| Summary: | Recent experience demonstrates that waterfront structures are vulnerable to
earthquake damage. The poor seismic performance of these facilities has been
primarily due to liquefaction of backfill and/or foundation soils and the lack of
seismic design standards for waterfront structures. The seismic performance of
waterfront structures is a key issue in the evaluation of the unimpeded operations of
the port system and affiliated facilities following earthquakes. The widespread
economic consequences of earthquake-induced damage to waterfront structures and
required serviceability of port components after earthquakes highlight the need for
improved performance-based design methods.
The weak foundation soils and high water tables that are common at ports
result in a high vulnerability to seismically-induced ground failures and corresponding
damage to adjacent structures. Liquefaction of backfill and foundation soils next to
waterfront structures contributes to an increase in active lateral earth pressures against
walls, loss of stability of rock dike, excessive ground settlements, and lateral soil
movements. Current pseudostatic methods are not well suited to account for the
influence of excess pore pressure generation as well as amplification of acceleration. In order to limit earthquake-induced deformations of waterfront structures, various ground treatment strategies have been used to mitigate liquefaction hazards at numerous ports. However, very few guidelines exist for specifying the extent of remedial soil treatment required to insure the serviceability of the waterfront components after a design-level earthquake.
This research has investigated the seismic response of waterfront structures, specifically concrete caissons and pile-supported wharves, during past earthquakes. A numerical model was validated by comparing the computed response to field performance. A series of parametric studies were conducted for waterfront structures in improved soils. The effectiveness of soil improvement in controlling permanent seismically-induced deformations of the waterfront structures is evaluated as functions of wall geometry, the density of backfill soils, the stiffness of piles, the extent of the improved soil, and the characteristics of the strong ground motions. The results were synthesized into simplified, practice-oriented design charts for deformation-based analysis, and preliminary guidelines for estimating the extent of ground treatment that is required given allowable deformation limits for the caissons and pile-supported systems. === Graduation date: 1999
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