A semi-active SMA-MRF structural stability element for seismic control in marine structures

The stability and integrity of structures under indeterminant external loadings, particularly earthquakes, is a vital issue for the design and safe operation of marine and offshore structures. Over the past decades, many structural control systems, such as viscous-based systems, have been developed and embedded in marine and offshore structures, particularly oil platforms to maintain the stability and mitigate the seismic hazards. Rapid improvement in intelligent materials, including shape memory alloys (SMAs) and Magnetorheological fluid (MRF), have led to the design and development of efficient structural control elements. The present work aims to establish a framework for the structural control element in which the controllability of magnetorheological fluid and superelasticity effect of shape memory alloy have been combined to generate a new structural control element with an ability to dissipate a significant amount of energy while controlling the inter-element displacement in marine structures. The dynamic responses of a simplified 2DOF structure equipped with structural control elements have been conducted using the Open System for Earthquake Engineering Simulation (OpenSees). A comparison between the present SMA-MRF-based and the viscous-based systems has been performed. It is seen that the activated SMA-MRF-based control system in a wide range of the loading frequency spectrum decreases the maximum inter-story displacements of the frame as well as drift ratios. A comparison between the most common stability control element and the present system for seismic conditions has been conducted.