低周反复荷载下再生混凝土梁柱节点纵筋粘结性能试验研究

Experimental study on bond behavior of longitudinal reinforcements of recycled aggregate concrete beam-column joints under low-cyclic reversed loading

为研究低周反复荷载作用下贯穿于再生混凝土节点的纵向钢筋粘结性能,制作2榀再生混凝土框架中节点并进行试验。通过在柱两侧梁端的纵筋上预埋应变片,得到纵筋荷载-应变滞回曲线。根据同一根纵筋上两个测点应变差来计算区段内的平均粘结应力,进而获得了加载过程中节点试件通裂阶段、极限阶段、破坏阶段的纵筋相对粘结强度。试验结果表明,在试件通裂阶段和极限阶段,纵筋保有较为稳定的粘结应力,能够满足再生混凝土构件钢筋与混凝土之间通过粘结应力传递应力及协调变形的要求。粘结应力分布与钢筋直径有关,钢筋直径越大粘结应力退化越严重;柱侧梁端截面受压区混凝土达到极限压应变时,纵筋受压强度不能得到充分发挥,受压钢筋应力相对滞后。

In order to study the bond behavior of longitudinal reinforcement throughout recycled concrete joints under low-cyclic reversed loading,two pieces of interior beam-column joint of recycled concrete frames were fabricated and tested. The load-strain hysteretic curve of the longitudinal steel bar was obtained by embedding the strain gauges on the longitudinal ribs at both ends of the column. According to the strain difference between the two measuring points of the same longitudinal reinforcement,the average bond stress in the section was calculated,and the relative strengths of the longitudinal bars in the crack propagation stage,the limit stage and the failure stage were obtained. The test results show that in the specimen crack stage and ultimate stage,longitudinal reinforcement maintains a relatively stable bond stress and can meet the requirement of transfer of stress and deformation coordination requirements through bond strength between steel and concrete of recycled concrete components. The bond stress distribution is related to the steel bar diameter,and the steel bar diameter is proportional to degradation of bond strength; when concrete in compression zone of beam end section at column side reaches the ultimate compressive strain,the longitudinal compressive strength of reinforced cannot be fully realized and compressive reinforcement stress is relatively lag.