.ORG/ACI318 90
WWW.CONCRETE.ORG/ACI318 91
WWW.CONCRETE.ORG/ACI318 92
WWW.CONCRETE.ORG/ACI318 93 Design of Formwork for P-T (26.11.1.2 (5) and (6)) • Members may move when P-T strand is stressed • Movement may redistribute loads • Added requirement to allow for movement during tensioning • Added requirement to consider redistribution of loads on formwork from tensioning of the prestressing reinforcement
WWW.CONCRETE.ORG/ACI318 94 Changes to the Concrete Design Standard ACI 318-19 Precast/Prestressed
WWW.CONCRETE.ORG/ACI318 95 Precast/Prestressed Concrete • Confinement for column/pedestal tops • Connection forces • Construction document requirement • f at ends of precast members
WWW.CONCRETE.ORG/ACI318 96 Confinement • 10.7.6.1.5: confinement required at tops of columns/pedestals • Assists in load transfer • Not a new provision 5 in. Two No. 4 or Three No. 3 ties Anchor bolts
WWW.CONCRETE.ORG/ACI318 97 Confinement • 10.7.6.1.6: extends confinement requirement to precast columns/pedestals 5 in. Two No. 4 or Three No. 3 ties Mechanical coupler Future precast member
WWW.CONCRETE.ORG/ACI318 98 Volume Change in Precast Connections • Volume change – Creep – Shrinkage – Temperature • May induce connection reactions if restrained
WWW.CONCRETE.ORG/ACI318 99 Volume Change in Precast Connections • Load magnitude? • Load factor? • Past guidance for brackets and corbels – Use Nuc ≥ 0.2Vu as restraint force – Use a 1.6 load factor • Approach was often to design around forces
WWW.CONCRETE.ORG/ACI318 100 Volume Change and Connections 318-19 changes (16.2.2.3) • Nuc = factored restraint force, shall be (a) or (b) – (a) restraint force x LL factor (no bearing pad) – (b) 1.6 x 0.2(sustained unfactored vertical load) for connections on bearing pads • Nuc,max ≤ connection capacity x LL factor • Nuc,max ≤ 1.6 x μ x (sustained unfactored vertical load) if μ is known, (See 16.2.2.4)
WWW.CONCRETE.ORG/ACI318 101 Brackets and Corbels • 26.6.4.1(a) Details for welding of anchor bars at the front face of brackets or corbels designed by the licensed design professional in accordance with 16.5.6.3(a). Fig. R16.5.6.3b Fig. R16.5.1b
WWW.CONCRETE.ORG/ACI318 102 Strength Reduction Factor Near end of precast member • Linear interpolation of f • f p depends on state of stress
WWW.CONCRETE.ORG/ACI318 103 Strength Reduction Factor Near end of precast member • Similar for debonded strand
WWW.CONCRETE.ORG/ACI318 104 Changes to the Concrete Design Standard ACI 318-19 Circular Sections
WWW.CONCRETE.ORG/ACI318 105 Variable definitions (22.5) • 22.5 One-way shear – Interpretation for hollow circular sections d ? bw ? ρw ? opening
WWW.CONCRETE.ORG/ACI318 106 Variable definitions (22.5) • 22.5.2.2 – calculation of Vc and Vs – d = 0.8 x diameter – bw = diameter (solid circles) – bw = 2 x wall thickness (hollow circles) d = 0.8D bw = D ρw = As/bwd bw = 2t opening t
WWW.CONCRETE.ORG/ACI318 107 Variable definitions (22.5) • What about As? (2/3)D As
WWW.CONCRETE.ORG/ACI318 108 Torsion for circular sections (R22.7.6.1.1) • Do ACI 318 torsion equations apply to circular cross sections? • Code Eqns are based on thin-tube theory • Examples added to figure 125
WWW.CONCRETE.ORG/ACI318 109 Circular Column Joints • Based on equivalent square column – Aj for joint shear strength (15.4.2) – Width of transverse beams required for joint to be considered confined (15.2.8) – Column width ≥ 20 db for special moment frames (18.8.2.3) h = 0.89D
WWW.CONCRETE.ORG/ACI318 110 Changes to the Concrete Design Standard ACI 318-19 Walls
WWW.CONCRETE.ORG/ACI318 111 Scope of walls • Change in scope 11.1.4 - Design of cantilever retaining walls shall be in accordance with Chapter 13 (Foundations)
WWW.CONCRETE.ORG/ACI318 112 Scope of walls • Added scope 11.1.6 - CIP walls with insulated forms shall be permitted by this code for use in one or two-story buildings • Design according to Chapter 11 • Guidance – ACI 560R and PCA 100-2017 • Unique construction issues Photo courtesy Larry Novak
WWW.CONCRETE.ORG/ACI318 113 11.7.2.3 Bar placement • If wall thickness h > 10 in. • Two layers of bars one near each face • Exception, single story basement walls • 318-14 • ½ to 2/3 of reinf. placed near exterior face • Balance of reinf. placed near interior face • Confusion with exterior and interior – Face versus wall location • ½ to 2/3 was arbitrary
WWW.CONCRETE.ORG/ACI318 114 14.6 Plain concrete At windows, door openings, and similarly sized openings • At least two No. 5 bars (similar to walls 11.7.5.1) • Extend 24 in. beyond or to develop fy ≥ 24 in. 2-No. 5 bars
WWW.CONCRETE.ORG/ACI318 115 Changes to the Concrete Design Standard ACI 318-19 Foundations
WWW.CONCRETE.ORG/ACI318 116 Ch. 13 – Foundations – significant changes • Added design provisions – Cantilever retaining walls – Deep foundation design • Other – Minimum concrete strengths for shallow and deep foundations – Cover
WWW.CONCRETE.ORG/ACI318 117 Foundations and 318 • ACI 318-71 to ACI 318-11 (Ch. 15) • Shallow footings, pile caps • ACI 318-14 (Ch. 13) • Shallow footings, pile caps
WWW.CONCRETE.ORG/ACI318 118 Foundations and 318 • ACI 318-71 to ACI 318-11 (Ch. 15) • Shallow footings, pile caps • ACI 318-14 (Ch. 13) • Shallow footings, pile caps • ACI 318-19 (Ch. 13) • Shallow footings, pile caps, deep foundations, and walls of cantilevered retaining walls
WWW.CONCRETE.ORG/ACI318 119 Cantilever retaining walls It’s a wall (2014) It’s a slab (2019)
WWW.CONCRETE.ORG/ACI318 120 13.3.6.1—Cantilever stem walls • Design as one-way slab (Ch. 7)
WWW.CONCRETE.ORG/ACI318 121 13.3.6.2—Cantilever stem wall with counterfort • Design as two-way slab (Ch. 8)
WWW.CONCRETE.ORG/ACI318 122 Maximum bar spacing in stem wall Wall Slab Stem wall reinforcement Maximum bar spacing (2014) Design as wall (2014) Maximum bar spacing (2019) Design as one-way slab (2019) Long. (Wall) or Flexural(Slab) 3h, or 18 in. 11.7.2.1 Lesser of: 7.7.2.2 (24.3) Trans. (Wall) or S & T (Slab) 3h, or 18 in. 11.7.3.1 5h, or 18 in. 7.7.6.2.1 s Transverse bars Longitudinal bars 40,000 15 2.5 c s c f   −     40,000 12 s f      
WWW.CONCRETE.ORG/ACI318 123 ACI 318-14 ACI 318-19 Minimum reinforcement, ρ Designas wall Minimum reinforcement As,min Designas one-way slab ≤ No. 5 ρℓ = 0.0012 > No. 5 ρℓ = 0.0015 11.6.1 As,min = 0.0018 Ag 7.6.1.1 ≤ No. 5 ρt = 0.0020 > No. 5 ρt = 0.0025 11.6.2 AS+T = 0.0018 Ag 7.6.4.1 (24.4) Minimum reinforcement in stem wall
WWW.CONCRETE.ORG/ACI318 124 1.4.7— Scope changes – deep foundations • Scope: This code does not govern design and installation of portions of concrete pile, drilled piers, and caissons embedded in ground, except as provided in (a) through (c) • (a) For portions in air or water,or in soil incapable of providing adequate lateral restraint to prevent buckling throughout their length • (b) For precast concrete piles supporting structures assigned to SDC A and B • (c) For deep foundation elements supporting structures assigned to SDC C, D, E, and F (SDC C is added to scope)
WWW.CONCRETE.ORG/ACI318 125 Deep Foundations (13.4) • 13.4.1 General • 13.4.2 Allowable axial strength • 13.4.3 Strength design • 13.4.4 Cast-in-place deep foundations • 13.4.5 Precast concrete piles • 13.4.6 Pile caps
WWW.CONCRETE.ORG/ACI318 126 Deep foundation – combine IBC & ASCE 7 • ACI 318 – 19 – – combined IBC 2015, ASCE 7-10, and ACI 318-14 with regards to design of deep foundations for earthquake resistant structures (SDC C, D, E, and F) ACI 318 - 19 Allowable axial strength/stress capacities ACI 318-14 ASCE 7 IBC 2015
WWW.CONCRETE.ORG/ACI318 127 Pre- ACI 318-19 – design of deep foundations • ACI 543 - Piles (diam. < 30 in.) • ACI 336.3 - Design of drilled piers (diam. ≥ 30 in.) Not code language documents Also used deep footing provisions from: IBC and ASCE/SEI 7
WWW.CONCRETE.ORG/ACI318 128 Design of deep foundation members- compressive axial force (13.4.1) • Design axial strength of members in accordance to two methods: – Allowable Axial Strength Design (13.4.2) – Strength Design (13.4.3) Photos courtesy Larry Novak
WWW.CONCRETE.ORG/ACI318 129 Allowable axial strength method (13.4.2) 13.4.2.1 It shall be permitted to design a deep foundation member using load combinations for allowable stress design in ASCE / SEI 7, Section 2.4, and the allowable strength specified in Table 13.4.2.1 if (a) and (b) are satisfied (a)Deep foundation is laterally supported for its entire height (b)Applied forces causing bending moments less than moment due to an accidental eccentricity of 5 percent of the pile diameter or width.
WWW.CONCRETE.ORG/ACI318 130 13.4.2 deep foundation design
WWW.CONCRETE.ORG/ACI318 131 Confinement of metal casing (13.4.2.3): • not used to resist axial load • sealed tip and mandrel-driven • seamless or welded seamless Physical properties • wall thickness ≥ 14 ga. (0.068 in.) • fy ≥ 30,000 psi • fy ≥ 6 f’c , and • nominal diameter ≤ 16 in. Metal casing Sealed tip Diam ≤ 16 in.
WWW.CONCRETE.ORG/ACI318 132 Deep foundations – strength design (13.4.3) • Method may be used any time • Method must be used when pile does not meet criteria for allowable axial strength design – Soils do not provide lateral support – Moment is not negligible • Use Section 10.5 (columns) – 𝝓 Pn ≥ Pu – 𝝓 Mn ≥ Mu – Combined Pn and Mn calculated by 22.4 Mu≥ 0 Pu
WWW.CONCRETE.ORG/ACI318 133 Strength design (13.4.3) – axial force, no moment Nominal axial compressive strength; Pn 𝝓 Pn,max ≥ Pu Maximum axial strength - For deep foundations members with ties conforming to Ch. 13 (new in Table 22.4.2.1) Pn,max = 0.80 Po Where: Po = nominal axial strength at zero eccentricity Po = 0.85f’c(Ag – Ast) + fyAst Mu= 0 Pu
WWW.CONCRETE.ORG/ACI318 134 Mu= 0 Strength design (13.4.3) – axial force, no moment • Reduction factor – Table 13.4.3.2 Pu 0.55 to 0.70
WWW.CONCRETE.ORG/ACI318 135 Deep foundations 13.4.4.1 CIP deep foundations that are subject to (a) uplift or (b) Mu > 0.4Mcr shall be reinforced, unless enclosed by a steel pipe or tube Confined for ductility Reinforced for flexure Reinforced for tension Unreinforced
WWW.CONCRETE.ORG/ACI318 136 Table 19.2.1.1 – Additional minimum strength, f’c Shallow foundations Min. f’c (psi) Foundations in SDC A, B, or C 2500 Foundation for Residential and Utility …. 2 stories or less ….stud bearing construction …… SDC D, E, or F 2500 Foundation for Residential and Utility …. More than 2 stories….stud bearing construction …… SDC D, E, or F 3000 Deep foundations Drilled shafts or piers 4000 Precast nonprestressed driven piles 4000 Precast prestressed driven piers 5000
WWW.CONCRETE.ORG/ACI318 137 Concrete cover – deep foundations Table 20.5.1.3.4 3 in. Cast-in-place against ground 1.5 in. Cast-in-place enclosed by steel pipe, permanent casing, or stable rock socket Steel pipe
WWW.CONCRETE.ORG/ACI318 138 Concrete cover – deep foundations In contact with ground 2.5 in. precast nonprestressed 2 in. precast prestressed Exposed to seawater 1.5 in. precast nonprestressed and precast prestressed Table 20.5.1.3.4
WWW.CONCRETE.ORG/ACI318 139 Changes to the Concrete Design Standard ACI 318-19 Anchorage to Concrete
WWW.CONCRETE.ORG/ACI318 140 Chapter 17 – Anchoring to Concrete • Reorganized • New content/design information – Screw anchors added – Shear lugs added
WWW.CONCRETE.ORG/ACI318 141 Sections • 17.1 Scope • 17.2 General • 17.3 Design limits • 17.4 Required strength • 17.5 Design strength • 17.6 Tensile strength • 17.7 Shear strength • 17.8 Tension and shear interaction • 17.9 Edge distances, spacings, and thicknesses to preclude splitting failure • 17.10 Earthquake- resistant design requirements • 17.11 Attachments with shear lugs
WWW.CONCRETE.ORG/ACI318 142 Ch. 17 – Anchoring to Concrete Scope • Headed studs and headed bolts • Hooked bolts • Post-installed undercut anchors • Post-installed expansion anchors • Post-installed adhesive anchors
WWW.CONCRETE.ORG/ACI318 143 New Content/Design Information • Post-installed screw anchors – pre-qualification per ACI 355.2 • Attachments with shear lugs
WWW.CONCRETE.ORG/ACI318 144 Screw Anchors (17.3.4) • For screw anchors satisfying: – hef ≥ 1.5 in. and – 5da ≤ hef ≤ 10da • Manufacturer provides hef, Aef, and pullout strength • Concrete breakout evaluated similar to other anchors – 17.6.2 in tension – 17.7.2 in shear
WWW.CONCRETE.ORG/ACI318 145 Minimum Spacing (17.9.2a) • Screw anchor spacing limited per Table 17.9.2a Spacing > 0.6hef and 6da Greatest of: (a) Cover (b) 2 x max. agg. (c) 6da or per ACI 355.2
WWW.CONCRETE.ORG/ACI318 146 17.1.6 – Reinforcement used as anchorage Check anchorage for bars developed per Ch. 25 • Check concrete breakout in tension (and maybe shear) • Greater development length should be considered
WWW.CONCRETE.ORG/ACI318 147 17.1.6 – Reinforcement used as anchorage • Straight bars behave like adhesive anchors • Hooked and headed bars behave like headed anchors • Anchor reinforcement may be an alternative
WWW.CONCRETE.ORG/ACI318 148 Shear Lugs (17.11.1) Shear lugs are fabricated from: • Rectangular plates or • Steel shapes composed of plate- like elements, welded to an attachment base plate
WWW.CONCRETE.ORG/ACI318 149 Shear Lugs (17.11.1) • Minimum four anchors • Anchors do not need to resist shear forces if not welded • Anchors welded to steel plate carry portion of total shear load
WWW.CONCRETE.ORG/ACI318 150 Shear Lug Detailing (17.11.1.1.8) • Anchors in tension, satisfy both (a) and (b): (a) hef/hsl ≥ 2.5 (b) hef/csl ≥ 2.5
WWW.CONCRETE.ORG/ACI318 151 Shear Lug Detailing (17.11.1.2) • Steel plate to have 1 in. dia. (min.) hole • Single plate – one on each side • Cross / cruciform plate - one each quadrant • More vent holes are not detrimental
WWW.CONCRETE.ORG/ACI318 152 Shear Lug Overturning (17.11.1.1.9) hef hsl tsl Csl
WWW.CONCRETE.ORG/ACI318 153 Bearing (17.11.2) • f Vbrg,sl ≥ Vu • Where f = 0.65 Source: Peter Carrato
WWW.CONCRETE.ORG/ACI318 154 Bearing Strength (17.11.2) • Bearing strength: • Aef,sl is the surface perpendicular to the applied shear: 2tsl 2tsl 2tsl ' , , , 1.7 brg sl c ef sl brg sl V f A =  tsl
WWW.CONCRETE.ORG/ACI318 155 Bearing Area Directionof shearload Directionof shearload
WWW.CONCRETE.ORG/ACI318 156 Stiffeners • 17.11.2.3 - If used, the length of shear lug stiffeners in the direction of the shear load shall not be less than 0.5hsl 0.5hsl hsl Shear lug Stiffener T/Conc
WWW.CONCRETE.ORG/ACI318 157 17.11.2.2 – Bearing factor Tension load • Ψbrg,sl = 1 + Pu/(nNsa) ≤ 1.0 • Pu – negative for tension • n – number of anchors in tension • Nsa – Nominal tension strength of a single anchor No applied axial load: Ψbrg,st = 1 Compression load: Ψbrg,sl = 1 + 4Pu/(Abpfc’) ≤ 2.0 • Pu – positive for compression ' , , , 1.7 brg sl brg sl c ef sl V f A  =
WWW.CONCRETE.ORG/ACI318 158 17.11.2.4 – Bearing for Multiple Shear Lugs • If τ ≤ 0.2 f’c, use bearing from both lugs A1 A2 τ = Vu/(A1 + A2)
WWW.CONCRETE.ORG/ACI318 159 17.11.3 – Concrete breakout strength of shear lugs • Nominal concrete breakout strength of a shear lug – Use Anchor provisions of 17.7.2 • Where: , , , , Vc cb sl ed V c V h V b Vco A V V A =    ' 1.5 1 9 ( ) b a c a V f c = 
WWW.CONCRETE.ORG/ACI318 160 17.11.3.4 – Breakout for Multiple Shear Lugs • Determine for each potential breakout surface • Commentary directs to Fig. R17.7.2.1b
WWW.CONCRETE.ORG/ACI318 161 Shear Lug Example • Reinforced Concrete Design Manual • Anchorage example 20 • See handout DV = 60 Kips LV = 75 Kips WV = ±170 Kips DH = ± 8 Kips LH = ± 9 Kips WH = ±12 Kips
WWW.CONCRETE.ORG/ACI318 162 Shear Lug Example • Can we replace upper ties with shear lug? – Remove shear from anchor rod design – May reduce bolt size/length – Simplify design
WWW.CONCRETE.ORG/ACI318 163 Size Shear Lug • Size shear lug so entire lug is effective – tsl = 1.5 in. – Width = 1.5 in. + 4(1.5 in.) = 7.5 in. – Depth = 3 in. + 3 in. = 6 in. – Stiffeners at least 0.5 hsl or 1.5 in. wide T/Conc V 3 in. 1.5 in.
WWW.CONCRETE.ORG/ACI318 164 Shear Lug Example • Check anchor rod depth (only required if attachment has tension) – hef/hsl ≥ 2.5 → hef = 2.5 (3 in.) = 7.5 in. – hef/csl ≥ 2.5 → hef = 2.5 (8 in.) = 20 in. <= controls – Increase rod embedment from 18 in. to 20 in. 16” hsl = 3” csl = 8” hef
WWW.CONCRETE.ORG/ACI318 165 Strength Checks • Vua,g ≤ f Vbrg,sl (bearing) ≤ f Vcb,sl (concrete breakout) • f = 0.65
WWW.CONCRETE.ORG/ACI318 166 Bearing Strength Check • Vua,g ≤ f Vbrg,sl (bearing) – Vua,g = 30 kip – Vbrg,sl = 1.7 f’c Aef,sl Ψbrg,sl • For tension on attachment, bearing is reduced – Ψbrg,sl = 1+Pu/(nNsa) – = 1+(-116 kip)/(4 rods(72.7 kip/rod))= 0.601 – Vbrg,sl = 1.7 (4500 psi)(7.5 in.)(3 in.)(0.601) = 103 kip • f Vbrg,sl = 0.65 (103 kip) = 67 kip > 30 kip OK 1.7 f’c V
WWW.CONCRETE.ORG/ACI318 167 Concrete Breakout Strength Check • Vua,g ≤ f Vcb,sl (concrete breakout) • Vcb,sl = (AVc/AVc0) Ψed,V Ψc,V Ψh,V Vb – AVc = [3” + 1.5 (32” -1.5”)/2](32”)-(3”)(7.5”) = 805 in.2 32 in. 32 in. 3 in. 22.9 in. ca1 = 15.25 in. V
WWW.CONCRETE.ORG/ACI318 168 Concrete Breakout Strength Check • Vcb,sl = (AVc/AVc0) Ψed,V Ψc,V Ψh,V Vb – AVc0 = 4.5 ca1 2 = 4.5(15.25“)2 = 1047 in.2 32 in. ca1 = 15.25 in. 1.5 ca1 1.5 ca1
WWW.CONCRETE.ORG/ACI318 169 Concrete Breakout Strength Check • Vcb,sl = (AVc/AVc0) Ψed,V Ψc,V Ψh,V Vb – Ψed,V = edge effect modification factor = 0.7 + 0.3ca2/(1.5ca1) = 0.7+0.3(12.25”)/(1.5(15.25”))=0.861 32 in. ca1 = 15.25 in. ca2 = 12.25 in.
WWW.CONCRETE.ORG/ACI318 170 Concrete Breakout Strength Check • Vcb,sl = (AVc/AVc0) Ψed,V Ψc,V Ψh,V Vb – Ψc,V = concrete cracking modification factor – Assume cracking and No. 4 ties between lug and edge (see Table 17.7.2.5.1) – Ψc,V = 1.2 – Ψh,V = member thickness modification factor =1.0 (depth > 1.5 ca1) – Vb = 9λaf’c(ca1)1.5 = 9(1)(4500 psi)(15.25”)1.5 = 36,000 lb
WWW.CONCRETE.ORG/ACI318 171 Concrete Breakout Strength Check • Vcb,sl = (AVc/AVc0) Ψed,V Ψc,V Ψh,V Vb = (805 in.2/1047 in.2)(0.861)(1.2)(1.0)(36 kip) = 28.6 kip • f Vcb,sl = 0.65(28.6 kip) = 18.6 kip < 30 kip NG
WWW.CONCRETE.ORG/ACI318 172 Shear parallel to an edge or at a corner • Shear parallel to an edge – 17.11.3.2 → 17.7.2.1(c) • Shear at a corner – 17.11.3.3 → 17.7.2.1(d)
WWW.CONCRETE.ORG/ACI318 173 Summary • f Vcb,sl = 18.6 kip < 30 kip  anchor reinforcement required • From example: – all 4 rods resisting and supplementary reinforcement → f Vcbg = 29.4 kip – back 2 rods resisting and supplementary reinforcement → f Vcb,sl = 21.7 kip • Shear lugs not helpful for breakout • Helpful when shear in rods is controlling
WWW.CONCRETE.ORG/ACI318 174 Changes to the Concrete Design Standard ACI 318-19 Seismic Design Philosophy
WWW.CONCRETE.ORG/ACI318 175 Seismic • Both concrete and reinforcement are permitted to respond in the inelastic range • This is consistent with the strength design approach adopted throughout the Code
WWW.CONCRETE.ORG/ACI318 176 Seismic – Ω, Cd, and R Factors (ASCE 7)
WWW.CONCRETE.ORG/ACI318 177 1 Parameter in ASCE 7-16 Table 12.2-1 Example Seismic Force Resisting System Special reinforced concrete shear walls (building frame system) ASCE 7 Section Where Detailing Requirements Are Specified ASCE 7 Section 14.2 “Concrete” Response Modification Coefficient, R 6 Overstrength Factor, Ω0 2.5 Deflection Amplification Factor, Cd 5 Structural System Limitations, Including Structural Height Limits SDC B No limit SDC CNo limit SDC D160 ft SDC E 160 ft SDC F 100 ft Seismic – Parameters
WWW.CONCRETE.ORG/ACI318 178 Seismic • Controlled inelastic action is permitted at pre- determined locations, called plastic hinges • Typical plastic hinge locations are at the ends of beams in moment frames, and at the bases of shear walls
WWW.CONCRETE.ORG/ACI318 179 Seismic • Prescriptive rules for detailing of reinforcement are enforced, creating robust plastic hinges • Plastic hinging reduces the stiffness of the structure, which lengthens the period; and plastic hinges dissipate earthquake energy
WWW.CONCRETE.ORG/ACI318 180 Changes to the Concrete Design Standard ACI 318-19 Special Moment Frames
WWW.CONCRETE.ORG/ACI318 181 18.6.3.1 and 18.8.2.3—Special moment frame beams (and joints) • Longitudinal Reinforcement hc hb 𝑀𝑛2 + ≥ 𝑀𝑛2 − 2 𝑀𝑛2 − ≥ 2ℎ𝑏 𝑀𝑛1 + ≥ 𝑀𝑛1 − 2 𝑀𝑛1 − @ interior joints,𝑑𝑏 ≤ 𝑀𝑛 + 𝑜𝑟 𝑀𝑛 − at any section ≥ max 𝑀𝑛 at either joint 4 0.025𝑏𝑤𝑑 (Gr 60) 𝟎. 𝟎𝟐𝟎𝒃𝒘𝒅 (Gr 80) hc/20 (Gr 60) hc/26 (Gr 80) ≥ 𝐴𝑠 − or 𝐴𝑠 + ≥ max 200𝑏𝑤 𝑑 𝑓𝑦 3 𝑓𝑐 ′ 𝑏𝑤𝑑 𝑓𝑦 min 2 bars continuous a) b) c)
WWW.CONCRETE.ORG/ACI318 182 18.6.4.4—Special moment frame beams • Transverse reinforcement hb Stirrups with seismic hooks Hoops along 2hb Hoops @ lap splice d/4 6 in. 6db (Gr 60), 5db (Gr 80) s ≤ d/4 4 in. s ≤ 𝑠 ≤ 𝑑/2 hc ≤ 2 𝑖𝑛.
