The document discusses structural engineering concepts related to the design of tall buildings, including the design process, analysis methods, and design philosophies. It covers topics such as the overall design process from conception to detailing, different design levels from analytical to empirical, evolution of design codes and approaches, and limit state design concepts. Diagrams are presented illustrating the relationships between loads, analysis, member actions, material response, and design.

1. Dr. Naveed Anwar
Executive Director, AIT Consulting
Affiliated Faculty, Structural Engineering
Director, ACECOMS
Design of Tall Buildings
Hybrid Learning System

2. Dr. Naveed Anwar
Executive Director, AIT Consulting
Affiliated Faculty, Structural Engineering
Director, ACECOMS
Lecture 2: Design Philosophy
Design of Tall Buildings

3. Dr. Naveed Anwar
Design Process
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Structural Engineering Spectrum
Engineer
Activity Conception – Analysis – Design – Detailing, etc.
Structure Buildings – Bridges – Trusses – Shells – Towers, etc.
Code American – British – European – Japanese, etc.
Material Concrete – PSC – Steel – Timber, etc.
Model 2D Frame/Truss – 3D Frame/Truss – Full 3D FEM, etc.
Analysis Linear Static – NL Static – Linear Dynamic – Large Disp., etc.
Solution Equation Solution – Finite Elements – Programming, etc.
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Structural Design Office: Activities
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Overall Design Process
• Conception
• Modeling
• Analysis
• Design
• Detailing
• Drafting
• Costing
Integrated Design Process
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Final Design
Output
Acceptable ?
Trial
Members/Sections
Revise
Members/Sections
Structural
System
Modeling
Analysis
Member
Design
Detailing
No
Yes
Structure Design Process
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Design Process
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CAD in Structural Engineering
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Structural Design Concepts
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Design Philosophy and Process
“Structural Design is the process of proportioning the structure to safely
resist the applied forces in the most cost effective and friendly manner”
Load Effects
Requirements
Constraints
Design
Material Specifications
Cross-section Details
Member Sizes and
Configurations
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• Structural idealization into load bearing frame elements for analysis and
design
• Estimation of loads
• Structural analysis
• Design of sections and reinforcement for beams, column, slabs, etc.
• Production of arrangement and detail drawings and bar schedules
Structural Design
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• Structural design can be based on:
– Rigorous Analytical Theories
– Semi-Analytical, Semi-Numerical Solutions
– Rigorous Numerical Solutions
– Simplified Numerical and Empirical Solutions
– Specified Design Procedures
Design Levels
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• Structural Analysis
– Fairly General, Unified (FEM, BEM, etc.)
– Output: Element/Member Actions, Displacements, etc.
• Structural Design
– Structural Material (RC, PSC, HRS, CFS, timber, etc.)
– Design Code (ACI, BS Codes, EuroCode, JIS, etc.)
– Design Approach (working stress, ultimate strength, limit state, etc.)
– Structural Members (beams, columns, slabs, footings, etc.)
– Local Construction Techniques and Practices
– Output: Element/Member Cross-section, Reinforcement, etc.
Structural Analysis vs. Design
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Rigorous
Analytical
Semi
Analytical
Rigorous
Numerical
Simplified
Numerical
Specified
Procedures
Design Levels
Partial
Differential
Equations
Closed Form
with
Approximations
Full 3D,
Nonlinear,
Inelastic
Dynamic FEA
2D/3D Linear
Static
FEA/Matrix
Equations,
Charts, Tables,
Rules, Limits
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Design Methodologies and
Technologies
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Evolution of Design Approaches
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The First Code
- Hammurabi's Code (1772 BC)
Clause 229: If a builder builds a house for someone,
and does not construct it properly, and the house
which he built falls in and kills its owner, then that
builder shall be put to death.
PerformanceConsequence
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History of Building Codes
- Law of Moses (1300 BC)
“In case you build a new house, you must also make a parapet for your
roof, that you may not place bloodguilt upon your house because
someone falling might fall from it”.
- The Bible, Book of Deuteronomy, Chapter 22, Verse 8
Life Safety
Ultimately: Performance is desired.
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Prescriptive Codes
(ACI 318 – 11)
Do this … … your structure is safe
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• Traditional codes govern design of general, normal buildings
– Over 95% buildings are covered, which are less than about 50 m
• Not specifically developed for tall buildings > 50 m tall
• Prescriptive in nature, no explicit check on outcome
• Permit a limited number of structural systems
• Do not include framing systems appropriate for high-rise
• Based on elastic methods of analysis
• Enforce uniform detailing rules on all members
• Enforce unreasonable demand distribution rules
• Do not take advantage of recent computing tools
Shortcomings of the Traditional Codes

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• Implicit Performance Objective
– Resist minor earthquake without damage, which is anticipated to occur
several times during the life of a building, without damage to structural and
non-structural components
– Resist the design level of earthquake with damage without causing loss of life
– Resist strongest earthquake with substantial damage but a very low
probability of collapse
• Explicit verification not specified or required
Unsuitability of Traditional Design Codes
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Performance-based Engineering
Design for the achievement of specified results rather than adherence
to particular technologies or prescribed means.
- Peter May, 2004
Now, instead of worrying about mix proportions of concrete, you can
directly ask the contractor for a 60 MPa concrete
Courtesy: Performance-based approach
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Performance-based Design Approach
Client Designer
Independent Engineer
Guidelines:
PEER, TBI, ATC, FEMA, CTBUH, etc.
What to expect?
How to achieve this kind of approach?
Knowledge – Skills – Tools
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Consequence-based Engineering
A New Engineering Paradigm
(Abrams D.P., 2002)
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Core Research Thrust Areas
(Abrams D.P, 2002)
Stakeholder Thrust Areas
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Latest Guidelines and Specifications
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http://peer.berkeley.edu/tbi/
Tall Buildings Initiative
Guidelines
A Project of Pacific Earthquake
Engineering Research Center
(PEER)
Council of Tall Buildings and Urban
Habitat (CTBUH)
http://www.ctbuh.org/
National Earthquake Hazards
Reduction Program
http://www.nehrp.gov/

