Seismic response of a typical New Zealand pile-supported wharf configuration

Abstract

Ports are an important part of a country’s infrastructure, both in terms of facilitating trade and aiding recovery immediately following an earthquake. In New Zealand ports facilitate the transfer of up to 99% of all exports and imports by volume and thus are important to the success of the country’s economy. Past earthquakes have demonstrated that port facilities suffer extensive damage due to poor foundations and backfill soils that are common in waterfront environments. In collaboration with New Zealand port authorities, generic wharf configurations representative of New Zealand structural and geotechnical characteristics have been developed. This paper presents the modelling approach and preliminary results for two common wharf configurations founded in three non-liquefiable soil profiles. The numerical models were created using OpenSees, a non-linear finite element analysis program and subjected to static nonlinear pushover analyses and dynamic time-history analyses. The wharf and the soil-pile interface have been modelled in order to account for the effects of nonlinear behaviour of pile elements and their connections to the wharf deck, and effects of nonlinear dynamic pile-soil interaction. The models were then used to develop fragility curves that are used to predict the probability of a model reaching a defined damage state given a PGA For low intensity earthquakes there was limited variability in performance between the different wharf models. However as earthquake intensity increased there was a pronounced difference between models with a raked-pile configuration and ones with a tie-back configuration, with the tie-back configuration having lower probabilities of damage. There appears to be no clear pattern with regards to the raked-pile configuration located in different soil profiles.