Seismic Response Assessment of Topside Equipment on Fixed Offshore Platforms

Abstract

The seismic performance of large equipment on offshore oil production platforms is vital for ensuring personnel safety and maintaining the structural integrity of the platform. Seismic failure of equipment can result in catastrophic hazards such as explosions, platform damage or collapse, significant economic losses, and environmental disasters. This paper evaluates the seismic performance of various types of commonly used equipment on offshore platforms in upstream operations. The seismic response of the equipment, modeled together with the platform, is assessed using nonlinear time-history analysis under three-component, 22 different high-magnitude recorded earthquake records, and analyzed through both coupled and uncoupled dynamic analyses. The findings reveal that offshore earthquakes significantly affect equipment on offshore platforms, with results indicating a positive correlation between peak ground acceleration (PGA) and material yielding in equipment supports, while peak ground velocity (PGV) and the PGA/PGV ratio significantly affect the seismic performance of the platform. Equipment that is horizontally positioned and supported is found to be more vulnerable than vertically positioned equipment, regardless of the first mode shape. The findings of this study establish seismic design recommendations for topside equipment, propose specific PGA thresholds for various types of equipment, and provide recommendations for enhanced equipment saddle designs to improve the seismic performance of topside equipment on offshore platforms.