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October 9, 2013
An Important note from the Principal Investigator Abolhassan ASTANEH-ASL on the document that follows:
The following PowerPoint was prepared for Internal use of research team.
Abolhassan ASTANEH-ASL, Ph.D., P.E.
Professor and Principal Investigator for the NSF Funded UC Berkeley WTC Project (Duration: 10-2001 to 9-2002)
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Toppled Towers
Lessons Learned By
Abolhassan Astaneh-Asl, Ph.D., P.E.
Professor
University of California, Berkeley
Credit:Wtcphotos.com
This document is part of the “World Trade Center Post-Disaster Reconnaissance and Perishable Structural
Engineering Data Collection”, a research project funded by the U.S. National Science Foundation at the Univ. of
California Berkeley with Prof. Abolhassan ASTANEH-ASL as Principal Investigator
(http://www.ce.berkeley.edu/~astaneh) as the Principal Investigator. Duration of the project was from 10/2001 to
9/2002. Further Information and project archives are at http://lib.berkeley.edu/ENGI/WTC. © 2001 Abolhassan
ASTANEH-ASL.
"This work is licensed under a Creative Commons Attribution-NonCommercial -No Derivatives License."
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Dedicated to the memories of
all victims of 9/11 attacks and
to the firefighters and rescuers
who so heroically sacrificed
their lives to save others.
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1. Terrorist attacks on buildings
2. Protection against the attacks
3. Pentagon
4. World Trade Center
5. Lessons learned and future work
Outline:
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Terrorist attacks on US buildings since 1983 Year
of
Event
Cause of
Damage or
Collapse
Building, Location, and Consequences
1983
Car bomb.
US embassy in Beirut, (2 killed.)
1984
Car bomb
East Beirut US embassy bombing, (11 killed.)
1986
Explosion
La Belle disco in West Berlin, (2 killed.)
1993
Car bomb
World Trade Center in New York, (6 killed.)
1995
Explosion
Riyadh, Saudi Arabia, (No Casualties).
1995
Car bomb
Oklahoma City, Murrah Building, (168 killed.)
1996
Car bomb
Khobar Towers, Saudi Arabia, ( 19 killed.)
1998
Car bomb
US embassy, Tanzania
1998
Car bomb
US embassy, Kenya
2001
Plane
Attack
World Trade Center
2001
Plane
Attack
Pentagon
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Protecting Structures Against Terrorist Attacks
Ref: Developing Blast Resistant Structures , A. Astaneh-Asl (UC-Berkeley) and David McCallen (LLNL)
1)
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We have tapped resources and talents of both UC-Berkeley
and LLNL to form our research and development team.
Developing Effective
Barriers
(at LLNL)
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Protecting Structures Against Terrorist Attacks
Collaborative Work of
Abolhassan Astaneh-Asl et al., University of
California Berkeley and
David B. McCallen et al. Lawrence Livermore
National Laboratory
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The Case of Progressive Collapse of
Murrah Building, Oklahoma City, 1995
Murrah Building Before Attack
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The car bomb exploded too close to the building,
knocking out columns and transfer girders. Then due
to progressive collapse, ½ of the building collapse
under gravity load.
The Case of Progressive Collapse of
Murrah Building, Oklahoma City, 1995
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Effects of Blast Waves
on the Structure
Von Mises Stresses
(combined Shear and Normal Stresses)
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Specimen to Test Floor Catenary Action
Floor and Cables
Develop
Catenary Action
Cables in the Floor
Specimen
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Analysis at LLNL and Actual Full Size
Test at Univ. of California at Berkeley
Vertical Displacement of 20.8 inches
Cables
A.Astaneh-Asl, D. McCallen, E. Madsen, B.