WWW.CONCRETE.ORG/ACI318 183 18.4.3.3—Columns in intermediate moment frames • Hoops or spirals required • First hoop at so/2 from the joint face o ℓu /6 clear span [c1, c2]max 18 in. so ℓo ℓo 8db (Gr 60) and 8 in. 6db (Gr 80) and 6 in. 1/2[c1, c2]min so ≤ ℓo ≥
WWW.CONCRETE.ORG/ACI318 184 18.7.2, 18.7.3—Columns of SMF Strong Column/Weak Beam • Column dimensional limits, 18.7.2 – Smallest dimension ≥ 12 in. – Short side/long side ≥ 0.4 • Flexural strength check, 18.7.3.2 – ∑Mnc ≥ (6/5)∑Mnb, – Exception, 18.7.3.1 • Ignore check at top story where 𝑷𝒖 ≤ 𝟎. 𝟏𝑨𝒈𝒇𝒄 ′ Beam Column Mnb Mnb Mnc Mnc
WWW.CONCRETE.ORG/ACI318 185 18.7.4.3—Bond splitting failure in columns Splitting can be controlled by restricting the longitudinal bar size to meet 1.25ℓd ≤ ℓu/2 Woodward and Jirsa(1984) Umehara and Jirsa (1982) Sokoli and Ghannoum (2016)
WWW.CONCRETE.ORG/ACI318 186 18.7.5.3 and 18.7.5.5—Columns in special moment frames • First hoop at so/2 from the joint face so ℓo ℓu/6 clear span [c1, c2]max 18 in. s 6db,min (Gr 60), 5db,min (Gr 80) 6 in. ℓo so 6db,min (Gr 60), 5db,min (Gr 80) ¼[c1, c2]min 4 + 14−ℎ𝑥 3 , ≤ 6 in.; ≥ 4 in. ℓo ≥ s ≤ so ≤
WWW.CONCRETE.ORG/ACI318 187 18.14.3.2—Nonparticipating columns Clarification • Transverse spacing over full length is the lesser of – 6db of the smallest long. bar – 6 in. • Transverse detailing along ℓo is according to 18.7.5.2 (a) through (e) – 18.7.5.2(f) is not required ℓo ℓo
WWW.CONCRETE.ORG/ACI318 188 Changes to the Concrete Design Standard ACI 318-19 Special Structural Walls
WWW.CONCRETE.ORG/ACI318 189 Ch. 18.10—Special structural wall • Cutoff of longitudinal bars in special boundary elements • Reinforcement ratios at ends of walls • Shear demand • Drift capacity check • Detailing in special boundary elements • Ductile coupled walls Shear wall Pu Mu Vu ℓw hw Special boundary element δu
WWW.CONCRETE.ORG/ACI318 190 18.10.2.3(a)—Longitudinal bars • Previously, – tension (vertical boundary) reinforcement in special structural walls to extend 0.8ℓw beyond the point at which it is no longer required to resist flexure • Overly conservative – This was an approximation of d – Similar to beams which extend d, 12db and ℓn/16 – Actual behavior is different
WWW.CONCRETE.ORG/ACI318 191 18.10.2.3(a)—Longitudinal bars (a) Except at the top of a wall, longitudinal reinforcement shall extend at least 12 ft above the point at which it is no longer required to resist flexure but need not extend more than ℓd above the next floor level. ≥ 12 ft ℓd Bars “a” no longer required Bars “a” Floor level Floor level
WWW.CONCRETE.ORG/ACI318 192 18.10.2.3(c)—Longitudinal bars • Lap splices not permitted over hsx above (20 ft, max) and ℓd below critical sections
WWW.CONCRETE.ORG/ACI318 193 18.10.2.4—Longitudinal reinforcement ratio at ends of walls hw/ℓw ≥ 2.0 • Failures in Chile and New Zealand • 1 or 2 large cracks • Minor secondary cracks Crack patterns for walls with fixed minimum longitudinal reinforcementcontentof 0.25% (Lu et al. 2017)
WWW.CONCRETE.ORG/ACI318 194 18.10.2.4—Longitudinal reinforcement ratio at ends of walls New ratio • Many well distributed cracks • Flexure yielding over length ' 6 c y f f  = Crack patterns for walls with ρ according to equation (Lu et al. 2017)
WWW.CONCRETE.ORG/ACI318 195 18.10.2.4—Longitudinal reinforcement ratio at ends of walls Bar Cutoff • Mu/2Vu similar to wall with full reinforcement • Mu/3Vu good distribution • Mu/4Vu significant strain above cut off Mu/2Vu Mu/3Vu Mu/4Vu
WWW.CONCRETE.ORG/ACI318 196 18.10.2.4—Longitudinal reinforcement ratio at ends of walls
WWW.CONCRETE.ORG/ACI318 197 18.10.2.4—Longitudinal reinforcement ratio at ends of walls Walls or wall piers with hw/ℓw ≥ 2.0 must satisfy: a) Long. reinf. ratio within 0.15 ℓw and minimum b) Long. reinf. extends above and below critical section the greater of ℓw and Mu/3Vu c) Max. 50% of reinf. terminated at one section ' 6 c y f f  =
WWW.CONCRETE.ORG/ACI318 198 18.10.3—Shear amplification • Similar to approach in New Zealand Standard, NZS 3101
WWW.CONCRETE.ORG/ACI318 199 18.10.3—Shear amplification 18.10.3.1 The design shear force Ve shall be calculated by: 3 e v v u u V V V =    Vu = the shear force obtained from code lateral load analysis with factored load combinations Ωv = overstrength factor equal to the ratio of Mpr/Mu at the wall critical section. v = factor to account for dynamic shear amplification. Gogus and Wallace, 2015
WWW.CONCRETE.ORG/ACI318 200 18.10.3—Shear amplification 18.10.3.1.2 – Calculation of Ωv Table 18.10.3.1.2—Overstrengthfactor Ωv at critical section [1] For the load combination producing the largest value of Ωv. [2] Unless a more detailed analysis demonstrated a smaller value, but not less than 1.0. Condition Ωv hwcs/ℓw > 1.5 Greater of Mpr/Mu [1] 1.5[2] hwcs/ℓw ≤ 1.5 1.0
WWW.CONCRETE.ORG/ACI318 201 18.10.3—Shear Amplification 18.10.3.1.3 – Calculation of ωv hwcs/ℓw < 2.0 ➔ ωv = 1.0 hwcs/ℓw ≥ 2.0 ➔ ωv = 0.9 + ns/10 for ns ≤ 6 ωv = 1.3 + ns/30 ≤ 1.8 for ns > 6 where ns ≥ 0.007hwcs ns = number of stories above the critical section.
WWW.CONCRETE.ORG/ACI318 202 18.10.4.1—Shear strength, Vn No Change • The code shows change bars at this location; rewording only • Shear calculations for Chapters 11 and 18 were harmonized • 11.5.4.3 is now similar to 18.10.4.1
WWW.CONCRETE.ORG/ACI318 203 18.10.4.4—Clarification of Acv Acv = gross area of concrete section bounded by web thickness and length of section in the direction of shear force considered in the case of walls, and gross area of concrete section in the case of diaphragms. Gross area is total area of the defined section minus area of any openings. 1 2 3 Acv wall = Acw1+Acw2+Acw3 Acw2 Vertical wall segments
WWW.CONCRETE.ORG/ACI318 204 18.10.6.2—Displacement based approach Boundary elements of special structural walls: • Walls or wall piers with hwcs/ℓw ≥ 2.0 • Continuous – Uniform for full height • Single critical (yielding) section – Plastic hinge Continuous Single critical section
WWW.CONCRETE.ORG/ACI318 205 18.10.6.2—Displacement based approach (a) Compression zone with special boundary elements required if: • c = [Pu, fMn]max in direction of design displacement du and • du/hwcs ≥ 0.005 1.5 600 u w wcs h c d  Single critical section hwcs du Extreme compression fiber
WWW.CONCRETE.ORG/ACI318 206 18.10.6.2—Displacement based approach (b) Boundary elements req’d, then (i) and either (ii) or (iii) i. Transv. reinf. extends above and below critical section [ℓw, Mu/4Vu]max ii. iii. dc/hwcs ≥ 1.5 du / hwcs , where ' 1 1 4 0.015 100 50 8 c w e wcs c cv c V h b b f A   d      = − −            0.025 w b c  Errata
WWW.CONCRETE.ORG/ACI318 207 18.10.6.4—Special Boundary Elements • Single perimeter hoops with 90-135 or 135- 135 degree crossties, inadequate
WWW.CONCRETE.ORG/ACI318 208 18.10.6.4(f)—Special Boundary Elements Longitudinal bars supported by a seismic hook or corner of a hoop
WWW.CONCRETE.ORG/ACI318 209 18.10.6.4(h)—Special Boundary Elements • Concrete within the thickness of the floor system at the special boundary element location shall have specified compressive strength at least 0.7 times f′ c of the wall.
WWW.CONCRETE.ORG/ACI318 210 18.10.6.4(i)—Special Boundary Elements • 18.10.6.4(i) – for a distance specified in 18.10.6.2(b) above and below the critical section, web vertical reinforcement shall have lateral support – crossties vertical spacing, sv ≤ 12 in.
WWW.CONCRETE.ORG/ACI318 211 18.10.6.5(b)—If the maximum longitudinal  at the wall boundary exceeds 400/fy Grade of primary flexural reinforcing bar Transverse reinforcement required Vertical spacing of transverse reinforcement1 60 Within the greater of ℓw and Mu/4Vu aboveand below critical sections2 Lesser of: 6 db 6 in. Other locations Lesser of: 8 db 8 in. 80 Within the greater of ℓw and Mu/4Vu aboveand below critical sections2 Lesser of: 5 db 6 in. Other locations Lesser of: 6 db 6 in. 100 Within the greater of ℓw and Mu/4Vu aboveand below critical sections2 Lesser of: 4db 6 in. Other locations Lesser of: 6db 6 in. Table 18.10.6.5b—Maximum vertical spacing of transverse reinforcement at wall boundary
WWW.CONCRETE.ORG/ACI318 212 18.10.9—Ductile Coupled Walls Issues preventing ductile behavior • Inadequate quantity or distribution of qualifying coupling beams • Presence of squat walls causes the primary mechanism to be shear and/or strut-and-tie failure in walls • Coupling beams are inadequately developed to provide full energy dissipation ℓw ℓw ℓn hwcs h
WWW.CONCRETE.ORG/ACI318 213 18.10.9—Ductile Coupled Walls • Individual walls satisfy – hwcs/ℓw ≥ 2 • All coupling beams must satisfy: – ℓn/h ≥ 2 at all levels – ℓn/h ≤ 5 at a floor level in at least 90% of the levels of the building – Development into adjacent wall segments, 1.25fy (18.10.2.5) ℓw ℓw ℓn hwcs h
WWW.CONCRETE.ORG/ACI318 214 Changes to the Concrete Design Standard ACI 318-19 Foundations
WWW.CONCRETE.ORG/ACI318 215 18.13.4—Foundation seismic ties SDC C through F • Seismic ties or by other means SDC D, E, or F, with Site Class E or F • Seismic ties required Other means, 18.13.4.3 • Reinforced concrete beams within the slab-on- ground • Reinforced concrete slabs-on-ground • Confinement by competent rock, hard cohesive soils, or very dense granular soils • Other means approved by the building official
WWW.CONCRETE.ORG/ACI318 216 18.13.4.3—Seismic ties Minimum tensile and compressive force in tie • Load from pile cap or column – Largest at either end • 0.1SDS x Column factored dead and factored live load Tie force Column load
WWW.CONCRETE.ORG/ACI318 217 18.13.5—Deep foundations • (a) Uncased CIP concrete drilled or augered piles • (b) Metal cased concrete piles • (c) Concrete filled pipe piles • (d) Precast concrete piles
WWW.CONCRETE.ORG/ACI318 218 18.13.5.2—Deep foundations SDC C through F • Resisting tension loads → Continuous longitudinal reinforcement over full length to resist design tension Source: Ground Developments
WWW.CONCRETE.ORG/ACI318 219 18.13.5.3—Deep foundations SDC C through F • Transverse and longitudinal reinforcement to extend: – Over entire unsupported length in air, water, or loose soil not laterally supported Pile cap
WWW.CONCRETE.ORG/ACI318 220 18.13.5.4 and 18.13.5.5—Deep foundations SDC C through F • Hoops, spirals or ties terminate in seismic hooks SDC D, E, or F, with Site Class E or F • Transv. reinf. per column req. within seven member diameter • ASCE 7, soil strata Soft strata Hard strata D 7D 7D
WWW.CONCRETE.ORG/ACI318 221 18.13.5.6—Deep foundations • SDC D, E, or F – Piles, piers, or caissons and foundation ties supporting one- and two-story stud bearing walls – Exempt from transv. reinf. of 18.13.5.3 through 18.13.5.5 Errata
WWW.CONCRETE.ORG/ACI318 222 18.13.5.7—Uncased cast-in place piles Pile cap SDC C 1/3 ℓpile •ℓbar ≥ 10 ft 3dpile Distance to 0.4Mcr > Mu •Transverse confinement zone • 3 dpile from bottom of pile cap • s ≤ 6 in.; 8db long. bar •Extended trans. reinf. • s ≤ 16db long. bar min ≥ 0.0025 ℓ bar Closed ties or spirals≥ No.3 s dpile ℓbar = minimum reinforcedpile length
WWW.CONCRETE.ORG/ACI318 223 18.13.5.7—Uncased cast-in place piles Pile cap SDC D, E, and F with Site Class A, B, C, and D 1/2 ℓpile • ℓbar ≥ 10 ft 3dpile Distance to 0.4Mcr > Mu •Transverse confinement zone • 3 dpile from bottom of pile cap • s of 18.7.5.3 • min ≥ 0.06 fc′/fyt •Extended trans. reinf. 12db long. bar s ≤ 0.5dpile 12 in. min ≥ 0.005 ℓ bar Closed ties or spirals ≥ No. 3 (≤ 20 in.) or No. 4 (> 20 in.); 18.7.5.2 s dpile ℓbar = minimum reinforcedpile length
WWW.CONCRETE.ORG/ACI318 224 18.13.5.7—Uncased cast-in place piles Pile cap SDC D, E, and F with Site Class E and F •ℓbar Full length of pile (some exceptions) •Transverse confinement zone • 7 dpile from bottom of pile cap • s of 18.7.5.3 • min ≥ 0.06 fc′/fyt •Extended trans. reinf. 12db long. bar s ≤ 0.5dpile 12 in. min ≥ 0.005 ℓ bar Closed ties or spirals ≥ No. 3 (≤ 20 in.) or No. 4 (> 20 in.); 18.7.5.2 s dpile ℓbar = minimum reinforcedpile length
WWW.CONCRETE.ORG/ACI318 225 18.13.5.8—Metal cased concrete piles Pile cap SDC C through F •Longitudinal same as uncased piles •Metal casing replaces transverse reinforcement in uncased piles •Extend casing for ℓbar t ≥ 14 gauge ℓ bar dpile
WWW.CONCRETE.ORG/ACI318 226 18.13.5.9—Concrete-filled pipe piles Pile cap SDC C through F •min ≥ 0.01 •ℓd,pile ≥ 2ℓpilecap ℓdt,bar Steel pipe 2ℓ pile cap ≥ ℓ d dpile ℓ pile cap
WWW.CONCRETE.ORG/ACI318 227 18.13.5.10—Precast nonprestressed piles Pile cap SDC C •ℓbar Full length of pile •Transverse confinement zone • 3 dpile from bottom of pile cap • s ≤ 6 in.; 8db long. bar •Extended trans. reinf. • s ≤ 6 in. min ≥ 0.01 ℓ bar s dpile Closed ties or spirals ≥ No. 3 (≤ 20 in.) or No. 4 (> 20 in.); 18.7.5.2
WWW.CONCRETE.ORG/ACI318 228 18.13.5.10—Precast nonprestressed piles Pile cap SDC D, E, and F •Same as SDC C •Satisfy Table 18.13.5.7.1 for SDC D, E, and F min ≥ 0.01 ℓ bar s dpile Closed ties or spirals ≥ No. 3 (≤ 20 in.) or No. 4 (> 20 in.); 18.7.5.2
WWW.CONCRETE.ORG/ACI318 229 18.13.5.10—Precast prestressed piles Pile cap SDC C through F •Satisfy 18.13.5.10.4 through 18.13.5.10.6 •Minimum amount and spacing of transverse reinforcement ℓ bar s dpile
WWW.CONCRETE.ORG/ACI318 230 18.13.6—Anchorage of piles, piers and caissons SDC C—F • Tension loads: load path to piles, piers, or caissons • Transfer to longitudinal reinforcement in deep foundation Source: Dailycivil Source: Stockqueries
WWW.CONCRETE.ORG/ACI318 231 18.13.6—Anchorage of piles, piers and caissons ℓd compr. ℓdt tension Dowel 1.25fy Source: Gayle Johnson 18.13.6.2 SDC C—F • Anchor dowel between piles and pile cap 18.13.6.3 SDC D—F • If tension forces and dowel post- installed in precast pile • Grouting system to develop min. 1.25 fy (shown by test)
WWW.CONCRETE.ORG/ACI318 232 21.2.4.3—ϕ, Foundation elements SDC C—F • For foundation elements supporting the primary seismic-force-resisting system • ϕ for shear shall ≤ the least value of – ϕ for shear used for special column – ϕ for shear used for special wall
WWW.CONCRETE.ORG/ACI318 233 Changes to the Concrete Design Standard ACI 318-19 High-Strength Reinforcement
WWW.CONCRETE.ORG/ACI318 234 Ch. 20 – Yield strength determination • 318-19, 20.2.1.2: Nonprestressed bar yield strength determination: – The yield point by the halt-of-force method – T he offset method, using 0.2 percent offset • 20.2.1.3 – A615 and A706 additional requirements
WWW.CONCRETE.ORG/ACI318 235 Ch. 3 – Update of ASTM A615-18e1 • Latest ASTM A615 allows: – Gr. 100 – Bars up to No. 20 • ACI 318-19 allows – No. 18 and smaller – Gr. 80 & 100 with restrictions • No. 20 not acceptable: – Development length – Bar bends
WWW.CONCRETE.ORG/ACI318 236 Table 20.2.2.4(a) • Main changes – Gr. 80 – Gr. 100 – Footnotes – Clarifications
WWW.CONCRETE.ORG/ACI318 237 Ch. 20 – Steel Reinforcement Properties
WWW.CONCRETE.ORG/ACI318 238 Ch. 20 –Seismic Requirements for A615 Gr. 60 • Section 20.2.2.5 specifies – ASTM A706 Gr. 60 allowed – Requirements for ASTM A615, Gr. 60 • Section 20.2.2.5(a) permits ASTM A706 – Grade 60 – Grade 80 – Grade 100 – (as discussed previously)
WWW.CONCRETE.ORG/ACI318 239 Ch. 20 –Seismic Requirements for A615 Gr. 60 • Section 20.2.2.5(b) permits ASTM A615 Grade 60 if: – fy,actual ≤ fy + 18,000 psi – Provides adequate ductility (min. ft/fy ≥ 1.25) – Min. fracture elongation in 8 in. (10-14%) – Minimum uniform elongation (6-9%) • Section 20.2.2.5(b) provides the A706 elongation properties
WWW.CONCRETE.ORG/ACI318 240 Ch. 20 – Seismic Requirements for A615 • For seismic design ASTM A615 GR. 80 and 100 are not permitted
WWW.CONCRETE.ORG/ACI318 241 Ch. 20 – Steel Reinforcement Properties
WWW.CONCRETE.ORG/ACI318 242 Ch. 20 – Steel Reinforcement Properties
WWW.CONCRETE.ORG/ACI318 243 Ch. 26 – Tolerances for seismic hoops 26.6.2.1(c)
WWW.CONCRETE.ORG/ACI318 244 Design limits et ≥ 0.005 et ≥ (ety + 0.003) ACI 318-14 ACI 318-19
WWW.CONCRETE.ORG/ACI318 245 Design limits et ≥ (ety + 0.003) ACI 318-19 ACI 318-19 Provisions 7.3.3.1, 8.3.3.1, and 9.3.3.1 require slabs and beams be tension controlled y ty s f E e =
WWW.CONCRETE.ORG/ACI318 246 Design limits ACI 318-14
WWW.CONCRETE.ORG/ACI318 247 Design limits ACI 318-19
WWW.CONCRETE.ORG/ACI318 248 Design limits f’c = 4000 psi f’c = 10,000 psi GR 60 et ≥ 0.0051 1.79% 3.42% GR 80 et ≥ 0.00575 1.24% 2.37% GR 100 et ≥ 0.0065 0.92% 1.75% Reinforcement ratio, tcl y ty s f E e =
WWW.CONCRETE.ORG/ACI318 249 Design limits Grade f’c = 4 ksi f’c = 10 ksi 60 1.79% 3.42% 80 1.24% 2.37% 100 0.92% 1.75% 16 x 24 in. beam d = 21 in. f’c = 4000 psi GR 60 As,tcl = 6 in.2 Mn,tcl = 544 ft-kip Reinforcement ratio, tcl Approximately 50% of reinforcement achieved 88% of nominal moment GR 100 As,tcl = 3.1 in.2 Mn,tcl = 479 ft-kip
WWW.CONCRETE.ORG/ACI318 250 Changes to the Concrete Design Standard ACI 318-19 Development Length
WWW.CONCRETE.ORG/ACI318 251 Development Length • Deformed Bars and Deformed Wires in Tension – Simple modification to 318-14 – Accounts for Grade 80 and 100 • Standard Hooks and Headed Deformed Bars – Substantial changes from 318-14
WWW.CONCRETE.ORG/ACI318 252 Development Length • Deformed Bars and Deformed Wires in Tension • Standard Hooks in Tension • Headed Deformed Bars in Tension
WWW.CONCRETE.ORG/ACI318 253 Development Length of Deformed Bars and Deformed Wires in Tension Unconfined Test Results ftest = reinforcement stress at the time of failure fcalc = calculated stress by solving ACI 318-14 Equation 25.4.2.3a Confined Test Results
WWW.CONCRETE.ORG/ACI318 254 Development Length of Deformed Bars and Deformed Wires in Tension • Modification in simplified provisions of 25.4.2.3 • Ψg : new modification factor based on grade of reinforcement • Modification in Table 25.4.2.3
WWW.CONCRETE.ORG/ACI318 255 Development Length of Deformed Bars and Deformed Wires in Tension • Modification in general development length equation 25.4.2.4(a) • Provision 25.4.2.2 Ktr ≥ 0.5db for fy ≥ 80,000 psi , if longitudinal bar spacing < 6 in. Modification factors  : Lightweight t : Casting position e : Epoxy s : Size g : Reinforcementgrade