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Latest Guidelines and Specifications
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Federal Emergency Management Agency
http://www.fema.gov/earthquake-publications
Applied Technology Council
https://www.atcouncil.org/

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Traditional Design Methods
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• Prime Concern: “Balance External Actions with Internal Stress Resultants
with adequate margin for safety”
Sd >= FOS * Fa
• Check for:
– Deflections, Deformations, Durability
– Vibrations, Crack Width, Fire Protections, Permeability, Chemical Attacks
– Ductility and other special considerations
Proportioning for Safety
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• Working Stress Design
– Allowable Stress Design (ASD)
– Working Stress Design (WSD)
• Load Factor Design
• Ultimate Strength Design
– Ultimate Strength Design (USD)
– Strength Design (SD)
– Load and Resistance Factor Design (LRFD)
• Performance-based Design
– Pushover Analysis
– Capacity-based Design
Various Methods of Structural Design
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Obtained from
Analysis
Actions
Loads and Stress Resultants
Section Capacity/Section Design Process
Loads
Stresses
Stress
Resultants
Deformation
Depends on Stiffness
(Section and Rebars)
Strains
Dependson
SectionandRebars
FOS
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The Response and DesignFromLoadstoStresses
FromStrainstoResponse
Applied Loads
Building Analysis
Member Actions
Cross-section Actions
Material Stress/Strain
Material Response
Section Response
Member Response
Building Response
Load Capacity
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From Serviceability to Performance
Serviceability
Design
Strength Design
Performance
Design
Allowable material, control on
deformation limits for design loads
Material failure criteria, section capacity
for factored loads
Ductility considerations, deformation
capacity, load capacity at large
deformations. Extraordinary load
considerations
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• Satisfying one design level does not ensure that other design levels will be
satisfied
– Serviceability design only ensures that deflections and vibrations, etc., for
service loads are within limits but is irrelevant to strength.
– Strength design ensures that a certain factor of safety against overload is
available within a member or a cross-section but is insignificant to what
happens if the load exceeds the design level.
– Performance design ensures that the structure as a whole reaches a specified
demand level. Performance design can include both service and strength
design levels.
From Serviceability to Performance
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Limit State Design Concept
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Limit State Design Concept
Types of Limit State Description
Ultimate limit states
-Loss of equilibrium
-Rupture
-Progressive collapse
-Formation of plastic mechanism
-Instability
-Fatigue
Serviceability limit states
-Excessive deflections
-Excessive crack width
-Undesirable vibration
Special limit states
Due to abnormal conditions and abnormal loading such as:
-Damage or collapse in extreme earthquakes
-Structural effects of fire, explosion
-Corrosion or deterioration
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• Limit state design involves:
– Identification of all potential modes of failure
(i.e. identify significant limit states)
– Determination of acceptable levels of safety against occurrence of
each limit state
– Consideration by the designer of significant limit states
Limit State Design Concept
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Limit State Design Concept
• Safety Factors
– Material Safety Factor γm
– Member Factor γb
– Load Factor γf
– Structural Analysis Factor γa
– Structure Factor γi
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Limit State Design Concept
Safety Factors for Performance Verification
Characteristic value of
material basic strength
Design strength
γm
Design member
capacity
Characteristic value of
load
Design load
γf
Design member
capacity
γa
Verification γi
γb
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Limit State Design Concept
Material/Stress Type γm
Reinforcement 1.15
Concrete in flexure or axial load 1.50
Concrete shear strength without shear
reinforcement
1.25
Concrete bond strength 1.40
Concrete other >1.50
Values of γm (BS8110)
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Limit State Design Concept
Load
Combination
Load Type
Dead Load Imposed Load Wind
Adverse Beneficial Adverse Beneficial
Dead and
Imposed 1.4 1 1.6 0 -
Dead and wind 1.4 1 - - 1.4
Dead, wind
and imposed 1.2 1.2 1.2 1.2 1.2
Design Load= γf x Characteristic Load
Values of γf (BS8110)
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Special Design Considerations
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Structural Design Considerations
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• Story Drift for Occupant Perception
• Stability and Overturning
• Axial Shortening of Columns
• Transfer Girders and Deep Beams
• Shear Wall Design and Detailing
• Construction Sequence Analysis
• Design for Lateral Loads
• Seismic Performance

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• Weather Comfort
– Temperature 26 Degree Celsius
– Related Humidity 54%
• Motion Comfort Criteria
• Other Function-based Criteria
Other Comfort Criteria
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Human Motion Perception
Typical Values of
Acceleration
0.0 % g - 0.5% g
No perception
0.5% g - 1.5% g
Threshold of
perception
1.5% g - 5.0% g
Annoying
5.0% g - 15% g
Very Annoying
> 15% g
Intolerable
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47. Dr. Naveed Anwar
• Taranath, B.S. (2010). Reinforced Concrete Design of Tall Buildings. Taylor and
Francis Group, LLC.
• Fintel, M. (1986). Handbook of Concrete Engineering. CBS Publishers.
• Kong, F.K., Evans, R.H., Cohen, E., Roll, F. (1983). Handbook of Structural Concrete.
McGraw-Hill Book Co.
• Workshop Notes from ACECOMS
References
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48. Dr. Naveed Anwar
Executive Director, AIT Consulting
Affiliated Faculty, Structural Engineering
Director, ACECOMS
Thank You