SlideShare a Scribd company logo
1 of 25
Erbil Polytechnic University
Erbil Technical Engineering College
Civil Engineering Techniques
Designing pile caps according to ACI 318-19
Supervisors
1. Prof. Dr. Mereen Hasan Fahmi
2. Mr. Deedar Hussein
Prepared by (G6)
1. Paywand Shakir 2. Ziyad Asaad
3. Mohammed Jalal
4. Rasan Nuradin 5. Ismail Mukhlis
6. Ahmed Karim
(2023-2024)
【 Concrete Foundation Structures 】
Contents
Introduction 1
Pile Cap Plan Dimensions 4
•Two-Way Shear at the Column 5
•One-Way Shear at the Column 7
•Two-Way Shear at Corner Pile 9
•One-Way Shear at Corner Pile 9
•Two-Way Shear at Interior Piles 10
•Pile Cap Overall Depth Requirements 11
Pile Cap Shear Strength and Thickness 5
•Factored Moments 12
•Required Flexural Reinforcement12
Pile Cap Flexural Strength and Reinforcement 11
Reinforcement Bar Development Length 14
•Flexure16
•Shear 16
Design Results Comparison and Conclusions 16
Discussion 17
2024/04/14 Concrete Foundation Structures 2
Introduction
Based on a geotechnical study, a pile supported foundation is required to
support a heavily loaded building column. Design the pile cap shown in
the following figure with 12 in. diameter piles and a service load capacity
of 50 tons each. The pile cap has normal-weight concrete with a
compressive strength of 5800 psi and Grade 60 reinforcement. And the
piles are embedded 4 in. into the pile cap. The axial loads on the column
are due to dead and live loads and are equal to 425 and 250 kips,
respectively. This report explains how we'll figure out and design pile
caps by hand, following the rules in ACI 318-19. We're making sure
everything meets safety standards for strong, stable structures. We'll use
this hand solution to compare it with the reference result.
2024/04/14 Concrete Foundation Structures 3
2024/04/14 Concrete Foundation Structures 4
Code
Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19)
Design Data
fc’ = 5,800 psi normal weight concrete
fy = 60,000 psi
Dead load, D = 425 kips
Live load, L = 250 kips
Pile Diameter, dp = 12 in.
Piles are embedded 4 in. into the pile cap
2024/04/14 Concrete Foundation Structures 5
Pile Cap Plan Dimensions
The plan dimensions of a pile cap depend on the number of piles that are needed to support the load. Number
and arrangement of piles were determined from unfactored forces and moments transmitted to piles and
permissible pile capacity selected through geotechnical
engineering principles. These calculations are not part of the
scope of this example. ACI 318-19 (13.4.1.1)
Pile spacing is generally a function of pile type and capacity.
The following figure shows the piles configuration selected
by the reference for this example with the associated pile cap
plan dimensions.
2024/04/14 Concrete Foundation Structures 6
Pile Cap Shear Strength and Thickness
The thickness of the pile cap is initially determined based on the following key parameters:
1) Two-way shear requirements around the column,
1) One-way shear requirements at the column, and
1) One-way and two-way shear requirements around the piles
1) Pile cap overall depth minimum requirements
Both one-way and two-way shear are investigated at the critical sections around the vertical elements (columns)
supported by the pile cap with the requirements of ACI 318-19 (13.4.6). Factored loads are used to compute the shear
forces at the critical sections around columns as well as piles. Like footings, it is common practice not to use shear
reinforcement in pile caps. One-way shear checks are shown for illustration as two-way shear normally governs the
design. The overall depth of pile cap shall also be selected such that the effective depth of bottom reinforcement is at
least 12 inches.
2024/04/14 Concrete Foundation Structures 7
Two-Way Shear at the Column
The total factored axial load on the column:
Pu = 1.2´ PD +1.6´ PL = 1.2´ 425 +1.6´ 250 = 910 kips
Consider a uniform distribution of column load to the provided piles. Because of the rigidity of the pile cap
Pu per pile =
910
8
= 114 kips
Assuming that the centers of the two piles closest to the column are located dp/2 = 6 in. or more inside the perimeter of
the critical section for two-way shear, their contribution to the total shear can then be neglected. This assumption will be
verified later. ACI 318-19 (13.4.6.5(b))
Therefore, the factored shear force at the critical section is calculated based on six of the eight piles only:
Vu = 12/2 ´114 = 684 kips
The design shear strength for the interior column:
ϕV=ϕ 4 λs λ 𝑓′𝑐 bo d
ϕv= 0.75 x 4 x 0.95 x 1 x 5800 4x(22+d) d ACI 318-19 (22.6.5.2(a))
2024/04/14 Concrete Foundation Structures 8
Where ϕ = 0.75, λs =
2
1
+
𝑑
10
≤ 1 λs=0.95 ACI 318-19 (Table 21.2.1)
The minimum required d for the pile cap foundation can be calculated by setting Vu = ϕVc as follows:
ϕVc = Vu
684,000 = 0.75 x 4 x 0.95 x 1 x 5800 4x(22+d) d
d = 19.15 in. ➞ 21 in.
By using d = 21 in., the center of the two piles closest to the column is located (43/2) - 18 = 3.5 in. inside the critical
section which less than dp/2 = 6 in. (see the following figure). Thus, the initial assumption is not valid. That is part of the
reactions from these two piles must be considered in the shear force at the critical section, or a bigger d must be selected.
By increasing d to 26 in., the center of the piles is located at dp/2 inside the critical section, and these reactions can be
neglected and the assumption made earlier is validated (see the following figure). These configuration changes are for
illustration only and may not represent optimal design which is left up to the design professional based on project criteria.
2024/04/14 Concrete Foundation Structures 9
2024/04/14 Concrete Foundation Structures 10
The design shear strength for the interior column:
ϕV=ϕ 4 λs λ 𝑓′𝑐 bo d ACI 318-19 (22.6.5.2(a))
ϕVc = 0.75´ 4´0.95´1.0´ 5800 ´(4´(22 + 26))´ 26/1000 = 1083 kips > Vu = 684 kips  o.k.
Thus, Two-way shear requirement around the column is satisfied.
One-Way Shear at the Column
North/South Direction:
The critical section for one-way shear is located at a distance d
from the face of the column as shown in the previous figure.
The center of the three piles is located 5.5 in. inside of the
critical section, which is less than dp/2 (see the previous figure).
In this case, the pile reaction shall be based on a linear
interpolation between full value at dp/2 outside the section and
zero value at dp /2 inside the section. ACI 318-19 (13.4.6.5(c))
2024/04/14 Concrete Foundation Structures 11
d - dp/2 = 26 - 12/2 = 20 in.  the reaction from each pile = 0 kips
d - dp/2 = 26 + 12/2 = 32 in.  the reaction from each pile = 114 kips
By performing interpolation with the center of the three piles is located at 26 – 5.5 = 20.5 in. from the face of the column:
the reaction from each pile=114´(
20.5
32−20
-1.667) = 5 kips Therefore, Vu = 3 x 5 = 15 kips.
ϕVc = ϕ ´8´ λs ´λ´(r)1/3 𝑓′𝑐 L ´ d ACI 318-19 (22.5.5.1(c))
ϕVc = 0.75´ 8´0.95´1.0´(0.0018)1/3 5800 (8.5´12)´ 26 /1000 = 140 kips
Vu < ϕVc  o.k.
East/West Direction:
The critical section for one-way shear is located at a distance d
from the face of the column as shown in the previous figure.
The center of the pile closest to the column is located 19 in.
inside of the critical section, which is greater than dp/2 (see the
previous figure). Thus, the reaction from this pile is not
considered.
2024/04/14 Concrete Foundation Structures 12
The two remaining piles are located 26 - (36 - 11) = 1 in. inside of the critical section, which is less than dp/2. In this
case, the reaction for those piles shall be based on a linear interpolation between full value at dp/2 outside the section
and zero value at dp /2 inside the section. ACI 318-19 (13.4.6.5(c))
d - dp/2 = 26 - 12/2 = 20 in.  the reaction from each pile = 0 kips
d - dp/2 = 26 + 12/2 = 32 in.  the reaction from each pile = 114 kips
By performing interpolation with the center of the three piles is located at 26 – 1 = 25 in. from the face of the column:
