Response characteristics of structures subjected to blasting-induced ground motion

This paper presents a conceptual discussion on structural response to ground shocks. Numerical parametric analyses are performed on a simplified linear structural model to investigate the special features of structural response brought by short duration, large amplitude and high frequency excitations, which are the basic characteristics of ground shocks induced by blasting. Nonlinear finite element analyses on a two-storey RC frame subjected to ground shocks are carried out to qualitatively understand building response to blasting. This study shows that maximum structural response to blasting depends primarily on the amount of impulse, and it generally occurs after the major ground shock has ceased. To capture the maximum response, it is hence necessary to consider additional time duration beyond the major ground shock period in blasting analysis. It is found that the response in the forced-vibration phase includes high frequency vibration modes with small displacement but large acceleration, thus inducing high inertial shear force. However, the free-vibration response is dominated by lower frequency modes with larger displacement but smaller acceleration. Hence, buildings subjected to strong ground shocks might experience a sudden shear failure of its components. Nevertheless, if a building's strength is enough to avoid the sudden shear failure during the major shock, it may be damaged after the ground shock during the free vibration, and the extent of damage depends on the ground shock magnitude.