October 9, 2013
An Important note from the Principal Investigator Abolhassan ASTANEH-ASL on the document that follows:
The following PowerPoint was presented at a meeting of Civil Engineering Student Honor Society, Chi Epsilon (XE) in 2002 on the
Campus of UC Berkeley.
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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Protection of Buildings Against Terrorist Attacks
and the Collapse of the World Trade Center By
Abolhassan Astaneh-Asl, Ph.D., P.E.
Professor
University of California, Berkeley
Credit:Wtcphotos.com
Organized by the UC Berkeley
Chapter of Chi Epsilon
XE 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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Outline 1. Terrorist attacks on buildings
2. Protection against the attacks
3. Pentagon
4. World Trade Center
5. Lessons learned and future work
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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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Protecting Structures Against Terrorist Attacks
Collaborative Work by
Abolhassan Astaneh-Asl et al., University of California Berkeley and
David B. McCallen et al. Lawrence Livermore National Laboratory
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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
A.Astaneh-Asl, D. McCallen, E. Madsen, B. Jones, R. Jong, W. Li,
Y.Zhao,
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World Trade Center Design,
Construction,
Collapse and;
Lessons Learned
Credit:Photographer Unknown
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The Architect
Minoru Yamasaki
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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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World Trade Center
Structural Aspects
Credit:Photographer Unknown
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The Structural Engineer
Leslie E. Robertson
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The Structural System
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The Tube System
Credit: PANYNJ
Column Section 20 of 55
Floors
Credit: PANYNJ
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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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Wind Effects on WTC
Credit:SpaceImages.com
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Wind Effects on WTC
12500 kips
9.5 million
ft-kips
Designed for 140
mile / hr wind
Wind Tunnel Tests Were
Conducted
Copyright © 2001 Abolhassan ASTANEH-ASL
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Wind Induced Vibrations
were controlled by 3M viscous dampers
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Fireproofing
Credit:NYTimes
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World Trade Center
Construction
Credit:PANYNJPhotographer Unknown
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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
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People Trapped in the Upper Floors
Credit: Photo by Jeff Christensen Reuter
1993
2001 31 of 55
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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Causes of Collapse Leading theories on collapse of the towers
1. Fire weakened the floor trusses that connected the
exterior and interior columns, causing the trusses
to sag and eventually separate from the external
walls.
2. Initial impact of the planes was so great that the
towers were on the verge of collapsing when the
fire weakened external columns.
3. The initial impact caused the weight of the upper
floors to be shifted from exterior to interior
columns.
Copyright © 2002, Newsday, Inc.
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What was done in the aftermath of 9/11
1.National Science Foundation awarded 8 grants to
study various aspects of the collapse. UC-Berkeley
Project was for structural engineering aspects.
2.FEMA funded a study by Building Performance
Assessment Team.
3. A congressional Hearing was held.
What is in the planning:
4.NIST will lead a comprehensive study for $40M.
5. NSF is funding research in this field.
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Post Collapse Investigation of
Steel Structure
Research Funded by National
Science Foundation
Photo by William Farrington for A. Astaneh’s WTC NSF Project. Copyright © 2001 UC Board of Regents
http://lib.berkeley.edu/ENGI/WTC
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Investing Steel Structure
http://lib.berkeley.edu/ENGI/WTC
Copyright © 2001 Abolhassan ASTANEH-ASL
http://lib.berkeley.edu/ENGI/WTC
Copyright © 2001 Abolhassan ASTANEH-ASL
http://lib.berkeley.edu/ENGI/WTC
Copyright © 2001 Abolhassan ASTANEH-ASL
http://lib.berkeley.edu/ENGI/WTC Copyright © 2001 Abolhassan ASTANEH-ASL
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An Interior Column hit by the engine?
767 Engine http://lib.berkeley.edu/ENGI/WTC
Copyright © 2001 Abolhassan ASTANEH-ASL
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Member Identification
http://lib.berkeley.edu/ENGI/WTC
Copyright © 2001 Abolhassan ASTANEH-ASL
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Congressional Hearing
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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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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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What can we do about airplanes crashing
into buildings?
Today’s crash of a plane into a 30-
story building in Milan Italy
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Developing Protective Systems
At University of California, Berkeley
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Composite Shear Walls Can Be Used
Around Stairwells to Protect Egress
Routes
Relatively
Thin Steel
Plate Welded
to Steel
Structure
Lightly
Reinforced,
Lightweight
Concrete
Panel
Connected
to Steel Plate
Steel Plate Resists the
Pressure by Membrane Action.
Concrete Panel Bent and
Damaged.
Components of the
Proposed Wall
Membrane Action of Steel
Plate Behind Concrete Panel
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Composite Shear Walls Can Be Used
Around Stairwells to Protect Egress
Routes
Research Data on Fire Resistance Can be Useful
http://lib.berkeley.edu/ENGI/WTC Copyright © 2001 Abolhassan ASTANEH-ASL
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Wish you were here Concluding Remarks:
We need to undertake a scientific study of this
threat and find out how vulnerable our buildings
are. Then through sustained research and
development programs respond to this threat and
save the lives of people who can become the victims
of this type of attack. We owe it to the memory of
those who lost their lives during the 9/11 barbaric
attacks.
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