http://www.nist.gov/el/disasterstudies/wtc/wtc_contracts.cfm 1

Awarded Contracts for External Experts to Support the 

NIST World Trade Center (WTC) Disaster Investigation

Contract No. Awarded to Date Awarded

SB1341-06-8-0539 Applied Research Associates 8/22/2006

WTC 7 STRUCTURAL ANALYSIS AND COLLAPSE HYPOTHESES, CONTRACT MODIFICATIONS 

FOR STRUCTURAL AND BLAST ANALYSES 

Under GSA Contract number GS23F0278M, NIST Order No. SB1341-06-8-0539, as a firm fixed price 

effort, has been awarded to APPLIED RESEARCH ASSOCIATES, INC. (ARA) of Albuquerque, New 

Mexico, to append the following tasks to the original contract awarded on March 31, 2006. Under the 

appended tasks, the ARA (1) shall conduct analyses of impact damage and fire effects to provide 

candidate initiating events which may lead to structural failures and global collapse, and (2) shall 

determine if there is any scenario of a hypothetical blast event or events that could have occurred in WTC 

7 on September 11, 2001. 

As part of determining likely modes of failure in WTC 7, impact by falling debris from WTC 1, fire events, 

and hypothetical blast events are being considered for their contribution to the collapse of WTC 7. NIST 

has documented debris damage and fire growth and spread in WTC 7, based on available evidence. 

NIST is analyzing scenarios for the event that initiated the collapse of the building. As a part of this work, 

NIST is considering whether hypothetical blast events could have played a role in initiating the collapse. 

While NIST has found no evidence of a blast or controlled demolition event, NIST would like to determine 

the magnitude of hypothetical blast scenarios that could have led to the structural failure of one or more 

critical elements as a result of blast.

ARA is an engineering firm founded in 1979 that performs research and design studies for complex 

defense, security, environmental, transportation, and readiness problems. This study will be managed 

from the Silicon Valley Office of ARA that specializes in finite element analysis and nonlinear structural 

dynamics under blast and impact loading, impact and penetration mechanics, failure analysis, and blast 

effects and the analysis of progressive collapse in buildings. ARA is partnering with Simpson Gumpertz & 

Heger Inc. (SGH) of Waltham, Massachusetts, to conduct the appended tasks, and with Loizeaux Group 

International (LGI), the consulting services branch of Controlled Demolition Incorporated (CDI) of 

Phoenix, Maryland. 

SGH is an engineering firm that specializes in design, investigation and retrofit of buildings and structures 

of all types. SGH has expertise in building structures, materials, and investigations and conducted the 

thermal-structural response analyses of each WTC tower, as part of their contract for the WTC towers 

investigation. 

Loizeaux Group International (LGI) has expertise in a wide range of demolition, explosion and explosivesassociated technology. This includes explosive processes and their direct and collateral effects of blast 

and resulting vibration, projectiles, and overpressure. They have conducted investigations involving 

commercial explosives, terrorist devices, commercial gas, and industrial accidents involving dusts, hot 

metals, and combustion processes. 
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The specific tasks that ARA will perform with SGH (task 1) and LGI (task 2) include:

1. Identify and analyze hypothetical blast scenarios in three phases, with the results from each 

phase being used to decide if the analyses in the next phase is required: 

A. Identify hypothetical blast scenarios, using analysis and/or experience, to determine 

conditions that would fail specified column sections by direct attachment of explosive 

materials. 

B. Analyze the overpressure produced by the blast load and determine if the overpressure 

would have failed windows in WTC 7. 

C. Determine if the overpressure would result in sound levels transmitted through intact 

WTC 7 windows that could be heard outside the building. 

2. Conduct the following analyses using a three-dimensional ANSYS model (provided by NIST) of 

the lower 16 floors of WTC 7: 

A. Review the ANSYS model provided by NIST for conducting structural analysis of damage 

to components and the effect of time-varying temperatures. Identify possible 

revisions/improvements to the ANSYS model that may improve efficiency, accuracy 

and/or capture of critical failure modes. 

