America just recently observed the 10 year anniversary of the September 11th terrorist attacks. With that came a day full of remembrance, humility and grief for many. The events and consequences of that day remain a major turning point in history especially for the youth of this nation such as myself. That day had a major impact on the civil engineering community as well because of the structural failures that occurred at the World Trade Center complex. The two 110-story twin towers collapsed to the ground due to a progressive collapse that began at the impact sites of the airplanes on each building. The structural steel members were significantly weakened from the force of the plane crashes as well as the explosive fires that burned afterward.
A research project has been put into place at Purdue University recently to test effects of fire on steel. Structural steel comes in a variety of choices based on how it is prepared and what types of alloys are used in it. Steel structures can lose around 40% of their strength if the steel temp is in excess of 500 degrees Celsius. Sometimes building fires can reach 1000 degrees Celsius however. Most buildings have fireproofing material applied throughout to protect the structural integrity in the even a fire does happen so the building's occupants can get to safety. There is speculation that the plane impacts to the World Trade Center unfortunately disturbed that fireproofing rendering the steel members vulnerable to the fires burning.
Researchers at Purdue constructed a large structural lab that basically emulates a giant toaster in which large coils heat steel specimens that are also loaded simultaneously to simulate the behavior of structural steel in a building fire. The models and results from these experiments have been found to be quite accurate when compared to real world building fires. These models and results will be used not only to examine the effects of fire on structural steel members in buildings, but perhaps more importantly the extra stress and strain that structural joints experience as a result of weakening members that they connect.
I like how you took a current event and something that we all know about to talk about civil engineering. I think that is a really effective way to engage the audience, so nice job!
ReplyDeleteLoved the topic. My only wish is that you would have spoke more in depth about the modeling. I thought it was very interesting. I'm going to have to go somewhere else to get some more information.
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