The Earthquake Engineering Online Archive

Analysis of the nonlinear response of structures supported on pile foundations

Badoni, Deepak; Makris, Nicos

UCB/EERC-97/07, Earthquake Engineering Research Center, University of California, Berkeley, 1997-07, 175 pages (520.6/B22/1997)

In this research, the problem of nonlinear pile foundation-superstructure interaction is addressed by adopting a substructure approach and developing appropriate time-domain methodologies for the analysis of each subsystem, as well as procedures to analyze the global system response. The need for nonlinear modeling and the importance of foundation dynamics to overall system response is established first by studying the response of the Painter Street bridge excited by the Petrolia earthquake of 1994. Subsequently, the problem of a yielding superstructure on a linear foundation is studied. The superstructure is modeled by a two degree-of-freedom system that involves a Bouc-Wen model to simulate nonlinear behavior. Two different solution methods are developed to obtain the system response. The first method models the restoring force from the foundation by means of a convolution of the velocity history of the pile-cap relative motion and the dynamic relaxation stiffness of the pile foundation, while the second utilizes a state-space representation. Both methods are validated at the linear limit by comparing time with frequency domain analyses. A time-domain procedure is then presented to compute nonlinear axial dynamic response of pile groups under inertial loading using a nonlinear Winkler foundation model for the soil-pile interface and utilizing linear wave propagation theory to compute pile-to-pile interaction. The model is calibrated using two sets of field data obtained for single piles and is subsequently used to provide equivalent linear stiffnesses and damping for pile-groups.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-97-07.pdf (12 MB)