B. Work with NIST staff to incorporate agreed upon changes to the ANSYS model. 

C. Determine the structural response of WTC 7 for up to six scenarios of structural damage 

from debris impact and temperature histories provided by NIST. NIST will conduct 

analyses of other scenarios in parallel. Work with NIST to identify the structural response 

and failure modes for each analysis. 

The ARA team has expertise and experience in failure analysis, nonlinear structural analysis, damage of 

steel and concrete structures, progressive collapse analyses, nonlinear constitutive and damage 

modeling, analysis of structures subjected to thermal loads, and blast effects on structures. The team will 

be led by Dr. Steven W. Kirkpatrick. Select experience of key project personnel is summarized below: 

Dr. Steven W. Kirkpatrick is the program manager for this project. Dr. Kirkpatrick is a Principal 

Engineer with 21 years of experience in structural dynamics, failure analysis, finite element 

analysis, impact and blast/penetration mechanics, and vehicle crashworthiness. He has more 

than 40 publications in these areas. His research experience includes a wide range of 

government and commercial projects for rail, highway, civil, military, and aerospace applications. 

He has been a program leader for many studies requiring close collaboration between 

experimental and computational efforts with emphasis on model validation. Dr. Kirkpatrick was 

previously the PI for the ARA participation in the NIST WTC investigation in performing the 

aircraft impact analyses. Dr. Kirkpatrick has a doctorate in mechanical engineering from Stanford 

University. 

Mr. Charles Needham is a Principal Engineer for the Southwest Division of ARA. He has 

experience with numerical hydrodynamics, shock, fireball and thermal effects modeling, 

conventional explosives and munitions effects and structure interaction, explosive safety and 

storage. He has 14 years specific experience with SHAMRC, a state-of-the-art hydrodynamic 

code for two- and three-dimensional fluid dynamics problems with applications for conventional 

munitions. Mr. Needham has a master’s degree in astrophysics from the University of New 

Mexico. 

Mr. Joseph Crepeau is a Principal Computer Scientist for the Southwest Division of ARA. His 

responsibilities include the maintenance and development of features for SHAMRC, as well as 

training for its applications. Mr. Crepeau has a master’s degree in computer science from the 

University of New Mexico. 

Ms. Lee Ann Young is a Principal Engineer I for the Southwest Division of ARA. She has spent 

the last 14 years at ARA working in the areas of human vulnerability to explosions, penetration 

mechanics, and conventional weapon effects. Ms. Young has a master’s degree in applied 

statistics from the University of New Mexico. 
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Dr. Mehdi Zharghamee is a Principal and Head of the Engineering Mechanics and Infrastructure 

Division at SGH and has 30 years of engineering experience in analysis and design of precision 

structures. He has been responsible for analysis, design, and failure investigation of complex 

structural and mechanical systems. Dr. Zarghamee has a doctorate in structural engineering from 

the University of Illinois and his S.M. in Mathematics from the Massachusetts Institute of 

Technology. 

Dr. Omer Erbay is a Senior Engineer with SGH and has experience with the analysis of the 

structural response of the WTC towers to impact damage and fire conditions and structural 

analysis of buildings and bridge piers. Dr. Erbay has a doctorate in structural engineering from 

the University of Illinois. 

Frank Kan, a Senior Project Manager, has been with SGH for 16 years. He has been involved in 

structural and seismic analysis, design, and investigation of buildings, bridges and special 

structures. Mr. Kan received his M.S. in Civil Engineering from the Massachusetts Institute of 

Technology. 

Mr. Mark Loizeaux is CEO of LGI and President of CDI, and has been responsible for the design 

and performance of CDI’s projects since 1976, including the felling of major steel industrial, 

commercial and office buildings across the United States and internationally. Several of these 

buildings were major structures up to 439 ft tall, with column flanges ranging from 6 in. thick 

(laminated steel flanges) to 4 in. thick (hot-rolled flanges). His experience with steel structures 

includes the demolition of major steel bridges and construction and communication towers as tall 

as 1,200 ft. He is responsible for all aspects of CDI explosives demolition design and control of 

related consequences, including control of fly of debris, air overpressure, vibration and debris 

impact on surrounding structures. He has been recognized as an expert in demolition and 

explosives operations in U.S. Federal Court and the Courts of Australia.