高温后套筒灌浆连接受力性能试验研究

套筒灌浆连接已发展为预制混凝土结构钢筋连接的主要方式，但其在高温作用后循环荷载作用下受力性能的研究仍有待深入。为此，针对钢筋直径为20mm的36个套筒灌浆连接开展高温后受力性能试验研究，设置常温、200℃、400℃、600℃等四种历经温度作为试验变量，采用单向拉伸、高应力反复拉压、大变形反复拉压等三种加载工况。结果表明：升降温过程中高强灌浆料未出现爆裂现象；连接极限荷载随温度下降但是降低幅度最大不超过7.6%；当经历最高温度不超过400℃时，发生套筒外钢筋断裂失效，而经历最高温度为600℃时，发生钢筋与灌浆料黏结滑移失效；当经历最高温度为600℃时，套筒中部仍然保持弹性状态；采用屈服比(不小于1.0)、强度比(不小于1.25)与延性比(不小于4.0)评价套筒灌浆连接性能，其相应取值分别为1.2～1.3、1.4～1.6、8.2～18.7。此外，基于套筒灌浆连接材料组成与受力特征的分析，认为其可能的失效模式为套筒外钢筋断裂、钢筋与灌浆料黏结滑移两种形式之一，且承载力取决于二者之间的较小值。

Experimental study on mechanical behaviors of grouted sleeve splices after high temperatures

The grouted sleeve splice has become to the mainstream of rebar splicing in the precast concrete structures, but the research on mechanical behaviors of heat-damaged splices under cyclic loadings is rare. Experiments were carried out to study performance of grouted sleeve splices after being exposed to high temperatures based on 36 specimens with steel rebar with diameter of 20mm, which include four levels of temperatures(ambient temperature, 200 ℃, 400 ℃ and 600 ℃) and three loading styles, namely, uniaxial tensile loading, cycle loading at high stress and cycle loading at large strain. Basing on the experimental results, there are several findings as follows: explosive spalling of high strength grout is not found during heating and cooling; ultimate loads of grouted sleeve splices decrease as the increase of temperature but the difference is no more than 7.6%; after being exposed to 400 ℃, the failure mode of specimens is rebar fracture beyond the sleeve, and after being exposed to 600 ℃, the failure mode is rebar pull out from the grout; after being exposed to 600 ℃, the middle of sleeve is still elastic; the ratio of yield strength（not less than 1.0）, the ratio of ultimate strength（not less than 1.25） and the ductiling ratio （not less than 4.0）, are used to evaluate the performance of grouted sleeve splice and from 1.2 to 1.3, 1.4 to 1.6, and 8.2 to 18.7, respectively. After analyzing the material formation and loading mechanism of grouted sleeve splices, it is suggested that the failure mode of the splice may be the rebar fracture beyond the sleeve or rebar pull-out from the grout and the capacity should be the smaller one from the splice with both of failure modes in turn.