WWW.CONCRETE.ORG/ACI318 256 Development Length of Deformed Bars and Deformed Wires in Tension Modificationfactor Condition Value of factor Lightweightλ Lightweight concrete 0.75 Normalweightconcrete 1.0 Reinforcement gradeg Grade40 or Grade60 1.0 Grade80 1.15 Grade100 1.3 Epoxy[1] e Epoxy-coated or zinc and epoxy dual-coated reinforcement with clear cover less than 3db or clear spacing less than 6db 1.5 Epoxy-coated or zinc and epoxy dual-coated reinforcementfor all other conditions 1.2 Uncoated or zinc-coated (galvanized) reinforcement 1.0 Sizes No. 7 and larger bars 1.0 No. 6 and smaller bars and deformed wires 0.8 Casting position[1] t More than 12 in. of fresh concreteplaced below horizontal reinforcement 1.3 Other 1.0 Table 25.4.2.5—Modification factors for development of deformed bars and deformed wires in tension
WWW.CONCRETE.ORG/ACI318 257 Check development length of No. 8 longitudinal bar in a beam. Assume f’c = 4000 psi NWC, Grade 80 reinforcement, 2 in. cover and no epoxy coating. Example—Development Length of Deformed Bars and Deformed Wires in Tension g Grade 40 or Grade 60 1.0 Grade 80 1.15 Grade 100 1.3 From Table 25.4.2.5 confinement term (cb + Ktr)/db = 2.5 (using the upper limit)  = 1.0 e = 1.0 s = 1.0 t = 1.0 te = 1.0 < 1.7 g = 1.15
WWW.CONCRETE.ORG/ACI318 258 Substituting in Eq. 25.4.2.4a: Example—Development Length of Deformed Bars and Deformed Wires in Tension ℓ𝑑 = 3 40 80,000 1 4000 1 1 1 1.15 2.5 (1.0) = 43.6 in. ℓ𝑑 = 3 40 60,000 1 4000 1 1 1 1 2.5 (1.0) = 28.5 in. In comparison a similar bar with Grade 60 reinforcement; Increase of ~ 50 percent in development length for Grade 80
WWW.CONCRETE.ORG/ACI318 259 Development Length of Deformed Bars and Deformed Wires in Tension • Differences in higher grade steel for 4000 psi concrete Grade g ℓd,Gr#/ℓd,Gr60 60 1.0 1.0 80 1.15 1.5 100 1.3 2.2
WWW.CONCRETE.ORG/ACI318 260 Development Length • Deformed Bars and Deformed Wires in Tension • Standard Hooks in Tension • Headed Deformed Bars in Tension
WWW.CONCRETE.ORG/ACI318 261 Development Length of Std. Hooks in Tension • Failure Modes • Mostly, front and side failures – Dominant front failure (pullout and blowout) – Blowouts were more sudden in nature Front Pullout Front Blowout Side splitting Tail kickout Side blowout
WWW.CONCRETE.ORG/ACI318 262 Development Length of Std. Hooks in Tension fsu = stress at anchorage failure for the hooked bar fs,ACI = stress predictedby the ACI development lengthequation Confined Test Results 𝐴𝐶𝐼 318 − 14: ℓ𝑑ℎ = 𝑓 𝑦𝜓𝑒𝝍𝒄𝝍𝒓 50𝜆 𝑓 𝑐 ′ 𝑑𝑏 Unconfined Test Results
WWW.CONCRETE.ORG/ACI318 263 Development Length of Std. Hooks in Tension - 25.4.3.1—Development length of standard hooks in tension is the greater of (a) through (c): (a) (b) 8db (c) 6 in - Modification factors 𝝍𝒓 : Confining reinforcement (redefined) 𝝍𝒐 : Location (new) 𝝍𝒄 : Concrete strength (new – used for coverin the past) ACI 318- 14
WWW.CONCRETE.ORG/ACI318 264 Development Length of Std. Hooks in Tension Modification factor Condition Value of factor 318-14 Confining reinforcement, r For 90-degree hooks of No. 11 and smaller bars (1) enclosed along ℓdh within ties or stirrups perpendicularto ℓdh at s ≤ 3db, or (2) enclosed along the bar extension beyond hook includingthe bend within ties or stirrups perpendicularto ℓext at s ≤ 3db 0.8 Other 1.0 318-19 Confining reinforcement, r For No.11 and smaller bars with Ath ≥ 0.4Ahs or s ≥ 6db 1.0 Other 1.6 Table 25.4.3.2: Modification factors for development of hooked bars in tension
WWW.CONCRETE.ORG/ACI318 265 Development Length of Std. Hooks in Tension 25.4.3.3: • Confining reinforcement (Ath) shall consists of (a) or (b) – (a) Ties or stirrups that enclose the hook and satisfy 25.3.2 – (b) Other reinf. that extends at least 0.75ℓdh from the enclosed hook in the direction of the bar in tension and in accordance with (1) or (2) • parallel or perpendicular (Fig. R25.4.3.3a and Fig. R25.4.3.3b) Fig. R25.4.3.3a Fig. R25.4.3.3b
WWW.CONCRETE.ORG/ACI318 266 Development Length of Std. Hooks in Tension • (1) Confining reinforcement placed parallel to the bar (Typical in beam-columnjoint) – Two or more ties or stirrups parallel to ℓdh enclosing the hooks – Evenly distributed with a center-to-center spacing ≤ 8db – within 15db of the centerline of the straight portion of the hooked bars Fig. R25.4.3.3a
WWW.CONCRETE.ORG/ACI318 267 Development Length of Std. Hooks in Tension • (2) Confining reinforcement placed perpendicular to the bar – Two or more ties or stirrups perpendicular to ℓdh enclosing the hooks – Evenly distributed with a center-to-center spacing ≤ 8db Fig. R25.4.3.3b
WWW.CONCRETE.ORG/ACI318 268 Development Length of Std. Hooks in Tension Modification factor Condition Value of factor 318-14 Cover ψc For No. 11 bar and smaller hooks with side cover (normal to planeof hook) ≥ 2-1/2 in. and for 90-degree hook with cover on bar extension beyond hook ≥ 2 in. 0.7 Other 1.0 318-19 Location, o For No.11 and smaller diameter hooked bars (1) Terminating inside column core w/ side cover normal to plane of hook ≥ 2.5 in., or (2) with side cover normal to plane of hook ≥ 6db 1.0 Other 1.25 Table 25.4.3.2: Modification factors for development of hooked bars in tension
WWW.CONCRETE.ORG/ACI318 269 Development Length of Std. Hooks in Tension Modification factor Condition Value of factor Concrete strength, c For f’c < 6000 psi f’c/15,000 +0.6 For f’c ≥ 6000 psi 1.0 Table 25.4.3.2: Modificationfactors for development of hooked bars in tension
WWW.CONCRETE.ORG/ACI318 270 Example—Development Length of Std Hook Check hooked bar anchorage of longitudinal beam reinforcement, 3-No. 10 bars in a 20 x 20 in. exterior column. Assume f’c = 4000 psi NWC, Grade 60 reinforcement, 2.5 in. cover normal to plane of hook, and no epoxy coating. Steel confinement is provided such that Ath = 0.4 Ahs.  = 1.0 e = 1.0 r = 1.0 o = 1.0 c = f’c/15,000 + 0.6 = 4,000/15,000 + 0.6 = 0.87
WWW.CONCRETE.ORG/ACI318 271 Example—Development Length of Std Hook Substituting in the equation: ℓdh = 21.5 in. > 20 in. NG In comparison to the equation in 318-14: ℓdh(318-14) = 16.9 in. < 20 in. OK ℓ𝑑ℎ = 60,000 1.0 1.0 1.0 0.87 55 1.0 4,000 (1.27)1.5 e = 1.0 c = 0.7 (2 -1/2 in. side cover and 2 in. back cover) r = 1.0
WWW.CONCRETE.ORG/ACI318 272 Example—Development Length of Std Hook 0 5 10 15 20 25 30 0.5 0.7 0.9 1.1 1.3 1.5 Development Length, ℓ dh (i n.) Bar Diameter, in. Standard Hooked Bars; f'c = 4000 psi 318-14 318-19 0.00 5.00 10.00 15.00 20.00 25.00 0.5 0.7 0.9 1.1 1.3 1.5 Development Length, ℓ dh (i n.) Bardiameter;in. Standard Hooked Bars; f'c =6000 psi 318-14 318-19
WWW.CONCRETE.ORG/ACI318 273 Development Length • Deformed Bars and Deformed Wires in Tension • Standard Hooks in Tension • Headed Deformed Bars in Tension
WWW.CONCRETE.ORG/ACI318 274 Development Length of Headed Deformed Bars in Tension 25.4.4.1 Use of a head to develop a deformed bar in tension shall be permitted if conditions (a) through (f) are satisfied: (a)Bar shall conform to 20.2.1.6 (b)Bar fy shall not exceed 60,000 psi (b) Bar size shall not exceed No. 11 (c) Net bearing area of head Abrg shall be at least 4Ab (d) Concrete shall be normalweight (e) Clear coverfor bar shall be at least 2db (f) Center-to-center spacing between bars shall be at least 3db
WWW.CONCRETE.ORG/ACI318 275 Development Length of Headed Deformed Bars in Tension fsu = stress at anchorage failure for the hooked bar fs,ACI = stress predictedby the ACI development lengthequation 𝐴𝐶𝐼 318 − 14: ℓ𝑑𝑡 = 0.016𝑓𝑦𝜓𝑒 𝑓 𝑐 ′ 𝑑𝑏 Unconfined Test Results Confined Test Results
WWW.CONCRETE.ORG/ACI318 276 Development Length of Headed Deformed Bars in Tension - 25.4.4.2: Development length ℓdt for headed deformed bars in tension shall be the longest of (a) through (c): (a) (b) 8db (c) 6 in. - Modification factors 𝝍𝒑 : Parallel tie reinforcement 𝝍𝒐 : Location 𝝍𝒄 : Concrete strength ACI 318- 14 f’ c ≤ 6000 psi
WWW.CONCRETE.ORG/ACI318 277 Development length of Headed Deformed Bars in Tension Modification factor Condition Value of factor Parallel tie reinforcement, p For No.11 and smaller bars with Att ≥ 0.3Ahs or s ≥ 6db 1.0 Other 1.6 Location, o For headed bars (1) Terminating inside column core w/ side cover to bar ≥ 2.5 in., or (2) with side cover to bar ≥ 6db 1.0 Others 1.25 Concrete strength, c For f’c < 6000 psi f’c/15,000+0.6 For f’c ≥ 6000 psi 1.0 Table 25.4.4.3—Modification factors for development of headed bars in tension
WWW.CONCRETE.ORG/ACI318 278 Development Length of Headed Deformed Bars in Tension • Parallel tie reinforcement (Att) – locate within 8db of the centerline of the headed bar towardthe middleof the joint
WWW.CONCRETE.ORG/ACI318 279 Example—Development Length of Headed Deformed Bars in Tension Check development length of No. 9 longitudinal bar in a beam. Assume f’c = 4000 psi NWC, Grade 60 reinforcement, 2.5 in. cover, and no epoxy coating. Steel confinement is provided such that Att = 0.3 Ahs. e = 1.0 p = 1.0 o = 1.0 c = f’c/15,000 + 0.6 = 4,000/15,000+0.6 = 0.87
WWW.CONCRETE.ORG/ACI318 280 Example—Development Length of Headed Deformed Bars in Tension Substituting in the equation : ℓdt = 13.2 in. ℓ𝑑𝑡 = 60,000 1.0 1.0 1.0 0.87 75 4,000 (1.128)1.5 In comparison to the equation in 318-14: ℓdt(318-14) = 17.1 in. • Decrease in development lengthof headed bars in tension as per 318-19 in this example – No.11 and smaller bars with Att 0.3Ats – bars terminating inside column core with side cover to bar ≥ 2.5 in ℓ𝑑𝑡 = 0.016 1.0 60,000 4,000 (1.128)
WWW.CONCRETE.ORG/ACI318 281 Example—Development Length of Headed Deformed Bars in Tension ℓ𝑑𝑡 = 𝑓 𝑦𝜓𝑒𝜓𝑝𝜓𝑜𝜓𝑐 75 𝑓 𝑐 ′ 𝑑𝑏 1.5 ℓ𝑑𝑡 = 0.016𝑓 𝑦𝜓𝑒 𝑓 𝑐 ′ 𝑑𝑏 0 5 10 15 20 25 0.5 0.7 0.9 1.1 1.3 1.5 Development Length, ℓ dt (in.) Bar diameter; in. Headedbars, f'c = 4000 psi, confined 318-14 318-19 0 2 4 6 8 10 12 14 16 0.5 0.7 0.9 1.1 1.3 1.5 Development Length, ℓ dt (in.) Bar diameter; in. Headedbars, f'c = 10,000 psi, confined 318-14 318-19 0 5 10 15 20 25 30 35 0.5 0.7 0.9 1.1 1.3 1.5 Development Length, ℓ dt (in.) Bar diameter; in. Headedbars, f'c = 4000 psi, Unconfined 318-14 318-19
WWW.CONCRETE.ORG/ACI318 282 Changes to the Concrete Design Standard ACI 318-19 Shear Modifications
WWW.CONCRETE.ORG/ACI318 283 Shear equations change • One-way beam/slab shear – provision 22.5 – Size effect – Reinforcement ratio • Two-way slab shear – provision 22.6 – Size effect – Reinforcement ratio
WWW.CONCRETE.ORG/ACI318 284 Why shear equations changed in 318-19 • Reasons for changes – Evidence shows • Size effect • Low w effect • More prevalent – Deeper beams – Deep transfer slabs 4
WWW.CONCRETE.ORG/ACI318 285 Other shear changes • Wall shear equations – Chapter 11 now similar to Chapter 18 • Shear leg spacing – Section spacing requirements • Biaxial shear – Engineer must consider • Hanger reinforcement – Commentary suggestion
WWW.CONCRETE.ORG/ACI318 286 Changes to the Concrete Design Standard ACI 318-19 One-way Shear Equations
WWW.CONCRETE.ORG/ACI318 287 Why one-way shear equations changed in 318-19 • ACI 445, Shear and Torsion – Four databases vetted and checked 7 Beam types in database Number of samples Reinforced concrete w/o min shear reinforcement 784 Reinforced concrete with min. shear reinforcement 170 Prestressed concrete w/o min. shear reinforcement 214 Prestressed concrete with min. shear reinforcement 117 Totalsamples 1285
WWW.CONCRETE.ORG/ACI318 288 Why one-way shear equations changed in 318-19 288 Figure: Strength Ratio (Vtest/Vn) that was calculated by 318-14 Simplified d = 10 in. – s, size effect factor Vtest/Vn = 1 ,min v v A A 
WWW.CONCRETE.ORG/ACI318 289 Why one-way shear equations changed in 318-19 289 Figure: Strength Ratio (Vtest/Vn) that was calculated by both ACI 318-14 Simplified and Detailed d = 10 in. – s, size effect factor Vtest/Vn = 1 ,min v v A A 
WWW.CONCRETE.ORG/ACI318 290 Why one-way shear equations changed in 318-19 290 Figure: Strength Ratio (Vtest/Vn) that was calculated by the Simplified Method of ACI318-19 including size effect Vtest/Vn = 1 0.0018 – min. slab w ,min v v A A  0.015 – w effect
WWW.CONCRETE.ORG/ACI318 291 Why one-way shear equations changed in 318-19 291 Figure: Strength Ratio (Vtest/Vn) that was calculated by the Simplified Method of ACI 318-14 d = 10 in. – s, size effect factor Vtest/Vn = 1 ,min v v A A 
WWW.CONCRETE.ORG/ACI318 292 Why one-way shear equations changed in 318-19 • Six different proposals considered – Proposals vetted and considered by • ACI 445 • ACI 318 Subcommittee • Public discussion • Concrete International articles • ACI 318 selected one proposal
WWW.CONCRETE.ORG/ACI318 293 Initial one-way shear provision: goals • Include nonprestressed and prestressed • Include axial loading and size effect • Include effect of (w) • Continue to be proportional to √f’ c • And simple – Reduce total number of shear equations – Avoid increase in variables – Easy to use
WWW.CONCRETE.ORG/ACI318 294 Initial one-way shear provision: issues • Initial proposal had issues – Unified expressions ≠ Vci, Vcw – What happened to “2 √f’ c”???
WWW.CONCRETE.ORG/ACI318 295 Initial one-way shear provision: goals • Include nonprestressed and prestressed • Include axial loading and size effect • Include effect of () • Continue to be proportional to √f’ c • And simple
WWW.CONCRETE.ORG/ACI318 296 ACI 318-19 New one-way shear equations Table 22.5.5.1 - Vc for nonprestressed members Criteria Vc Av ≥ Av,min Either of: (a) (b) Av < Av,min (c) Notes: 1. Axial load, Nu, is positive for compressionand negative for tension 2. Vc shall not be taken less than zero.
WWW.CONCRETE.ORG/ACI318 297 0 0.5 1 1.5 2 2.5 0.3% 0.4% 0.5% 0.6% 0.7% 0.8% 0.9% 1.0% 1.1% 1.2% 1.3% 1.4% 1.5% 1.6% 1.7% 1.8% 1.9% 2.0% 2.1% 2.2% 2.3% 2.4% 2.5% Vn / sqrt(f’c) Longitudinal Reinforcement Ratio (As/bd) ACI 318-19 Shear Equation 8𝜆 𝜌𝑤 Τ 1 3 Effect of ρw
WWW.CONCRETE.ORG/ACI318 298 Size effect – what is s? 2 1.0 1 10 s d  =  + Provision 22.5.5.1.3 defines s as:
WWW.CONCRETE.ORG/ACI318 299 Size effect – what is s? 0 0.2 0.4 0.6 0.8 1 1.2 0 12 24 36 48 60 72 84 96 108 120 λ s Depth in inches 2 1.0 1 10 s d  =  +
WWW.CONCRETE.ORG/ACI318 300 Other limitations for Table 22.5.5.1 • Provision 22.5.5.1.1: – Limits the maximum value of Vc • Provision 22.5.5.1.2: – Limits the maximum value of the Nu/6Ag term ' 5 c c w V f b d   ' 0.05 6 u c g N f A 
WWW.CONCRETE.ORG/ACI318 301 9.6.3.1 - Minimum shear reinforcement • ACI 318-14 – Av,min required if Vu > 0.5 fVc • ACI 318-19 – Av,min required if Vu > fλf’ c bwd • Exceptions in Table 9.6.3.1
WWW.CONCRETE.ORG/ACI318 302 22.5.6.2.3—Prestressed members:
WWW.CONCRETE.ORG/ACI318 303 Examples: SP-17(14) 5.7 One-way slab Example 1 • Span = 14 ft • Live load = 100 psf • Slab = 7 in. thick • f’ c = 5000 psi • No. 5 bars at 12 in. • d~6 in. • b = 12 in. • Av = 0 in.2 • As = 0.31 in.2/ft • Vu= 2.4 kip/ft
WWW.CONCRETE.ORG/ACI318 304 Examples: SP-17(14) 5.7 One-way slab Example 1 • SP-17(14) One-way shear calc ACI 318-14 ' 2 (0.75)(2)(1) 5000 (12 .)(6 .) 7.6 2.4 c c c c V f bd V psi in in V kip kip OK f f  f f = = =  
WWW.CONCRETE.ORG/ACI318 305 Examples: SP-17(14) 5.7 One-way slab Example 1 • SP-17(14) One-way shear calc ACI 318-19 • Av ≤ Av,min, therefore use Eq. 22.5.5.1(c) ( ) 1 ' 3 1 3 8 ( ) 0.31 0.0043 low (12)(6) (0.75)(8)(1)(1) 0.0043 5000 (12 .)(6 .) 5.0 2.4 c s w c w w c c V f bd V psi in in V kip kip OK f f      f f = = =  = =  
WWW.CONCRETE.ORG/ACI318 306 Examples: SP-17(14) 5.7 One-way slab Example 1 • fVc ACI 318-19 < fVc ACI 318-14 – 318-19 for the example given is ~2/3 of ACI 318-14 – Effect of low ρw • Design impact – Thicker slabs if depth was controlled by shear in 318-14. – No change if one-way slab thickness was controlled by flexure or deflections
WWW.CONCRETE.ORG/ACI318 307 Examples: Beam discussion • How many engineers design beams without minimum shear reinforcement? • One-way shear capacity impacted: – Av,min not required and Av,min not used
WWW.CONCRETE.ORG/ACI318 308 Examples: Beam discussion • Where Av,min installed, Eq. 22.5.5.1(a) Vc= (2√f’ c), – ACI 318-14 ~ ACI 318-19 – Eq. 22.5.5.1(b) of Table 22.5.5.1 permitted • fVc ↑ w > 0.015 • Provisions encourage Av,min
WWW.CONCRETE.ORG/ACI318 309 Examples: SP-17(14) 11.6 Foundation Example 1 • ℓ = 12 ft • h = 30 in. • d~25.5 in. • f’ c = 4000 psi • 13-No. 8 bars • b = 12 ft • Av = 0 in.2 • As = 10.27 in.2 • Analysis Vu= 231 kip 3 ft – 0 in.
WWW.CONCRETE.ORG/ACI318 310 Examples: SP-17(14) 11.6 Foundation Example 1 • SP-17(14) One-way shear calc ACI 318-14 ' 2 (0.75)(2)(1) 4000 (144 .)(25.5 .) 348 231 c c c c V f bd V psi in in V kip kip OK f f  f f = = =  
WWW.CONCRETE.ORG/ACI318 311 Examples: SP-17(14) 11.6 Foundation Example 1 • SP-17(14) One-way shear calc ACI 318-19 • Av ≤ Av,min, Eq. 22.5.5.1(c) • Per ACI 318-19 (13.2.6.2), neglect size effect for: – One-way shallow foundations – Two-way isolated footings – Two-way combined and mat foundations 1 ' 3 8 ( ) c w c V f bd f f   =
WWW.CONCRETE.ORG/ACI318 312 Examples: SP-17(14) 11.6 Foundation Example 1 • SP-17(14) One-way shear calc ACI 318-19 • Av ≤ Av,min, Eq. 22.5.5.1(c) ( ) 1 ' 3 2 1 3 8 ( ) 10.27 in. 0.0028 (144 in.)(25.5 in.) (0.75)(8)(1) 0.0028 4000 (144 .)(25.5 .) 196 231 c w c w c c V f bd V psi in in V kip kip NG f f    f f = = = = =  
WWW.CONCRETE.ORG/ACI318 313 Examples: SP-17(14) 11.6 Foundation Example 1 • SP-17(14) One-way shear using ACI 318-19 • Av ≤ Av,min, Eq. 22.5.5.1(c) • Per ACI 318-19, 13.2.6.2, neglect size effect • Add 6in. thickness ( ) 1 ' 3 2 1 3 8 ( ) 10.27 in. 0.0023 (144 in.)(31.5 in.) (0.75)(8)(1) 0.0023 4000 psi(144 in.)(31.5 in.) 226 kip 231 kip Say OK? c w c w c c V f bd V V f f    f f = = = = =  
WWW.CONCRETE.ORG/ACI318 314 Examples: SP-17(14) 11.6 Foundation Example 1 • Foundation fVc ACI 318-19 < fVc ACI 318-14 – 318-19 for this example given is ~1/2 of ACI 318-14 – Effect of low ρw • Design impact – Increased thickness; or – Increase flexural reinforcement; or – Increase concrete strength; or – Combination
WWW.CONCRETE.ORG/ACI318 315 Examples: Grade beam • Infill wall – Vu~1 kip/ft – Vu~8.3 kip ea. end • Grade beam – bw =12 in. – d = 20 in. (h = 24 in.) – f’ c = 4000 psi – ℓ = 20 ft – w = 0.0033 Infill Wall Grade Beam Ftg. Ftg.
