| Numerical solutions are presented for the static, dynamic, and seismic response of single piles, pile groups, and pile-supported structures in homogeneous, inhomogeneous, and layered soil deposits. The seismic analysis considers both the kinematic and inertial interaction between the foundation and the superstructure in the frequency and time domains.; The proposed methods make use of dynamic finite-element formulations equipped with pertinent absorbing boundaries, spatial Fourier expansions, and other special analysis techniques. The role of soil inhomogeneity is investigated considering the presence of (1) pre-existing inhomogeneity (in the vertical direction) arising from soil layering and overburden; (2) stress-induced inhomogeneity (in both horizontal and vertical directions) due to pile installation and loading. It is shown that ignoring soil inhomogeneity may substantially underestimate pile head stiffness and overestimate damping. In addition, modeling an inhomogeneous deposit as a homogeneous layer providing the same static stiffness to the pile, may grossly overestimate radiation damping, leading to un-conservative predictions of dynamic response. The accuracy of the proposed theoretical solutions is demonstrated by comparing their predictions with the measured response of actual piles and pile groups.; Two case histories involving pile-supported bridges are presented: The first bridge, Ohba Ohashi, instrumented by the Institute of Technology of Shimizu Corporation, has been subjected to several moderate earthquake motions. Successful comparisons between predicted and measured response are presented. The role of valley effects, non-uniform seismic excitation, and structural connections on seismic response is discussed.; The second case study refers to the Fukae Section (a 630m segment) of the elevated Hanshin Expressway, which collapsed during the 1995 Kobe earthquake. Analytical and recorded evidence suggest a detrimental role of soil in the collapse. It is shown that: (1) the soil modified the incoming seismic waves such that the resulting ground surface motion became very severe for the particular bridge; (2) the presence of compliant soil in the foundation resulted to an increase in natural period of the bridge which moved the system to a region of stronger response; (3) the compliance of the foundation increased the participation of the fundamental mode, inducing stronger response. Implications of the above effects in design are discussed. |
