Lehigh expert says: World Trade Center collapsed under intense heat

The Federal Emergency Management Agency (FEMA) and the American Society of Civil Engineers (ASCE) announced the results and recommendations of their investigation into the collapse of the World Trade Center. Lehigh expert John Fisher was one of the report's authors.

Fisher, professor of civil engineering and co-director of the Engineering Research Center for Advanced Technology for Large Structural Systems (ATLSS) at Lehigh University, is one of the members of the panel that prepared the FEMA and ASCE report. He also was involved in the original design of the towers.

Comparing the impact of the planes hitting the towers with an atomic blast, Fisher says no building can be designed to withstand such an impact and ensuing heat from the jet fuel. The impact and heat were orders of magnitude larger than anything in history. We can design buildings to better withstand lesser impacts from smaller aircraft, and certain types explosions and fires, he says. We have always learned from failures, and we'll learn quite a lot from this one. But it is impractical to build a structure to sustain the kind of load and heat that hit the towers.

Fisher also says the connections that hold vertical columns and horizontal girders together in a steel structure can be improved, and he expects more research to be done in this area. He also notes that fire and structural engineers must work more closely than in the past. Fire was not something structural engineers designed for; fire engineers would come in, assess the level of fire protection needed and make recommendations, Fisher says. More collaboration will lead to better structural design and fire protection.

The Lehigh professor says the investigation was the most intensely emotional experience among of the dozens he has conducted throughout his career, because of the sheer magnitude and loss of life. He says he and his fellow panelists felt an urgency to complete what they considered a report critical to the nation's future security.

Fisher is known around the world for his investigations into many major steel-structure failures in the past 30 years, including the collapse of the Mianus River Bridge on I-95 in Connecticut in 1983 and the collapse of the Hyatt Regency Hotel in Kansas City in 1981. In 1987, Fisher was named Construction's Man of the Year by Engineering News-Record, the weekly magazine for the construction industry.

The ATLSS Center Fisher co-directs conducts research on the impact of everything from earthquakes to high seas on large structures from building to ships.

William Johnson
wjj0@lehigh.edu