WWW.CONCRETE.ORG/ACI318 316 Examples: Grade beam • Infill wall – Vu~1 kip/ft – Vu~8.3 kip ea. end • Grade beam – bw =12 in. – d = 20 in. (h = 24 in.) – f’ c = 4000 psi – ℓ = 20 ft – w = 0.0033 • ACI 318-14 • ACI 318-19 ' ,min 2 0.75(2)(1) 4000(12)(20) 22.8 (1/ 2) not required c c w c c u c v V f b d V V kip OK V V A f f  f f f = = =    1 ' 3 1 3 ' ,min 8 ( ) 2 0.82 20 1 10 0.75(8)(0.82)(1)(0.0033) 4000(12)(20) 11.1 11.4 not required c s w c w s c c u c w v V f b d V V kip OK V f b d kip A f f     f f f = = = + = =   = 
WWW.CONCRETE.ORG/ACI318 317 Changes to the Concrete Design Standard ACI 318-19 Two-way Shear Equations
WWW.CONCRETE.ORG/ACI318 318 Why two-way shear provisions changed in 318-19 • Eqn. developed in 1963 for slabs with t < 5 in. and  > 1% • Two issues similar to one-way shear – Size effect – Low ρ vc Least of (a), (b), and (c): (a) (b) (c) ' 4 c f  ' 4 2 c f   +       ' 2 s c o d f b    +      Table 22.6.5.2 – Calculation of vc for two-way shear
WWW.CONCRETE.ORG/ACI318 319 Two-way shear size effect • Table 22.6.5.2—vc for two-way members without shear reinforcement where vc Least of (a), (b), and (c): (a) (b) (c) ' 4 c s f   ' 4 2 c s f   +        ' 2 s s c o d f b     +     2 1 1 10 s d  =  +
WWW.CONCRETE.ORG/ACI318 320 Two-way shear low  effect • D, L only, cracking ~2 𝒇𝒄 ′ ; punching 4 𝒇𝒄 ′ • Aggregate interlock • Low  ➔ bar yielding, ↑ rotation, ↑crack size, allows sliding of reinforcement • Punching loads < 4 𝒇𝒄 ′ Source: Performance and design of punching – shearreinforcing system, Ruiz et al, fib 2010
WWW.CONCRETE.ORG/ACI318 321 Why two-way shear provisions changed in 318-19: New two-way slab reinforcement limits 8.6.1—Reinforcement limits • As,min ≥ 0.0018Ag • If on the critical section • Then ,min 5 uv slab o s s y v b b A f  f ' 2 uv s c v f  f  
WWW.CONCRETE.ORG/ACI318 322 Why two-way shear provisions changed in 318-19: 8.4.2.2.3
WWW.CONCRETE.ORG/ACI318 323 h 1.5h Slab edge bslab h 1.5h bslab 1.5h Slab edge bslab is the lesser of: Table 8.4.2.2.3
WWW.CONCRETE.ORG/ACI318 324 bslab is the lesser of: h 1.5h bslab Slab edge 1.5hdrop Table 8.4.2.2.3 h 1.5h hcap 1.5 hcap bslab hdrop 1.5h 1.5 hcap
WWW.CONCRETE.ORG/ACI318 325 Changes to the Concrete Design Standard ACI 318-19 Wall Shear Equations
WWW.CONCRETE.ORG/ACI318 326 Coordination of Chap. 11 and 18 Wall Shear Eqs. • ACI 318-83 introduced seismic equation – Two wall shear equation forms • Equation forms gave similar results • Committee 318 wanted consistency in form
WWW.CONCRETE.ORG/ACI318 327 • Chapter 11: all changes • Chapter 18: no change • 318-14 simplified compression eq. (Table 11.5.4.6) ' 2 v yt n c A f d V f hd s  = + Coordination of Chap. 11 and 18 Wall Shear Eqs.
WWW.CONCRETE.ORG/ACI318 328 • 318-19 Eq. 11.5.4.3 • 318-19 Eq. 18.10.4.1 (same as -14) • c Coordination of Chap. 11 and 18 Wall Shear Eqs. ( ) ' n c c t yt cv V f f A    = + ( ) ' n c c t yt cv V f f A    = +
WWW.CONCRETE.ORG/ACI318 329 • Impact minor • Similar results 318-14 to 19 • Note use of ℓw in 318-19 vs d in 318-14 – d in 318-14 assumed 0.8 ℓw – Results in a “lower” max Vn: 𝑉 𝑛 = 10 𝑓𝑐 ′ℎ𝑑 (318 − 14) 𝑉 𝑛 = 8 𝑓𝑐 ′ℎℓ𝑤 (318 − 19) = 8 𝑓𝑐 ′𝐴𝑐𝑣 Coordination of Chap. 11 and 18 Wall Shear Eqs.
WWW.CONCRETE.ORG/ACI318 330 Changes to the Concrete Design Standard ACI 318-19 Spacing of Shear Reinforcement
WWW.CONCRETE.ORG/ACI318 331 Source: Lubell et. al, “Shear ReinforcementSpacing in Wide Members, ACI StructuralJournal2009 Maximum spacing of legs of shear reinforcement
WWW.CONCRETE.ORG/ACI318 332 Table 9.7.6.2.2—Maximum spacing of legs of shear reinforcement RequiredVs Maximum s, in. Nonprestressed beam Prestressed beam Along length Across width Along length Across width Lesser of: d/2 d 3h/4 3h/2 24 in. Lesser of d/4 d/2 3h/8 3h/4 12 in. ' 4 c w f b d  ' 4 c w f b d 
WWW.CONCRETE.ORG/ACI318 333 Beam stirrup configurationwith three closed stirrups distributedacross the beam width Single U-stirrup (with 135-degree hooks) across the net width of the beam, two identicalU-stirrups (each with 135-degree hooks) distributedacross the beam interior, and a stirrup cap Single U-stirrup across the net width of the beam, two smaller-width U-stirrups nested in the beam interior, and a stirrup cap Maximum spacing of legs of shear reinforcement s maximum = d or d/2 nonprestressed, 3h/2 or 3h/4 prestressed s maximum = d or d/2 nonprestressed, 3h/2 or 3h/4 prestressed s maximum = d or d/2 nonprestressed, 3h/2 or 3h/4 prestressed
WWW.CONCRETE.ORG/ACI318 334 Changes to the Concrete Design Standard ACI 318-19 Bi-directional Shear
WWW.CONCRETE.ORG/ACI318 335 Interaction of shear forces • Biaxial shear • Symmetrical RC circular sections – fVc equal about any axis – Vu on 2 centroidal axes, Vu = resultant 2 2 , , ( ) ( ) u u x u y v v v = + vu,x vu,y
WWW.CONCRETE.ORG/ACI318 336 Interaction of shear forces • Biaxial shear • Rectangular RC sections – fVc differs between axes – Vu on 2 axes, fVc≠ resultant vu,x vu vu,y
WWW.CONCRETE.ORG/ACI318 337 Interaction of shear forces • Biaxial shear on non-circular cross section • fVc = Elliptical interaction diagram 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 2.5 Vexp(y)/Vpre(y) Vexp(x)/Vpre(x) Interaction Curve N>0 N=0 N<0
WWW.CONCRETE.ORG/ACI318 338 Interaction of shear forces • 22.5.1.10 Neglect interaction of shear forces If vu,x/fvn,x ≤ 0.5, or vu,y/fvn,y ≤ 0.5 • 22.5.1.11 requires interaction consideration If vu,x/fvn,x > 0.5, and vu,y/fvn,y > 0.5, then 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 Vexp(y)/Vpre(y) Vexp(x)/Vpre(x) Interaction Cu N>0 N=0 N<0
WWW.CONCRETE.ORG/ACI318 339 Changes to the Concrete Design Standard ACI 318-19 Hanger Reinforcement
WWW.CONCRETE.ORG/ACI318 340 Monolithic beam-to-beam joints: Hanger steel • Commentary added: R9.7.6.2 • Hanger reinforcement – Suggested where both the following are true: – Beam depth ≥ 0.5 girder depth – Stress transmitted from beam to girder ≥ 3√f’ c of the beam
WWW.CONCRETE.ORG/ACI318 341 Monolithic beam-to-beam joints: Hanger steel
WWW.CONCRETE.ORG/ACI318 342 Changes to the Concrete Design Standard ACI 318-19 Concrete Durability and Materials
WWW.CONCRETE.ORG/ACI318 343 Changes in durability and materials • Changes in material properties (19.2) – Additional minimumf’c requirements – Ec requirements • Changes in durability (19.3) – Calculating chloride ion content – Sulfate exposure class S3 – Water exposure class W – Corrosion exposure class C0 • Changes in material (26.4.1) – Alternative cements – New aggregates • Recycled aggregates • Mineral fillers • Evaluation and acceptance (26.12) – Strength tests • Inspection (26.13)
WWW.CONCRETE.ORG/ACI318 344 Table 19.2.1.1 – Additional minimum strength, f’c Structural walls in SDC D, E, and F Min. f’c (psi) Special structural walls with Grade 100 reinforcement 5000 Higher strength concrete used with higher strength steel • Enhances bar anchorage • Reduces neutral axis depth for improved performance
WWW.CONCRETE.ORG/ACI318 345 19.2.2.1R Modulus of Elasticity • Ec from Code equations is appropriate for most applications • Large differences for HSC (f′c > 8000 psi), LWC, and mixtures with low coarse of aggregate volume
WWW.CONCRETE.ORG/ACI318 346 19.2.2.2 Modulus of Elasticity Ec can be specified based on testing of concrete mixtures: a) Use of specified EC for proportioning concrete mixture b) Test for specified EC c) Test for EC at 28 days or as indicated in construction documents Source: Engineering discoveries
WWW.CONCRETE.ORG/ACI318 347 Contract Document Information • Members for which Ec testing of concrete mixtures is required (26.3.1(c)) • Proportioning (26.4.3.1(c)) – Ec is average of 3 cylinders – Cylinders made and cured in the lab – Ec ≥ specified value Source: Engineering Discoveries
WWW.CONCRETE.ORG/ACI318 348 Changes in durability and materials • Changes in durability (19.3) – Calculating chloride ion content – Sulfate exposure class S3 – Water exposure class W – Corrosion exposure class C0
WWW.CONCRETE.ORG/ACI318 349 Table 19.3.2.1 – Allowable chloride limits • Percent mass of total cementitious materials rather than percent weight of cement Class Max w/cm Min. f’c, psi Maximum water-soluble chloride ion (Cl–) content in concrete, by percent mass of cementitious materials Additional provisions Non- prestressed concrete Prestressed concrete C0 N/A 2500 1.00 0.06 None C1 N/A 2500 0.30 0.06 C2 0.40 5000 0.15 0.06 Cover per 20.5 For calculation, cementitious materials ≤ cement
WWW.CONCRETE.ORG/ACI318 350 Determining chloride ion content • 26.4.2.2(e) - 2 methods to calculate total chloride ion content (1) Calculated from chloride ion content from concrete materials and concrete mixture proportions (2) Measured on hardened concrete in accordance with ASTM C1218 at age between 28 and 42 days
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard
ACI 318-19 Presentation - changes to the concrete design standard

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ACI 318-19 Presentation - changes to the concrete design standard

  • 1. WWW.CONCRETE.ORG/ACI318 1 Changes to the Concrete Design Standard ACI 318-19
  • 2. WWW.CONCRETE.ORG/ACI318 2 American Concrete Institute is a RegisteredProvider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completionof this program will be reported to AIA/CES for AIA members. Certificates of Completionfor both AIA members and non-AIA members will be emailed to you soon after the seminar. This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any methodor manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials,methods, and services will be addressed at the conclusionof this presentation. The American Institute of Architects has approved this session for 7.5 AIA/CES LU/HSW Learning Units.
  • 3. WWW.CONCRETE.ORG/ACI318 3 Learning Objectives 1. Understand where higher grades of reinforcement are accepted and changes to the requirements for structural concrete to allow the higher reinforcement grades, including development lengths and phi- factors. 2. Identify the added requirements to address shotcrete as a concrete placement method. 3. Explain the expanded scope of deep foundation provisions, including seismic requirements.
  • 4. WWW.CONCRETE.ORG/ACI318 4 Learning Objectives 4. Learn the new requirements for post- installed screw type anchors and shear lug design for anchoring to concrete. 5. Describe the changes to shear design provisions and equations. 6. Identify new tension longitudinal reinforcement requirements in special structural walls
  • 5. WWW.CONCRETE.ORG/ACI318 5 Speakers Speaker bios are included in your handouts for the presentation
  • 6. WWW.CONCRETE.ORG/ACI318 6 Changes to the Concrete Design Standard ACI 318-19 Introduction
  • 7. WWW.CONCRETE.ORG/ACI318 7 Today’s Seminar • Major changes • Grouped by topic • Organization • Existing structures • Loads & analysis • Slabs • Post-tensioning • Precast/Prestressed • Circular sections • Walls • Foundations • Anchorage to concrete • Seismic
  • 8. WWW.CONCRETE.ORG/ACI318 8 Today’s Seminar • Major changes • Grouped by topic • High-strength reinforcement • Development length • Shear modifications • Durability and materials • Strut-and-tie method • Shotcrete • Appendix A
  • 9. WWW.CONCRETE.ORG/ACI318 9 • Changes from ACI 318-14 to ACI 318-19 318-14 318-19 Today’s Seminar
  • 10. WWW.CONCRETE.ORG/ACI318 10 Why Do We Change ACI 318? • Reflects new research • Construction practices change • Sometimes tragic events provide introspect – Earthquakes or other natural disasters – Collapses or construction accidents – Observed in-service performance • New materials – Or better ways of making established materials • More powerful analytical tools
  • 11. WWW.CONCRETE.ORG/ACI318 11 Resources • ACI 318 • Speaker notes • ACI Reinforced Concrete Design Handbook • ACI 318 Building Code Portal
  • 12. WWW.CONCRETE.ORG/ACI318 12 ACI 318-19 Variety of formats, including: • Printed copy – Softcover and hardcover • Enhanced PDF Versions • English • Spanish • In.-lb units • SI units
  • 14. WWW.CONCRETE.ORG/ACI318 14 ACI Design Handbook • 15 chapters • Explanatory text • Design aids • 2019 version expected early next year
  • 15. WWW.CONCRETE.ORG/ACI318 15 ACI Design Handbook • 1: Building Systems • 2: Structural Systems • 3: Structural Analysis • 4: Durability • 5: One-Way Slabs • 6: Two-Way Slabs • 7: Beams • 8: Diaphragms • 9: Columns • 10: Walls • 11: Foundations • 12: Retaining Walls • 13: Serviceability • 14: Strut-and-Tie • 15: Anchorage
  • 16. WWW.CONCRETE.ORG/ACI318 16 ACI 318 Building Code Portal
  • 17. WWW.CONCRETE.ORG/ACI318 17 Changes to the Concrete Design Standard ACI 318-19 Organization
  • 18. WWW.CONCRETE.ORG/ACI318 18 Major goals of ACI 318 organization • Ease of use • Find the information you need quickly – Consistent organization – Organized in the order of design • Increase certainty that a design fully meets the Code – A chapter for each member type – All member design provisions in one chapter
  • 22. WWW.CONCRETE.ORG/ACI318 22 Navigation 10 Parts • General • Loads & Analysis • Members • Joints/Connections/ Anchors • Seismic • Materials & Durability • Strength & Serviceability • Reinforcement • Construction • Evaluation
  • 23. WWW.CONCRETE.ORG/ACI318 23 Part 1: General • 1: General • 2: Notation and Terminology – dagg = nominal maximum size of coarse aggregate, in. – aggregate—granular material, such as sand, gravel, crushed stone, iron blast-furnace slag, or recycled aggregates including crushed hydraulic cement concrete, used with a cementing medium to form concrete or mortar.
  • 24. WWW.CONCRETE.ORG/ACI318 24 Part 1: General • 3: Referenced Standards • 4: Structural System Requirements Materials Design loads Load paths Structural analysis Strength Serviceability Durability Sustainability Structural integrity Fire Safety Precast/ Prestressed Inspection
  • 25. WWW.CONCRETE.ORG/ACI318 25 Part 2: Loads & Analysis • 5: Loads • 6: Structural Analysis – Simplified, first-order, second-order – Linear, nonlinear – Slenderness – Materials and section properties
  • 26. WWW.CONCRETE.ORG/ACI318 26 Part 3: Members • 7: One-Way Slabs • 8: Two-Way Slabs • 9: Beams • 10: Columns • 11: Walls • 12: Diaphragms • 13: Foundations • 14: Plain Concrete
  • 27. WWW.CONCRETE.ORG/ACI318 27 Typical member chapter sections • X.1 Scope • X.2 General • X.3 Design Limits • X.4 Required Strength • X.5 Design Strength • X.6 Reinforcement Limits • X.7 Reinforcement Detailing • X.? ?
  • 29. WWW.CONCRETE.ORG/ACI318 29 Part 4: Joints / Connections / Anchors • 15: Beam-column and slab-column joints • 16: Connections between members • 17: Anchoring to concrete
  • 30. WWW.CONCRETE.ORG/ACI318 30 Part 5: Seismic • 18: Earthquake Resistant Structures
  • 31. WWW.CONCRETE.ORG/ACI318 31 Part 6: Materials & Durability • 19: Concrete: Design and Durability Properties • 20: Steel Reinforcement Properties, Durability, and Embedments (Credit: PCA)
  • 32. WWW.CONCRETE.ORG/ACI318 32 Part 7: Strength & Serviceability • 21: Strength Reduction Factors • 22: Sectional Strength
  • 33. WWW.CONCRETE.ORG/ACI318 33 Organization Member Chapter 9.5 — Design strength 9.5.2 — Moment 9.5.2.1 — If Pu < 0.10f’cAg, Mn shall be calculated in accordance with 22.3. 9.5.2.2 — If Pu ≥ 0.10f’cAg, Mn shall be calculated in accordance with 22.4. Toolbox Chapter 22.3 —Flexural strength… 22.3.3.4 … 22.4 — Axial strength or combined flexural and axial strength… 22.4.3.1 …
  • 34. WWW.CONCRETE.ORG/ACI318 34 Part 7: Strength & Serviceability • 23: Strut-and-Tie Method • 24: Serviceability ,
  • 35. WWW.CONCRETE.ORG/ACI318 35 Part 8: Reinforcement • 25: Reinforcement Details
  • 36. WWW.CONCRETE.ORG/ACI318 36 Part 9: Construction • 26: Construction Documents and Inspection – 318 is written to the engineer, not the contractor. – Construction requirements must be communicated on the construction documents. – All construction requirements are gathered together in Chapter 26. – Design information – job specific – Compliance requirements – general quality – Inspection requirements
  • 37. WWW.CONCRETE.ORG/ACI318 37 Part 10: Evaluation • 27: Strength Evaluation of Existing Structures – Applies when strength is in doubt – Well understood – analytical evaluation – Not well understood – load test
  • 38. WWW.CONCRETE.ORG/ACI318 38 Benefits of ACI 318 organization • Organized from a designer’s perspective • Easier to find specific requirements • Intuitive location of information • Clarified cross references • Tables improve speed of understanding • Consistent language in text • Single idea for each requirement
  • 39. WWW.CONCRETE.ORG/ACI318 39 Changes to the Concrete Design Standard ACI 318-19 Existing Structures
  • 40. WWW.CONCRETE.ORG/ACI318 40 1.4—Applicability 1.4.1 This Code shall apply to concrete structures designed and constructed under the requirements of the general building code. … 1.4.3 Applicable provisions of this Code shall be permitted to be used for structures not governed by the general building code.
  • 41. WWW.CONCRETE.ORG/ACI318 41 307 - Chimneys 562 - Repair 216 - Fire 313 - Silos 359 – Nuclear Contain. 349 – Nuclear Facilities 350 – Environmental 369 – Seismic Retrofit 376 – RLG Containment 332 – Residential 437 – Strength Evaluation Concrete designs governed by other ACI codes
  • 42. WWW.CONCRETE.ORG/ACI318 42 Design recommendations provided in guides • Slabs-on-ground (ACI 360R) • Blast-resistant structures (ACI 370R) • Wire Wrapped Tanks (ACI 372R)
  • 43. WWW.CONCRETE.ORG/ACI318 43 1.4.2—Repair 1.4.2 Provisions of this Code shall be permitted to be used for the assessment, repair, and rehabilitation of existing structures. R1.4.2 Specific provisions for assessment, repair, and rehabilitation of existing concrete structures are provided in ACI 562-19. Existing structures in ACI 562 are defined as structures that are complete and permitted for use.
  • 44. WWW.CONCRETE.ORG/ACI318 44 Chapter 27 – Strength Evaluation of Existing Structures Applies when strength is in doubt • Well understood – analytical evaluation • Not well understood – load test – Monotonic procedure, ACI 318 – Cyclic procedure, ACI 437.2
  • 45. WWW.CONCRETE.ORG/ACI318 45 27.4.6.2—Total test load, Tt Greatest of: (a) Tt = 1.15D + 1.5L + 0.4(Lr or S or R) →Tt = 1.0Dw + 1.1Ds + 1.6L + 0.5(Lr or S or R) (b) Tt = 1.15D + 0.9L + 1.5(Lr or S or R) → Tt = 1.0Dw + 1.1Ds + 1.0L + 1.6(Lr or S or R) (c) Tt = 1.3D →Tt = 1.3(Dw + Ds)
  • 46. WWW.CONCRETE.ORG/ACI318 46 Changes to the Concrete Design Standard ACI 318-19 Loads & Analysis
  • 47. WWW.CONCRETE.ORG/ACI318 47 Superposition of loads (R5.3.1) • Added commentary – If the load effects such as internal forces and moments are linearly related to the loads, the required strength U may be expressed in terms of load effects with the identical result. If the load effects are nonlinearly related to the loads, such as frame P-delta effects (Rogowsky et al. 2010), the loads are factored prior to determining the load effects. Typical practice for foundation design is discussed in R13.2.6.1. Nonlinear finite element analysis using factored load cases is discussed in R6.9.3.
