Disproportionate Collapse Research Needs

Mechanisms of progressive collapse resistance are described which help identify new design requirements that effectively improve collapse resistance of structures. Criteria must be established to identify structures for which progressive collapse resistance may need to be enhanced through the implementation of additional design requirements. Enforcing disproportionate collapse-resistant design criteria beyond current practice for all structures may not be justified because most buildings are not at significant risk. Simplified approaches may be sufficient for buildings that require explicit evaluation of their progressive collapse resistance following column removal. One such approach is based on a comparison between the strength of the structure under a downward force at the location of removed column and the axial compressive force in the column. If the structure is identified to be susceptible to collapse, more advanced analysis is justified. Such analyses may be required more often in evaluation of existing structures than in design of new structures. The results of such analyses involve significant uncertainty and their reliability heavily depends on the modeling and analysis assumptions. One of the more important assumptions that require further investigation is the deformation capacity of elements subjected to interacting actions (such as tension combined with flexure and/or shear). Features that are important in modeling structures for collapse analysis as well as parameters that are important in developing progressive collapse resistant mechanisms require further studies.