Performance Criterion for Selecting Columns to Be Removed in the Alternate Load Path (ALP) Analysis for Progressive Collapse Assessment

The alternate load path (ALP) method is an event-independent approach in analysing robustness against progressive collapse, where the actual load arising from the complicated triggering event is not considered. The method proposes the removal of one or more load-bearing elements of a structure, such as a column, and the consequences following from the location of removed column onto the investigated structure will be analysed in terms of its ability to redistribute the gravity loads to the remaining intact structural elements. Since the assessment of structural robustness using the ALP method is highly dependent on the location of the lost column, it is important that selection of the critical column position that needs to be removed for detail progressive collapsed assessment is undertaken with care. If this is not the case, the results generated will not be able to show the actual level of the robustness of the structure. In this paper, a new, performance criterion namely, the computation of the total number of overstressed remaining members was introduced to determine the most critical column location for further evaluation of the structural resistance against progressive collapse. SAP2000 structural design software and MATLAB were used as tools for the collapse analysis. A ten-storey moment-resisting steel frame structure was used to demonstrate the implementation of the proposed criterion. It can be concluded that the proposed criterion has the potential to be a useful and quick indicator to determine the critical column location for a more detail progressive collapse analysis of a structure.