the reaction from each pile =114´(
25
32−20
-1.667) = 48 kips
Therefore, Vu = 2 x 48 = 96 kips.
ϕVc = ϕ ´8´ λs ´λ´(r)1/3 𝑓′𝑐 B ´ d ACI 318-19 (22.5.5.1(c))
ϕVc = 0.75´ 8´0.95´1.0´(0.0018)1/3 5800 (7.75´12)´ 26 /1000 = 127 kips
Vu < ϕVc  o.k.
2024/04/14 Concrete Foundation Structures 13
Two-Way Shear at Corner Pile
Vu = Pile reaction = 114 kips
ϕV=ϕ 4 λs λ 𝑓′𝑐 bo d ACI 318-19 (22.6.5.2(a))
Where bo = π (dp + d) normally for an interior circular pile.
For the corner pile however, bo is calculated as shown in the following figure:
ϕVc = 0.75´ 4´0.95´1.0´ 5800 ´(
𝜋
4
´(12 + 26)+(2´15)´ 26/1000 = 337 kips
Vu < ϕVc  o.k.
The calculations above may be simplified using the approximation of
equivalent sections as shown in ACI 8.10.1.3
2024/04/14 Concrete Foundation Structures 14
One-Way Shear at Corner Pile
The one-way shear is checked at a distance d, but no more than 13 in., from the face of a corner pile as stated in the
reference. The critical section occurs at a 45ᴼ angle with respect to the edges of the pile cap.
Vu = the reaction of the pile = 114 kips
ϕVc = ϕ ´8´ λs ´λ´(r)1/3 𝑓′𝑐 b ´ d ACI 318-19 (22.5.5.1(c)
Where b is calculated as shown in the following figure.
ϕVc = 0.75´ 8´0.95´1.0´(0.0018)1/3 5800 (2´40.2)´ 26 /1000 = 115 kips Vu < ϕVc  o.k.
2024/04/14 Concrete Foundation Structures 15
Two-Way Shear at Interior Piles
For interior piles, if two-way shear perimeters overlap, the modified critical shear perimeter should be taken as
that portion of the smallest envelope of individual shear perimeters that will actually resist the critical shear for
group under consideration as shown in the following figure. ACI 318-19 (R13.2.7.2)
Vu = Pile reactions = 2 x 114 = 228 kips
ϕV=ϕ 4 λs λ 𝑓′𝑐 bo d ACI 318-19 (22.6.5.2(a))
Where bo is calculated as shown in the following figure.
ϕVc = 0.75´ 4´0.95´1.0´ 5800 ´[(2π´(
12
2
+
26
2
)+(2´36)]´
26/1000 = 1080kips
Vu < ϕVc  o.k.
2024/04/14 Concrete Foundation Structures 16
Pile Cap Overall Depth Requirements
Overall depth of pile cap shall be selected such that the effective depth of bottom reinforcement is at least 12 in. ACI
318-14 (13.4.2.1)
hmin = 12 in. + cover + embedment = 12 + 3+ 4 = 19 in.
h = 26 + 3 + 4 = 33 in.>hmin
Thus, use a final pile cap thickness of 33 in.
2024/04/14 Concrete Foundation Structures 17
Pile Cap Flexural Strength and Reinforcement
In a pile cap foundation design, flexural moments are evaluated in two orthogonal directions (Mx and My). To simplify
design calculations, an average value of d is used to represent both reinforcement curtains in the x and y directions.
1. Factored Moments
Short Direction
The factored moment at the critical section is obtained by multiplying the reactions from three piles by the distance
from the center of the piles to the critical section (at the face of the column) as follows:
Mu x = (3´114) (
7.75
2
− 1.25 −
22
2×12
) = 584.3 kips-ft
Long Direction
The factored moment at the critical section is obtained by multiplying the reactions from three piles by the distance
from the center of the piles to the critical section (at the face of the column) as follows:
Mu y = 114´(1.5 −
22
2×12
) + (2 × 114) × (3 −
22
2×12
) = 541.5 kips-ft
2024/04/14 Concrete Foundation Structures 18
Required Flexural Reinforcement
Short Direction
Mux = 584.3 kips-ft
d = 26 in.
To determine the area of steel, assumptions have to be made whether the section is tension or compression controlled,
and regarding the distance between the resultant compression and tension forces along the footing section (jd). In this
example, tension-controlled section will be assumed so the reduction factor ϕ is equal to 0.9, and jd will be taken
equal to 0.983d. The assumptions will be verified once the reinforcement area is finalized.
Assume jd = 0.983´ d = 25.56 in.
As =
𝑀𝑢
∅ 𝑓𝑦 𝑗𝑑
=
584.3×12000
0.9×60000×25.56
= 5.08 𝑖𝑛.2
𝜀 =
0.003
𝑐
𝑑𝑡 − 0.003 =
0.003
1.03
26 − 0.003 = 0.073 > 0.05
Therefore, the assumption that section is tension-controlled is valid.
2024/04/14 Concrete Foundation Structures 19
ACI 318-19 (7.6.1.1)
Providing 11#7 bars with As = 6.60 in.2 satisfies strength requirements.
For rectangular foundation, a portion of the total reinforcement (γsAs) in the short direction shall be distributed
uniformly over a band width equal to the length of short side of footing, centered on centerline of column.
Remainder of reinforcement required in the short direction ((1-γs) As) shall be distributed uniformly outside the
center band width of footing. ACI 318-19 (13.3.3.3)
2024/04/14 Concrete Foundation Structures 20
This requirement is also helpful to address the effects resulting from load concentration near the column and
two-way behavior in foundation structures. This is a similar effect to what is required in elevated slab supported
by columns.
ACI 318-19 (Eq. 13.3.3.3)
Provide 10#7 bars at 9 in. on centers (≤ smax) in the center band, and add one additional bar outside of the center
band. Thus, provide 12#7 in the short direction.
Long Direction
Mux = 541.5 kips-ft
d = 26 in.
To determine the area of steel, assumptions have to be made whether the section is tension or compression
controlled, and regarding the distance between the resultant compression and tension forces along the footing
section (jd). In this example, tension-controlled section will be assumed so the reduction factor ϕ is equal to 0.9, and
jd will be taken equal to 0.983d. The assumptions will be verified once the reinforcement area is finalized.
2024/04/14 Concrete Foundation Structures 21
Therefore, the assumption that section is tension-controlled is valid.
Provide 10#7 in the long direction. These bars are spaced
uniformly over the width of the pile cap.
2024/04/14 Concrete Foundation Structures 22
Reinforcement Bar Development Length
Flexural reinforcement must be properly developed in a concrete foundation in order for the foundation to perform as
intended in accordance with the strength design method. The concept of the development length is stated as follows:
minimum lengths of reinforcement must be provided beyond the locations of peak stress (critical sections) in the
reinforcement in order to fully develop the bars.
The development length for the pile cap is calculated as follows:
ACI 318-19 (Eq. 25.4.2.4a)
2024/04/14 Concrete Foundation Structures 23
The provided bar length is equal to:
Because the available development length is greater in the long direction, the bars in that direction can be fully developed.
2024/04/14 Concrete Foundation Structures 24
Design Results
1. Flexure
Table 1 – Pile Cap Analysis and Design Results (Flexural)
Solution Short Direction Long Direction
Mdesign (kips-ft) As,required (in.2) Mdesign (kips-ft) As,required (in.2)
Hand 584.3 6.06 541.5 5.52
2. Shear
Table 2 – Pile Cap Analysis and Design Results (Two-Way Shear)
Solution Around Column Around Interior Piles Around Corner Piles
vu, psi ϕvc, psi vu, psi ϕvc, psi vu, psi ϕvc, psi
Hand 684 1083 228 1080 114 337
2024/04/14 Concrete Foundation Structures 25
Discussion
In our report, we looked closely at how strong and stable our pile caps are in two main ways: flexure (bending)
and shear (sideways force).
When we checked flexure, we found that in the short direction, our pile caps could handle up to 584.3 kips-ft of
force, needing about 6.06 square inches of reinforcement. In the long direction, they could handle up to 541.5
kips-ft, needing about 5.52 square inches of reinforcement.
Then, we studied shear. We looked at how much force the pile caps could take around the column, near the
center piles, and at the corners. In these situations, our pile caps could resist forces like 684 psi, 228 psi, and 114
psi, respectively. This means they can handle a lot of pressure from different directions.
These findings show that our pile caps are well-designed to handle bending and sideways forces, ensuring
they're strong enough to support whatever's built on top of them.

