Methodologies for Progressive Collapse Analysis

Abstract

Existing building codes contain some guidance on progressive collapse analysis and design. Unfortunately, in most of the U.S. building codes and standards that contain progressive collapse provisions, the available guidance is either vague, or does not define, the key issues that must be addressed. This lack of guidance has resulted in conflicting interpretations as to how one should approach progressive collapse analysis and design. The General Services Administration (GSA) and Department of Defense Unified Facilities Criteria (UFC) Progressive Collapse Guidelines [1-3] are currently the most complete sets of criteria in terms of providing usable guidance to the designer. However, only through experience can one identify the most appropriate modeling technique for a particular application. New and retrofit building designs commonly require only simplified estimates or low-fidelity analysis approaches to evaluate the potential for progressive collapse. These methods are typically conservative and are applied to evaluate the potential for collapse but do not determine the detailed mechanism for collapse and subsequent interaction once a collapse initiates. In some cases more detail is desired to pinpoint causes of failure and to accurately capture the sequence of failures leading to a progressive collapse. Methods for such analyses are complex, typically requiring detailed, nonlinear dynamic models that can take weeks or months to analyze on parallel processing computers. As such, these methods have only recently been possible and will continue to become more practical with further advances in computing technology. In the following sections, basic, upfront design approaches for mitigating progressive collapse are first discussed. Next, progressive collapse analysis approaches are discussed. Within this section, a lower fidelity analysis approach commonly used for design evaluation is discussed, which is followed by a discussion of modeling methods used in high-fidelity progressive collapse investigations.