Metallic Dampers for Retrofit of Pile-Supported Wharves

Commonly, there are two types of damages induced to pile-supported wharves during a ground motion, liquefaction-induced displacement and pile drift. Accordingly, in absence of liquefactionconditions, pile drift can be considered as a suitable index in order to evaluate the performance ofthese short period structures under seismic events. Some techniques which rely on increasingstiffness, namely inclined piles, have been investigated in earlier studies [1-3] as a method in orderto suppressing displacement of pile-supported wharves which is a costly alternative. Some othertechniques such as soil improvement in the backfill and installation of a sheet pile wall at the toe ofthe embankment have been also proposed, by Salah-Mars et al [4], in order to suppressingpermanent displacement. Nowadays passive controls are increasingly using in civil engineeringstructures to mitigating vibrations which some of them have been described by Soong and Dargush [5]. Earlier studies on passive control methods are commonly restricted to long period structures, such as tall buildings, long-span bridges etc., and there are a few studies about effects of thesemethods on short period systems. In this study, a passive control method was investigated in order to reduce the response of pile-supported wharves which fall into short period structures class. Among various passive controllers, metallic yielding damper seems to be more suitable forimplementing in pile-supported wharves, because they are low cost and easy to manufacture and also virtually they need no maintenance. Supplemental energy dissipation devices have been firstproposed by Bergman and Hanson in 1989 and then developed by Xia and Hanson [6]. Up to nowmany studies have been focused on metallic yielding dampers as an energy dissipation device and their parameters have been optimized [6- 8] for building structures which were implemented in conjunction with chevron braces. Pile-supported wharves commonly have a relatively short periodbut in this study flexible wharves were also considered. Flexible wharves are considered because nowadays by increasing the size of ships, it is necessary to deepen berth of wharves and this means that new generation of pile-supported wharves will have relatively larger periods. It should be notedthat in the case of a building structure there is no limitation on selecting the yielding force of the metallic damper but in the case of a pile-supported wharf, with respect to position of the metallic damper, as depicted in Fig. 1, the stability conditions of the retaining wall, which can be a sheet pile, caisson etc., dictate the maximum allowable yielding force of the metallic damper.

کلیدواژه ها:

Energy dissipation devices ، Passive control ، Optimization ، Wharf ، Seismic excitation