高恢复性钢筋混凝土圆柱的抗震试验研究

Experimental Study on Seismic Behavior of Resilient Circular Concrete Columns

为了使钢筋混凝土圆柱在遭遇超过现行规范设定水准的巨大地震时仍能保持正刚性且残余变形足够小,提出了采用高强低粘结的无预应力钢绞线作为柱纵筋的办法.为了验证这种方法的有效性,进行了4根钢筋混凝土圆柱的常轴压低周水平往复试验,其中3根采用钢绞线纵筋,1根采用普通钢筋作纵筋,研究了剪跨比和塑性铰区横向约束方式对钢绞线混凝土柱抗震性能的影响.试验结果表明:剪跨比为3和4的配置钢绞线为纵筋的钢筋混凝土圆柱位移角达6%时,仍保持正刚性,且残余位移角在2%以内;和普通钢筋混凝土圆柱相比,当位移角为6%时,钢绞线混凝土圆柱的侧向承载力提高了90%,残余变形降低了73%;在柱的塑性铰区(1.5D,D为截面直径)采用螺栓连接的钢板进行横向约束可将柱的侧向承载力进一步提高15%,残余变形进一步降低21%;由于钢绞线存在明显的粘结-滑移效应,基于平截面假定的分析方法不适用于采用钢绞线的钢筋混凝土柱侧向承载力的评估.

In order to maintain the positive stiffness and small residual deformation of reinforced concrete columns when they are subjected to tremendous earthquakes that exceed the standard set by current codes,a method of using high-strength and low-bond non-prestressed steel strands as longitudinal reinforcement bars of columns is proposed.In order to verify the effectiveness of this method,horizontal low-frequency cyclic loading tests were performed on four circular reinforced concrete columns under a constant axial load,of which three were reinforced with the above-mentioned longitudinal steel strands(hereinafter referred to as‘new type columns’)and one with normal-strength(NS)rebars.The effects of shear-span ratios and transverse confinement modes within the potential plastic hinge region on the seismic behavior of the new type columns were studied.The test results show that when the drift ratio of the new type columns with a shear-span ratio of 3 to 4 reaches 6%,it still maintains positive stiffness and the residual drift ratio is less than 2%.Compared with the concrete column reinforced with NS rebars,the lateral bearing capacity of the new type column was increased by 90%and the residual deformation was reduced by 73%at the drift ratio of 6%.Besides,the lateral bearing capacity of the new column can be further increased by 15%and the residual deformation can be further reduced by 21%by adding transverse confinement with bolted steel plates in the plastic hinge zone of the column(1.5D).Comparisons between the experimental and analytical results indicate that the flexural analysis based on Navier’s hypothesis is not suitable for prediction of the lateral bearing capacity of the concrete columns reinforced with steel strands due to the the obvious bond-slip effect of steel strands.