THEORY, PRACTICE AND RESEARCH IN THE EVOLUTION OF DESIGN STANDARDS FOR CIVIL ENGINEERING INFRASTRUCT

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THEORY, PRACTICE AND RESEARCH IN THE EVOLUTION OF
DESIGN STANDARDS FOR CIVIL ENGINEERING
INFRASTRUCTURE

• TED GALAMBOS
• UNIVERSITY OF MINNESOTA

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THEME OF LECTURE

• EVOLUTION OF DESIGN STANDARDS FOR STRUCTURAL
  DESIGN

• EXAMPLES
• AISC SPECIFICATION
• ACI CODE
• AA SPECIFICATIONS
• ETC.

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DEFINITIONS

• INFRASTRUCTURE ARTIFACTS NECESSARY FOR
  CIVILIZATION TO EXIST
• STRUCTURES SKELETONS UPHOLDING
  INFRASTRUCTURE-ESSENTIAL BUT OTHERWISE
  UNIMPORTANT

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DEFINITION PRACTICE

• THIS IS WHAT STRUCTURAL DESIGN ENGINEERS DO FOR A
  LIVING DESIGN STRUCTURES THAT ARE SAFE,
  SERVICEABLE, AND ECONOMICAL

• INTELLECTUAL EQUIPMENT OF STRUCTURAL ENGINEER
• ART
• SKILL
• SCIENCE
• EXPERIENCE
• JUDGMENT
• INTEGRITY

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DEFINITION THEORY

• SCIENTIFIC BASIS FOR UNDERSTANDING THE BEHAVIOR
  OF STRUCTURES UNDER LOAD

• SOLID AND FLUID MECHANICS
• MATHEMATICS
• MATERIALS SCIENCE
• PROBABILITY THEORY
• SYSTEMS SCIENCE
• ETC.

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DEFINITION RESEARCH

• THE ACTIVITY THAT CONNECTS THEORY WITH PRACTICE

• COMPUTATION METHODS
• PHYSICAL AND COMPUTATIONAL EXPERIMENTS
• ORGANIZATION OF DATA AND DESIGN ACTIVITIES
• ETC.

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FEATURES OF STRUCTURAL DESIGNCREATION OF A
STRUCTURE THAT WILL

• PERFORM SATISFACTORILY DURING ITS INTENDED
  LIFETIME
• NOT COLLAPSE OR EXPERIENCE EXCESSIVE DAMAGE
  DURING ITS INTENDED LIFETIME
• BE ECONOMICAL TO DESIGN, BUILD AND MAINTAIN

• SERVICEABILITY
• SAFETY
• ECONOMY

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EXPECTATIONS FROM STRUCTURAL DESIGN

• STRUCTURE IS UNCONDITIONALLY SAFE AND RIGID
• SAFETY, SERVICEABILITY, ECONOMY DURING INTENDED
  LIFETIME WHEN USED FOR PLANNED FUNCTION
• BUILDING CODE REQUIREMENTS MUST BE MET
• CHANCE OF EXCEEDING A LIMIT STATE DURING THE
  INTENDED LIFETIME MUST BE ACCEPTABLY SMALL

• GENERAL PUBLIC
• STRUCTURAL ENGINEER
• BUILDING AUTHORITY
• CODE COMMITTEE

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HOW TO ATTAIN SAFE STRUCTURAL DESIGNS?

• MINIMIZE HUMAN ERROR
• QUALITY CONTROL

• ENSURE THAT CHANCE OF EXCEEDING LIMIT STATE IS
  ACCEPTABLY SMALL
• LOAD STANDARDS AND DESIGN CODES

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PYRAMID OF DESIGN REQUIREMENTS
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STRUCTURAL DESIGN SPECIFICATIONS

• LEGALLY BINDING MINIMUM REQUIREMENTS FOR THE SAFE
  DESIGN OF STRUCTURES
• ENFORCED BY GOVERNMENT (LOCAL, REGIONAL, NATIONAL)

• ORIGINATING AGENCIES
• VOLUNTARY COMMITTEES OF EXPERTSWORKING ON A
  NATIONAL OR INTERNATIONAL BASIS

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STRUCTURAL DESIGN SPECIFICATIONS