  • 48. WWW.CONCRETE.ORG/ACI318 48 Superposition of loads (R5.3.1) In other words: • First order, linear analysis M1.2D+1.6L = 1.2 MD + 1.6 ML • Second order or nonlinear analysis M1.2D+1.6L ≠ 1.2 MD + 1.6 ML
  • 49. WWW.CONCRETE.ORG/ACI318 49 Wind Loads (R5.3.5) • Added commentary – ASCE 7-05 • Wind = service-levelwind • Use 1.6 load factor – ASCE 7-10 & ASCE 7-16 • Wind = strength-level wind • Use 1.0 load factor
  • 50. WWW.CONCRETE.ORG/ACI318 50 Inelastic First-Order Analysis (Chapter 6) • Not mentioned in ACI 318-14 • Nonlinear material properties • Equilibrium satisfied in undeformed shape • Several revisions – Must consider column slenderness – No further redistribution – Clarifies requirements for each type of analysis Moment Curvature
  • 51. WWW.CONCRETE.ORG/ACI318 51 Consistent Stiffness Assumptions (6.3.1.1) • ACI 318-14 dropped “consistent throughout the analysis” language No top steel required No bottom steel required No steel required
  • 52. WWW.CONCRETE.ORG/ACI318 52 Torsional Stiffness (R6.3.1.1) • Clarification in commentary • Two factors – Torsional vs. flexural stiffnesses – Equilibrium requirements GJ vs. EI
  • 53. WWW.CONCRETE.ORG/ACI318 53 Torsional Stiffness Equilibriumtorsion • Torsion in beam required to maintain equilibrium • Torsion and torsional stiffness of the beam must be considered Beam Cantilever slab
  • 54. WWW.CONCRETE.ORG/ACI318 54 Torsional Stiffness Compatibilitytorsion • Torsion in girder not required to maintain equilibrium • Torsion and torsional stiffness of the beam may be neglected Beam Interior girder
  • 55. WWW.CONCRETE.ORG/ACI318 55 Torsional Stiffness Compatibilitytorsion • Torsion in girder not required to maintain equilibrium • Torsion and torsional stiffness of the girder should be included Beam Exterior girder
  • 56. WWW.CONCRETE.ORG/ACI318 56 Shear Area (6.6.3.1) Member and condition Moment of inertia Cross-sectional area for axial deformations Cross-sectional area for shear deformations Columns 0.70Ig 1.0Ag bwh Walls Uncracked 0.70Ig Cracked 0.35Ig Beams 0.35Ig Flat plates and flat slabs 0.25Ig Table 6.6.3.1.1(a)— Moments of Inertia and cross-sectionalareaspermitted for elastic analysisat factoredload level • No previous guidance
  • 57. WWW.CONCRETE.ORG/ACI318 57 Floor Vibrations (R24.1) • Typical floors – Good performance • Areas of concern – Long/open spans – High-performance (precision machinery) – Rhythmic loading or vibrating machinery – Precast • Commentary references
  • 58. WWW.CONCRETE.ORG/ACI318 58 Floor Vibrations • Resources – ATC Design Guide 1, “Minimizing Floor Vibration,” – Fanella, D.A., and Mota, M., “Design Guide for Vibrations of Reinforced Concrete Floor Systems,” – Wilford, M.R., and Young, P., “A Design Guide for Footfall Induced Vibration of Structures,” – PCI Design Handbook – Mast, R.F., “Vibration of Precast Prestressed Concrete Floors – West, J.S.; Innocenzi, M.J.; Ulloa, F.V.; and Poston, R.W., “Assessing Vibrations” • No specific requirements CIP Precast P-T
  • 59. WWW.CONCRETE.ORG/ACI318 59 Concerns about deflection calculations • Service level deflections based on Branson’s equation underpredicted deflections for ρ below ≈ 0.8% • Reports of excessive slab deflections (Kopczynski, Stivaros) • High-strength reinforcement may result in lower reinforcement ratios
  • 60. WWW.CONCRETE.ORG/ACI318 60 Heavily reinforced Midspan deflection Midspan moment Experimental Branson’s Eq. Bischoff’s Eq.
  • 61. WWW.CONCRETE.ORG/ACI318 61 Lightly reinforced Midspan deflection Midspan moment Experimental Branson’s Eq. Bischoff’s Eq.
  • 62. WWW.CONCRETE.ORG/ACI318 62 Ie should be the average of flexibilities
  • 63. WWW.CONCRETE.ORG/ACI318 63 • Branson • Bischoff Branson combines stiffnesses. Bischoff combines flexibilities. Comparison of Branson’s and Bischoff’s Ie
  • 64. WWW.CONCRETE.ORG/ACI318 64 • Table 24.2.3.5 ~ Inverse of Bischoff Eqn. • 2/3 factor added to account for: – restraint that reduces effective cracking moment – reduced concrete tensile strength during construction • Prestressed concrete Effective Moment of Inertia 𝑀𝑎 > Τ 2 3 𝑀𝑐𝑟, 𝐼𝑒 = 𝐼𝑐𝑟 1 − Τ 2 3 𝑀𝑐𝑟 𝑀𝑎 2 1 − 𝐼𝑐𝑟 𝐼𝑔 𝑀𝑎 ≤ Τ 2 3 𝑀𝑐𝑟, 𝐼𝑒 = 𝐼𝑔
  • 65. WWW.CONCRETE.ORG/ACI318 65 Changes to the Concrete Design Standard ACI 318-19 One-Way Slabs
  • 66. WWW.CONCRETE.ORG/ACI318 66 Structural Integrity Reinforcement Structural integrity provisions have been added • To improve structural integrity – To ensure that failure of a portion of a slab does not lead to disproportional collapse • To be similar to that for beams – bring one-way cast-in-place slab structural integrity in line with beam structural integrity provisions
  • 67. WWW.CONCRETE.ORG/ACI318 67 Structural Integrity Reinforcement • 7.7.7 Structural integrity reinforcement in cast-in-place one-way slabs – 7.7.7.1 Longitudinal reinf. consists of at least ¼ of max. positive moment to be continuous Beam 1/4 M+ continuous
  • 68. WWW.CONCRETE.ORG/ACI318 68 Structural Integrity Reinforcement – 7.7.7.2 Longitudinal reinf. at noncontinuous supports to be anchored to develop fy at the face of the support Beam
  • 69. WWW.CONCRETE.ORG/ACI318 69 Structural Integrity Reinforcement – 7.7.7.3 Splices • Splice near supports • mechanical or welded in accordance with25.5.2 or 25.5.7 • or Class B tension lap splices in accordance with 25.5.2 Beam Splice
  • 70. WWW.CONCRETE.ORG/ACI318 70 Shrinkage and Temperature Reinforcement 7.6.4.1 → 24.4 Shrinkage and temperature reinforcement 24.4.3.2 : Ratio of deformed shrinkage and temperature reinforcement area to gross concrete area • 318-14: as per Table 24.4.3.2 • 318-19: Ratio ≥ 0.0018 0
  • 71. WWW.CONCRETE.ORG/ACI318 71 Minimum Flexural Reinforcement in Nonprestressed Slabs – One way 7.6.1.1: • 318-14: As,min as per Table 7.6.1.1 • 318-19: As,min = 0.0018Ag 1
  • 72. WWW.CONCRETE.ORG/ACI318 72 Changes to the Concrete Design Standard ACI 318-19 Two-Way Slabs
  • 73. WWW.CONCRETE.ORG/ACI318 73 The Direct Design Method and The Equivalent Frame Method – Removed: The direct design method (8.10) and the equivalent frame method (8.11) – Provisions in 318-14 – 8.2.1 … The direct design method or the equivalent frame method is permitted. – 6.2.4.1 Two-way slabs shall be permitted to be analyzed for gravity loads in accordance with (a) or (b): (a) Direct design method for nonprestressed slabs (b) Equivalent frame method for nonprestressed and prestressed slabs
  • 74. WWW.CONCRETE.ORG/ACI318 74 Shearheads • Removed Shearhead provisions in 318-14 – 8.4.4.1.3 Slabs reinforced with shearheads shall be evaluated for two-way shear at critical sections in accordance with 22.6.9.8.
  • 75. WWW.CONCRETE.ORG/ACI318 75 Opening in Slab Systems Without Beams Fig. R22.6.4.3—Effect of openings and free edges (effective perimeter shown with dashed lines) Note: Openings shown are located within 10h of the column periphery ACI 318 -14: 8.5.4.2(d) • within a column strip or closer than 10h from a concentrated load or reaction area satisfy – 22.6.4.3 for slabs without shearheads – or 22.6.9.9 for slabs with shearheads • 22.6.4.3: Reduced perimeter of critical section (bo) – Fig. R22.6.4.3 • 22.6.9.9: Reduction to bo is ½ of that given in 22.6.4.3
  • 76. WWW.CONCRETE.ORG/ACI318 76 Opening in Slab Systems Without Beams Fig. R22.6.4.3—Effect of openings and free edges (effective perimeter shown with dashed lines). ACI 318 -19: 8.5.4.2(d) • closer than 4h from the periphery of a column, concentrated load or reaction area satisfying 22.6.4.3 • 22.6.4.3: Reduced perimeter of critical section (bo) – Fig. R22.6.4.3
  • 77. WWW.CONCRETE.ORG/ACI318 77 Minimum Flexural Reinforcement in Nonprestressed Slabs – Two way 8.6.1.1 • 318-14 : As,min as per Table 8.6.1.1. • 318-19: As,min of 0.0018Ag, or as defined in 8.6.1.2 (discussed under two-way shear) 7
  • 78. WWW.CONCRETE.ORG/ACI318 78 Reinforcement Extensions for Slabs without Beams ACI 318-14: 8.7.4.1.3 - Column strip top bars • Extend to at least 0.3ℓn • May not be sufficient for thick slabs – may not intercept critical punching shear crack – Reduce punching shear strength Punchingshear cracks in slabs with reinforcementextensions
  • 79. WWW.CONCRETE.ORG/ACI318 79 Punching shear failure - Podium Slab • The failure crack did not intercept the top reinforcement.
  • 80. WWW.CONCRETE.ORG/ACI318 80 Reinforcement Extensions for Two-Way Slabs without Beams ACI 318-19: 8.7.4.1.3 - Column strip top bars • Extend to at least 0.3ℓn but, not less than 5d Fig. R8.7.4.1.3- Punching shear cracks in ordinary and thick slabs d d
  • 81. WWW.CONCRETE.ORG/ACI318 81 Reinforcement Extensions for Two-Way Slabs without Beams
  • 82. WWW.CONCRETE.ORG/ACI318 82 Changes to the Concrete Design Standard ACI 318-19 Post-tensioning
  • 83. WWW.CONCRETE.ORG/ACI318 83 Residential P-T Slabs (1.4.6) • Past confusion about P-T slab foundation design on expansive soils – Intent was for residential, but not mentioned with residential design provisions • Commentary clarifies use of PTI DC10.5-12 for P-T residential slabs and foundations on expansive soils
  • 84. WWW.CONCRETE.ORG/ACI318 84 Residential P-T Slabs (1.4.6) • Coordinates with 2015 IBC requirements • Adds reference to ACI 360 if not on expansive soil
  • 85. WWW.CONCRETE.ORG/ACI318 85 Max. Spacing of Deformed Reinf. (7.7.2.3) • Class C (Cracked) and T (Transition) one- way slabs with unbonded tendons rely on bonded reinforcement for crack control • Previously no limits for spacing of deformed reinforcement for Class C and T prestressed slabs • Industry feedback provided
  • 86. WWW.CONCRETE.ORG/ACI318 86 Max. Spacing of Deformed Reinf. (7.7.2.3) • New limit is s ≤ 3h and 18 in. • Same as non-prestressed slabs Unbonded P-T Deformed reinforcement Slab Section s ≤ 3h and 18 in.
  • 87. WWW.CONCRETE.ORG/ACI318 87 P-T Anchorage Zone Reinforcement (25.9.4.4.6) • Referenced from slab and beam chapters • Applies for groups of 6 or more anchors in thick slabs • Anchorage zone requires backup bars for bearing and hairpins for bursting • Hairpins must be anchored at the corners Backup bars Anchor bars Hairpins
  • 89. WWW.CONCRETE.ORG/ACI318 89 P-T Anchorage Zone Reinforcement (25.9.4.4.6) • Thin slabs ≤ 8 in. → Anchor bars serve as backup bars • Thick slabs > 8 in. → Both backup bars and anchor bars required Backup bars Anchor bars Hairpins
  • 93. WWW.CONCRETE.ORG/ACI318 93 Design of Formwork for P-T (26.11.1.2 (5) and (6)) • Members may move when P-T strand is stressed • Movement may redistribute loads • Added requirement to allow for movement during tensioning • Added requirement to consider redistribution of loads on formwork from tensioning of the prestressing reinforcement
  • 94. WWW.CONCRETE.ORG/ACI318 94 Changes to the Concrete Design Standard ACI 318-19 Precast/Prestressed
  • 95. WWW.CONCRETE.ORG/ACI318 95 Precast/Prestressed Concrete • Confinement for column/pedestal tops • Connection forces • Construction document requirement • f at ends of precast members
  • 96. WWW.CONCRETE.ORG/ACI318 96 Confinement • 10.7.6.1.5: confinement required at tops of columns/pedestals • Assists in load transfer • Not a new provision 5 in. Two No. 4 or Three No. 3 ties Anchor bolts
  • 97. WWW.CONCRETE.ORG/ACI318 97 Confinement • 10.7.6.1.6: extends confinement requirement to precast columns/pedestals 5 in. Two No. 4 or Three No. 3 ties Mechanical coupler Future precast member
  • 98. WWW.CONCRETE.ORG/ACI318 98 Volume Change in Precast Connections • Volume change – Creep – Shrinkage – Temperature • May induce connection reactions if restrained
  • 99. WWW.CONCRETE.ORG/ACI318 99 Volume Change in Precast Connections • Load magnitude? • Load factor? • Past guidance for brackets and corbels – Use Nuc ≥ 0.2Vu as restraint force – Use a 1.6 load factor • Approach was often to design around forces
  • 100. WWW.CONCRETE.ORG/ACI318 100 Volume Change and Connections 318-19 changes (16.2.2.3) • Nuc = factored restraint force, shall be (a) or (b) – (a) restraint force x LL factor (no bearing pad) – (b) 1.6 x 0.2(sustained unfactored vertical load) for connections on bearing pads • Nuc,max ≤ connection capacity x LL factor • Nuc,max ≤ 1.6 x μ x (sustained unfactored vertical load) if μ is known, (See 16.2.2.4)
  • 101. WWW.CONCRETE.ORG/ACI318 101 Brackets and Corbels • 26.6.4.1(a) Details for welding of anchor bars at the front face of brackets or corbels designed by the licensed design professional in accordance with 16.5.6.3(a). Fig. R16.5.6.3b Fig. R16.5.1b
  • 102. WWW.CONCRETE.ORG/ACI318 102 Strength Reduction Factor Near end of precast member • Linear interpolation of f • f p depends on state of stress
  • 103. WWW.CONCRETE.ORG/ACI318 103 Strength Reduction Factor Near end of precast member • Similar for debonded strand
  • 104. WWW.CONCRETE.ORG/ACI318 104 Changes to the Concrete Design Standard ACI 318-19 Circular Sections
  • 105. WWW.CONCRETE.ORG/ACI318 105 Variable definitions (22.5) • 22.5 One-way shear – Interpretation for hollow circular sections d ? bw ? ρw ? opening
  • 106. WWW.CONCRETE.ORG/ACI318 106 Variable definitions (22.5) • 22.5.2.2 – calculation of Vc and Vs – d = 0.8 x diameter – bw = diameter (solid circles) – bw = 2 x wall thickness (hollow circles) d = 0.8D bw = D ρw = As/bwd bw = 2t opening t
  • 107. WWW.CONCRETE.ORG/ACI318 107 Variable definitions (22.5) • What about As? (2/3)D As
  • 108. WWW.CONCRETE.ORG/ACI318 108 Torsion for circular sections (R22.7.6.1.1) • Do ACI 318 torsion equations apply to circular cross sections? • Code Eqns are based on thin-tube theory • Examples added to figure 125
  • 109. WWW.CONCRETE.ORG/ACI318 109 Circular Column Joints • Based on equivalent square column – Aj for joint shear strength (15.4.2) – Width of transverse beams required for joint to be considered confined (15.2.8) – Column width ≥ 20 db for special moment frames (18.8.2.3) h = 0.89D
  • 110. WWW.CONCRETE.ORG/ACI318 110 Changes to the Concrete Design Standard ACI 318-19 Walls
  • 111. WWW.CONCRETE.ORG/ACI318 111 Scope of walls • Change in scope 11.1.4 - Design of cantilever retaining walls shall be in accordance with Chapter 13 (Foundations)
  • 112. WWW.CONCRETE.ORG/ACI318 112 Scope of walls • Added scope 11.1.6 - CIP walls with insulated forms shall be permitted by this code for use in one or two-story buildings • Design according to Chapter 11 • Guidance – ACI 560R and PCA 100-2017 • Unique construction issues Photo courtesy Larry Novak
  • 113. WWW.CONCRETE.ORG/ACI318 113 11.7.2.3 Bar placement • If wall thickness h > 10 in. • Two layers of bars one near each face • Exception, single story basement walls • 318-14 • ½ to 2/3 of reinf. placed near exterior face • Balance of reinf. placed near interior face • Confusion with exterior and interior – Face versus wall location • ½ to 2/3 was arbitrary
  • 114. WWW.CONCRETE.ORG/ACI318 114 14.6 Plain concrete At windows, door openings, and similarly sized openings • At least two No. 5 bars (similar to walls 11.7.5.1) • Extend 24 in. beyond or to develop fy ≥ 24 in. 2-No. 5 bars
  • 115. WWW.CONCRETE.ORG/ACI318 115 Changes to the Concrete Design Standard ACI 318-19 Foundations
  • 116. WWW.CONCRETE.ORG/ACI318 116 Ch. 13 – Foundations – significant changes • Added design provisions – Cantilever retaining walls – Deep foundation design • Other – Minimum concrete strengths for shallow and deep foundations – Cover
  • 117. WWW.CONCRETE.ORG/ACI318 117 Foundations and 318 • ACI 318-71 to ACI 318-11 (Ch. 15) • Shallow footings, pile caps • ACI 318-14 (Ch. 13) • Shallow footings, pile caps
  • 118. WWW.CONCRETE.ORG/ACI318 118 Foundations and 318 • ACI 318-71 to ACI 318-11 (Ch. 15) • Shallow footings, pile caps • ACI 318-14 (Ch. 13) • Shallow footings, pile caps • ACI 318-19 (Ch. 13) • Shallow footings, pile caps, deep foundations, and walls of cantilevered retaining walls
  • 119. WWW.CONCRETE.ORG/ACI318 119 Cantilever retaining walls It’s a wall (2014) It’s a slab (2019)
  • 120. WWW.CONCRETE.ORG/ACI318 120 13.3.6.1—Cantilever stem walls • Design as one-way slab (Ch. 7)
  • 121. WWW.CONCRETE.ORG/ACI318 121 13.3.6.2—Cantilever stem wall with counterfort • Design as two-way slab (Ch. 8)
  • 122. WWW.CONCRETE.ORG/ACI318 122 Maximum bar spacing in stem wall Wall Slab Stem wall reinforcement Maximum bar spacing (2014) Design as wall (2014) Maximum bar spacing (2019) Design as one-way slab (2019) Long. (Wall) or Flexural(Slab) 3h, or 18 in. 11.7.2.1 Lesser of: 7.7.2.2 (24.3) Trans. (Wall) or S & T (Slab) 3h, or 18 in. 11.7.3.1 5h, or 18 in. 7.7.6.2.1 s Transverse bars Longitudinal bars 40,000 15 2.5 c s c f   −     40,000 12 s f      
  • 123. WWW.CONCRETE.ORG/ACI318 123 ACI 318-14 ACI 318-19 Minimum reinforcement, ρ Designas wall Minimum reinforcement As,min Designas one-way slab ≤ No. 5 ρℓ = 0.0012 > No. 5 ρℓ = 0.0015 11.6.1 As,min = 0.0018 Ag 7.6.1.1 ≤ No. 5 ρt = 0.0020 > No. 5 ρt = 0.0025 11.6.2 AS+T = 0.0018 Ag 7.6.4.1 (24.4) Minimum reinforcement in stem wall
  • 124. WWW.CONCRETE.ORG/ACI318 124 1.4.7— Scope changes – deep foundations • Scope: This code does not govern design and installation of portions of concrete pile, drilled piers, and caissons embedded in ground, except as provided in (a) through (c) • (a) For portions in air or water,or in soil incapable of providing adequate lateral restraint to prevent buckling throughout their length • (b) For precast concrete piles supporting structures assigned to SDC A and B • (c) For deep foundation elements supporting structures assigned to SDC C, D, E, and F (SDC C is added to scope)
  • 125. WWW.CONCRETE.ORG/ACI318 125 Deep Foundations (13.4) • 13.4.1 General • 13.4.2 Allowable axial strength • 13.4.3 Strength design • 13.4.4 Cast-in-place deep foundations • 13.4.5 Precast concrete piles • 13.4.6 Pile caps
  • 126. WWW.CONCRETE.ORG/ACI318 126 Deep foundation – combine IBC & ASCE 7 • ACI 318 – 19 – – combined IBC 2015, ASCE 7-10, and ACI 318-14 with regards to design of deep foundations for earthquake resistant structures (SDC C, D, E, and F) ACI 318 - 19 Allowable axial strength/stress capacities ACI 318-14 ASCE 7 IBC 2015
  • 127. WWW.CONCRETE.ORG/ACI318 127 Pre- ACI 318-19 – design of deep foundations • ACI 543 - Piles (diam. < 30 in.) • ACI 336.3 - Design of drilled piers (diam. ≥ 30 in.) Not code language documents Also used deep footing provisions from: IBC and ASCE/SEI 7
  • 128. WWW.CONCRETE.ORG/ACI318 128 Design of deep foundation members- compressive axial force (13.4.1) • Design axial strength of members in accordance to two methods: – Allowable Axial Strength Design (13.4.2) – Strength Design (13.4.3) Photos courtesy Larry Novak
  • 129. WWW.CONCRETE.ORG/ACI318 129 Allowable axial strength method (13.4.2) 13.4.2.1 It shall be permitted to design a deep foundation member using load combinations for allowable stress design in ASCE / SEI 7, Section 2.4, and the allowable strength specified in Table 13.4.2.1 if (a) and (b) are satisfied (a)Deep foundation is laterally supported for its entire height (b)Applied forces causing bending moments less than moment due to an accidental eccentricity of 5 percent of the pile diameter or width.
  • 131. WWW.CONCRETE.ORG/ACI318 131 Confinement of metal casing (13.4.2.3): • not used to resist axial load • sealed tip and mandrel-driven • seamless or welded seamless Physical properties • wall thickness ≥ 14 ga. (0.068 in.) • fy ≥ 30,000 psi • fy ≥ 6 f’c , and • nominal diameter ≤ 16 in. Metal casing Sealed tip Diam ≤ 16 in.
