an important note from the principal investigator...

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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http://www.ce.berkeley.edu/~astaneh

http://lib.berkeley.edu/ENGI/WTC

http://creativecommons.org/licenses/by-nc/3.0/





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


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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


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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



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Ensuing Fire

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Ensuing Fires

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Ensuing Fire and Collapse of Floor Joists

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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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http://www.newsday.com/

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


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An Interior Column hit by the engine?

767 Engine http://lib.berkeley.edu/ENGI/WTC


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Member Identification



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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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an important note from the principal investigator...

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