Seismic assessment of an innovative eccentrically braced frame with shape memory alloy

Strong earthquake impacts the structure and creates plastic hinges in some parts of the structure. Performance and serviceability of structure are significant after the earthquake, so it is necessary to decrease residual deformations created by the earthquake. In modern design, the plastic behavior of the structure is concentrated in some members, called fuse members. If the residual deformation of fuse members is decreased, the residual displacement of the structure is decreased. The eccentrically braced frame with vertical link (V-EBF) is a very ductile structure, and the link beam plays as a fuse member. The present study tries to use shape memory alloy (SMA) to decrease the residual deformation of the link beam. Eight and twelve-story V-EBF (with and without SMA rods) were designed. The design method includes the design of the structure for design earthquake, the design of SMA rods based on the properties of the link beam, and the design of all members except link beams and SMA rods for forces and moments of link beams and SMA rods. Designed structures were analyzed by OpenSees software. Pushover, time history, and incremental dynamic analysis were done, and the effect of SMA rods was investigated in the performance of designed structures, so the ratio of ultimate shear to yield base shear, residual displacements, and drifts was investigated in this study. Time history analysis showed that using SMA rods decreases residual displacement considerably, and the residual displacement of the frame equipped with SMA rods is more uniform than the frame without SMA rods. And using SMA rods decreases maximum inter-story residual drift. The analysis showed that using SMA rods often increases the spectral acceleration of the first mode at the collapse threshold. The ratio of ultimate base shear to yield base shear increases when V-EBF is equipped with SMA rods. SMA rods will be effective if the seismic requirements and design methodology are met.