More Related Content

What's hot

EFFECT OF RECRON FIBRES ON FLEXURAL BEHAVIOR ON CONCRETE
EFFECT OF RECRON FIBRES ON FLEXURAL BEHAVIOR ON CONCRETEEFFECT OF RECRON FIBRES ON FLEXURAL BEHAVIOR ON CONCRETE
EFFECT OF RECRON FIBRES ON FLEXURAL BEHAVIOR ON CONCRETES.m. Kumar
 
Analysis of g+3 rcc storied building
Analysis of g+3 rcc storied buildingAnalysis of g+3 rcc storied building
Analysis of g+3 rcc storied buildingTarun kumar
 
Steel Design 6th Edition Segui Solutions Manual
Steel Design 6th Edition Segui Solutions ManualSteel Design 6th Edition Segui Solutions Manual
Steel Design 6th Edition Segui Solutions ManualLittleMarah
 
Elastic flexural torsional buckling
Elastic flexural torsional bucklingElastic flexural torsional buckling
Elastic flexural torsional bucklingBhavin Shah
 
Basement wall design
Basement wall designBasement wall design
Basement wall designCETCBIM
 
Tower design-Chapter 2-pile caps design
Tower design-Chapter 2-pile caps designTower design-Chapter 2-pile caps design
Tower design-Chapter 2-pile caps designNada Zarrak
 
Footing design
Footing designFooting design
Footing designYasin J
 
Gantry girder Analyse & design
Gantry girder Analyse & designGantry girder Analyse & design
Gantry girder Analyse & designGhawsudin
 
Design for Short Axially Loaded Columns ACI318
Design for Short  Axially  Loaded Columns ACI318Design for Short  Axially  Loaded Columns ACI318
Design for Short Axially Loaded Columns ACI318Abdullah Khair
 
Unki Warehouse Portal Frame Design - Prokon Design Sheets REV01
Unki Warehouse Portal Frame Design - Prokon Design Sheets REV01Unki Warehouse Portal Frame Design - Prokon Design Sheets REV01
Unki Warehouse Portal Frame Design - Prokon Design Sheets REV01Magdel Kotze
 
presentation based on Truss and Frame
presentation based on Truss and Framepresentation based on Truss and Frame
presentation based on Truss and FrameMohotasimur Anik
 
Design ppt
Design pptDesign ppt
Design ppttishu001
 
Design and Detailing of RC Deep beams as per IS 456-2000
Design and Detailing of RC Deep beams as per IS 456-2000Design and Detailing of RC Deep beams as per IS 456-2000
Design and Detailing of RC Deep beams as per IS 456-2000VVIETCIVIL
 
New Building Materials
New Building MaterialsNew Building Materials
New Building MaterialsDr K M SONI
 
Design aids for tension members as per revised is 800 2007
Design aids for tension members as per revised is  800 2007Design aids for tension members as per revised is  800 2007
Design aids for tension members as per revised is 800 2007eSAT Journals
 
Tower design using etabs- Nada Zarrak
Tower design using etabs- Nada Zarrak Tower design using etabs- Nada Zarrak
Tower design using etabs- Nada Zarrak Nada Zarrak
 

What's hot (20)

EFFECT OF RECRON FIBRES ON FLEXURAL BEHAVIOR ON CONCRETE
EFFECT OF RECRON FIBRES ON FLEXURAL BEHAVIOR ON CONCRETEEFFECT OF RECRON FIBRES ON FLEXURAL BEHAVIOR ON CONCRETE
EFFECT OF RECRON FIBRES ON FLEXURAL BEHAVIOR ON CONCRETE
 
Analysis of g+3 rcc storied building
Analysis of g+3 rcc storied buildingAnalysis of g+3 rcc storied building
Analysis of g+3 rcc storied building
 
Steel Design 6th Edition Segui Solutions Manual
Steel Design 6th Edition Segui Solutions ManualSteel Design 6th Edition Segui Solutions Manual
Steel Design 6th Edition Segui Solutions Manual
 
Elastic flexural torsional buckling
Elastic flexural torsional bucklingElastic flexural torsional buckling
Elastic flexural torsional buckling
 
Beam and slab design
Beam and slab designBeam and slab design
Beam and slab design
 
Basement wall design
Basement wall designBasement wall design
Basement wall design
 
Tower design-Chapter 2-pile caps design
Tower design-Chapter 2-pile caps designTower design-Chapter 2-pile caps design
Tower design-Chapter 2-pile caps design
 
