An Adaptive Finite Element Code Using Linear Timoshenko Beam Elements and Its Applications


An adaptive finite element code using linear Timoshenko beam elements called the adaptively shifted integration (ASI) technique and its modified version, the ASI-Gauss technique, have been applied to various numerical simulations on the collapse of framed structures. One of its recent applications was a full model simulation of the aircraft impact with the New York World Trade Center (WTC) Tower 2 in 9/11 terrorist attack in 2001. According to the simulation, springback phenomena due to rapid unloading occurred in the core columns during the impact, which might have caused the destruction of member joints. Another simulation carried out was that of the fire-induced collapse of a high-rise tower mimicking the collapse of WTC 2. The results clearly show the effect of the weak member joints, which were reported to be 20 to 30 % of the strength of the members in WTC towers, and also the effect of the strength reduction due to elevated temperatures.