Uniform Pushdown Approach for Quantifying Building-Frame Robustness and the Consequence of Disproportionate Collapse

Abstract

This paper proposes a framework for quantifying the structural robustness of building frames that utilizes a relative numerical interpretation of the strength degradation in response to a damage event. The approach leverages uniform pushdown methods in the context of the current design procedures for resisting progressive and/or disproportionate collapse. The primary metric used to evaluate the structure’s collapse resistance is the magnitude of applied load that the damaged system can support relative to both the design loads and the capacity of the undamaged system. By leveraging several aspects of current alternate path approaches to progressive collapse–resistant design, the framework provides practicing engineers with an accessible tool for evaluating the relative robustness of structural systems. A prototype eight-story, precast/prestressed concrete moment frame system is used as a case study to demonstrate the utility of this procedure. The prototype system is modified to increase its collapse resistance and is analyzed via uniform pushdown analysis for several damage scenarios to obtain values of robustness. This case study demonstrates the ability of the proposed framework to efficiently and rationally compare design alternatives based on their relative robustness and the consequences of potential overload.