Numerical modeling for assessing progressive collapse risk of RC buildings exposed to blast loads

The safety of strategic structures against accidental loading (such as blast-generated waves) has recently received much attention from practicing structural engineers. Terrorist attacks in the proximity of urban environments may bring blast threats close to the perimeter of the buildings, thereby making them exposed to progressive collapse. This paper aims at investigating the progressive collapse possibility of an existing RC (reinforced concrete) building against blast-generated waves. Data was collected for a typical RC building constructed in a congested area in Riyadh city. A simple NLD (nonlinear dynamic) analysis approach was carried out to examine the progressive collapse possibility of the building when exposed to blast threat events. In this regard, 3D nonlinear two-stage FEA (finite element analysis) was conducted. In the first stage, a local model was created for a typical individual RC column. The local model was validated utilizing the published results of an RC column subjected to blast load. The goal of the local analysis is to evaluate the individual column response against blast load and to come up with the critical stand-off distance at which the column gets severely damaged. In the second stage, a global model (comprising shell and beam elements) was created for the whole building. The goal of the global analysis is to examine the global behavior of the building owing to the removal of the columns identified from the local model stage. The progress of damage caused to different structural elements and the state of stress in these elements was studied. The results enhanced the knowledge about the progressive collapse potential in RC buildings and will be helpful in the development of mitigation strategies.