Gravity Load Collapse and Vulnerability of Existing Buildings

Vertical collapse performance of existing multi-story buildings has been investigated through field experiments and computational simulations. Four reinforced concrete (RC), two masonry, and three steel frame buildings have been tested in recent years. During the experiments, single or multiple first-story columns were physically removed from the buildings, which were demolished immediately after the experiments. Due to lack of full-scale building test data, the data produced in this research has been a valuable addition to the state of knowledge on gravity collapse of buildings. The main goal of field experiments was to simulate the structural dynamic and static response of buildings that may experience collapse after sudden loss of column(s) due to, say column shear failure in a reinforced concrete building. Another objective was to investigate how the internal forces are redistributed within the building after each column is removed. In this study, two- and three-dimensional models of the buildings were used to simulate the building performance and collapse potential. Computational models and simulations were examined and compared to the experimental data from the field tests. It is noted that the current nonlinear modeling and progressive collapse assessment guidelines (GSA 2013) use nonlinear analysis parameters found in the seismic assessment of existing buildings (ASCE/SEI 41, 2013), e.g., performance limit states and m-factors to evaluate nonlinear performance. This study showed robustness of existing buildings and contribution of different structural components to collapse resistance.