拉压变轴力下小剪跨比预应力混凝土墙往复受剪试验研究

Experimental study on cyclic shear behavior of low-aspect-ratio prestressed concrete walls under variable axial tension-compression forces

为了研究预应力混凝土(PC)剪力墙的抗震性能,提出剪力墙在拉压变轴力作用下的水平往复加载试验加载制度,完成3片剪跨比为1.0的预应力混凝土墙在恒定轴拉力、恒定轴压力和拉压变轴力作用下的水平往复加载试验,研究其破坏模式、滞回性能、承载力、变形能力、刚度和残余裂缝宽度,并与型钢混凝土(SRC)墙和普通RC墙的抗震性能进行了对比。试验结果表明:恒定轴拉力试验中,预应力混凝土墙发生了腹板剪切破坏;恒定轴力试验中墙体发生了斜压破坏;拉压变轴力试验中,墙体在压剪方向加载时发生剪压破坏。拉压变轴力加载导致预应力混凝土墙拉剪和压剪承载力分别降低了18.7%和10.5%。预应力混凝土墙在恒定轴拉力和拉压变轴力作用下的极限位移角为1.2%~1.6%,变形能力大于JGJ 3—2010《高层建筑混凝土结构技术规程》规定的弹塑性位移角限值(1/100);恒定轴压力试验中水平峰值荷载超过了墙体截面受剪承载力限值,出现斜压破坏,极限位移角仅为0.6%。预应力混凝土墙试件与SRC墙试件的刚度、承载力和变形能力接近,前者的残余裂缝宽度小于后者的,表现出更好的震后可修复性。由于预应力有效抑制了墙体水平贯通裂缝的形成、防止出现沿水平裂面的滑移破坏,因此在较大轴拉力水平时预应力混凝土墙比普通RC墙的抗侧刚度和承载能力均显著提高。总体来看,预应力混凝土墙抗震性能优良,是一种改善高层建筑中受拉剪力墙抗震性能的有效手段。

In order to investigate the seismic behavior of prestressed concrete(PC) walls, the loading protocol of the shear walls subjected to variable axial tension-compression forces and cyclic shear loading was proposed. Quasi-static cyclic shear loading tests were conducted on three prestressed concrete walls that had the shear-to-span ratio of 1.0, where one specimen was under a constant axial tensile force, another under a constant axial compressive force, and the other under variable axial tension-compression forces. The failure modes, hysteretic responses, strength, deformation capacity, lateral stiffness, and residual crack width of PC wall specimens were investigated, and they were compared to those of the steel reinforced concrete(SRC) wall and reinforced concrete(RC) wall. The test results indicate that the PC wall specimen under a constant axial tensile force failed in web shear failure mode, the wall under a constant compressive force failed in diagonal compression failure mode, and the wall under variable axial tension-compression forces failed in shear compression failure mode. The variable axial tension-compression forces decrease the tensile-shear strength and compressive-shear strength of the PC wall specimens by 18.7% and 10.5%, respectively. The PC wall specimens under the constant axial tensile force and variable axial tension-compressive forces have the ultimate drift ratio ranging from 1.2% to 1.6%, which exceeds the inelastic drift limit of 1/100 specified in the Chinese technical specification for concrete structures of tall buildings(JGJ 3-2010). Because the PC wall specimen with the constant axial compressive force had the maximum shear load exceeding the upper limit of the wall’s shear strength, it failed in diagonal compression failure at a small ultimate drift ratio of 0.6%. The PC wall specimen has similar lateral stiffness, strength, and deformation capacity as the SRC wall specimen. The former has smaller residual crack width than the latter, indicating superior reparability of PC walls. Because the prestressed force controls the development of thorough horizontal cracks and prevents the shear sliding failure along the horizontal cracks, the PC wall specimen with high axial tensile force has significantly larger lateral stiffness and strength than conventional RC wall specimen. In general, the PC walls show excellent seismic behavior and thus can be used as an effective approach to improve the seismic performance for walls subject to tension load in high-rise buildings.