Seismic performance of aged jacket platforms subjected to onshore and offshore earthquakes

Abstract

The aging effect represents a critical factor in seismic research for jacket platforms. This study investigated the seismic performance of aged jacket platforms with consideration of the soil-pile-structure interaction (SPSI). Shaking table tests with a 1/20 scaled model that incorporates the corrosion effects of jacket platforms with service lives of 0, 20, and 30 years were conducted to compare the dynamic characteristics and structural responses of these models under onshore and offshore earthquake excitations. To complement the experimental study, three corresponding finite element (FE) models considering SPSI effects were developed to enable detailed seismic fragility analyses for aged jacket platforms. The results suggest that jacket platforms exhibit significantly higher collapse transcendence probability under offshore earthquake, with 2–3 times larger responses than those under onshore events. Furthermore, after 20 years of service life, the collapse transcendence probability of these platforms increases substantially—by about 20 %–40 % compared to jacket platforms with 0 years of service life—primarily due to extensive corrosion. The experimental and numerical results obtained through this study serve as a valuable basis for risk assessment and seismic design of aged offshore jacket platforms.