GA-based optimum design of a shape memory alloy device for seismic responsemitigation

Abstract

Damping systems discussed in this work are optimized so that a three-story steel framestructure and its shape memory alloy (SMA) bracing system minimize response metrics dueto a custom-tailored earthquake excitation. Multiple-objective numerical optimization thatsimultaneously minimizes displacements and accelerations of the structure is carried outwith a genetic algorithm (GA) in order to optimize SMA bracing elements within thestructure. After design of an optimal SMA damping system is complete, full-scaleexperimental shake table tests are conducted on a large-scale steel frame that is equippedwith the optimal SMA devices. A fuzzy inference system is developed from data collectedduring the testing to simulate the dynamic material response of the SMA bracingsubcomponents. Finally, nonlinear analyses of a three-story braced frame are carried out toevaluate the performance of comparable SMA and commonly used steel bracesunder dynamic loading conditions and to assess the effectiveness of GA-optimizedSMA bracing design as compared to alternative designs of SMA braces. It isshown that peak displacement of a structure can be reduced without causingsignificant acceleration response amplification through a judicious selection ofphysical characteristics of the SMA devices. Also, SMA devices provide a recenteringmechanism for the structure to return to its original position after a seismic event.