Ground shaking and ground deformation are the major causes of damage to waterfront improvements including bridges and port facilities. Large cyclic and/or permanent ground deformations related to slope displacements are the main source of distress to the foundations and structural elements of waterfront structures. Modeling this soil structure interaction (SSI) problem analytically is difficult because it involves kinematic soil-foundation interaction during large (cyclic and permanent) ground deformations as well as inertial foundation-superstructure interaction during shaking, all of which occur while the soil and possibly structural properties rapidly degrade with time. The paper presents an example from the Port of Oakland's Berth 37, which suffered significant damage during the 1989 Loma Prieta Earthquake. The example is a parametric study performed to calibrate geotechnical/structural properties based on the damage observed to Berth 37 from the directional ground shaking during this earthquake. The calibration study shows the complexity of the dynamic SSI problem and current limitations in obtaining solutions to such problems. The study also shows the drawbacks of the use of simple FEMA 273 pushover analyses with slight modifications to analyze the complex kinematic soil-foundation interaction behavior of waterfront structures. Finally, the paper describes ways to capture the SSI information for the kinematic problem from FLAC models for its proper seismological-geotechnical-structural handshake in the pushover analyses of the waterfront structures.
Port of Oakland has embarked upon a Wharf and Embankment Strengthening Program (WESP) as a part of proposed channel deepening, likely to Elevation –52 or –57 feet from the current channel dredge depth of –44 feet. This program required a vulnerability study of the existing wharf structures and retrofit design alternatives evaluation of the current and proposed deepened conditions for three levels of ground motions and their related performance levels, summarized in Table 1.
