超高性能混凝土预制板现浇湿接缝抗弯性能试验研究

Experimental study on flexural performance of prefabricated UHPC slab with cast-in-situ joints

为明确接缝及接缝内纵筋不同构造对超高性能混凝土(Ultra-high Performance Concrete,UHPC)预制板现浇湿接缝受弯性能的影响,以接缝设置及接缝内纵向钢筋连接方式为试验参数,对5块UHPC预制板试件的抗弯性能进行试验研究,获得UHPC板全过程的受力变形行为,推导了无缝和带接缝UHPC桥面板抗弯承载力的统一计算公式。研究结果表明:接缝试件的破坏形态均为接缝截面受拉钢筋屈服后受压区UHPC压碎的正截面破坏。与纵筋连续的无缝整浇试件相比,接缝内纵筋采用直筋连续、直筋搭接、水平环形搭接和垂直环形搭接接缝试件的开裂荷载分别减少了54.6%,52.0%,51.0%和54.6%;屈服荷载分别减少了34.4%,35.7%,34.5%和33.3%;峰值荷载分别减少了29.7%,29.6%,34.7%和29.5%;延性分别提高了17.6%,2.9%,8.8%和5.9%。接缝试件的抗裂性能和抗弯性能是由接缝截面的性能所控制。当现浇接缝段内纵筋直筋部分的搭接长度满足规范要求时,接缝段内纵筋的不同构造形式对试件的抗弯性能影响较小,实际工程中,可采用较为简便的直筋搭接方式。提出了无缝和带接缝UHPC桥面板抗弯承载力统一计算方法,并且采用本文和其他文献试验结果验证了其适用性。

To clarify the effects of joints and configuration modes of longitudinal joint reinforcements on the flexural properties of cast-in-place joints in Ultra-High-Performance Concrete(UHPC)precast slabs,an experimental study was performed on the flexural properties of five UHPC precast slab specimens with and without joints,respectively.The complete behavior of UHPC slabs under loading was obtained,and unified equations for predicting the capacity of the UHPC slabs with and without joints were developed.The results show that the failure of specimens with joints occurred at joint interfaces by UHPC crushing after tensile reinforcement yielding.As compared to the whole casting specimens with continuous longitudinal bars,the cracking loads of the specimens with continuous straight bars,straight bar lap,horizontal ring lap and vertical ring lap joints are reduced by 54.6%,52.0%,51.0%and 54.6%,respectively.The yield loads decreased by 34.4%,35.7%,34.5%and 33.3%,respectively.The peak loads decreased by 29.7%,29.6%,34.7%and 29.5%,respectively.The ductility index increased by 17.6%,2.9%,8.8%and 5.9%,respectively.The crack resistance and flexural capacity of joint specimens are governed by the performance of cast-in-situ joint interfaces.As long as the straight lap lengths of bars satisfy the requirements of specifications,the flexural properties of specimens are barely affected by configuration modes of longitudinal bars in joints,and a relatively simple straight bar lap can be adopted in actual engineering applications.The predictive equations for flexural capacity of UHPC slabs with and without joints were proposed,and its feasibility was well verified by the experimental results of this paper and other references.