Search

This paper presents some findings of the FEMA and SEI/ASCE sponsored studies of structural performance of New York’s World Trade Center (WTC) following the attacks of September 11, 2001, and the Murrah Building following the April 19, 1995, Oklahoma City bombing. The WTC collapses were caused not by aircraft impact alone but by the combination of impact and the resulting fire that weakened structural members and connections. On the other hand, the Murrah Building collapsed as a direct result of the blast. Although these studies call for further research in a number of areas, this report summarizes some of the lessons learned. [ABSTRACT FROM AUTHOR]

Following the collapse of the World Trade Center towers in September 2001, there has been heightened interest among building owners and government entities in evaluating the progressive collapse potential of existing buildings and in designing new buildings to resist this type of collapse. The General Services Administration and Department of Defense have issued general guidelines for evaluating a building’s progressive collapse potential. However, little detailed information is available to enable engineers to confidently perform a systematic progressive collapse analysis satisfying these guidelines. In this paper, we present four successively more sophisticated analysis procedures for evaluating the progressive collapse hazard: linear-elastic static; nonlinear static; linear-elastic dynamic; and nonlinear dynamic. We discuss the advantages and disadvantages of each method. We conclude that the most effective analysis procedure for progressive collapse evaluation incorporates the advantageous parts of all four procedures by systematically applying increasingly comprehensive analysis procedures to confirm that the possibility of progressive collapse is high. [ABSTRACT FROM AUTHOR]

The neighborhood-level destination offers the potential for diversion from automobile travel to walking, and design that minimizes neighborhood walking distances should be encouraged. This paper illustrates the use of a geographic information systems (GIS) based approach to compare the average walking accessibility between alternative neighborhood designs. Three neighborhood plans for an actual 23.3-ha site are considered: the development's original layout, the original layout without pedestrian walkways, and a more “sustainable” redesign. Schools, open space, and transit stops are considered as neighborhood destinations and a difference in pedestrian accessibility for the alternative plans is documented. Results suggest that empirical evaluation of neighborhood accessibility for subdivision layouts should be undertaken; that pedestrian walkways are an excellent means to improve walking accessibility within neighborhoods; and that with only minor changes to a site plan, many residents unfortunately remain beyond currently accepted walking distances for neighborhood-level destinations. [ABSTRACT FROM AUTHOR]

The article focuses on the article published in the July 2002, issue of the "Journal of Engineering Mechanics," on various preventive measures that could have prevented the collapse of World Trade Center. According to the author, when a lateral load hits the intermediate stories of a tall building, the vertical load transmission path gets disrupted. Consequently, the intermediate stories hang on to the undamaged top portion of the building and exert an enormous pull with their massive self-weight. Because of this phenomenon, the WTC towers had a collapse failure and this was aided by the conflagration of the aircraft fuel spilled inside the building. The conflagration due to aircraft fuel in the WTC towers apparently heated the building to a temperature of over 800°C. Obviously, the various energy-absorbing materials considered cannot withstand such a sustained temperature. The author explains the possible constructional features to prevent the collapse of tall buildings like WTC. The article also presents an acknowledgement of thanks from writers of the discussion to the article's writer to clarify their papers.

The article focuses on the article published in the July 2002, issue of the "Journal of Engineering Mechanics," on various preventive measures that could have prevented the collapse of World Trade Center. According to the author, when a lateral load hits the intermediate stories of a tall building, the vertical load transmission path gets disrupted. Consequently, the intermediate stories hang on to the undamaged top portion of the building and exert an enormous pull with their massive self-weight. Because of this phenomenon, the WTC towers had a collapse failure and this was aided by the conflagration of the aircraft fuel spilled inside the building. The conflagration due to aircraft fuel in the WTC towers apparently heated the building to a temperature of over 800°C. Obviously, the various energy-absorbing materials considered cannot withstand such a sustained temperature. The author explains the possible constructional features to prevent the collapse of tall buildings like WTC. The article also presents an acknowledgement of thanks from writers of the discussion to the article's writer to clarify their papers.