超高性能混凝土中钢筋早龄期搭接黏结试验研究

Experimental Study on Bond of Early-age Rebar in Ultra-high Performance Concrete

超高性能混凝土(UHPC)作为预制结构湿接头时的传力性能是至关重要的。在这种情况下,接头中采用钢筋搭接的方式进行传力是一种方法。当接头中钢筋的搭接空间有限时,需要研究后浇UHPC中钢筋的黏结行为,特别是在施工的早期阶段。就这一问题进行了试验研究,对处于3d龄期的UHPC,进行了搭接拉拔试验,考虑了钢筋锚固长度、搭接长度和钢筋净间距对搭接黏结行为的影响。结果表明:对于施工早期的后浇UHPC接头,锚固长度为6倍钢筋直径已可满足结构设计要求,相比普通混凝土,有效缩减了钢筋锚固长度;在钢筋保护层厚度大于钢筋净间距条件下,钢筋净间距对搭接黏结强度的影响较小;存在最优搭接长度,建议搭接长度为锚固长度的1/3能最大程度发挥搭接情况下UHPC对钢筋的黏结锚固性能。

The load transfer behavior of ultra-high performance concrete(UHPC)is critical when used as a wet joint in precast structures.In this case,it is a method to transfer the force by overlapping the steel bars in the joint.The bond behavior of the reinforcement in post-cast UHPC needs to be studied when the lap space of the reinforcement in the joint is limited,especially in the early stages of construction.An experimental study was carried out to investigate the bond behavior of UHPC at the age of 3 days.The effects of anchorage length,lap length and clear spacing on the bond behavior of UHPC were investigated.The results show that the anchorage length of 6 times the diameter of the steel bar can meet the design requirements for the post-cast UHPC joints in the early stage of construction,and compared with ordinary concrete,the anchorage length of the steel bar is effectively reduced.When the thickness of the protective layer is greater than the net spacing,the net spacing has little effect on the bond strength;There is an optimal overlap length,and it is suggested that the overlap length should be 1/3 of the anchorage length to maximize the bonding and anchorage performance of UHPC to steel bars in the case of overlap.