套筒约束两根钢筋浆锚搭接拉伸试验研究

为了改善预制构件钢筋连接的施工便利性及提高连接效率,提出两根钢筋套筒约束浆锚搭接接头,进行了12个以搭接长度为变化参数的Ⅱ型搭接接头、63个以搭接长度和钢筋直径为变化参数的Ⅲ型搭接接头的拉伸试验,研究了试件的破坏形态、极限承载力、力-位移曲线及钢筋和套筒的应变,提出搭接接头的平均黏接应力的计算公式.与单根钢筋的I型搭接接头的相同之处为:试件破坏形态有套筒外钢筋拉断及钢筋与灌浆料滑移两种,套筒端部环向拉应变大于套筒中部,套筒中部近钢筋处拉应变大于远钢筋处.直径相同的钢筋拉断试件,套筒中部远钢筋侧环向应变随搭接长度增加而减小;不同处:Ⅲ型接头椭圆型套筒对灌浆料的约束力小于I型接头圆形套筒,造成Ⅲ型接头加载后期套筒外钢筋未表现出明显的屈服台阶,Ⅲ型接头钢筋滑移试件极限荷载时套筒中部远钢筋处环向应变未表现出I型接头随直径d增大而增大的趋势,Ⅲ型接头的搭接长度较大.

Experimental Study of Grouted Sleeve Lapping Connectors of Two Bars under Tensile Load

To improve the construction convenience of precast component reinforcement connectors and connection efficiency, grouted sleeve lapping connector of two bars was put forward, and 12 type II specimens with varied lap length and 63 type III specimens with varied lap length and bar diameter were tested under tensile load. The failure modes, ultimate bearing capabilities, load-displacement curves, and strains of bars and sleeves were discussed. The formulas of the average bonding stress were proposed. Like type I joint with single reinforcement, bar fracture and bar-grout bond-slip are two typical failure modes of the specimens. The tensile strain in the ring direction at the end of the sleeve is greater than that in the middle of the sleeve. In the middle of the sleeve, the tensile strain in the ring direction near bars is greater than that away from bars. For specimens with the same diameter that failed due to bar fracture, transverse confinement provided by the sleeve decreases as the lap length increases. The restraint force of elliptical sleeve of type III joint on grouting material is less than that of circular sleeve of type I joint, so there is not obvious yield steps on rebar outside of sleeve connector type III at late loading. This is also the reason why the tensile strain in the ring direction, at far away bars in the middle of the sleeve, does not show the increasing trend with the increase of diameter, but connector type I shows. Besides, the lap length of type III joints is more larger.