Experimental studies on behavior of fully grouted reinforced-concrete masonry shear walls

An experimental study is conducted on fully grouted reinforced masonry shear walls (RMSWs) made from concrete blocks with a new configuration. Ten RMSWs are tested under reversed cyclic lateral load to investigate the influence of different reinforcements and applied axial stress values on their seismic behavior. The results show that flexural strength increases with the applied axial stress, and shear strength dominated by diagonal cracking increases with both the amount of horizontal reinforcement and applied axial stress. Yield displacement, ductility, and energy dissipation capability can be improved substantially by increasing the amount of horizontal reinforcement. The critical parameters for the walls are derived from the experiment: displacement ductility values corresponding to 15% strength degradation of the walls reach up to 2.6 and 4.5 in the shear and flexure failure modes, respectively; stiffness values of flexure- and shear-dominated walls rapidly degrade to 17%–19% and 48%–57% of initial stiffness at 0.50 Dmax (displacement at peak load). The experiment suggests that RMSWs could be assigned a higher damping ratio (～14%) for collapse prevention design and a lower damping value (～7%) for a fully operational limit state or serviceability limit state.

Study on optimum arrangement of hysteretic dampers in frame structure

The earthquake mitigation effect of hysteretic dampers is not only related to the number, stiffness, strength, deformation ability of dampers but also to the strength and stiffness of the structure. This paper studied the condition that structures should be in when the hysteretic dampers mitigated seismic action most effectively and made appropriate numerical analysis to verify the effectiveness of theory derivation. The inelastic seismic responses were analyzed for the SDOF system that the shear strength ratio of the damper system was taken differently and the result showed that when the ratio was in the vicinity of the optimum strength ratio of the damper system, the displacement of the structure was minimum and the energy dissipation of dampers was maximum, which indicated that the dampers mitigated seismic action most effectively. The result also indicated that the hysteretic dampers had significant earthquake mitigation effect when the strength ratio β changed in a relatively wide range.