Effects of Fluid-Structure Interaction on Nonlinear Seismic Response of Deep-Water Hollow Bridge Pier

This paper uses numerical method to investigate the characteristics of nonlinear seismic responses of a typical deep-water hollow bridge pier. With the bilinear moment-curvature beam elements and 3D solid elements modeling the hollow pier and potential-based fluid elements modeling the water domain, three dimensional finite element models for the typical deep-water bridge pier are built, and the numerical model is verified to be reliable. Through nonlinear time history analyses, seismic responses of the deep-water bridge pier under different water levels are studied for two cases where the hollow piers contact with outer water only and both outer and inner water. The numerical results indicates that seismic responses of the deep water hollow pier increase generally with water level, especially the shear force response of the pier bottom which is obviously enlarged by fluid-structure interaction since a low water level. For bridge piers submerged in deep water, the bending moment of the pier bottom is greater than that of dry bridge piers, which makes it easier for the pier bottom to yield. When the yielding happens, the curvature ductility demand of the bottom section is significantly amplified, and the damage index of the bridge pier is distinctly expanded. The existence of the inner water would cause further demand of the curvature ductility which may lead to aggravated damages to the deep-water piers. These findings can provide valuable guidance for future deep-water bridge design.