Experimental evaluation of the dynamic properties of a wharf structure

Abstract

This paper presents the results from a series of experimental tests carried out to determine the damping characteristics of a section of a 375 m long pile-supported wharf structure under forced excitation. The test program was designed with two primary objectives: (1) to identify the fundamental damping of the structure by using structural microvibration signals produced by tides, wind and microtremors, and (2) to evaluate the variation of the dynamic properties as a function of response amplitude by applying initial displacements of varying amplitude to the deck using a pull mechanism. Although the wharf was designed as a series of independent deck sections, the study revealed that the non-structural frames and piping supported on top of the wharf tie adjacent sections together and have a significant influence on the dynamic behaviour, particularly in the longitudinal direction. Care must be taken in to provide sliding connections for wharf supported structures or to include the influence of these elements in the original design. From our review of the properties identified under the different excitation levels, it was determined that the wharf has relatively linear behaviour with an equivalent viscous damping of about 3%. This is a good reference damping value to be used for the analysis of the pile-supported wharf structures under operational loads and low magnitude seismic events.