IABMAS2010, The Fifth International Conference on Bridge Maintenance, Safety and Management, July 11-15, 2010, Philadelphia, USA 1 INTRODUCTION Disproportionate collapse is a complex problem for which the existing terminology and procedures are inadequate. A multitude of terms is used to describe structural characteristics and concepts in the context of disproportionate collapse. This paper attempts to make a contribution to terminology and procedures. First, it seems useful to distinguish the terms col- lapse resistance, robustness and vulnerability. Work- ing definitions are suggested. Next, the basis of current reliability-based design codes for general structures is reviewed with par- ticular regard to their suitability to prevent dispro- portionate collapse. Their inadequateness regarding the prevention of disproportionate collapse is out- lined. To give immediate guidance to the practicing en- gineer, a pragmatic design approach is proposed in which probability-based design procedures as de- scribed in the codes are complemented by an addi- tional assessment with particular regard to dispro- portionate collapse. A performance-based framework for designing against disproportionate collapse – ap- plicable to any kind of structure, and thus also to bridges – is presented. 2 DISPROPORTIONATE VS. PROGRESSIVE COLLAPSE A disproportionate collapse is characterized by a pronounced disproportion between a relatively mi- nor event and the ensuing collapse of a major part or the whole of a structure. The term progressive col- lapse denotes a collapse that commences with the failure of one or a few structural components and then progresses over successively affected other components. In spite of different meanings, the terms dispro- portionate collapse and progressive collapse are of- ten used interchangeably because disproportionate collapse often occurs in a progressive manner and progressive collapse can be disproportionate. The term disproportionate collapse is more appropriate in the context of design and performance because a precise definition of disproportionate requires refer- ence to design objectives: a collapse is dispropor- tionate if the hazard scenarios lead to an extent of damage that violates the performance objectives. The term progressive collapse is more suitable when referring to the physical phenomenon and mecha- nism of collapse. A progressive collapse can involve different mechanisms of collapse that depend on the type and form of a structure and its orientation in space, as well as on the triggering abnormal event (Starossek 2007, 2009). 3 PREVENT DISPROPORTIONATE COLLAPSE The term abnormal event refers to an event that is unforeseeable or occurs with very low probability and is not considered in the ordinary design of a structure, although it may cause an initial local fail- ure and thus trigger a disproportionate collapse. Terminology for treating disproportionate collapse Marco Haberland & Uwe Starossek Hamburg University of Technology, Germany ABSTRACT: A multitude of terms is used to describe structural characteristics and concepts in the context of disproportionate collapse. Some of them, namely collapse resistance, structural robustness and vulnerability are discussed in this paper. This paper distinguishes these terms and the associated structural characteristics, and suggests working definitions. Additionally, a performance-based general framework for preventing dis- proportionate collapse is presented.