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World Trade Center | Sep. 11th, 2001 

As the structural engineers of the World Trade Center, the men and women of LERA have a special bond with the buildings. Our Leslie E. Robertson directed the original design. Further, we have provided professional services for the complex continuously for almost forty years, including the reconstruction from the bombing in 1993. 

From our office, we watched as the second plane hit the South Tower. As did you, we suffered through the collapse, knowing that thousands of lives were being lost... and we feared for many of our friends, some of whom died in the attack. 

We designed the towers to resist the accidental impact of a Boeing 707, perhaps lost in the fog while seeking to land. The impact of the Boeing 767s, commandeered by the terrorists, even though larger and flying much faster, was still unable to bring down the towers. The fire-resistive systems, however, did not and could not have contemplated the subsequent fire fueled by thousands of gallons of jet fuel. 

Despite the enormous tragedy and loss, we are thankful that the towers stood as long as they did, allowing so many to evacuate.

The FEMA/ASCE Report

As noted in their report, the purpose of the Federal Emergency Management Agency/ American Society of Civil Engineers (FEMA/ASCE) team was to examine the damage caused by these events, collect data, develop an understanding of the response of each affected building, identify the causes of observed behavior, and identify studies that should be performed. 

LERA has advised and has cooperated with the FEMA/ASCE committee in their studies. 

Should you be interested in the FEMA/ASCE report here are the links:




World Trade Center and NIST"In response to the WTC tragedy, the National Institute of Standards and Technology is conducting a three-part plan: a 24-month building and fire safety investigation to study the factors contributing to the probable cause (or causes) of post-impact collapse of the WTC Towers (WTC 1 and 2) and WTC 7; a research and development program to provide the technical basis for improved building and fire codes, standards, and practices; and a dissemination and technical assistance program to engage leaders of the construction and building community in implementing proposed changes to practices, standards and codes. Also it will provide practical guidance and tools to better prepare facility owners, contractors, architects, engineers, emergency responders, and regulatory authorities to respond to future disasters."LERA participated in the development of a database of structural information for the two towers of the World Trade Center (WTC1 and 2).


For further information, please contact: 

SawTeen See
Managing Partner
Leslie E. Robertson Associates, R.L.L.P.


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