Abstract
In this paper, an evolutionary multi-objective optimization algorithm named NSGA-II was used to determine the optimum radius for shape memory alloy (SMA) wires employed in conjunction with the lead rubber bearing (LRB), referred to as an SMA-LRB isolator. This algorithm simultaneously minimizes the mid-span displacement and the base shear force. Then, the optimized SMA-LRBs were implemented in a benchmark bridge to reduce excessive displacements. The results obtained from the nonlinear dynamic analysis show that the implemented approach could effectively optimize the SMA-LRBs. These improved smart isolators can noticeably reduce the maximum displacements and residual deformations of the structure; meanwhile, the base shear and deck acceleration remain less than those of the non-isolated benchmark bridge. This isolator can reduce the maximum mid-span displacement of the bridge by up to 61%, and the mid-span residual deformations by up to 100%, compared to an uncontrolled isolated bridge under different ground motions. This optimized passive system was compared with nonlinear dampers, passive SMA dampers, and a negative stiffness device. The results indicate that the optimized SMA-LRB isolators are generally more successful in reducing and recovering displacements than the other controllers.
Highlights
Bridges are critical infrastructure and play essential roles in transportation networks
The findings proved that the rubber bearing with Nitinol shape memory alloy was able to decrease the deck displacements
The optimized shape memory alloy (SMA) isolators were applied in the benchmark bridge in phase II, and the results were compared with three other passive control methods used for this bridge: Nonlinear dampers, passive SMA dampers, and a new negative stiffness device
Summary
Bridges are critical infrastructure and play essential roles in transportation networks. Zhang et al [27] suggested a damper with SMA for controlling the displacements of the second phase of the benchmark bridge These researchers studied the effect of the temperature changes on the behavior of SMA and their presented device. Investigated the seismic performance of a new SMA device in the second phase of the benchmark bridge Their passive SMA damper considerably reduced the maximum displacement of the base isolator and displacements. With a large elastic strain was used in SMA-LRBs. The optimized SMA isolators were applied in the benchmark bridge in phase II, and the results were compared with three other passive control methods used for this bridge: Nonlinear dampers, passive SMA dampers, and a new negative stiffness device.
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