Prof. Dr.-Ing., P.E. Uwe Starossek (TUHH), Germany

PROGRESSIVE COLLAPSE OF STRUCTURES
Uwe Starossek
Prof. Dr.-Ing., P.E.
Structural Analysis and Steel Structures Institute
Hamburg University of Technology (TUHH), Germany
E-mail: starossek@tuhh.de

In terms of tragedy and losses the above mentioned cases of failure were far exceeded by the collapse on September 11th, 2001 of the twin towers of the World Trade Center. The impact of the airplane and the subsequent fire initiated local failures in the area of impact. The ensuing loss in vertical bearing capacity was limited to a few stories but extended over the complete cross section of the respective tower [9, 10]. The upper part of the structure started to move downwards and accumulated kinetic energy. The subsequent collision with the lower part of the structure, which was still intact, caused enormous impact forces which were far beyond the reserve capacities
of the structure. This, in turn, led to the complete loss of vertical bearing capacity in the area of the impact. Failure progressed in this manner and led to a total collapse.