Abstract:
The damage to pile-supported bridges and wharves due to liquefaction-induced lateral spreading has been documented in many earthquake case histories where soil displacements exceeding 1 m was reported as the likely cause of damage. While it is required by most design standards to design piles for the effects of liquefaction-induced lateral spreading, the existing guidelines vary significantly on how to estimate the soil displacements (i.e. kinematic demands). First, there are large uncertainties in estimating seismic slope displacements using the commonly used Newmark’ s sliding block analysis. Second, there are practical challenges on how and when to apply the restraining effects of piles (also known as pile pinning effects). Highway bridge agencies have provided some guidelines on how to account for pile-pinning effects in estimating lateral ground deformations (e.g., Caltrans 2016). However, the applicability of these guidelines to maritime transportation structures, such as wharves and piers, that are commonly supported on a large number of closely-spaced relatively-flexible piles (steel or concrete piles up to 2 feet diameter) is questionable and needs to be assessed.
This paper addresses this issue using a unique set of experimental data from five centrifuge tests on pile-supported wharves to develop design guidelines that are backed by experiments and can be implemented in equivalent static analysis (ESA) using p-y solution tools. Each test was subjected to two shaking events producing 10 unique experimental data points covering a range of soil profiles, pile properties, and ground motions. The data were used to evaluate the accuracy of existing methodologies in estimating kinematic demands on piles and propose design modifications.