Port Terminal Design in a Region of Moderate Seismicity: Engineering and Economic Considerations

The vulnerability of port waterfront structures to seismic ground motions of moderate intensity has been demonstrated during numerous recent earthquakes around the world. In most instances the damage to quay walls is manifested as limited deformations, as opposed to catastrophic failures or the collapse of structures. Although these permanent deformations are often repairable, the economic losses sustained by the ports due to business interruption during repair and reconstruction is commonly viewed as unacceptable by many port authorities. In light of the economic risk associated with limited earthquake-induced deformations of waterfront structures the development and application of seismic performance criteria is becoming routine in the design process for ports in regions of low- to moderate-seismicity. This paper addresses the seismic design of quay walls for a proposed major terminal in such a region, with an emphasis on performance-based design concepts and the construction costs associated with specific quay configurations and requisite soil improvement for mitigation of seismic hazards. The primary factors contributing to the selection of proposed waterfront structures for the final design phase of the project included: (1) the allowable deformation limits of the quay walls structures established by the design team in consultation with the port authority; (2) the cost associated with construction of the specific wharf alternative and soil treatment satisfying the seismic performance criteria; (3) the anticipated seismic performance of the proposed waterfront structures and ancillary components; (4) coastal engineering considerations such as wave characteristics in the harbor and ship motion; and (5) design-life considerations. The structural and construction factors have been optimized from a cost-benefit standpoint in a manner that satisfies the seismic performance criteria for the terminal.