Macromodel-Based Simulation of Progressive Collapse: RC Frame Structures

Abstract

The potential for progressive collapse of a typical reinforced concrete (RC) moment frame structure initiated through the loss of one or more first-story columns is numerically simulated using a macromodel-based approach. The development of the simulation model is guided by the realization that the characterization of nonlinear behavior associated with the transfer of forces through the joint is critical to predict the large deformation response associated with progressive collapse. A simplified simulation model of a beam-column joint is used to represent essential and critical actions in the floor beams and the transfer of these forces through the joint region to the vertical elements. The validity of the macromodel developed is evaluated through comparison of both overall response and element actions with those obtained from high-fidelity finite-element analyses. Two prototype buildings designed for lateral load requirements in a nonseismic and seismic region are considered in progressive collapse studies. Two-dimensional models of the frames are subjected to gravity loads and then one or more first-story columns are removed, and the resulting large displacement inelastic dynamic response of each frame is investigated. It is demonstrated that the proposed approach using a validated macromodel is a viable methodology for progressive collapse analysis. The study also finds that special RC moment frames detailed and designed in zones of high seismicity perform better and are less vulnerable to progressive collapse than RC frame structures designed for low to moderate seismic risk.