Passive and semi-active bracing systems for seismic protection: a comparative study

This article analyses comparatively the seismic response of structures equipped by two types of dissipative bracing systems: passive devices with variable friction and semi-active devices with magnetoreological fluids. Both passive and semi-active seismic devices have hysteresis force-displacement characteristics with butterfly shape, controlled by the instantaneous inter-story drift. This type of hysteresis behavior can be achieved by appropriate design of passive friction coupling and semi-active control strategy implemented for magnet-orheological dampers. The forces developed by both protection devices are calibrated such as to dissipate the same amount of energy per hysteresis loop for imposed cyclic motion The efficiency of passive and semi-active protection systems, installed in a shear frame structure, is assessed by numerical analysis for Vrancea 1977 earthquake.