Footing design
Footing designFooting design
Footing design
 
Gantry girder Analyse & design
Gantry girder Analyse & designGantry girder Analyse & design
Gantry girder Analyse & design
 
Design for Short Axially Loaded Columns ACI318
Design for Short  Axially  Loaded Columns ACI318Design for Short  Axially  Loaded Columns ACI318
Design for Short Axially Loaded Columns ACI318
 
Unki Warehouse Portal Frame Design - Prokon Design Sheets REV01
Unki Warehouse Portal Frame Design - Prokon Design Sheets REV01Unki Warehouse Portal Frame Design - Prokon Design Sheets REV01
Unki Warehouse Portal Frame Design - Prokon Design Sheets REV01
 
presentation based on Truss and Frame
presentation based on Truss and Framepresentation based on Truss and Frame
presentation based on Truss and Frame
 
Design ppt
Design pptDesign ppt
Design ppt
 
Shear wall and its design guidelines
Shear wall and its design guidelinesShear wall and its design guidelines
Shear wall and its design guidelines
 
Trulift presentation
Trulift presentationTrulift presentation
Trulift presentation
 
Design and Detailing of RC Deep beams as per IS 456-2000
Design and Detailing of RC Deep beams as per IS 456-2000Design and Detailing of RC Deep beams as per IS 456-2000
Design and Detailing of RC Deep beams as per IS 456-2000
 
Columns
ColumnsColumns
Columns
 
New Building Materials
New Building MaterialsNew Building Materials
New Building Materials
 
Design aids for tension members as per revised is 800 2007
Design aids for tension members as per revised is  800 2007Design aids for tension members as per revised is  800 2007
Design aids for tension members as per revised is 800 2007
 
Tower design using etabs- Nada Zarrak
Tower design using etabs- Nada Zarrak Tower design using etabs- Nada Zarrak
Tower design using etabs- Nada Zarrak
 

Similar to Designing pile caps according to ACI 318-19.pptx

CEE598_Gummaraj_Bharath_Final_Project
CEE598_Gummaraj_Bharath_Final_ProjectCEE598_Gummaraj_Bharath_Final_Project
CEE598_Gummaraj_Bharath_Final_ProjectBharath Gummaraj
 
Reinforced concrete Course assignments, 2019
Reinforced concrete Course assignments, 2019Reinforced concrete Course assignments, 2019
Reinforced concrete Course assignments, 2019JanneHanka
 
Worked example extract_flat_slabs
Worked example extract_flat_slabsWorked example extract_flat_slabs
Worked example extract_flat_slabsLuan Truong Van
 
Design of Flat Slab and Bridges
Design of Flat Slab and BridgesDesign of Flat Slab and Bridges
Design of Flat Slab and BridgesAnanthakumar75
 
Fire Resistance of Materials & Structures - Analysing the Steel Structure
Fire Resistance of Materials & Structures - Analysing the Steel StructureFire Resistance of Materials & Structures - Analysing the Steel Structure
Fire Resistance of Materials & Structures - Analysing the Steel StructureArshia Mousavi
 
Passive Cooling Design Feature for Energy Efficient in PERI Auditorium
Passive Cooling Design Feature for Energy Efficient in PERI AuditoriumPassive Cooling Design Feature for Energy Efficient in PERI Auditorium
Passive Cooling Design Feature for Energy Efficient in PERI AuditoriumIRJET Journal
 
Worked example extract_flat_slabs
Worked example extract_flat_slabsWorked example extract_flat_slabs
Worked example extract_flat_slabsluantvconst
 
finalprojectreportg2-141218075116-conversion-gate01 (1).pdf
finalprojectreportg2-141218075116-conversion-gate01 (1).pdffinalprojectreportg2-141218075116-conversion-gate01 (1).pdf
finalprojectreportg2-141218075116-conversion-gate01 (1).pdfAbdurRazzak187410
 
Unit 5 Approximate method of analysis (1).pdf
Unit 5 Approximate method of analysis (1).pdfUnit 5 Approximate method of analysis (1).pdf
Unit 5 Approximate method of analysis (1).pdfSathyaPrabha20
 
140204-5-PTI EDC-130-Continuous Members-41.pdf
140204-5-PTI EDC-130-Continuous Members-41.pdf140204-5-PTI EDC-130-Continuous Members-41.pdf
140204-5-PTI EDC-130-Continuous Members-41.pdfephrem53
 
Design of transformer
Design of transformerDesign of transformer
Design of transformerSubrata Dey
 
Design of concrete structure 2 project-Loay Qabaha &Basel Salame
Design of concrete structure 2 project-Loay Qabaha &Basel SalameDesign of concrete structure 2 project-Loay Qabaha &Basel Salame
Design of concrete structure 2 project-Loay Qabaha &Basel SalameLoay Qabaha
 
Chapter 6 column
Chapter 6   columnChapter 6   column
Chapter 6 columnSimon Foo
 
Tranformer Design
Tranformer DesignTranformer Design
Tranformer DesignArnab Nandi
 
Design of Structures Chapter2.pdf
Design of Structures Chapter2.pdfDesign of Structures Chapter2.pdf
Design of Structures Chapter2.pdfUmarSaba1
 

Similar to Designing pile caps according to ACI 318-19.pptx (20)

CEE598_Gummaraj_Bharath_Final_Project
CEE598_Gummaraj_Bharath_Final_ProjectCEE598_Gummaraj_Bharath_Final_Project
CEE598_Gummaraj_Bharath_Final_Project
 
Reinforced concrete Course assignments, 2019
Reinforced concrete Course assignments, 2019Reinforced concrete Course assignments, 2019
Reinforced concrete Course assignments, 2019
 
Reinfored beam
Reinfored beamReinfored beam
Reinfored beam
 
presentation1_28.pptx
presentation1_28.pptxpresentation1_28.pptx
presentation1_28.pptx
 
Worked example extract_flat_slabs
Worked example extract_flat_slabsWorked example extract_flat_slabs
Worked example extract_flat_slabs
 
Design of Flat Slab and Bridges
Design of Flat Slab and BridgesDesign of Flat Slab and Bridges
Design of Flat Slab and Bridges
 
Fire Resistance of Materials & Structures - Analysing the Steel Structure
Fire Resistance of Materials & Structures - Analysing the Steel StructureFire Resistance of Materials & Structures - Analysing the Steel Structure
Fire Resistance of Materials & Structures - Analysing the Steel Structure
 
Passive Cooling Design Feature for Energy Efficient in PERI Auditorium
Passive Cooling Design Feature for Energy Efficient in PERI AuditoriumPassive Cooling Design Feature for Energy Efficient in PERI Auditorium
Passive Cooling Design Feature for Energy Efficient in PERI Auditorium
 
Design and analasys of a g+2 residential building
Design and analasys of a g+2 residential building Design and analasys of a g+2 residential building
Design and analasys of a g+2 residential building
 
Worked example extract_flat_slabs
Worked example extract_flat_slabsWorked example extract_flat_slabs
Worked example extract_flat_slabs
 
