Experimental investigation and simplified stiffness degradation model of concrete shear wall with steel connectors

Premature damage of the post-cast concrete joints of precast concrete shear walls (PSWs) was observed in the past earthquakes due to the poor connection details and stress concentration of the wall-beam-slab joints. To avoid the potential failure, a new connection method featuring steel connectors, applied in the PSWs, is firstly proposed based on the plastic damage relocation design concept. Five 1/3 scaled specimens, including one monolithic concrete shear wall (MSW) and four PSWs, were constructed and tested under quasi-static cyclic loading. Seismic performances in terms of damage modes, drift ratio versus shear force behaviors, equivalent viscous damping ratio, deformation components, and stiffness degradation characteristics of PSWs were in-vestigated. It shows that concrete cracks are developed at the bottom of the precast shear wall panel initially and its crack widths are decreased. The connection method can provide efficient stiffness and strength for the precast concrete shear wall system as no significant degradation of shear force occurs before a drift ratio of 1/50. Precast concrete shear wall having T-shaped with non-full length type connectors (TPSW-N) has the lowest cracking shear force and one having H-shaped connectors (HPSW) possesses a more stable lateral force-resisting capacity. The equivalent viscous damping ratios of the PSWs are higher than that of the MSW up to a drift ratio of 1/100. Among the PSWs, the HPSW shows the best seismic performance by comprehensively considering the damage mode, shear force characteristics and energy dissipation capacity. The flexural deformation at the middle of the precast shear wall panel is decreased compared with that of the wall panel of the MSW. The proposed connection method moves the critical region outside the week connection zones, which could be an alternative for the conventional post-cast concrete connection scheme. A simplified five-line stiffness degradation model of PSWs, controlled by elastic, cracking, yield, peak and ultimate points, is established and verified. The simplified model can be used to estimate the stiffness degradation properties of the proposed PSWs.