The Pentagon Building Performance Study

1The special section contained in this issue archives the study of the Pentagon building performance conducted by ASCE following the September 11, 2001 terrorist attack. The five papers document the structure, the crash loading, and the damaged induced. Then, through basic analyses, plausible hypotheses of structural and thermal response are evaluated. The results provide the basis for important lessons that apply to all of the structures in which the public works and lives.

The term “lessons learned” commonly conjures up an experience in which a lapse has been responsible for a failure. Indeed some of the case studies that have been chronicled in this journal and other publications describe such occurrences. It is important to make a note of these and gain experience from them. However, the forensic engineering profession can and should also learn from positive incidents in which superior practice has avoided or mitigated a serious problem.

The structural response of the Pentagon to the September 11, 2001 terrorist attack represents such a positive episode. While the loss of 184 lives in the event is a terrible tragedy, certain superior practices incorporated into the original design of the building prevented even worse damage. As described in the papers of this special section, the structural detailing of this building provided continuity, redundancy, energy-absorbing capacity, and reserve strength in the structural frame. We should make note of these superior practices as we engineer structures to resist general collapse following localized damage from whatever cause.

It is further valuable to compare the response of the Pentagon described herein to that of the Murrah Federal Office Building in the 1995 Oklahoma City terrorist bombing. ASCE also conducted a building performance study of that tragedy that was reported in a special section of this journal in August 1998. That study concluded that the engineering of the structure met the minimum standards for buildings. However, a catastrophic general collapse occurred following comparatively localized damage.