Presentation
PresentationPresentation
Presentation
 
finalprojectreportg2-141218075116-conversion-gate01 (1).pdf
finalprojectreportg2-141218075116-conversion-gate01 (1).pdffinalprojectreportg2-141218075116-conversion-gate01 (1).pdf
finalprojectreportg2-141218075116-conversion-gate01 (1).pdf
 
Crack Width
Crack WidthCrack Width
Crack Width
 
Unit 5 Approximate method of analysis (1).pdf
Unit 5 Approximate method of analysis (1).pdfUnit 5 Approximate method of analysis (1).pdf
Unit 5 Approximate method of analysis (1).pdf
 
140204-5-PTI EDC-130-Continuous Members-41.pdf
140204-5-PTI EDC-130-Continuous Members-41.pdf140204-5-PTI EDC-130-Continuous Members-41.pdf
140204-5-PTI EDC-130-Continuous Members-41.pdf
 
Design of transformer
Design of transformerDesign of transformer
Design of transformer
 
Design of concrete structure 2 project-Loay Qabaha &Basel Salame
Design of concrete structure 2 project-Loay Qabaha &Basel SalameDesign of concrete structure 2 project-Loay Qabaha &Basel Salame
Design of concrete structure 2 project-Loay Qabaha &Basel Salame
 
Chapter 6 column
Chapter 6   columnChapter 6   column
Chapter 6 column
 
Tranformer Design
Tranformer DesignTranformer Design
Tranformer Design
 
Design of Structures Chapter2.pdf
Design of Structures Chapter2.pdfDesign of Structures Chapter2.pdf
Design of Structures Chapter2.pdf
 

Recently uploaded

handbook on reinforce concrete and detailing
handbook on reinforce concrete and detailinghandbook on reinforce concrete and detailing
handbook on reinforce concrete and detailingAshishSingh1301
 
Geometric constructions Engineering Drawing.pdf
Geometric constructions Engineering Drawing.pdfGeometric constructions Engineering Drawing.pdf
Geometric constructions Engineering Drawing.pdfJNTUA
 
Fuzzy logic method-based stress detector with blood pressure and body tempera...
Fuzzy logic method-based stress detector with blood pressure and body tempera...Fuzzy logic method-based stress detector with blood pressure and body tempera...
Fuzzy logic method-based stress detector with blood pressure and body tempera...IJECEIAES
 
SLIDESHARE PPT-DECISION MAKING METHODS.pptx
SLIDESHARE PPT-DECISION MAKING METHODS.pptxSLIDESHARE PPT-DECISION MAKING METHODS.pptx
SLIDESHARE PPT-DECISION MAKING METHODS.pptxCHAIRMAN M
 
8th International Conference on Soft Computing, Mathematics and Control (SMC ...
8th International Conference on Soft Computing, Mathematics and Control (SMC ...8th International Conference on Soft Computing, Mathematics and Control (SMC ...
8th International Conference on Soft Computing, Mathematics and Control (SMC ...josephjonse
 
Artificial Intelligence in due diligence
Artificial Intelligence in due diligenceArtificial Intelligence in due diligence
Artificial Intelligence in due diligencemahaffeycheryld
 
Passive Air Cooling System and Solar Water Heater.ppt
Passive Air Cooling System and Solar Water Heater.pptPassive Air Cooling System and Solar Water Heater.ppt
Passive Air Cooling System and Solar Water Heater.pptamrabdallah9
 
AI in Healthcare Innovative use cases and applications.pdf
AI in Healthcare Innovative use cases and applications.pdfAI in Healthcare Innovative use cases and applications.pdf
AI in Healthcare Innovative use cases and applications.pdfmahaffeycheryld
 
5G and 6G refer to generations of mobile network technology, each representin...
5G and 6G refer to generations of mobile network technology, each representin...5G and 6G refer to generations of mobile network technology, each representin...
5G and 6G refer to generations of mobile network technology, each representin...archanaece3
 
Diploma Engineering Drawing Qp-2024 Ece .pdf
Diploma Engineering Drawing Qp-2024 Ece .pdfDiploma Engineering Drawing Qp-2024 Ece .pdf
Diploma Engineering Drawing Qp-2024 Ece .pdfJNTUA
 
What is Coordinate Measuring Machine? CMM Types, Features, Functions
What is Coordinate Measuring Machine? CMM Types, Features, FunctionsWhat is Coordinate Measuring Machine? CMM Types, Features, Functions
What is Coordinate Measuring Machine? CMM Types, Features, FunctionsVIEW
 
Introduction to Artificial Intelligence and History of AI
Introduction to Artificial Intelligence and History of AIIntroduction to Artificial Intelligence and History of AI
Introduction to Artificial Intelligence and History of AISheetal Jain
 
Dynamo Scripts for Task IDs and Space Naming.pptx
Dynamo Scripts for Task IDs and Space Naming.pptxDynamo Scripts for Task IDs and Space Naming.pptx
Dynamo Scripts for Task IDs and Space Naming.pptxMustafa Ahmed
 
Seizure stage detection of epileptic seizure using convolutional neural networks
Seizure stage detection of epileptic seizure using convolutional neural networksSeizure stage detection of epileptic seizure using convolutional neural networks
Seizure stage detection of epileptic seizure using convolutional neural networksIJECEIAES
 
Piping and instrumentation diagram p.pdf
Piping and instrumentation diagram p.pdfPiping and instrumentation diagram p.pdf
Piping and instrumentation diagram p.pdfAshrafRagab14
 
Lab Manual Arduino UNO Microcontrollar.docx
Lab Manual Arduino UNO Microcontrollar.docxLab Manual Arduino UNO Microcontrollar.docx
Lab Manual Arduino UNO Microcontrollar.docxRashidFaridChishti
 
Operating System chapter 9 (Virtual Memory)
Operating System chapter 9 (Virtual Memory)Operating System chapter 9 (Virtual Memory)
Operating System chapter 9 (Virtual Memory)NareenAsad
 
CLOUD COMPUTING SERVICES - Cloud Reference Modal
CLOUD COMPUTING SERVICES - Cloud Reference ModalCLOUD COMPUTING SERVICES - Cloud Reference Modal
CLOUD COMPUTING SERVICES - Cloud Reference ModalSwarnaSLcse
 
"United Nations Park" Site Visit Report.
"United Nations Park" Site  Visit Report."United Nations Park" Site  Visit Report.
"United Nations Park" Site Visit Report.MdManikurRahman
 
litvinenko_Henry_Intrusion_Hong-Kong_2024.pdf
litvinenko_Henry_Intrusion_Hong-Kong_2024.pdflitvinenko_Henry_Intrusion_Hong-Kong_2024.pdf
litvinenko_Henry_Intrusion_Hong-Kong_2024.pdfAlexander Litvinenko
 

Recently uploaded (20)

handbook on reinforce concrete and detailing
handbook on reinforce concrete and detailinghandbook on reinforce concrete and detailing
handbook on reinforce concrete and detailing
 
Geometric constructions Engineering Drawing.pdf
Geometric constructions Engineering Drawing.pdfGeometric constructions Engineering Drawing.pdf
Geometric constructions Engineering Drawing.pdf
 
Fuzzy logic method-based stress detector with blood pressure and body tempera...
Fuzzy logic method-based stress detector with blood pressure and body tempera...Fuzzy logic method-based stress detector with blood pressure and body tempera...
Fuzzy logic method-based stress detector with blood pressure and body tempera...
 
