Seismic response of geostructures to obliquely incident pulse-type near-fault P and SV waves

Abstract

The assumption of vertical propagation for near-fault ground motions is often inadequate. Such ground motions produce pulse-like excitation with forward-directivity effects. This paper investigates the response of a geostructure (i.e., coupled dam-foundation-reservoir system) to near-fault pulse-like ground motions characterized by P and SV waves, including both symmetric and anti-symmetric pulses. Seismic wave propagation is simulated using a semi-analytical method in conjunction with the domain reduction method. The analysis encompasses equivalent pulses generated by modified Gabor wavelets and real near-fault ground motions with varied frequency content and pulse types. This paper further considers post-critical incident angles and inhomogeneous wave propagation. Over 800 transient simulations are conducted. To generalize the outcome, variability in pulse type, wave type, incident angle, number of pulse cycles, frequency content, pulse amplitude, and pulse period are assessed. Moreover, a series of sensitivity analyses are conducted to evaluate the elasticity ratio of super-structure to foundation, and structure-to-pulse period ratio. The results demonstrate a significant impact of most these parameters on the dynamic response of the system. The maximum response under SV waves is observed just beyond the critical angle, with results showing a 20%–60% increase over the vertical propagation case. For P waves, the normalized response with respect to the vertical propagation case may be up to 3.6 times at a 70-degree angle. The findings underscore the necessity of considering oblique pulse-type ground motions in seismic risk analysis of geostructures within near-fault zones.