  • 132. WWW.CONCRETE.ORG/ACI318 132 Deep foundations – strength design (13.4.3) • Method may be used any time • Method must be used when pile does not meet criteria for allowable axial strength design – Soils do not provide lateral support – Moment is not negligible • Use Section 10.5 (columns) – 𝝓 Pn ≥ Pu – 𝝓 Mn ≥ Mu – Combined Pn and Mn calculated by 22.4 Mu≥ 0 Pu
  • 133. WWW.CONCRETE.ORG/ACI318 133 Strength design (13.4.3) – axial force, no moment Nominal axial compressive strength; Pn 𝝓 Pn,max ≥ Pu Maximum axial strength - For deep foundations members with ties conforming to Ch. 13 (new in Table 22.4.2.1) Pn,max = 0.80 Po Where: Po = nominal axial strength at zero eccentricity Po = 0.85f’c(Ag – Ast) + fyAst Mu= 0 Pu
  • 134. WWW.CONCRETE.ORG/ACI318 134 Mu= 0 Strength design (13.4.3) – axial force, no moment • Reduction factor – Table 13.4.3.2 Pu 0.55 to 0.70
  • 135. WWW.CONCRETE.ORG/ACI318 135 Deep foundations 13.4.4.1 CIP deep foundations that are subject to (a) uplift or (b) Mu > 0.4Mcr shall be reinforced, unless enclosed by a steel pipe or tube Confined for ductility Reinforced for flexure Reinforced for tension Unreinforced
  • 136. WWW.CONCRETE.ORG/ACI318 136 Table 19.2.1.1 – Additional minimum strength, f’c Shallow foundations Min. f’c (psi) Foundations in SDC A, B, or C 2500 Foundation for Residential and Utility …. 2 stories or less ….stud bearing construction …… SDC D, E, or F 2500 Foundation for Residential and Utility …. More than 2 stories….stud bearing construction …… SDC D, E, or F 3000 Deep foundations Drilled shafts or piers 4000 Precast nonprestressed driven piles 4000 Precast prestressed driven piers 5000
  • 137. WWW.CONCRETE.ORG/ACI318 137 Concrete cover – deep foundations Table 20.5.1.3.4 3 in. Cast-in-place against ground 1.5 in. Cast-in-place enclosed by steel pipe, permanent casing, or stable rock socket Steel pipe
  • 138. WWW.CONCRETE.ORG/ACI318 138 Concrete cover – deep foundations In contact with ground 2.5 in. precast nonprestressed 2 in. precast prestressed Exposed to seawater 1.5 in. precast nonprestressed and precast prestressed Table 20.5.1.3.4
  • 139. WWW.CONCRETE.ORG/ACI318 139 Changes to the Concrete Design Standard ACI 318-19 Anchorage to Concrete
  • 140. WWW.CONCRETE.ORG/ACI318 140 Chapter 17 – Anchoring to Concrete • Reorganized • New content/design information – Screw anchors added – Shear lugs added
  • 141. WWW.CONCRETE.ORG/ACI318 141 Sections • 17.1 Scope • 17.2 General • 17.3 Design limits • 17.4 Required strength • 17.5 Design strength • 17.6 Tensile strength • 17.7 Shear strength • 17.8 Tension and shear interaction • 17.9 Edge distances, spacings, and thicknesses to preclude splitting failure • 17.10 Earthquake- resistant design requirements • 17.11 Attachments with shear lugs
  • 142. WWW.CONCRETE.ORG/ACI318 142 Ch. 17 – Anchoring to Concrete Scope • Headed studs and headed bolts • Hooked bolts • Post-installed undercut anchors • Post-installed expansion anchors • Post-installed adhesive anchors
  • 143. WWW.CONCRETE.ORG/ACI318 143 New Content/Design Information • Post-installed screw anchors – pre-qualification per ACI 355.2 • Attachments with shear lugs
  • 144. WWW.CONCRETE.ORG/ACI318 144 Screw Anchors (17.3.4) • For screw anchors satisfying: – hef ≥ 1.5 in. and – 5da ≤ hef ≤ 10da • Manufacturer provides hef, Aef, and pullout strength • Concrete breakout evaluated similar to other anchors – 17.6.2 in tension – 17.7.2 in shear
  • 145. WWW.CONCRETE.ORG/ACI318 145 Minimum Spacing (17.9.2a) • Screw anchor spacing limited per Table 17.9.2a Spacing > 0.6hef and 6da Greatest of: (a) Cover (b) 2 x max. agg. (c) 6da or per ACI 355.2
  • 146. WWW.CONCRETE.ORG/ACI318 146 17.1.6 – Reinforcement used as anchorage Check anchorage for bars developed per Ch. 25 • Check concrete breakout in tension (and maybe shear) • Greater development length should be considered
  • 147. WWW.CONCRETE.ORG/ACI318 147 17.1.6 – Reinforcement used as anchorage • Straight bars behave like adhesive anchors • Hooked and headed bars behave like headed anchors • Anchor reinforcement may be an alternative
  • 148. WWW.CONCRETE.ORG/ACI318 148 Shear Lugs (17.11.1) Shear lugs are fabricated from: • Rectangular plates or • Steel shapes composed of plate- like elements, welded to an attachment base plate
  • 149. WWW.CONCRETE.ORG/ACI318 149 Shear Lugs (17.11.1) • Minimum four anchors • Anchors do not need to resist shear forces if not welded • Anchors welded to steel plate carry portion of total shear load
  • 150. WWW.CONCRETE.ORG/ACI318 150 Shear Lug Detailing (17.11.1.1.8) • Anchors in tension, satisfy both (a) and (b): (a) hef/hsl ≥ 2.5 (b) hef/csl ≥ 2.5
  • 151. WWW.CONCRETE.ORG/ACI318 151 Shear Lug Detailing (17.11.1.2) • Steel plate to have 1 in. dia. (min.) hole • Single plate – one on each side • Cross / cruciform plate - one each quadrant • More vent holes are not detrimental
  • 152. WWW.CONCRETE.ORG/ACI318 152 Shear Lug Overturning (17.11.1.1.9) hef hsl tsl Csl
  • 153. WWW.CONCRETE.ORG/ACI318 153 Bearing (17.11.2) • f Vbrg,sl ≥ Vu • Where f = 0.65 Source: Peter Carrato
  • 154. WWW.CONCRETE.ORG/ACI318 154 Bearing Strength (17.11.2) • Bearing strength: • Aef,sl is the surface perpendicular to the applied shear: 2tsl 2tsl 2tsl ' , , , 1.7 brg sl c ef sl brg sl V f A =  tsl
  • 156. WWW.CONCRETE.ORG/ACI318 156 Stiffeners • 17.11.2.3 - If used, the length of shear lug stiffeners in the direction of the shear load shall not be less than 0.5hsl 0.5hsl hsl Shear lug Stiffener T/Conc
  • 157. WWW.CONCRETE.ORG/ACI318 157 17.11.2.2 – Bearing factor Tension load • Ψbrg,sl = 1 + Pu/(nNsa) ≤ 1.0 • Pu – negative for tension • n – number of anchors in tension • Nsa – Nominal tension strength of a single anchor No applied axial load: Ψbrg,st = 1 Compression load: Ψbrg,sl = 1 + 4Pu/(Abpfc’) ≤ 2.0 • Pu – positive for compression ' , , , 1.7 brg sl brg sl c ef sl V f A  =
  • 158. WWW.CONCRETE.ORG/ACI318 158 17.11.2.4 – Bearing for Multiple Shear Lugs • If τ ≤ 0.2 f’c, use bearing from both lugs A1 A2 τ = Vu/(A1 + A2)
  • 159. WWW.CONCRETE.ORG/ACI318 159 17.11.3 – Concrete breakout strength of shear lugs • Nominal concrete breakout strength of a shear lug – Use Anchor provisions of 17.7.2 • Where: , , , , Vc cb sl ed V c V h V b Vco A V V A =    ' 1.5 1 9 ( ) b a c a V f c = 
  • 160. WWW.CONCRETE.ORG/ACI318 160 17.11.3.4 – Breakout for Multiple Shear Lugs • Determine for each potential breakout surface • Commentary directs to Fig. R17.7.2.1b
  • 161. WWW.CONCRETE.ORG/ACI318 161 Shear Lug Example • Reinforced Concrete Design Manual • Anchorage example 20 • See handout DV = 60 Kips LV = 75 Kips WV = ±170 Kips DH = ± 8 Kips LH = ± 9 Kips WH = ±12 Kips
  • 162. WWW.CONCRETE.ORG/ACI318 162 Shear Lug Example • Can we replace upper ties with shear lug? – Remove shear from anchor rod design – May reduce bolt size/length – Simplify design
  • 163. WWW.CONCRETE.ORG/ACI318 163 Size Shear Lug • Size shear lug so entire lug is effective – tsl = 1.5 in. – Width = 1.5 in. + 4(1.5 in.) = 7.5 in. – Depth = 3 in. + 3 in. = 6 in. – Stiffeners at least 0.5 hsl or 1.5 in. wide T/Conc V 3 in. 1.5 in.
  • 164. WWW.CONCRETE.ORG/ACI318 164 Shear Lug Example • Check anchor rod depth (only required if attachment has tension) – hef/hsl ≥ 2.5 → hef = 2.5 (3 in.) = 7.5 in. – hef/csl ≥ 2.5 → hef = 2.5 (8 in.) = 20 in. <= controls – Increase rod embedment from 18 in. to 20 in. 16” hsl = 3” csl = 8” hef
  • 165. WWW.CONCRETE.ORG/ACI318 165 Strength Checks • Vua,g ≤ f Vbrg,sl (bearing) ≤ f Vcb,sl (concrete breakout) • f = 0.65
  • 166. WWW.CONCRETE.ORG/ACI318 166 Bearing Strength Check • Vua,g ≤ f Vbrg,sl (bearing) – Vua,g = 30 kip – Vbrg,sl = 1.7 f’c Aef,sl Ψbrg,sl • For tension on attachment, bearing is reduced – Ψbrg,sl = 1+Pu/(nNsa) – = 1+(-116 kip)/(4 rods(72.7 kip/rod))= 0.601 – Vbrg,sl = 1.7 (4500 psi)(7.5 in.)(3 in.)(0.601) = 103 kip • f Vbrg,sl = 0.65 (103 kip) = 67 kip > 30 kip OK 1.7 f’c V
  • 167. WWW.CONCRETE.ORG/ACI318 167 Concrete Breakout Strength Check • Vua,g ≤ f Vcb,sl (concrete breakout) • Vcb,sl = (AVc/AVc0) Ψed,V Ψc,V Ψh,V Vb – AVc = [3” + 1.5 (32” -1.5”)/2](32”)-(3”)(7.5”) = 805 in.2 32 in. 32 in. 3 in. 22.9 in. ca1 = 15.25 in. V
  • 168. WWW.CONCRETE.ORG/ACI318 168 Concrete Breakout Strength Check • Vcb,sl = (AVc/AVc0) Ψed,V Ψc,V Ψh,V Vb – AVc0 = 4.5 ca1 2 = 4.5(15.25“)2 = 1047 in.2 32 in. ca1 = 15.25 in. 1.5 ca1 1.5 ca1
  • 169. WWW.CONCRETE.ORG/ACI318 169 Concrete Breakout Strength Check • Vcb,sl = (AVc/AVc0) Ψed,V Ψc,V Ψh,V Vb – Ψed,V = edge effect modification factor = 0.7 + 0.3ca2/(1.5ca1) = 0.7+0.3(12.25”)/(1.5(15.25”))=0.861 32 in. ca1 = 15.25 in. ca2 = 12.25 in.
  • 170. WWW.CONCRETE.ORG/ACI318 170 Concrete Breakout Strength Check • Vcb,sl = (AVc/AVc0) Ψed,V Ψc,V Ψh,V Vb – Ψc,V = concrete cracking modification factor – Assume cracking and No. 4 ties between lug and edge (see Table 17.7.2.5.1) – Ψc,V = 1.2 – Ψh,V = member thickness modification factor =1.0 (depth > 1.5 ca1) – Vb = 9λaf’c(ca1)1.5 = 9(1)(4500 psi)(15.25”)1.5 = 36,000 lb
  • 171. WWW.CONCRETE.ORG/ACI318 171 Concrete Breakout Strength Check • Vcb,sl = (AVc/AVc0) Ψed,V Ψc,V Ψh,V Vb = (805 in.2/1047 in.2)(0.861)(1.2)(1.0)(36 kip) = 28.6 kip • f Vcb,sl = 0.65(28.6 kip) = 18.6 kip < 30 kip NG
  • 172. WWW.CONCRETE.ORG/ACI318 172 Shear parallel to an edge or at a corner • Shear parallel to an edge – 17.11.3.2 → 17.7.2.1(c) • Shear at a corner – 17.11.3.3 → 17.7.2.1(d)
  • 173. WWW.CONCRETE.ORG/ACI318 173 Summary • f Vcb,sl = 18.6 kip < 30 kip  anchor reinforcement required • From example: – all 4 rods resisting and supplementary reinforcement → f Vcbg = 29.4 kip – back 2 rods resisting and supplementary reinforcement → f Vcb,sl = 21.7 kip • Shear lugs not helpful for breakout • Helpful when shear in rods is controlling
  • 174. WWW.CONCRETE.ORG/ACI318 174 Changes to the Concrete Design Standard ACI 318-19 Seismic Design Philosophy
  • 175. WWW.CONCRETE.ORG/ACI318 175 Seismic • Both concrete and reinforcement are permitted to respond in the inelastic range • This is consistent with the strength design approach adopted throughout the Code
  • 176. WWW.CONCRETE.ORG/ACI318 176 Seismic – Ω, Cd, and R Factors (ASCE 7)
  • 177. WWW.CONCRETE.ORG/ACI318 177 1 Parameter in ASCE 7-16 Table 12.2-1 Example Seismic Force Resisting System Special reinforced concrete shear walls (building frame system) ASCE 7 Section Where Detailing Requirements Are Specified ASCE 7 Section 14.2 “Concrete” Response Modification Coefficient, R 6 Overstrength Factor, Ω0 2.5 Deflection Amplification Factor, Cd 5 Structural System Limitations, Including Structural Height Limits SDC B No limit SDC CNo limit SDC D160 ft SDC E 160 ft SDC F 100 ft Seismic – Parameters
  • 178. WWW.CONCRETE.ORG/ACI318 178 Seismic • Controlled inelastic action is permitted at pre- determined locations, called plastic hinges • Typical plastic hinge locations are at the ends of beams in moment frames, and at the bases of shear walls
  • 179. WWW.CONCRETE.ORG/ACI318 179 Seismic • Prescriptive rules for detailing of reinforcement are enforced, creating robust plastic hinges • Plastic hinging reduces the stiffness of the structure, which lengthens the period; and plastic hinges dissipate earthquake energy
  • 180. WWW.CONCRETE.ORG/ACI318 180 Changes to the Concrete Design Standard ACI 318-19 Special Moment Frames
  • 181. WWW.CONCRETE.ORG/ACI318 181 18.6.3.1 and 18.8.2.3—Special moment frame beams (and joints) • Longitudinal Reinforcement hc hb 𝑀𝑛2 + ≥ 𝑀𝑛2 − 2 𝑀𝑛2 − ≥ 2ℎ𝑏 𝑀𝑛1 + ≥ 𝑀𝑛1 − 2 𝑀𝑛1 − @ interior joints,𝑑𝑏 ≤ 𝑀𝑛 + 𝑜𝑟 𝑀𝑛 − at any section ≥ max 𝑀𝑛 at either joint 4 0.025𝑏𝑤𝑑 (Gr 60) 𝟎. 𝟎𝟐𝟎𝒃𝒘𝒅 (Gr 80) hc/20 (Gr 60) hc/26 (Gr 80) ≥ 𝐴𝑠 − or 𝐴𝑠 + ≥ max 200𝑏𝑤 𝑑 𝑓𝑦 3 𝑓𝑐 ′ 𝑏𝑤𝑑 𝑓𝑦 min 2 bars continuous a) b) c)
  • 182. WWW.CONCRETE.ORG/ACI318 182 18.6.4.4—Special moment frame beams • Transverse reinforcement hb Stirrups with seismic hooks Hoops along 2hb Hoops @ lap splice d/4 6 in. 6db (Gr 60), 5db (Gr 80) s ≤ d/4 4 in. s ≤ 𝑠 ≤ 𝑑/2 hc ≤ 2 𝑖𝑛.
  • 183. WWW.CONCRETE.ORG/ACI318 183 18.4.3.3—Columns in intermediate moment frames • Hoops or spirals required • First hoop at so/2 from the joint face o ℓu /6 clear span [c1, c2]max 18 in. so ℓo ℓo 8db (Gr 60) and 8 in. 6db (Gr 80) and 6 in. 1/2[c1, c2]min so ≤ ℓo ≥
  • 184. WWW.CONCRETE.ORG/ACI318 184 18.7.2, 18.7.3—Columns of SMF Strong Column/Weak Beam • Column dimensional limits, 18.7.2 – Smallest dimension ≥ 12 in. – Short side/long side ≥ 0.4 • Flexural strength check, 18.7.3.2 – ∑Mnc ≥ (6/5)∑Mnb, – Exception, 18.7.3.1 • Ignore check at top story where 𝑷𝒖 ≤ 𝟎. 𝟏𝑨𝒈𝒇𝒄 ′ Beam Column Mnb Mnb Mnc Mnc
  • 185. WWW.CONCRETE.ORG/ACI318 185 18.7.4.3—Bond splitting failure in columns Splitting can be controlled by restricting the longitudinal bar size to meet 1.25ℓd ≤ ℓu/2 Woodward and Jirsa(1984) Umehara and Jirsa (1982) Sokoli and Ghannoum (2016)
  • 186. WWW.CONCRETE.ORG/ACI318 186 18.7.5.3 and 18.7.5.5—Columns in special moment frames • First hoop at so/2 from the joint face so ℓo ℓu/6 clear span [c1, c2]max 18 in. s 6db,min (Gr 60), 5db,min (Gr 80) 6 in. ℓo so 6db,min (Gr 60), 5db,min (Gr 80) ¼[c1, c2]min 4 + 14−ℎ𝑥 3 , ≤ 6 in.; ≥ 4 in. ℓo ≥ s ≤ so ≤
  • 187. WWW.CONCRETE.ORG/ACI318 187 18.14.3.2—Nonparticipating columns Clarification • Transverse spacing over full length is the lesser of – 6db of the smallest long. bar – 6 in. • Transverse detailing along ℓo is according to 18.7.5.2 (a) through (e) – 18.7.5.2(f) is not required ℓo ℓo
  • 188. WWW.CONCRETE.ORG/ACI318 188 Changes to the Concrete Design Standard ACI 318-19 Special Structural Walls
  • 189. WWW.CONCRETE.ORG/ACI318 189 Ch. 18.10—Special structural wall • Cutoff of longitudinal bars in special boundary elements • Reinforcement ratios at ends of walls • Shear demand • Drift capacity check • Detailing in special boundary elements • Ductile coupled walls Shear wall Pu Mu Vu ℓw hw Special boundary element δu
  • 190. WWW.CONCRETE.ORG/ACI318 190 18.10.2.3(a)—Longitudinal bars • Previously, – tension (vertical boundary) reinforcement in special structural walls to extend 0.8ℓw beyond the point at which it is no longer required to resist flexure • Overly conservative – This was an approximation of d – Similar to beams which extend d, 12db and ℓn/16 – Actual behavior is different
  • 191. WWW.CONCRETE.ORG/ACI318 191 18.10.2.3(a)—Longitudinal bars (a) Except at the top of a wall, longitudinal reinforcement shall extend at least 12 ft above the point at which it is no longer required to resist flexure but need not extend more than ℓd above the next floor level. ≥ 12 ft ℓd Bars “a” no longer required Bars “a” Floor level Floor level
  • 192. WWW.CONCRETE.ORG/ACI318 192 18.10.2.3(c)—Longitudinal bars • Lap splices not permitted over hsx above (20 ft, max) and ℓd below critical sections
  • 193. WWW.CONCRETE.ORG/ACI318 193 18.10.2.4—Longitudinal reinforcement ratio at ends of walls hw/ℓw ≥ 2.0 • Failures in Chile and New Zealand • 1 or 2 large cracks • Minor secondary cracks Crack patterns for walls with fixed minimum longitudinal reinforcementcontentof 0.25% (Lu et al. 2017)
  • 194. WWW.CONCRETE.ORG/ACI318 194 18.10.2.4—Longitudinal reinforcement ratio at ends of walls New ratio • Many well distributed cracks • Flexure yielding over length ' 6 c y f f  = Crack patterns for walls with ρ according to equation (Lu et al. 2017)
  • 195. WWW.CONCRETE.ORG/ACI318 195 18.10.2.4—Longitudinal reinforcement ratio at ends of walls Bar Cutoff • Mu/2Vu similar to wall with full reinforcement • Mu/3Vu good distribution • Mu/4Vu significant strain above cut off Mu/2Vu Mu/3Vu Mu/4Vu
  • 197. WWW.CONCRETE.ORG/ACI318 197 18.10.2.4—Longitudinal reinforcement ratio at ends of walls Walls or wall piers with hw/ℓw ≥ 2.0 must satisfy: a) Long. reinf. ratio within 0.15 ℓw and minimum b) Long. reinf. extends above and below critical section the greater of ℓw and Mu/3Vu c) Max. 50% of reinf. terminated at one section ' 6 c y f f  =
  • 198. WWW.CONCRETE.ORG/ACI318 198 18.10.3—Shear amplification • Similar to approach in New Zealand Standard, NZS 3101
  • 199. WWW.CONCRETE.ORG/ACI318 199 18.10.3—Shear amplification 18.10.3.1 The design shear force Ve shall be calculated by: 3 e v v u u V V V =    Vu = the shear force obtained from code lateral load analysis with factored load combinations Ωv = overstrength factor equal to the ratio of Mpr/Mu at the wall critical section. v = factor to account for dynamic shear amplification. Gogus and Wallace, 2015
  • 200. WWW.CONCRETE.ORG/ACI318 200 18.10.3—Shear amplification 18.10.3.1.2 – Calculation of Ωv Table 18.10.3.1.2—Overstrengthfactor Ωv at critical section [1] For the load combination producing the largest value of Ωv. [2] Unless a more detailed analysis demonstrated a smaller value, but not less than 1.0. Condition Ωv hwcs/ℓw > 1.5 Greater of Mpr/Mu [1] 1.5[2] hwcs/ℓw ≤ 1.5 1.0
  • 201. WWW.CONCRETE.ORG/ACI318 201 18.10.3—Shear Amplification 18.10.3.1.3 – Calculation of ωv hwcs/ℓw < 2.0 ➔ ωv = 1.0 hwcs/ℓw ≥ 2.0 ➔ ωv = 0.9 + ns/10 for ns ≤ 6 ωv = 1.3 + ns/30 ≤ 1.8 for ns > 6 where ns ≥ 0.007hwcs ns = number of stories above the critical section.
  • 202. WWW.CONCRETE.ORG/ACI318 202 18.10.4.1—Shear strength, Vn No Change • The code shows change bars at this location; rewording only • Shear calculations for Chapters 11 and 18 were harmonized • 11.5.4.3 is now similar to 18.10.4.1
  • 203. WWW.CONCRETE.ORG/ACI318 203 18.10.4.4—Clarification of Acv Acv = gross area of concrete section bounded by web thickness and length of section in the direction of shear force considered in the case of walls, and gross area of concrete section in the case of diaphragms. Gross area is total area of the defined section minus area of any openings. 1 2 3 Acv wall = Acw1+Acw2+Acw3 Acw2 Vertical wall segments
  • 204. WWW.CONCRETE.ORG/ACI318 204 18.10.6.2—Displacement based approach Boundary elements of special structural walls: • Walls or wall piers with hwcs/ℓw ≥ 2.0 • Continuous – Uniform for full height • Single critical (yielding) section – Plastic hinge Continuous Single critical section
  • 205. WWW.CONCRETE.ORG/ACI318 205 18.10.6.2—Displacement based approach (a) Compression zone with special boundary elements required if: • c = [Pu, fMn]max in direction of design displacement du and • du/hwcs ≥ 0.005 1.5 600 u w wcs h c d  Single critical section hwcs du Extreme compression fiber
  • 206. WWW.CONCRETE.ORG/ACI318 206 18.10.6.2—Displacement based approach (b) Boundary elements req’d, then (i) and either (ii) or (iii) i. Transv. reinf. extends above and below critical section [ℓw, Mu/4Vu]max ii. iii. dc/hwcs ≥ 1.5 du / hwcs , where ' 1 1 4 0.015 100 50 8 c w e wcs c cv c V h b b f A   d      = − −            0.025 w b c  Errata
  • 207. WWW.CONCRETE.ORG/ACI318 207 18.10.6.4—Special Boundary Elements • Single perimeter hoops with 90-135 or 135- 135 degree crossties, inadequate
  • 208. WWW.CONCRETE.ORG/ACI318 208 18.10.6.4(f)—Special Boundary Elements Longitudinal bars supported by a seismic hook or corner of a hoop
  • 209. WWW.CONCRETE.ORG/ACI318 209 18.10.6.4(h)—Special Boundary Elements • Concrete within the thickness of the floor system at the special boundary element location shall have specified compressive strength at least 0.7 times f′ c of the wall.
  • 210. WWW.CONCRETE.ORG/ACI318 210 18.10.6.4(i)—Special Boundary Elements • 18.10.6.4(i) – for a distance specified in 18.10.6.2(b) above and below the critical section, web vertical reinforcement shall have lateral support – crossties vertical spacing, sv ≤ 12 in.