SLIDESHARE PPT-DECISION MAKING METHODS.pptx
SLIDESHARE PPT-DECISION MAKING METHODS.pptxSLIDESHARE PPT-DECISION MAKING METHODS.pptx
SLIDESHARE PPT-DECISION MAKING METHODS.pptx
 
8th International Conference on Soft Computing, Mathematics and Control (SMC ...
8th International Conference on Soft Computing, Mathematics and Control (SMC ...8th International Conference on Soft Computing, Mathematics and Control (SMC ...
8th International Conference on Soft Computing, Mathematics and Control (SMC ...
 
Artificial Intelligence in due diligence
Artificial Intelligence in due diligenceArtificial Intelligence in due diligence
Artificial Intelligence in due diligence
 
Passive Air Cooling System and Solar Water Heater.ppt
Passive Air Cooling System and Solar Water Heater.pptPassive Air Cooling System and Solar Water Heater.ppt
Passive Air Cooling System and Solar Water Heater.ppt
 
AI in Healthcare Innovative use cases and applications.pdf
AI in Healthcare Innovative use cases and applications.pdfAI in Healthcare Innovative use cases and applications.pdf
AI in Healthcare Innovative use cases and applications.pdf
 
5G and 6G refer to generations of mobile network technology, each representin...
5G and 6G refer to generations of mobile network technology, each representin...5G and 6G refer to generations of mobile network technology, each representin...
5G and 6G refer to generations of mobile network technology, each representin...
 
Diploma Engineering Drawing Qp-2024 Ece .pdf
Diploma Engineering Drawing Qp-2024 Ece .pdfDiploma Engineering Drawing Qp-2024 Ece .pdf
Diploma Engineering Drawing Qp-2024 Ece .pdf
 
What is Coordinate Measuring Machine? CMM Types, Features, Functions
What is Coordinate Measuring Machine? CMM Types, Features, FunctionsWhat is Coordinate Measuring Machine? CMM Types, Features, Functions
What is Coordinate Measuring Machine? CMM Types, Features, Functions
 
Introduction to Artificial Intelligence and History of AI
Introduction to Artificial Intelligence and History of AIIntroduction to Artificial Intelligence and History of AI
Introduction to Artificial Intelligence and History of AI
 
Dynamo Scripts for Task IDs and Space Naming.pptx
Dynamo Scripts for Task IDs and Space Naming.pptxDynamo Scripts for Task IDs and Space Naming.pptx
Dynamo Scripts for Task IDs and Space Naming.pptx
 
Seizure stage detection of epileptic seizure using convolutional neural networks
Seizure stage detection of epileptic seizure using convolutional neural networksSeizure stage detection of epileptic seizure using convolutional neural networks
Seizure stage detection of epileptic seizure using convolutional neural networks
 
Piping and instrumentation diagram p.pdf
Piping and instrumentation diagram p.pdfPiping and instrumentation diagram p.pdf
Piping and instrumentation diagram p.pdf
 
Lab Manual Arduino UNO Microcontrollar.docx
Lab Manual Arduino UNO Microcontrollar.docxLab Manual Arduino UNO Microcontrollar.docx
Lab Manual Arduino UNO Microcontrollar.docx
 
Operating System chapter 9 (Virtual Memory)
Operating System chapter 9 (Virtual Memory)Operating System chapter 9 (Virtual Memory)
Operating System chapter 9 (Virtual Memory)
 
CLOUD COMPUTING SERVICES - Cloud Reference Modal
CLOUD COMPUTING SERVICES - Cloud Reference ModalCLOUD COMPUTING SERVICES - Cloud Reference Modal
CLOUD COMPUTING SERVICES - Cloud Reference Modal
 
"United Nations Park" Site Visit Report.
"United Nations Park" Site  Visit Report."United Nations Park" Site  Visit Report.
"United Nations Park" Site Visit Report.
 
litvinenko_Henry_Intrusion_Hong-Kong_2024.pdf
litvinenko_Henry_Intrusion_Hong-Kong_2024.pdflitvinenko_Henry_Intrusion_Hong-Kong_2024.pdf
litvinenko_Henry_Intrusion_Hong-Kong_2024.pdf
 

