Effect of Moored Vessels on the Seismic Response of Structures

In current design practice, any vessel at berth during an earthquake event is ignored when designing a structure for earthquake loads. This is rationalized based on the frequency of vessel calls in combination with the infrequency of significant earthquakes and the long response periods of vessels relative to earthquake motions. The ASCE 61 Standards Committee for Seismic Design of Piers and Wharves has formed a Task Committee to investigate whether facilities with high occupancy rates in high seismic regions should consider the effects of a vessel being present as part of the wharf seismic design. As no quantitative analysis of the combined vessel-structure seismic interaction has previously been performed, this paper presents original studies currently being performed by the Task Committee as part of its investigation. This paper highlights a simplified case considering a single vessel moored at a typical wharf during a significant earthquake. The intent of this evaluation is to determine effects on the mooring system and structure.