• ARE LEGAL, BUT THEY ARE NOT
• LAWS IN THE SENSE OF NEWTONS LAWS
• LAWS IN THE SENSE THAT LIGHTNING STRIKES IF YOU
  ARE 1 OVER
• A BIBLE THAT IS ETERNALLY CANONIZED BY THE SAINTS
  OF STRUCTURAL ENGINEERING

• STRUCTURAL ENGINEERS MUST KNOW THE BACKGROUND SO
  THAT THEY HONOR THE SPIRIT AND NOT THE LETTER OF
  THE SPECIFICATION

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EVOLUTION OF DESIGN CODES
First use
Time-tested satisfactory performance
Design Requirement
Disaster
Time
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Yarra River bridge Melbourne, Australia, August
1970
Pictures taken by Nick Trahair And Ted Galambos
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Two halves of span jacked into place on each
side of pier. The design of the box-girders went
beyond theory, test and experience
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Collapse of one approach span in October 1970. 36
people died.
The bridge was redesigned and rebuilt. It has
been in service for almost 30 years. I traveled
over it in June 2004.
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EVOLUTION IN AISC STEEL DESIGN SPEC.NUMBER OF
PAGES IN AISC SPECIFICATION

• 1923 15
• 1928 16
• 1936 19
• 1949 30
• 1963 134

• 1969 158
• 1978 162
• 1986 219
• 1993 276
• 1999 291
• 2005

CANNOT TELL YET BECAUSE THE SPECIFICATION IS
NOT YET PRINTED IN FINAL BOOK FORM. BUT IT WILL
BE LARGER THAN THE PREVIOUS ONES, FOR SURE
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EVOLUTION IN STEEL DESIGNYIELD STRESS OF MILD
STEEL

• DUBOIS, 1890 29 KSI
• KETCHUM, 1918 28 KSI
• AISC 1923 - 1963 33KSI
• AISC 1963 1999 36 KSI
• 2005 50 KSI

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RESEARCH
APPLICATION
THEORY
CRC COLUMN FORMULA IN AISC
COLUMN CURVES FORMULAS COLUMN TESTS RESIDUAL
STRESS MEASUREMENTS
PARADOX RESOLVED BY REASONING AND TEST (SHANLEY)
IMPORTANCE OF RESIDUAL STRESS RECOGNIZED
PERFECTLY STRAIGHT COLUMNS
TANGENT MODULUS REDUCED MODULUS (ENGESSER,
CONSIDERE)
ELASTIC THEORY (EULER, 1753)
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RESEARCH
APPLICATION
THEORY
MODERN DESIGN SPECIFICATIONS
NAGOYA DATA BANK
EUROPEAN COLUMNCURVES
BATTERMAN JOHNSTON TALL, BEER, SCHULTZ BJORHOVDE
SSRC COLUMN CURVES
EUROPEAN TESTS
LEHIGH TESTS
DIN 4114
CHWALLA, JEZEK COLUMN THEORY
ROS, BRUNNER COLUMN TESTS
WESTERGAARD, OSGOOD RESIDUAL STRESS
INITIALLY OUT-OF STRAIGHT COLUMNS
von KARMAN INELASTIC ANALYSIS
RANKINE (1861)
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UNSAFE
LOAD EFFECT
SAFE
RESISTANCE
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LOAD EFFECT Q
RESISTANCE R
PROBABILITY DENSITY
VALUE OF Q or R
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pQ(x)
pX(x)
x
pR(x)
PROBABILITY OF FAILURE
x
TWO INDEPENDENT EVENTS
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mean
Probability 0f failure
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b2.5
b3.9
b4.4
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SELECT BRIDGES (WSD, LFD)
RELIABILITY ANALYSIS b
TARGET RELIABILITY bT
DESIGN EQUATION FORMAT
RELIABILITY ANALYSIS FOR f FOR ELEMENT MATERIAL
OPTIMIZE gi FOR ALL TYPES OF LOADS AND
COMBINATIONS FOR ALL TYPES OF BRIDGES
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DESIGN STRENGTH2005 AISC SPECIFICATION
LOAD AND RESISTANCE FACTOR DESIGN
ALLOWABLE STRESS DESIGN
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2005 AISC Specification
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AISC 2005 SPECIFICATION
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SECOND-ORDER ELASTIC ANALYSIS FOR LRFD
LOAD
1.2Dn1.6Ln
FIRST ORDER ANALYSIS
SECOND-ORDER ANALYSIS
Mrequired
MOMENT
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SECOND-ORDER ELASTIC ANALYSIS FOR ASD
1.6Dn1.6Ln
LOAD
FIRST ORDER ANALYSIS
DnLn
SECOND-ORDER ANALYSIS
Mr
1.6Mr
MOMENT
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DEFINITION OF AMPLIFICATION FACTOR B2
LOAD
MOMENT
Mr1ST
Mr2NDB2 x Mr1ST
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AISC INTERACTION EQUATION
WATCH OUT NEXT FOR Pn AND Mr
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CHOICES FOR FORCE ANALYSIS
Y
DIRECT ANALYSIS
N
Y
1ST-ORDER ANALYSIS
N
2ND-ORDER ANALYSIS
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SECOND-ORDER ANALYSIS
2ND-ORDER ANALYSIS PROGRAM OR 1ST-ORDER ANALYSIS
PROGRAM WITH AMPLIFICATION FACTORS
Keff gt 1.0 IN CALCULATING Pn
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FIRST-ORDER ANALYSIS