Designing pile caps according to ACI 318-19.pptx

  • 1. Erbil Polytechnic University Erbil Technical Engineering College Civil Engineering Techniques Designing pile caps according to ACI 318-19 Supervisors 1. Prof. Dr. Mereen Hasan Fahmi 2. Mr. Deedar Hussein Prepared by (G6) 1. Paywand Shakir 2. Ziyad Asaad 3. Mohammed Jalal 4. Rasan Nuradin 5. Ismail Mukhlis 6. Ahmed Karim (2023-2024) 【 Concrete Foundation Structures 】
  • 2. Contents Introduction 1 Pile Cap Plan Dimensions 4 •Two-Way Shear at the Column 5 •One-Way Shear at the Column 7 •Two-Way Shear at Corner Pile 9 •One-Way Shear at Corner Pile 9 •Two-Way Shear at Interior Piles 10 •Pile Cap Overall Depth Requirements 11 Pile Cap Shear Strength and Thickness 5 •Factored Moments 12 •Required Flexural Reinforcement12 Pile Cap Flexural Strength and Reinforcement 11 Reinforcement Bar Development Length 14 •Flexure16 •Shear 16 Design Results Comparison and Conclusions 16 Discussion 17 2024/04/14 Concrete Foundation Structures 2
  • 3. Introduction Based on a geotechnical study, a pile supported foundation is required to support a heavily loaded building column. Design the pile cap shown in the following figure with 12 in. diameter piles and a service load capacity of 50 tons each. The pile cap has normal-weight concrete with a compressive strength of 5800 psi and Grade 60 reinforcement. And the piles are embedded 4 in. into the pile cap. The axial loads on the column are due to dead and live loads and are equal to 425 and 250 kips, respectively. This report explains how we'll figure out and design pile caps by hand, following the rules in ACI 318-19. We're making sure everything meets safety standards for strong, stable structures. We'll use this hand solution to compare it with the reference result. 2024/04/14 Concrete Foundation Structures 3
  • 4. 2024/04/14 Concrete Foundation Structures 4 Code Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19) Design Data fc’ = 5,800 psi normal weight concrete fy = 60,000 psi Dead load, D = 425 kips Live load, L = 250 kips Pile Diameter, dp = 12 in. Piles are embedded 4 in. into the pile cap
  • 5. 2024/04/14 Concrete Foundation Structures 5 Pile Cap Plan Dimensions The plan dimensions of a pile cap depend on the number of piles that are needed to support the load. Number and arrangement of piles were determined from unfactored forces and moments transmitted to piles and permissible pile capacity selected through geotechnical engineering principles. These calculations are not part of the scope of this example. ACI 318-19 (13.4.1.1) Pile spacing is generally a function of pile type and capacity. The following figure shows the piles configuration selected by the reference for this example with the associated pile cap plan dimensions.
  • 6. 2024/04/14 Concrete Foundation Structures 6 Pile Cap Shear Strength and Thickness The thickness of the pile cap is initially determined based on the following key parameters: 1) Two-way shear requirements around the column, 1) One-way shear requirements at the column, and 1) One-way and two-way shear requirements around the piles 1) Pile cap overall depth minimum requirements Both one-way and two-way shear are investigated at the critical sections around the vertical elements (columns) supported by the pile cap with the requirements of ACI 318-19 (13.4.6). Factored loads are used to compute the shear forces at the critical sections around columns as well as piles. Like footings, it is common practice not to use shear reinforcement in pile caps. One-way shear checks are shown for illustration as two-way shear normally governs the design. The overall depth of pile cap shall also be selected such that the effective depth of bottom reinforcement is at least 12 inches.
  • 7. 2024/04/14 Concrete Foundation Structures 7 Two-Way Shear at the Column The total factored axial load on the column: Pu = 1.2´ PD +1.6´ PL = 1.2´ 425 +1.6´ 250 = 910 kips Consider a uniform distribution of column load to the provided piles. Because of the rigidity of the pile cap Pu per pile = 910 8 = 114 kips Assuming that the centers of the two piles closest to the column are located dp/2 = 6 in. or more inside the perimeter of the critical section for two-way shear, their contribution to the total shear can then be neglected. This assumption will be verified later. ACI 318-19 (13.4.6.5(b)) Therefore, the factored shear force at the critical section is calculated based on six of the eight piles only: Vu = 12/2 ´114 = 684 kips The design shear strength for the interior column: ϕV=ϕ 4 λs λ 𝑓′𝑐 bo d ϕv= 0.75 x 4 x 0.95 x 1 x 5800 4x(22+d) d ACI 318-19 (22.6.5.2(a))
  • 8. 2024/04/14 Concrete Foundation Structures 8 Where ϕ = 0.75, λs = 2 1 + 𝑑 10 ≤ 1 λs=0.95 ACI 318-19 (Table 21.2.1) The minimum required d for the pile cap foundation can be calculated by setting Vu = ϕVc as follows: ϕVc = Vu 684,000 = 0.75 x 4 x 0.95 x 1 x 5800 4x(22+d) d d = 19.15 in. ➞ 21 in. By using d = 21 in., the center of the two piles closest to the column is located (43/2) - 18 = 3.5 in. inside the critical section which less than dp/2 = 6 in. (see the following figure). Thus, the initial assumption is not valid. That is part of the reactions from these two piles must be considered in the shear force at the critical section, or a bigger d must be selected. By increasing d to 26 in., the center of the piles is located at dp/2 inside the critical section, and these reactions can be neglected and the assumption made earlier is validated (see the following figure). These configuration changes are for illustration only and may not represent optimal design which is left up to the design professional based on project criteria.
  • 10. 2024/04/14 Concrete Foundation Structures 10 The design shear strength for the interior column: ϕV=ϕ 4 λs λ 𝑓′𝑐 bo d ACI 318-19 (22.6.5.2(a)) ϕVc = 0.75´ 4´0.95´1.0´ 5800 ´(4´(22 + 26))´ 26/1000 = 1083 kips > Vu = 684 kips  o.k. Thus, Two-way shear requirement around the column is satisfied. One-Way Shear at the Column North/South Direction: The critical section for one-way shear is located at a distance d from the face of the column as shown in the previous figure. The center of the three piles is located 5.5 in. inside of the critical section, which is less than dp/2 (see the previous figure). In this case, the pile reaction shall be based on a linear interpolation between full value at dp/2 outside the section and zero value at dp /2 inside the section. ACI 318-19 (13.4.6.5(c))
  • 11. 2024/04/14 Concrete Foundation Structures 11 d - dp/2 = 26 - 12/2 = 20 in.  the reaction from each pile = 0 kips d - dp/2 = 26 + 12/2 = 32 in.  the reaction from each pile = 114 kips By performing interpolation with the center of the three piles is located at 26 – 5.5 = 20.5 in. from the face of the column: the reaction from each pile=114´( 20.5 32−20 -1.667) = 5 kips Therefore, Vu = 3 x 5 = 15 kips. ϕVc = ϕ ´8´ λs ´λ´(r)1/3 𝑓′𝑐 L ´ d ACI 318-19 (22.5.5.1(c)) ϕVc = 0.75´ 8´0.95´1.0´(0.0018)1/3 5800 (8.5´12)´ 26 /1000 = 140 kips Vu < ϕVc  o.k. East/West Direction: The critical section for one-way shear is located at a distance d from the face of the column as shown in the previous figure. The center of the pile closest to the column is located 19 in. inside of the critical section, which is greater than dp/2 (see the previous figure). Thus, the reaction from this pile is not considered.
  • 12. 2024/04/14 Concrete Foundation Structures 12 The two remaining piles are located 26 - (36 - 11) = 1 in. inside of the critical section, which is less than dp/2. In this case, the reaction for those piles shall be based on a linear interpolation between full value at dp/2 outside the section and zero value at dp /2 inside the section. ACI 318-19 (13.4.6.5(c)) d - dp/2 = 26 - 12/2 = 20 in.  the reaction from each pile = 0 kips d - dp/2 = 26 + 12/2 = 32 in.  the reaction from each pile = 114 kips By performing interpolation with the center of the three piles is located at 26 – 1 = 25 in. from the face of the column: the reaction from each pile =114´( 25 32−20 -1.667) = 48 kips Therefore, Vu = 2 x 48 = 96 kips. ϕVc = ϕ ´8´ λs ´λ´(r)1/3 𝑓′𝑐 B ´ d ACI 318-19 (22.5.5.1(c)) ϕVc = 0.75´ 8´0.95´1.0´(0.0018)1/3 5800 (7.75´12)´ 26 /1000 = 127 kips Vu < ϕVc  o.k.