Jones, R. Jong, W. Li, Y.Zhao,
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Copyright © 2001 Abolhassan ASTANEH-ASL
http://lib.berkeley.edu/ENGI/WTC
Cracks in the Concrete Slab
Hair
Cracks Compression
Crushing
N
Open
Cracks
Plan view of Hair Cracks, Compression Crushing and Open Cracks
at the end of tests. 14 of 61
The 9/11 Attacks
World Trade Center
Credit:Photographer Unknown
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World Trade Center Design,
Construction,
Collapse and;
Lessons Learned
Credit:Photographer Unknown
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World Trade Center
Architectural Aspects
Credit:Photographer Unknown
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The Architect
Minoru Yamasaki
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Some of Yamasaki’s earlier work
Credit:NYNJPA
IBM Building
Seattle
WTC 19 of 61
Yamasaki’s Initial Designs, 1960’s
Credit:PANYNJ
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The problem of elevators
and the innovative solution
23 Express Elevators, 1600 foot per minute
72 local elevators
4 freight elevator
16 escalators
44
78
110
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Site Plan
Credit:PANYNJ
Seven Buildings were built on 16 acre lot.
N
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Tower Plan
Credit:PANYNJ
Tower had large column-free areas
209 ft
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Soaring Façades
Credit:Photographer Unknown
Every three closely spaced columns above the 3rd floor
were collected into one column.
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World Trade Center
Structural Aspects
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The Structural Engineer
Leslie E. Robertson
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The Tube Invented at WTC
Source: 100 World’s Tall Buildings
209 ft
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The Structural System
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The Tube System
Credit: PANYNJ
Column Section 29 of 61
Foundations are supported on the rock
Credit: PANYNJ
Column Base
Grillage 30 of 61
Floors
Credit: PANYNJ
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Floors
Credit: PANYNJ
Credit:Arch Record
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Structural Design
Structure of a building is designed to resist combined effects of:
1. Vertical Load (e.g. weight of the building)
2. Lateral Load (e.g. wind and earthquake forces)
3. Temperature, impact and other loads
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Typical floors
WTC Gravity Design
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Wind Effects on WTC
Credit:SpaceImages.com 35 of 61
Wind Effects on WTC
Wind pressure is applied to all sides but primarily large pressures are on the windward surface.
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Wind Effects on WTC
Designed for 140
mile / hr wind
Wind Tunnel Tests Were
Conducted
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Wind Induced Vibrations
were controlled by 3M viscous dampers
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Fireproofing
Credit:NYTimes
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Effects of Fire on Structural Steel
Credit:US Steel
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World Trade Center
Construction
Credit:PANYNJPhotographer Unknown
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Construction of WTC “Bathtub”
Credit:ENR
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Construction of WTC Tower
Credit:PANYNJ
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Construction of WTC Tower
Credit:PANYNJ
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World Trade Center
The 9/11 Attacks
Credit:Photographer Unknown
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3-D Plane Hit Areas and Casualties
46
External and Internal Columns as well as
floors were damaged in 3 floors
Plane Impacting the Structure
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Plane Impacting the Structure
External and Internal Columns as well as
floors were damaged in 3 floors
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External and Internal Columns as well as
floors were damaged in 3 floors
Ensuing Fire
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External and Internal Columns as well as
floors were damaged in 3 floors
Ensuing Fires
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External and Internal Columns as well as
floors were damaged in 3 floors
Ensuing Fire and Collapse of Floor Joists
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External and Internal Columns as well as
floors were damaged in 3 floors
Buckling of Columns due to Long
Unbraced Length
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The damaged
floor collapsed
dropping top
portion on the
lower part
collapsing the
entire structure
Final Collapse Due to Gravity
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9/11, Collapse of South Tower
Credit:Photographer Unknown
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Fully loaded plane entering the structure and damaging it..
Studies of World Trade Center, Principal Investigator: A. Astaneh-Asl , University of California, Berkeley
Sponsor: Civil and Mechanical Systems Program, National Science Foundation
University of California Berkeley and MSC Software Corporation
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University of California, Berkeley and MSC Software Corporation
Studies of the World Trade Center
Principal Investigator: A. Astaneh-Asl , Sponsor: National Science Foundation
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University of California, Berkeley and MSC Software Corporation
Studies of the World Trade Center
Principal Investigator: A. Astaneh-Asl , Sponsor: National Science Foundation
Fire Heating-
up Damaged
Structure,
Weakening it
and the
Structure
Collapses
under the
Gravity Load.
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Lessons Learned and Future Work
1. Need better fire protection
2. Need new systems that can prevent progressive collapse economically and in architecturally pleasing manner.
3. Review fire codes and structural engineering codes to ensure protection for “important” structures against terrorist attack.
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