Performance Evaluation of Low-Rise Concrete Frame Building Structures in Moderate Seismic Zones Subject to External Blast Loading

A methodology is presented for blast vulnerability assessment and design which is compatible with existing seismic procedures. The primary goal of this study is to determine the vulnerability of low-rise RC moment frame buildings designed to satisfy current provisions for a moderate seismic zone, to conventional external surface air blast and to quantify the performance and potential for progressive collapse of seismically designed structures under blast loading scenarios.;The procedure is aimed to provide a qualitative idea of the performance of seismically designed structures in blast loading scenarios and can be used for order of magnitude assessment of the demand due to pseudo-static blast loading for various blast scenarios.;At the member level, local vulnerabilities need to be identified in order to map the blast damage on the structure. The distribution of blast loading in terms of pressure coefficients on the building face is characterized. Pressure-impulse (P-I) curves corresponding to columns of low rise RC buildings, designed as per current code for dead, live and seismic loads, are computed, for various aspect ratios. Nonlinear dynamic SDOF models are used to characterize the damage dependence on intensity for a given structure class, thus relating simplified damage states to parameterized load intensity. The local damage due to blast and the subsequent loss of members is identified.;GSA recommended progressive collapse scenarios are utilized for determining the geometric and design parameters that are important for redistribution of the forces and progressive collapse resistance. The consequences of local failure on the surrounding structure, and the subsequent redistribution of loads at the sub-system level are determined, for various changes in the geometric parameters. The potential for catastrophic collapse is determined, based on virtual work methods and nonlinear static finite element analyses.;This work demonstrates a simplified mapping and design procedure that uses conventional FE analysis tools to account for blast effects and is complimentary with conventional procedures that account for seismic load effects. The performance evaluation also considers vulnerability to catastrophic collapse. A procedure for this is demonstrated that uses successive removal of damaged elements to determine likely failure scenarios under overload conditions.