Seismic interaction of underground RC ducts and neighboring bridge piers in liquefiable soil foundation

A coupled system of an underground reinforced concrete (RC) duct and a neighboring bridge pier supported by group piles is numerically investigated in sandy soil at both drained and undrained liquefiable states under seismic ground excitations. Parametric studies are conducted to evaluate influencing factors on seismic performances of these neighboring interactive structural systems. The numerical simulations are performed with the finite element code COM3 (COncrete Model for 3D) (Maekawa, Pimanmas and Okamura in Nonlinear mechanics of reinforced concrete, 2003), which is capable of simulation of inelastic performance of RC structure and high nonlinearity of soil medium, especially on the liquefiable loose sand. It is mechanically pointed out that liquefaction-induced uplift of underground ducts is substantially influenced by the presence of on-ground bridges. Alternatively, inertial forces induced to the on-ground bridge pier are also noticeably affected by the presence of the neighboring underground RC duct. It is pointed in practice of design that these nonlinear interacting responses between these neighboring infrastructures are greatly magnified on liquefiable soil foundations.