Estimation of the effect of surface blast on buildings

A surface blast generates both air pressure and ground shock on structures. Studies on the relative effects of the air pressure and ground shock on the responses of structures are meagre. In the present study, a preliminary estimate of the relative contributions of the ground shock and air pressure on building responses due to a surface blast is obtained by using an equivalent single-degree-of-freedom (SDOF) model. For this purpose, both linear and non-linear analyses of SDOF models of four reinforced concrete building frames of different heights are performed under different blast scenarios by varying the standoff distance and charge weight. In addition, the criticality of the surface blast in comparison to the free air blast is investigated with the help of the same SDOF models. The study reveals that the contribution of the ground shock is less than that of the air pressure on the responses of low-rise buildings. For high-rise buildings, the opposite trend is observed for smaller standoff distances (R < 15 m). Further, it is shown that the surface blast is more critical as compared to the free air blast for shorter buildings (fewer than six storeys), but the opposite holds good for taller buildings.