  • 211. WWW.CONCRETE.ORG/ACI318 211 18.10.6.5(b)—If the maximum longitudinal  at the wall boundary exceeds 400/fy Grade of primary flexural reinforcing bar Transverse reinforcement required Vertical spacing of transverse reinforcement1 60 Within the greater of ℓw and Mu/4Vu aboveand below critical sections2 Lesser of: 6 db 6 in. Other locations Lesser of: 8 db 8 in. 80 Within the greater of ℓw and Mu/4Vu aboveand below critical sections2 Lesser of: 5 db 6 in. Other locations Lesser of: 6 db 6 in. 100 Within the greater of ℓw and Mu/4Vu aboveand below critical sections2 Lesser of: 4db 6 in. Other locations Lesser of: 6db 6 in. Table 18.10.6.5b—Maximum vertical spacing of transverse reinforcement at wall boundary
  • 212. WWW.CONCRETE.ORG/ACI318 212 18.10.9—Ductile Coupled Walls Issues preventing ductile behavior • Inadequate quantity or distribution of qualifying coupling beams • Presence of squat walls causes the primary mechanism to be shear and/or strut-and-tie failure in walls • Coupling beams are inadequately developed to provide full energy dissipation ℓw ℓw ℓn hwcs h
  • 213. WWW.CONCRETE.ORG/ACI318 213 18.10.9—Ductile Coupled Walls • Individual walls satisfy – hwcs/ℓw ≥ 2 • All coupling beams must satisfy: – ℓn/h ≥ 2 at all levels – ℓn/h ≤ 5 at a floor level in at least 90% of the levels of the building – Development into adjacent wall segments, 1.25fy (18.10.2.5) ℓw ℓw ℓn hwcs h
  • 214. WWW.CONCRETE.ORG/ACI318 214 Changes to the Concrete Design Standard ACI 318-19 Foundations
  • 215. WWW.CONCRETE.ORG/ACI318 215 18.13.4—Foundation seismic ties SDC C through F • Seismic ties or by other means SDC D, E, or F, with Site Class E or F • Seismic ties required Other means, 18.13.4.3 • Reinforced concrete beams within the slab-on- ground • Reinforced concrete slabs-on-ground • Confinement by competent rock, hard cohesive soils, or very dense granular soils • Other means approved by the building official
  • 216. WWW.CONCRETE.ORG/ACI318 216 18.13.4.3—Seismic ties Minimum tensile and compressive force in tie • Load from pile cap or column – Largest at either end • 0.1SDS x Column factored dead and factored live load Tie force Column load
  • 217. WWW.CONCRETE.ORG/ACI318 217 18.13.5—Deep foundations • (a) Uncased CIP concrete drilled or augered piles • (b) Metal cased concrete piles • (c) Concrete filled pipe piles • (d) Precast concrete piles
  • 218. WWW.CONCRETE.ORG/ACI318 218 18.13.5.2—Deep foundations SDC C through F • Resisting tension loads → Continuous longitudinal reinforcement over full length to resist design tension Source: Ground Developments
  • 219. WWW.CONCRETE.ORG/ACI318 219 18.13.5.3—Deep foundations SDC C through F • Transverse and longitudinal reinforcement to extend: – Over entire unsupported length in air, water, or loose soil not laterally supported Pile cap
  • 220. WWW.CONCRETE.ORG/ACI318 220 18.13.5.4 and 18.13.5.5—Deep foundations SDC C through F • Hoops, spirals or ties terminate in seismic hooks SDC D, E, or F, with Site Class E or F • Transv. reinf. per column req. within seven member diameter • ASCE 7, soil strata Soft strata Hard strata D 7D 7D
  • 221. WWW.CONCRETE.ORG/ACI318 221 18.13.5.6—Deep foundations • SDC D, E, or F – Piles, piers, or caissons and foundation ties supporting one- and two-story stud bearing walls – Exempt from transv. reinf. of 18.13.5.3 through 18.13.5.5 Errata
  • 222. WWW.CONCRETE.ORG/ACI318 222 18.13.5.7—Uncased cast-in place piles Pile cap SDC C 1/3 ℓpile •ℓbar ≥ 10 ft 3dpile Distance to 0.4Mcr > Mu •Transverse confinement zone • 3 dpile from bottom of pile cap • s ≤ 6 in.; 8db long. bar •Extended trans. reinf. • s ≤ 16db long. bar min ≥ 0.0025 ℓ bar Closed ties or spirals≥ No.3 s dpile ℓbar = minimum reinforcedpile length
  • 223. WWW.CONCRETE.ORG/ACI318 223 18.13.5.7—Uncased cast-in place piles Pile cap SDC D, E, and F with Site Class A, B, C, and D 1/2 ℓpile • ℓbar ≥ 10 ft 3dpile Distance to 0.4Mcr > Mu •Transverse confinement zone • 3 dpile from bottom of pile cap • s of 18.7.5.3 • min ≥ 0.06 fc′/fyt •Extended trans. reinf. 12db long. bar s ≤ 0.5dpile 12 in. min ≥ 0.005 ℓ bar Closed ties or spirals ≥ No. 3 (≤ 20 in.) or No. 4 (> 20 in.); 18.7.5.2 s dpile ℓbar = minimum reinforcedpile length
  • 224. WWW.CONCRETE.ORG/ACI318 224 18.13.5.7—Uncased cast-in place piles Pile cap SDC D, E, and F with Site Class E and F •ℓbar Full length of pile (some exceptions) •Transverse confinement zone • 7 dpile from bottom of pile cap • s of 18.7.5.3 • min ≥ 0.06 fc′/fyt •Extended trans. reinf. 12db long. bar s ≤ 0.5dpile 12 in. min ≥ 0.005 ℓ bar Closed ties or spirals ≥ No. 3 (≤ 20 in.) or No. 4 (> 20 in.); 18.7.5.2 s dpile ℓbar = minimum reinforcedpile length
  • 225. WWW.CONCRETE.ORG/ACI318 225 18.13.5.8—Metal cased concrete piles Pile cap SDC C through F •Longitudinal same as uncased piles •Metal casing replaces transverse reinforcement in uncased piles •Extend casing for ℓbar t ≥ 14 gauge ℓ bar dpile
  • 226. WWW.CONCRETE.ORG/ACI318 226 18.13.5.9—Concrete-filled pipe piles Pile cap SDC C through F •min ≥ 0.01 •ℓd,pile ≥ 2ℓpilecap ℓdt,bar Steel pipe 2ℓ pile cap ≥ ℓ d dpile ℓ pile cap
  • 227. WWW.CONCRETE.ORG/ACI318 227 18.13.5.10—Precast nonprestressed piles Pile cap SDC C •ℓbar Full length of pile •Transverse confinement zone • 3 dpile from bottom of pile cap • s ≤ 6 in.; 8db long. bar •Extended trans. reinf. • s ≤ 6 in. min ≥ 0.01 ℓ bar s dpile Closed ties or spirals ≥ No. 3 (≤ 20 in.) or No. 4 (> 20 in.); 18.7.5.2
  • 228. WWW.CONCRETE.ORG/ACI318 228 18.13.5.10—Precast nonprestressed piles Pile cap SDC D, E, and F •Same as SDC C •Satisfy Table 18.13.5.7.1 for SDC D, E, and F min ≥ 0.01 ℓ bar s dpile Closed ties or spirals ≥ No. 3 (≤ 20 in.) or No. 4 (> 20 in.); 18.7.5.2
  • 229. WWW.CONCRETE.ORG/ACI318 229 18.13.5.10—Precast prestressed piles Pile cap SDC C through F •Satisfy 18.13.5.10.4 through 18.13.5.10.6 •Minimum amount and spacing of transverse reinforcement ℓ bar s dpile
  • 230. WWW.CONCRETE.ORG/ACI318 230 18.13.6—Anchorage of piles, piers and caissons SDC C—F • Tension loads: load path to piles, piers, or caissons • Transfer to longitudinal reinforcement in deep foundation Source: Dailycivil Source: Stockqueries
  • 231. WWW.CONCRETE.ORG/ACI318 231 18.13.6—Anchorage of piles, piers and caissons ℓd compr. ℓdt tension Dowel 1.25fy Source: Gayle Johnson 18.13.6.2 SDC C—F • Anchor dowel between piles and pile cap 18.13.6.3 SDC D—F • If tension forces and dowel post- installed in precast pile • Grouting system to develop min. 1.25 fy (shown by test)
  • 232. WWW.CONCRETE.ORG/ACI318 232 21.2.4.3—ϕ, Foundation elements SDC C—F • For foundation elements supporting the primary seismic-force-resisting system • ϕ for shear shall ≤ the least value of – ϕ for shear used for special column – ϕ for shear used for special wall
  • 233. WWW.CONCRETE.ORG/ACI318 233 Changes to the Concrete Design Standard ACI 318-19 High-Strength Reinforcement
  • 234. WWW.CONCRETE.ORG/ACI318 234 Ch. 20 – Yield strength determination • 318-19, 20.2.1.2: Nonprestressed bar yield strength determination: – The yield point by the halt-of-force method – T he offset method, using 0.2 percent offset • 20.2.1.3 – A615 and A706 additional requirements
  • 235. WWW.CONCRETE.ORG/ACI318 235 Ch. 3 – Update of ASTM A615-18e1 • Latest ASTM A615 allows: – Gr. 100 – Bars up to No. 20 • ACI 318-19 allows – No. 18 and smaller – Gr. 80 & 100 with restrictions • No. 20 not acceptable: – Development length – Bar bends
  • 236. WWW.CONCRETE.ORG/ACI318 236 Table 20.2.2.4(a) • Main changes – Gr. 80 – Gr. 100 – Footnotes – Clarifications
  • 237. WWW.CONCRETE.ORG/ACI318 237 Ch. 20 – Steel Reinforcement Properties
  • 238. WWW.CONCRETE.ORG/ACI318 238 Ch. 20 –Seismic Requirements for A615 Gr. 60 • Section 20.2.2.5 specifies – ASTM A706 Gr. 60 allowed – Requirements for ASTM A615, Gr. 60 • Section 20.2.2.5(a) permits ASTM A706 – Grade 60 – Grade 80 – Grade 100 – (as discussed previously)
  • 239. WWW.CONCRETE.ORG/ACI318 239 Ch. 20 –Seismic Requirements for A615 Gr. 60 • Section 20.2.2.5(b) permits ASTM A615 Grade 60 if: – fy,actual ≤ fy + 18,000 psi – Provides adequate ductility (min. ft/fy ≥ 1.25) – Min. fracture elongation in 8 in. (10-14%) – Minimum uniform elongation (6-9%) • Section 20.2.2.5(b) provides the A706 elongation properties
  • 240. WWW.CONCRETE.ORG/ACI318 240 Ch. 20 – Seismic Requirements for A615 • For seismic design ASTM A615 GR. 80 and 100 are not permitted
  • 241. WWW.CONCRETE.ORG/ACI318 241 Ch. 20 – Steel Reinforcement Properties
  • 242. WWW.CONCRETE.ORG/ACI318 242 Ch. 20 – Steel Reinforcement Properties
  • 243. WWW.CONCRETE.ORG/ACI318 243 Ch. 26 – Tolerances for seismic hoops 26.6.2.1(c)
  • 244. WWW.CONCRETE.ORG/ACI318 244 Design limits et ≥ 0.005 et ≥ (ety + 0.003) ACI 318-14 ACI 318-19
  • 245. WWW.CONCRETE.ORG/ACI318 245 Design limits et ≥ (ety + 0.003) ACI 318-19 ACI 318-19 Provisions 7.3.3.1, 8.3.3.1, and 9.3.3.1 require slabs and beams be tension controlled y ty s f E e =
  • 248. WWW.CONCRETE.ORG/ACI318 248 Design limits f’c = 4000 psi f’c = 10,000 psi GR 60 et ≥ 0.0051 1.79% 3.42% GR 80 et ≥ 0.00575 1.24% 2.37% GR 100 et ≥ 0.0065 0.92% 1.75% Reinforcement ratio, tcl y ty s f E e =
  • 249. WWW.CONCRETE.ORG/ACI318 249 Design limits Grade f’c = 4 ksi f’c = 10 ksi 60 1.79% 3.42% 80 1.24% 2.37% 100 0.92% 1.75% 16 x 24 in. beam d = 21 in. f’c = 4000 psi GR 60 As,tcl = 6 in.2 Mn,tcl = 544 ft-kip Reinforcement ratio, tcl Approximately 50% of reinforcement achieved 88% of nominal moment GR 100 As,tcl = 3.1 in.2 Mn,tcl = 479 ft-kip
  • 250. WWW.CONCRETE.ORG/ACI318 250 Changes to the Concrete Design Standard ACI 318-19 Development Length
  • 251. WWW.CONCRETE.ORG/ACI318 251 Development Length • Deformed Bars and Deformed Wires in Tension – Simple modification to 318-14 – Accounts for Grade 80 and 100 • Standard Hooks and Headed Deformed Bars – Substantial changes from 318-14
  • 252. WWW.CONCRETE.ORG/ACI318 252 Development Length • Deformed Bars and Deformed Wires in Tension • Standard Hooks in Tension • Headed Deformed Bars in Tension
  • 253. WWW.CONCRETE.ORG/ACI318 253 Development Length of Deformed Bars and Deformed Wires in Tension Unconfined Test Results ftest = reinforcement stress at the time of failure fcalc = calculated stress by solving ACI 318-14 Equation 25.4.2.3a Confined Test Results
  • 254. WWW.CONCRETE.ORG/ACI318 254 Development Length of Deformed Bars and Deformed Wires in Tension • Modification in simplified provisions of 25.4.2.3 • Ψg : new modification factor based on grade of reinforcement • Modification in Table 25.4.2.3
  • 255. WWW.CONCRETE.ORG/ACI318 255 Development Length of Deformed Bars and Deformed Wires in Tension • Modification in general development length equation 25.4.2.4(a) • Provision 25.4.2.2 Ktr ≥ 0.5db for fy ≥ 80,000 psi , if longitudinal bar spacing < 6 in. Modification factors  : Lightweight t : Casting position e : Epoxy s : Size g : Reinforcementgrade
  • 256. WWW.CONCRETE.ORG/ACI318 256 Development Length of Deformed Bars and Deformed Wires in Tension Modificationfactor Condition Value of factor Lightweightλ Lightweight concrete 0.75 Normalweightconcrete 1.0 Reinforcement gradeg Grade40 or Grade60 1.0 Grade80 1.15 Grade100 1.3 Epoxy[1] e Epoxy-coated or zinc and epoxy dual-coated reinforcement with clear cover less than 3db or clear spacing less than 6db 1.5 Epoxy-coated or zinc and epoxy dual-coated reinforcementfor all other conditions 1.2 Uncoated or zinc-coated (galvanized) reinforcement 1.0 Sizes No. 7 and larger bars 1.0 No. 6 and smaller bars and deformed wires 0.8 Casting position[1] t More than 12 in. of fresh concreteplaced below horizontal reinforcement 1.3 Other 1.0 Table 25.4.2.5—Modification factors for development of deformed bars and deformed wires in tension
  • 257. WWW.CONCRETE.ORG/ACI318 257 Check development length of No. 8 longitudinal bar in a beam. Assume f’c = 4000 psi NWC, Grade 80 reinforcement, 2 in. cover and no epoxy coating. Example—Development Length of Deformed Bars and Deformed Wires in Tension g Grade 40 or Grade 60 1.0 Grade 80 1.15 Grade 100 1.3 From Table 25.4.2.5 confinement term (cb + Ktr)/db = 2.5 (using the upper limit)  = 1.0 e = 1.0 s = 1.0 t = 1.0 te = 1.0 < 1.7 g = 1.15
  • 258. WWW.CONCRETE.ORG/ACI318 258 Substituting in Eq. 25.4.2.4a: Example—Development Length of Deformed Bars and Deformed Wires in Tension ℓ𝑑 = 3 40 80,000 1 4000 1 1 1 1.15 2.5 (1.0) = 43.6 in. ℓ𝑑 = 3 40 60,000 1 4000 1 1 1 1 2.5 (1.0) = 28.5 in. In comparison a similar bar with Grade 60 reinforcement; Increase of ~ 50 percent in development length for Grade 80
  • 259. WWW.CONCRETE.ORG/ACI318 259 Development Length of Deformed Bars and Deformed Wires in Tension • Differences in higher grade steel for 4000 psi concrete Grade g ℓd,Gr#/ℓd,Gr60 60 1.0 1.0 80 1.15 1.5 100 1.3 2.2
  • 260. WWW.CONCRETE.ORG/ACI318 260 Development Length • Deformed Bars and Deformed Wires in Tension • Standard Hooks in Tension • Headed Deformed Bars in Tension
  • 261. WWW.CONCRETE.ORG/ACI318 261 Development Length of Std. Hooks in Tension • Failure Modes • Mostly, front and side failures – Dominant front failure (pullout and blowout) – Blowouts were more sudden in nature Front Pullout Front Blowout Side splitting Tail kickout Side blowout
  • 262. WWW.CONCRETE.ORG/ACI318 262 Development Length of Std. Hooks in Tension fsu = stress at anchorage failure for the hooked bar fs,ACI = stress predictedby the ACI development lengthequation Confined Test Results 𝐴𝐶𝐼 318 − 14: ℓ𝑑ℎ = 𝑓 𝑦𝜓𝑒𝝍𝒄𝝍𝒓 50𝜆 𝑓 𝑐 ′ 𝑑𝑏 Unconfined Test Results
  • 263. WWW.CONCRETE.ORG/ACI318 263 Development Length of Std. Hooks in Tension - 25.4.3.1—Development length of standard hooks in tension is the greater of (a) through (c): (a) (b) 8db (c) 6 in - Modification factors 𝝍𝒓 : Confining reinforcement (redefined) 𝝍𝒐 : Location (new) 𝝍𝒄 : Concrete strength (new – used for coverin the past) ACI 318- 14
  • 264. WWW.CONCRETE.ORG/ACI318 264 Development Length of Std. Hooks in Tension Modification factor Condition Value of factor 318-14 Confining reinforcement, r For 90-degree hooks of No. 11 and smaller bars (1) enclosed along ℓdh within ties or stirrups perpendicularto ℓdh at s ≤ 3db, or (2) enclosed along the bar extension beyond hook includingthe bend within ties or stirrups perpendicularto ℓext at s ≤ 3db 0.8 Other 1.0 318-19 Confining reinforcement, r For No.11 and smaller bars with Ath ≥ 0.4Ahs or s ≥ 6db 1.0 Other 1.6 Table 25.4.3.2: Modification factors for development of hooked bars in tension
  • 265. WWW.CONCRETE.ORG/ACI318 265 Development Length of Std. Hooks in Tension 25.4.3.3: • Confining reinforcement (Ath) shall consists of (a) or (b) – (a) Ties or stirrups that enclose the hook and satisfy 25.3.2 – (b) Other reinf. that extends at least 0.75ℓdh from the enclosed hook in the direction of the bar in tension and in accordance with (1) or (2) • parallel or perpendicular (Fig. R25.4.3.3a and Fig. R25.4.3.3b) Fig. R25.4.3.3a Fig. R25.4.3.3b
  • 266. WWW.CONCRETE.ORG/ACI318 266 Development Length of Std. Hooks in Tension • (1) Confining reinforcement placed parallel to the bar (Typical in beam-columnjoint) – Two or more ties or stirrups parallel to ℓdh enclosing the hooks – Evenly distributed with a center-to-center spacing ≤ 8db – within 15db of the centerline of the straight portion of the hooked bars Fig. R25.4.3.3a
  • 267. WWW.CONCRETE.ORG/ACI318 267 Development Length of Std. Hooks in Tension • (2) Confining reinforcement placed perpendicular to the bar – Two or more ties or stirrups perpendicular to ℓdh enclosing the hooks – Evenly distributed with a center-to-center spacing ≤ 8db Fig. R25.4.3.3b
  • 268. WWW.CONCRETE.ORG/ACI318 268 Development Length of Std. Hooks in Tension Modification factor Condition Value of factor 318-14 Cover ψc For No. 11 bar and smaller hooks with side cover (normal to planeof hook) ≥ 2-1/2 in. and for 90-degree hook with cover on bar extension beyond hook ≥ 2 in. 0.7 Other 1.0 318-19 Location, o For No.11 and smaller diameter hooked bars (1) Terminating inside column core w/ side cover normal to plane of hook ≥ 2.5 in., or (2) with side cover normal to plane of hook ≥ 6db 1.0 Other 1.25 Table 25.4.3.2: Modification factors for development of hooked bars in tension
  • 269. WWW.CONCRETE.ORG/ACI318 269 Development Length of Std. Hooks in Tension Modification factor Condition Value of factor Concrete strength, c For f’c < 6000 psi f’c/15,000 +0.6 For f’c ≥ 6000 psi 1.0 Table 25.4.3.2: Modificationfactors for development of hooked bars in tension
  • 270. WWW.CONCRETE.ORG/ACI318 270 Example—Development Length of Std Hook Check hooked bar anchorage of longitudinal beam reinforcement, 3-No. 10 bars in a 20 x 20 in. exterior column. Assume f’c = 4000 psi NWC, Grade 60 reinforcement, 2.5 in. cover normal to plane of hook, and no epoxy coating. Steel confinement is provided such that Ath = 0.4 Ahs.  = 1.0 e = 1.0 r = 1.0 o = 1.0 c = f’c/15,000 + 0.6 = 4,000/15,000 + 0.6 = 0.87
  • 271. WWW.CONCRETE.ORG/ACI318 271 Example—Development Length of Std Hook Substituting in the equation: ℓdh = 21.5 in. > 20 in. NG In comparison to the equation in 318-14: ℓdh(318-14) = 16.9 in. < 20 in. OK ℓ𝑑ℎ = 60,000 1.0 1.0 1.0 0.87 55 1.0 4,000 (1.27)1.5 e = 1.0 c = 0.7 (2 -1/2 in. side cover and 2 in. back cover) r = 1.0
  • 272. WWW.CONCRETE.ORG/ACI318 272 Example—Development Length of Std Hook 0 5 10 15 20 25 30 0.5 0.7 0.9 1.1 1.3 1.5 Development Length, ℓ dh (i n.) Bar Diameter, in. Standard Hooked Bars; f'c = 4000 psi 318-14 318-19 0.00 5.00 10.00 15.00 20.00 25.00 0.5 0.7 0.9 1.1 1.3 1.5 Development Length, ℓ dh (i n.) Bardiameter;in. Standard Hooked Bars; f'c =6000 psi 318-14 318-19
  • 273. WWW.CONCRETE.ORG/ACI318 273 Development Length • Deformed Bars and Deformed Wires in Tension • Standard Hooks in Tension • Headed Deformed Bars in Tension
  • 274. WWW.CONCRETE.ORG/ACI318 274 Development Length of Headed Deformed Bars in Tension 25.4.4.1 Use of a head to develop a deformed bar in tension shall be permitted if conditions (a) through (f) are satisfied: (a)Bar shall conform to 20.2.1.6 (b)Bar fy shall not exceed 60,000 psi (b) Bar size shall not exceed No. 11 (c) Net bearing area of head Abrg shall be at least 4Ab (d) Concrete shall be normalweight (e) Clear coverfor bar shall be at least 2db (f) Center-to-center spacing between bars shall be at least 3db
  • 275. WWW.CONCRETE.ORG/ACI318 275 Development Length of Headed Deformed Bars in Tension fsu = stress at anchorage failure for the hooked bar fs,ACI = stress predictedby the ACI development lengthequation 𝐴𝐶𝐼 318 − 14: ℓ𝑑𝑡 = 0.016𝑓𝑦𝜓𝑒 𝑓 𝑐 ′ 𝑑𝑏 Unconfined Test Results Confined Test Results
  • 276. WWW.CONCRETE.ORG/ACI318 276 Development Length of Headed Deformed Bars in Tension - 25.4.4.2: Development length ℓdt for headed deformed bars in tension shall be the longest of (a) through (c): (a) (b) 8db (c) 6 in. - Modification factors 𝝍𝒑 : Parallel tie reinforcement 𝝍𝒐 : Location 𝝍𝒄 : Concrete strength ACI 318- 14 f’ c ≤ 6000 psi
  • 277. WWW.CONCRETE.ORG/ACI318 277 Development length of Headed Deformed Bars in Tension Modification factor Condition Value of factor Parallel tie reinforcement, p For No.11 and smaller bars with Att ≥ 0.3Ahs or s ≥ 6db 1.0 Other 1.6 Location, o For headed bars (1) Terminating inside column core w/ side cover to bar ≥ 2.5 in., or (2) with side cover to bar ≥ 6db 1.0 Others 1.25 Concrete strength, c For f’c < 6000 psi f’c/15,000+0.6 For f’c ≥ 6000 psi 1.0 Table 25.4.4.3—Modification factors for development of headed bars in tension
  • 278. WWW.CONCRETE.ORG/ACI318 278 Development Length of Headed Deformed Bars in Tension • Parallel tie reinforcement (Att) – locate within 8db of the centerline of the headed bar towardthe middleof the joint
  • 279. WWW.CONCRETE.ORG/ACI318 279 Example—Development Length of Headed Deformed Bars in Tension Check development length of No. 9 longitudinal bar in a beam. Assume f’c = 4000 psi NWC, Grade 60 reinforcement, 2.5 in. cover, and no epoxy coating. Steel confinement is provided such that Att = 0.3 Ahs. e = 1.0 p = 1.0 o = 1.0 c = f’c/15,000 + 0.6 = 4,000/15,000+0.6 = 0.87
  • 280. WWW.CONCRETE.ORG/ACI318 280 Example—Development Length of Headed Deformed Bars in Tension Substituting in the equation : ℓdt = 13.2 in. ℓ𝑑𝑡 = 60,000 1.0 1.0 1.0 0.87 75 4,000 (1.128)1.5 In comparison to the equation in 318-14: ℓdt(318-14) = 17.1 in. • Decrease in development lengthof headed bars in tension as per 318-19 in this example – No.11 and smaller bars with Att 0.3Ats – bars terminating inside column core with side cover to bar ≥ 2.5 in ℓ𝑑𝑡 = 0.016 1.0 60,000 4,000 (1.128)
  • 281. WWW.CONCRETE.ORG/ACI318 281 Example—Development Length of Headed Deformed Bars in Tension ℓ𝑑𝑡 = 𝑓 𝑦𝜓𝑒𝜓𝑝𝜓𝑜𝜓𝑐 75 𝑓 𝑐 ′ 𝑑𝑏 1.5 ℓ𝑑𝑡 = 0.016𝑓 𝑦𝜓𝑒 𝑓 𝑐 ′ 𝑑𝑏 0 5 10 15 20 25 0.5 0.7 0.9 1.1 1.3 1.5 Development Length, ℓ dt (in.) Bar diameter; in. Headedbars, f'c = 4000 psi, confined 318-14 318-19 0 2 4 6 8 10 12 14 16 0.5 0.7 0.9 1.1 1.3 1.5 Development Length, ℓ dt (in.) Bar diameter; in. Headedbars, f'c = 10,000 psi, confined 318-14 318-19 0 5 10 15 20 25 30 35 0.5 0.7 0.9 1.1 1.3 1.5 Development Length, ℓ dt (in.) Bar diameter; in. Headedbars, f'c = 4000 psi, Unconfined 318-14 318-19
  • 282. WWW.CONCRETE.ORG/ACI318 282 Changes to the Concrete Design Standard ACI 318-19 Shear Modifications
  • 283. WWW.CONCRETE.ORG/ACI318 283 Shear equations change • One-way beam/slab shear – provision 22.5 – Size effect – Reinforcement ratio • Two-way slab shear – provision 22.6 – Size effect – Reinforcement ratio
  • 284. WWW.CONCRETE.ORG/ACI318 284 Why shear equations changed in 318-19 • Reasons for changes – Evidence shows • Size effect • Low w effect • More prevalent – Deeper beams – Deep transfer slabs 4
  • 285. WWW.CONCRETE.ORG/ACI318 285 Other shear changes • Wall shear equations – Chapter 11 now similar to Chapter 18 • Shear leg spacing – Section spacing requirements • Biaxial shear – Engineer must consider • Hanger reinforcement – Commentary suggestion
  • 286. WWW.CONCRETE.ORG/ACI318 286 Changes to the Concrete Design Standard ACI 318-19 One-way Shear Equations
  • 287. WWW.CONCRETE.ORG/ACI318 287 Why one-way shear equations changed in 318-19 • ACI 445, Shear and Torsion – Four databases vetted and checked 7 Beam types in database Number of samples Reinforced concrete w/o min shear reinforcement 784 Reinforced concrete with min. shear reinforcement 170 Prestressed concrete w/o min. shear reinforcement 214 Prestressed concrete with min. shear reinforcement 117 Totalsamples 1285
  • 288. WWW.CONCRETE.ORG/ACI318 288 Why one-way shear equations changed in 318-19 288 Figure: Strength Ratio (Vtest/Vn) that was calculated by 318-14 Simplified d = 10 in. – s, size effect factor Vtest/Vn = 1 ,min v v A A 
  • 289. WWW.CONCRETE.ORG/ACI318 289 Why one-way shear equations changed in 318-19 289 Figure: Strength Ratio (Vtest/Vn) that was calculated by both ACI 318-14 Simplified and Detailed d = 10 in. – s, size effect factor Vtest/Vn = 1 ,min v v A A 
  • 290. WWW.CONCRETE.ORG/ACI318 290 Why one-way shear equations changed in 318-19 290 Figure: Strength Ratio (Vtest/Vn) that was calculated by the Simplified Method of ACI318-19 including size effect Vtest/Vn = 1 0.0018 – min. slab w ,min v v A A  0.015 – w effect
  • 291. WWW.CONCRETE.ORG/ACI318 291 Why one-way shear equations changed in 318-19 291 Figure: Strength Ratio (Vtest/Vn) that was calculated by the Simplified Method of ACI 318-14 d = 10 in. – s, size effect factor Vtest/Vn = 1 ,min v v A A 
  • 292. WWW.CONCRETE.ORG/ACI318 292 Why one-way shear equations changed in 318-19 • Six different proposals considered – Proposals vetted and considered by • ACI 445 • ACI 318 Subcommittee • Public discussion • Concrete International articles • ACI 318 selected one proposal
  • 293. WWW.CONCRETE.ORG/ACI318 293 Initial one-way shear provision: goals • Include nonprestressed and prestressed • Include axial loading and size effect • Include effect of (w) • Continue to be proportional to √f’ c • And simple – Reduce total number of shear equations – Avoid increase in variables – Easy to use
  • 294. WWW.CONCRETE.ORG/ACI318 294 Initial one-way shear provision: issues • Initial proposal had issues – Unified expressions ≠ Vci, Vcw – What happened to “2 √f’ c”???
