Enhancing the seismic performance of platforms in intermediate water depth using shape memory alloy dampers

Wharves supported by vertical piles are very common marine structures with suitable seismic responses. Nevertheless, they severely suffer from extensive lateral displacement in both design and service earthquake level state. Conversely, wharves with batter piles have limited displacement, but they are often restricted by numerous standards and guidelines due to the significant seismic base shear and undesirable failure modes such as buckling, pullout, and deck punching. This study aims to assess the efficacy of shape memory alloy (SMA) based dampers in controlling both displacement and seismic base shear within acceptable limits. To achieve this goal, a thorough investigation is conducted on an oil terminal platform, located north of Qesh in Iran, with a water depth of 20m, as a real case study. A structural system consisting of vertical and batter piles equipped with SMA dampers and base isolators is proposed, wherein batter piles were not directly connected to the deck. At first, three common scenarios (vertical piles, combination of vertical and batter piles, and friction dampers) are examined, and then the proposed SMA damper system is comprehensively evaluated and compares with the available solutions. The findings reveal that systems employing SMA dampers exhibit significantly reduced seismic base shear (20% reduction) and lateral displacement (68% reduction) compared to those with vertical piles. Additionally, the lateral displacement observed in systems utilizing SMA dampers falls within the range of those employing batter piles, while the seismic base shear is limited to only 40% of the system with batter piles.