Applicability of hydrodynamic added mass on seismic analysis of extended piles in water

Abstract

The influence of water on the structure's dynamic response can be simulated by using added mass, which is generally derived for a cantilever fixed on a rigid base. However, because the embedded pile portion cannot fully restrain the extended part, the base of the extended pile may not be fixed, and the conventional added mass may be inappropriate. Therefore, this study conducts several analyses by using COMSOL finite element software to confirm the suitability of theoretical (rigid-base) hydrodynamic added mass in the flexible base condition. Comparing hydrodynamic added mass values between theoretical and numerical results reveals that errors primarily concentrated around peak values rather than uniformly across frequencies and that the peak error under the flexible-base condition occurs at a lower frequency. After evaluating the response envelope in time domain analyses with actual seismic data, it is confirmed that the hydrodynamic added mass model is generally reliable.