• 1ST-ORDER ANALYSIS PROGRAM
• Keff 1.0 IN CALCULATING Pn

NOTIONAL LATERAL FORCE MUST BE ADDED TO
ACTUAL LATERAL FORCE
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DIRECT ANALYSIS
2ND-ORDER ANALYSIS PROGRAM
REDUCED FLEXURAL STIFFNESS EI 0.8tEI
REDUCED AXIAL STIFFNESS EA 0.8EA
NOTIONAL LATERAL FORCE 0.002 S PGRAVITY
KEFF 1.0
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PROGNOSIS ABOUT THE FUTURE OF CURRENT STRUCTURAL
DESIGN STANDARDS

• Convergence to LRFD/LSD format.
• International cooperation/harmonization.
• Changes and additions for new materials and
  structure types.
• Will be viewed as being too complicated by the
  practicing engineers.
• Paper versions will eventually become obsolete.
• Spread- sheets are necessary.

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NEW TRENDS IN STRUCTURAL STANDARDS

• Entirely probability-based design for members and
  joints (Marek, etc.).
• Project specific probabilistic systems design for
  major structures (offshore, nuclear, etc.).
• Performance-based design.
• Motivations
• Earthquake and fire engineering
• Security against terrorist acts

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PERFORMANCE-BASED DESIGN IN FIRE ENGINEERING

• Example
• AISC 2005 Appendix 4
• STRUCTURAL DESIGN FOR FIRE CONDITIONS.
• Topic and method 1st time in an AISC
  Specification.

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AISC DEFINITION OF PERFORMANCE-BASED DESIGN

• An engineering approach to structural design
  that is based on agreed-upon performance goals
  and objectives, engineering analysis and
  quantitative assessment of alternatives against
  those design goals and objectives using accepted
  engineering tools, methodologies and performance
  criteria.

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AISC DEFINITION OF PRESCRIPTIVE DESIGN

• A design method that documents compliance with
  general criteria established in a building code.

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AISC PERFORMANCE OBJECTIVE

• Structural components, members and building
  frame systems shall be designed so as to maintain
  their load-bearing function during the
  design-basis fire and to satisfy other
  performance requirements specified for the
  building occupancy.

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PERFORMANCE-BASED DESIGN IN EARTHQUAKE ENGINEERING

• EXAMPLE
• Recommended Seismic Design Criteria For New
  Steel Moment-Frame Buildings.
• FEMA 350, July 2000

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Building performance level
Immediate occupancy
Life safe
Near collapse
Operational
50 in 50yr
Frequent
Ground motion levels
M
2 in 50yr
MCE
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POST_EARTHQUAKE STRUCTURAL PERFORMANCE LEVEL
DEFINITIONS

• Collapse Prevention
• Structure is on the verge of partial or total
  collapse. Must carry gravity load demands.
• Immediate Occupancy
• Only limited structural damage has occurred.

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FEMA-350 PERFORMANCE DEFINITION

• Example
• A design shall provide a 95 level of confidence
  that the structure will provide Collapse
  Prevention or better performance for earthquake
  hazards with a 2 probability of exceedance in 50
  years.
• Methods are given for a simple or detailed
  evaluation of the level of confidence.

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THANK YOU VERY MUCH FOR YOUR KIND
ATTENTION. QUESTIONS OR DISCUSSION??