Although the conception and design of these buildings began some 40 years ago, they would still today comply structurally with the current New York Building Code. The lateral wind design force is four times larger than the zone 4 seismic forces in Los Angeles. Only 1/3 of the columns in any given floor are spliced at that floor level. The towers were designed to withstand the impact of a Boeing 707 flying at approximately 180 mph. The much larger jets used in the terrorist attacks were estimated to be traveling as much as 360 mph at impact (and fully loaded with fuel). There were 59 columns in each exterior face. It is believed that two thirds of the perimeter columns in the face of the building were badly damaged or destroyed at impact. Other columns may also have been damaged. As of 21 days after the attack, the fires were still burning and molten steel was still running. What concrete that wasn’t pulverized into

dust will continue to be removed for weeks to come. The structural steel is being removed and shipped by barge to be recycled. All photographs shown on television, shot-on-site were pre- approved by the FBI. We were shown photographs that were not released for public view. As a result of the events of September 11, the Structural Engineers Association of New York took upon the task of assisting in the search and rescue mission (and in the debris removal mission). Hundreds of New York structural engineers have volunteered to work in eight-hour shifts around the clock. They are also performing rapid visual inspections of some 400 other buildings in the area with potential damage. After the attack one tower stood for one hour, the other tower stood approximately 1 ¾ hours! This was enough time for many people to exit the building, and many lives were saved. As bad as this disaster was, it could have been much worse. The WTC