  • 13. 2024/04/14 Concrete Foundation Structures 13 Two-Way Shear at Corner Pile Vu = Pile reaction = 114 kips ϕV=ϕ 4 λs λ 𝑓′𝑐 bo d ACI 318-19 (22.6.5.2(a)) Where bo = π (dp + d) normally for an interior circular pile. For the corner pile however, bo is calculated as shown in the following figure: ϕVc = 0.75´ 4´0.95´1.0´ 5800 ´( 𝜋 4 ´(12 + 26)+(2´15)´ 26/1000 = 337 kips Vu < ϕVc  o.k. The calculations above may be simplified using the approximation of equivalent sections as shown in ACI 8.10.1.3
  • 14. 2024/04/14 Concrete Foundation Structures 14 One-Way Shear at Corner Pile The one-way shear is checked at a distance d, but no more than 13 in., from the face of a corner pile as stated in the reference. The critical section occurs at a 45ᴼ angle with respect to the edges of the pile cap. Vu = the reaction of the pile = 114 kips ϕVc = ϕ ´8´ λs ´λ´(r)1/3 𝑓′𝑐 b ´ d ACI 318-19 (22.5.5.1(c) Where b is calculated as shown in the following figure. ϕVc = 0.75´ 8´0.95´1.0´(0.0018)1/3 5800 (2´40.2)´ 26 /1000 = 115 kips Vu < ϕVc  o.k.
  • 15. 2024/04/14 Concrete Foundation Structures 15 Two-Way Shear at Interior Piles For interior piles, if two-way shear perimeters overlap, the modified critical shear perimeter should be taken as that portion of the smallest envelope of individual shear perimeters that will actually resist the critical shear for group under consideration as shown in the following figure. ACI 318-19 (R13.2.7.2) Vu = Pile reactions = 2 x 114 = 228 kips ϕV=ϕ 4 λs λ 𝑓′𝑐 bo d ACI 318-19 (22.6.5.2(a)) Where bo is calculated as shown in the following figure. ϕVc = 0.75´ 4´0.95´1.0´ 5800 ´[(2π´( 12 2 + 26 2 )+(2´36)]´ 26/1000 = 1080kips Vu < ϕVc  o.k.
  • 16. 2024/04/14 Concrete Foundation Structures 16 Pile Cap Overall Depth Requirements Overall depth of pile cap shall be selected such that the effective depth of bottom reinforcement is at least 12 in. ACI 318-14 (13.4.2.1) hmin = 12 in. + cover + embedment = 12 + 3+ 4 = 19 in. h = 26 + 3 + 4 = 33 in.>hmin Thus, use a final pile cap thickness of 33 in.
  • 17. 2024/04/14 Concrete Foundation Structures 17 Pile Cap Flexural Strength and Reinforcement In a pile cap foundation design, flexural moments are evaluated in two orthogonal directions (Mx and My). To simplify design calculations, an average value of d is used to represent both reinforcement curtains in the x and y directions. 1. Factored Moments Short Direction The factored moment at the critical section is obtained by multiplying the reactions from three piles by the distance from the center of the piles to the critical section (at the face of the column) as follows: Mu x = (3´114) ( 7.75 2 − 1.25 − 22 2×12 ) = 584.3 kips-ft Long Direction The factored moment at the critical section is obtained by multiplying the reactions from three piles by the distance from the center of the piles to the critical section (at the face of the column) as follows: Mu y = 114´(1.5 − 22 2×12 ) + (2 × 114) × (3 − 22 2×12 ) = 541.5 kips-ft
  • 18. 2024/04/14 Concrete Foundation Structures 18 Required Flexural Reinforcement Short Direction Mux = 584.3 kips-ft d = 26 in. To determine the area of steel, assumptions have to be made whether the section is tension or compression controlled, and regarding the distance between the resultant compression and tension forces along the footing section (jd). In this example, tension-controlled section will be assumed so the reduction factor ϕ is equal to 0.9, and jd will be taken equal to 0.983d. The assumptions will be verified once the reinforcement area is finalized. Assume jd = 0.983´ d = 25.56 in. As = 𝑀𝑢 ∅ 𝑓𝑦 𝑗𝑑 = 584.3×12000 0.9×60000×25.56 = 5.08 𝑖𝑛.2 𝜀 = 0.003 𝑐 𝑑𝑡 − 0.003 = 0.003 1.03 26 − 0.003 = 0.073 > 0.05 Therefore, the assumption that section is tension-controlled is valid.
  • 19. 2024/04/14 Concrete Foundation Structures 19 ACI 318-19 (7.6.1.1) Providing 11#7 bars with As = 6.60 in.2 satisfies strength requirements. For rectangular foundation, a portion of the total reinforcement (γsAs) in the short direction shall be distributed uniformly over a band width equal to the length of short side of footing, centered on centerline of column. Remainder of reinforcement required in the short direction ((1-γs) As) shall be distributed uniformly outside the center band width of footing. ACI 318-19 (13.3.3.3)
  • 20. 2024/04/14 Concrete Foundation Structures 20 This requirement is also helpful to address the effects resulting from load concentration near the column and two-way behavior in foundation structures. This is a similar effect to what is required in elevated slab supported by columns. ACI 318-19 (Eq. 13.3.3.3) Provide 10#7 bars at 9 in. on centers (≤ smax) in the center band, and add one additional bar outside of the center band. Thus, provide 12#7 in the short direction. Long Direction Mux = 541.5 kips-ft d = 26 in. To determine the area of steel, assumptions have to be made whether the section is tension or compression controlled, and regarding the distance between the resultant compression and tension forces along the footing section (jd). In this example, tension-controlled section will be assumed so the reduction factor ϕ is equal to 0.9, and jd will be taken equal to 0.983d. The assumptions will be verified once the reinforcement area is finalized.
  • 21. 2024/04/14 Concrete Foundation Structures 21 Therefore, the assumption that section is tension-controlled is valid. Provide 10#7 in the long direction. These bars are spaced uniformly over the width of the pile cap.
  • 22. 2024/04/14 Concrete Foundation Structures 22 Reinforcement Bar Development Length Flexural reinforcement must be properly developed in a concrete foundation in order for the foundation to perform as intended in accordance with the strength design method. The concept of the development length is stated as follows: minimum lengths of reinforcement must be provided beyond the locations of peak stress (critical sections) in the reinforcement in order to fully develop the bars. The development length for the pile cap is calculated as follows: ACI 318-19 (Eq. 25.4.2.4a)
  • 23. 2024/04/14 Concrete Foundation Structures 23 The provided bar length is equal to: Because the available development length is greater in the long direction, the bars in that direction can be fully developed.
  • 24. 2024/04/14 Concrete Foundation Structures 24 Design Results 1. Flexure Table 1 – Pile Cap Analysis and Design Results (Flexural) Solution Short Direction Long Direction Mdesign (kips-ft) As,required (in.2) Mdesign (kips-ft) As,required (in.2) Hand 584.3 6.06 541.5 5.52 2. Shear Table 2 – Pile Cap Analysis and Design Results (Two-Way Shear) Solution Around Column Around Interior Piles Around Corner Piles vu, psi ϕvc, psi vu, psi ϕvc, psi vu, psi ϕvc, psi Hand 684 1083 228 1080 114 337
  • 25. 2024/04/14 Concrete Foundation Structures 25 Discussion In our report, we looked closely at how strong and stable our pile caps are in two main ways: flexure (bending) and shear (sideways force). When we checked flexure, we found that in the short direction, our pile caps could handle up to 584.3 kips-ft of force, needing about 6.06 square inches of reinforcement. In the long direction, they could handle up to 541.5 kips-ft, needing about 5.52 square inches of reinforcement. Then, we studied shear. We looked at how much force the pile caps could take around the column, near the center piles, and at the corners. In these situations, our pile caps could resist forces like 684 psi, 228 psi, and 114 psi, respectively. This means they can handle a lot of pressure from different directions. These findings show that our pile caps are well-designed to handle bending and sideways forces, ensuring they're strong enough to support whatever's built on top of them.