  • 295. WWW.CONCRETE.ORG/ACI318 295 Initial one-way shear provision: goals • Include nonprestressed and prestressed • Include axial loading and size effect • Include effect of () • Continue to be proportional to √f’ c • And simple
  • 296. WWW.CONCRETE.ORG/ACI318 296 ACI 318-19 New one-way shear equations Table 22.5.5.1 - Vc for nonprestressed members Criteria Vc Av ≥ Av,min Either of: (a) (b) Av < Av,min (c) Notes: 1. Axial load, Nu, is positive for compressionand negative for tension 2. Vc shall not be taken less than zero.
  • 298. WWW.CONCRETE.ORG/ACI318 298 Size effect – what is s? 2 1.0 1 10 s d  =  + Provision 22.5.5.1.3 defines s as:
  • 299. WWW.CONCRETE.ORG/ACI318 299 Size effect – what is s? 0 0.2 0.4 0.6 0.8 1 1.2 0 12 24 36 48 60 72 84 96 108 120 λ s Depth in inches 2 1.0 1 10 s d  =  +
  • 300. WWW.CONCRETE.ORG/ACI318 300 Other limitations for Table 22.5.5.1 • Provision 22.5.5.1.1: – Limits the maximum value of Vc • Provision 22.5.5.1.2: – Limits the maximum value of the Nu/6Ag term ' 5 c c w V f b d   ' 0.05 6 u c g N f A 
  • 301. WWW.CONCRETE.ORG/ACI318 301 9.6.3.1 - Minimum shear reinforcement • ACI 318-14 – Av,min required if Vu > 0.5 fVc • ACI 318-19 – Av,min required if Vu > fλf’ c bwd • Exceptions in Table 9.6.3.1
  • 303. WWW.CONCRETE.ORG/ACI318 303 Examples: SP-17(14) 5.7 One-way slab Example 1 • Span = 14 ft • Live load = 100 psf • Slab = 7 in. thick • f’ c = 5000 psi • No. 5 bars at 12 in. • d~6 in. • b = 12 in. • Av = 0 in.2 • As = 0.31 in.2/ft • Vu= 2.4 kip/ft
  • 304. WWW.CONCRETE.ORG/ACI318 304 Examples: SP-17(14) 5.7 One-way slab Example 1 • SP-17(14) One-way shear calc ACI 318-14 ' 2 (0.75)(2)(1) 5000 (12 .)(6 .) 7.6 2.4 c c c c V f bd V psi in in V kip kip OK f f  f f = = =  
  • 305. WWW.CONCRETE.ORG/ACI318 305 Examples: SP-17(14) 5.7 One-way slab Example 1 • SP-17(14) One-way shear calc ACI 318-19 • Av ≤ Av,min, therefore use Eq. 22.5.5.1(c) ( ) 1 ' 3 1 3 8 ( ) 0.31 0.0043 low (12)(6) (0.75)(8)(1)(1) 0.0043 5000 (12 .)(6 .) 5.0 2.4 c s w c w w c c V f bd V psi in in V kip kip OK f f      f f = = =  = =  
  • 306. WWW.CONCRETE.ORG/ACI318 306 Examples: SP-17(14) 5.7 One-way slab Example 1 • fVc ACI 318-19 < fVc ACI 318-14 – 318-19 for the example given is ~2/3 of ACI 318-14 – Effect of low ρw • Design impact – Thicker slabs if depth was controlled by shear in 318-14. – No change if one-way slab thickness was controlled by flexure or deflections
  • 307. WWW.CONCRETE.ORG/ACI318 307 Examples: Beam discussion • How many engineers design beams without minimum shear reinforcement? • One-way shear capacity impacted: – Av,min not required and Av,min not used
  • 308. WWW.CONCRETE.ORG/ACI318 308 Examples: Beam discussion • Where Av,min installed, Eq. 22.5.5.1(a) Vc= (2√f’ c), – ACI 318-14 ~ ACI 318-19 – Eq. 22.5.5.1(b) of Table 22.5.5.1 permitted • fVc ↑ w > 0.015 • Provisions encourage Av,min
  • 309. WWW.CONCRETE.ORG/ACI318 309 Examples: SP-17(14) 11.6 Foundation Example 1 • ℓ = 12 ft • h = 30 in. • d~25.5 in. • f’ c = 4000 psi • 13-No. 8 bars • b = 12 ft • Av = 0 in.2 • As = 10.27 in.2 • Analysis Vu= 231 kip 3 ft – 0 in.
  • 310. WWW.CONCRETE.ORG/ACI318 310 Examples: SP-17(14) 11.6 Foundation Example 1 • SP-17(14) One-way shear calc ACI 318-14 ' 2 (0.75)(2)(1) 4000 (144 .)(25.5 .) 348 231 c c c c V f bd V psi in in V kip kip OK f f  f f = = =  
  • 311. WWW.CONCRETE.ORG/ACI318 311 Examples: SP-17(14) 11.6 Foundation Example 1 • SP-17(14) One-way shear calc ACI 318-19 • Av ≤ Av,min, Eq. 22.5.5.1(c) • Per ACI 318-19 (13.2.6.2), neglect size effect for: – One-way shallow foundations – Two-way isolated footings – Two-way combined and mat foundations 1 ' 3 8 ( ) c w c V f bd f f   =
  • 312. WWW.CONCRETE.ORG/ACI318 312 Examples: SP-17(14) 11.6 Foundation Example 1 • SP-17(14) One-way shear calc ACI 318-19 • Av ≤ Av,min, Eq. 22.5.5.1(c) ( ) 1 ' 3 2 1 3 8 ( ) 10.27 in. 0.0028 (144 in.)(25.5 in.) (0.75)(8)(1) 0.0028 4000 (144 .)(25.5 .) 196 231 c w c w c c V f bd V psi in in V kip kip NG f f    f f = = = = =  
  • 313. WWW.CONCRETE.ORG/ACI318 313 Examples: SP-17(14) 11.6 Foundation Example 1 • SP-17(14) One-way shear using ACI 318-19 • Av ≤ Av,min, Eq. 22.5.5.1(c) • Per ACI 318-19, 13.2.6.2, neglect size effect • Add 6in. thickness ( ) 1 ' 3 2 1 3 8 ( ) 10.27 in. 0.0023 (144 in.)(31.5 in.) (0.75)(8)(1) 0.0023 4000 psi(144 in.)(31.5 in.) 226 kip 231 kip Say OK? c w c w c c V f bd V V f f    f f = = = = =  
  • 314. WWW.CONCRETE.ORG/ACI318 314 Examples: SP-17(14) 11.6 Foundation Example 1 • Foundation fVc ACI 318-19 < fVc ACI 318-14 – 318-19 for this example given is ~1/2 of ACI 318-14 – Effect of low ρw • Design impact – Increased thickness; or – Increase flexural reinforcement; or – Increase concrete strength; or – Combination
  • 315. WWW.CONCRETE.ORG/ACI318 315 Examples: Grade beam • Infill wall – Vu~1 kip/ft – Vu~8.3 kip ea. end • Grade beam – bw =12 in. – d = 20 in. (h = 24 in.) – f’ c = 4000 psi – ℓ = 20 ft – w = 0.0033 Infill Wall Grade Beam Ftg. Ftg.
  • 316. WWW.CONCRETE.ORG/ACI318 316 Examples: Grade beam • Infill wall – Vu~1 kip/ft – Vu~8.3 kip ea. end • Grade beam – bw =12 in. – d = 20 in. (h = 24 in.) – f’ c = 4000 psi – ℓ = 20 ft – w = 0.0033 • ACI 318-14 • ACI 318-19 ' ,min 2 0.75(2)(1) 4000(12)(20) 22.8 (1/ 2) not required c c w c c u c v V f b d V V kip OK V V A f f  f f f = = =    1 ' 3 1 3 ' ,min 8 ( ) 2 0.82 20 1 10 0.75(8)(0.82)(1)(0.0033) 4000(12)(20) 11.1 11.4 not required c s w c w s c c u c w v V f b d V V kip OK V f b d kip A f f     f f f = = = + = =   = 
  • 317. WWW.CONCRETE.ORG/ACI318 317 Changes to the Concrete Design Standard ACI 318-19 Two-way Shear Equations
  • 318. WWW.CONCRETE.ORG/ACI318 318 Why two-way shear provisions changed in 318-19 • Eqn. developed in 1963 for slabs with t < 5 in. and  > 1% • Two issues similar to one-way shear – Size effect – Low ρ vc Least of (a), (b), and (c): (a) (b) (c) ' 4 c f  ' 4 2 c f   +       ' 2 s c o d f b    +      Table 22.6.5.2 – Calculation of vc for two-way shear
  • 319. WWW.CONCRETE.ORG/ACI318 319 Two-way shear size effect • Table 22.6.5.2—vc for two-way members without shear reinforcement where vc Least of (a), (b), and (c): (a) (b) (c) ' 4 c s f   ' 4 2 c s f   +        ' 2 s s c o d f b     +     2 1 1 10 s d  =  +
  • 320. WWW.CONCRETE.ORG/ACI318 320 Two-way shear low  effect • D, L only, cracking ~2 𝒇𝒄 ′ ; punching 4 𝒇𝒄 ′ • Aggregate interlock • Low  ➔ bar yielding, ↑ rotation, ↑crack size, allows sliding of reinforcement • Punching loads < 4 𝒇𝒄 ′ Source: Performance and design of punching – shearreinforcing system, Ruiz et al, fib 2010
  • 321. WWW.CONCRETE.ORG/ACI318 321 Why two-way shear provisions changed in 318-19: New two-way slab reinforcement limits 8.6.1—Reinforcement limits • As,min ≥ 0.0018Ag • If on the critical section • Then ,min 5 uv slab o s s y v b b A f  f ' 2 uv s c v f  f  
  • 322. WWW.CONCRETE.ORG/ACI318 322 Why two-way shear provisions changed in 318-19: 8.4.2.2.3
  • 324. WWW.CONCRETE.ORG/ACI318 324 bslab is the lesser of: h 1.5h bslab Slab edge 1.5hdrop Table 8.4.2.2.3 h 1.5h hcap 1.5 hcap bslab hdrop 1.5h 1.5 hcap
  • 325. WWW.CONCRETE.ORG/ACI318 325 Changes to the Concrete Design Standard ACI 318-19 Wall Shear Equations
  • 326. WWW.CONCRETE.ORG/ACI318 326 Coordination of Chap. 11 and 18 Wall Shear Eqs. • ACI 318-83 introduced seismic equation – Two wall shear equation forms • Equation forms gave similar results • Committee 318 wanted consistency in form
  • 327. WWW.CONCRETE.ORG/ACI318 327 • Chapter 11: all changes • Chapter 18: no change • 318-14 simplified compression eq. (Table 11.5.4.6) ' 2 v yt n c A f d V f hd s  = + Coordination of Chap. 11 and 18 Wall Shear Eqs.
  • 328. WWW.CONCRETE.ORG/ACI318 328 • 318-19 Eq. 11.5.4.3 • 318-19 Eq. 18.10.4.1 (same as -14) • c Coordination of Chap. 11 and 18 Wall Shear Eqs. ( ) ' n c c t yt cv V f f A    = + ( ) ' n c c t yt cv V f f A    = +
  • 329. WWW.CONCRETE.ORG/ACI318 329 • Impact minor • Similar results 318-14 to 19 • Note use of ℓw in 318-19 vs d in 318-14 – d in 318-14 assumed 0.8 ℓw – Results in a “lower” max Vn: 𝑉 𝑛 = 10 𝑓𝑐 ′ℎ𝑑 (318 − 14) 𝑉 𝑛 = 8 𝑓𝑐 ′ℎℓ𝑤 (318 − 19) = 8 𝑓𝑐 ′𝐴𝑐𝑣 Coordination of Chap. 11 and 18 Wall Shear Eqs.
  • 330. WWW.CONCRETE.ORG/ACI318 330 Changes to the Concrete Design Standard ACI 318-19 Spacing of Shear Reinforcement
  • 331. WWW.CONCRETE.ORG/ACI318 331 Source: Lubell et. al, “Shear ReinforcementSpacing in Wide Members, ACI StructuralJournal2009 Maximum spacing of legs of shear reinforcement
  • 332. WWW.CONCRETE.ORG/ACI318 332 Table 9.7.6.2.2—Maximum spacing of legs of shear reinforcement RequiredVs Maximum s, in. Nonprestressed beam Prestressed beam Along length Across width Along length Across width Lesser of: d/2 d 3h/4 3h/2 24 in. Lesser of d/4 d/2 3h/8 3h/4 12 in. ' 4 c w f b d  ' 4 c w f b d 
  • 333. WWW.CONCRETE.ORG/ACI318 333 Beam stirrup configurationwith three closed stirrups distributedacross the beam width Single U-stirrup (with 135-degree hooks) across the net width of the beam, two identicalU-stirrups (each with 135-degree hooks) distributedacross the beam interior, and a stirrup cap Single U-stirrup across the net width of the beam, two smaller-width U-stirrups nested in the beam interior, and a stirrup cap Maximum spacing of legs of shear reinforcement s maximum = d or d/2 nonprestressed, 3h/2 or 3h/4 prestressed s maximum = d or d/2 nonprestressed, 3h/2 or 3h/4 prestressed s maximum = d or d/2 nonprestressed, 3h/2 or 3h/4 prestressed
  • 334. WWW.CONCRETE.ORG/ACI318 334 Changes to the Concrete Design Standard ACI 318-19 Bi-directional Shear
  • 335. WWW.CONCRETE.ORG/ACI318 335 Interaction of shear forces • Biaxial shear • Symmetrical RC circular sections – fVc equal about any axis – Vu on 2 centroidal axes, Vu = resultant 2 2 , , ( ) ( ) u u x u y v v v = + vu,x vu,y
  • 336. WWW.CONCRETE.ORG/ACI318 336 Interaction of shear forces • Biaxial shear • Rectangular RC sections – fVc differs between axes – Vu on 2 axes, fVc≠ resultant vu,x vu vu,y
  • 337. WWW.CONCRETE.ORG/ACI318 337 Interaction of shear forces • Biaxial shear on non-circular cross section • fVc = Elliptical interaction diagram 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 2 2.5 Vexp(y)/Vpre(y) Vexp(x)/Vpre(x) Interaction Curve N>0 N=0 N<0
  • 338. WWW.CONCRETE.ORG/ACI318 338 Interaction of shear forces • 22.5.1.10 Neglect interaction of shear forces If vu,x/fvn,x ≤ 0.5, or vu,y/fvn,y ≤ 0.5 • 22.5.1.11 requires interaction consideration If vu,x/fvn,x > 0.5, and vu,y/fvn,y > 0.5, then 0 0.5 1 1.5 2 2.5 0 0.5 1 1.5 Vexp(y)/Vpre(y) Vexp(x)/Vpre(x) Interaction Cu N>0 N=0 N<0
  • 339. WWW.CONCRETE.ORG/ACI318 339 Changes to the Concrete Design Standard ACI 318-19 Hanger Reinforcement
  • 340. WWW.CONCRETE.ORG/ACI318 340 Monolithic beam-to-beam joints: Hanger steel • Commentary added: R9.7.6.2 • Hanger reinforcement – Suggested where both the following are true: – Beam depth ≥ 0.5 girder depth – Stress transmitted from beam to girder ≥ 3√f’ c of the beam
  • 342. WWW.CONCRETE.ORG/ACI318 342 Changes to the Concrete Design Standard ACI 318-19 Concrete Durability and Materials
  • 343. WWW.CONCRETE.ORG/ACI318 343 Changes in durability and materials • Changes in material properties (19.2) – Additional minimumf’c requirements – Ec requirements • Changes in durability (19.3) – Calculating chloride ion content – Sulfate exposure class S3 – Water exposure class W – Corrosion exposure class C0 • Changes in material (26.4.1) – Alternative cements – New aggregates • Recycled aggregates • Mineral fillers • Evaluation and acceptance (26.12) – Strength tests • Inspection (26.13)
  • 344. WWW.CONCRETE.ORG/ACI318 344 Table 19.2.1.1 – Additional minimum strength, f’c Structural walls in SDC D, E, and F Min. f’c (psi) Special structural walls with Grade 100 reinforcement 5000 Higher strength concrete used with higher strength steel • Enhances bar anchorage • Reduces neutral axis depth for improved performance
  • 345. WWW.CONCRETE.ORG/ACI318 345 19.2.2.1R Modulus of Elasticity • Ec from Code equations is appropriate for most applications • Large differences for HSC (f′c > 8000 psi), LWC, and mixtures with low coarse of aggregate volume
  • 346. WWW.CONCRETE.ORG/ACI318 346 19.2.2.2 Modulus of Elasticity Ec can be specified based on testing of concrete mixtures: a) Use of specified EC for proportioning concrete mixture b) Test for specified EC c) Test for EC at 28 days or as indicated in construction documents Source: Engineering discoveries
  • 347. WWW.CONCRETE.ORG/ACI318 347 Contract Document Information • Members for which Ec testing of concrete mixtures is required (26.3.1(c)) • Proportioning (26.4.3.1(c)) – Ec is average of 3 cylinders – Cylinders made and cured in the lab – Ec ≥ specified value Source: Engineering Discoveries
  • 348. WWW.CONCRETE.ORG/ACI318 348 Changes in durability and materials • Changes in durability (19.3) – Calculating chloride ion content – Sulfate exposure class S3 – Water exposure class W – Corrosion exposure class C0
  • 349. WWW.CONCRETE.ORG/ACI318 349 Table 19.3.2.1 – Allowable chloride limits • Percent mass of total cementitious materials rather than percent weight of cement Class Max w/cm Min. f’c, psi Maximum water-soluble chloride ion (Cl–) content in concrete, by percent mass of cementitious materials Additional provisions Non- prestressed concrete Prestressed concrete C0 N/A 2500 1.00 0.06 None C1 N/A 2500 0.30 0.06 C2 0.40 5000 0.15 0.06 Cover per 20.5 For calculation, cementitious materials ≤ cement
  • 350. WWW.CONCRETE.ORG/ACI318 350 Determining chloride ion content • 26.4.2.2(e) - 2 methods to calculate total chloride ion content (1) Calculated from chloride ion content from concrete materials and concrete mixture proportions (2) Measured on hardened concrete in accordance with ASTM C1218 at age between 28 and 42 days