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Columns are the key load-bearing elements in frame structures and exterior columns are probably the most vulnerable structural components to terrorist attacks. Column failure is normally the primary cause of progressive failure in frame structures. A high-fidelity physics-based computer program, LS-DYNA was utilized in this study to provide numerical simulations of the dynamic responses and residual axial strength of reinforced concrete columns subjected to short standoff blast conditions. The finite element (FE) model is discussed in detail and verified through correlated experimental studies. An extensive parametric study was carried out on a series of 12 columns to investigate the effects of transverse reinforcement ratio, axial load ratio, longitudinal reinforcement ratio, and column aspect ratio. These various parameters were incorporated into a proposed formula, capable of estimating the residual axial capacity ratio based on the mid-height displacement to height ratios. Accepted version

The model for the calculation of an equivalent static force (ESF) and the design procedure with ESF for single-degreeof- freedom (SDOF) systems presented in the first part of the two-part paper are extended into the design for a reinforced concrete (RC) frame structure under distant blast conditions. An empirical formula for the ESF factor involved in the ESF model is presented based on sample points obtained by comparing the nonlinear dynamic responses of frame structures under the blast loading with the corresponding nonlinear pushover analysis of the structure due to an ESF. The use of the method is demonstrated with two six-storey RC frame structures. Numerical verification of the method indicates that the maximum inter-storey drift ratios (MIDR) of the two designed frame structures in comparison to their respective targets are conservative to some extent. The reasons that may lead to the conservative designs are discussed.