含UHPC薄层的新型栓钉组合剪力键抗拔性能试验研究

Experimental study on the pull-out performance of a new stud combined shear connector with UHPC thin layer

基于超高性能混凝土(ultra-high performance concrete,简称为UHPC)良好的受力性能,提出了一种由钢板-UHPC薄层-普通混凝土叠合而成的新型栓钉组合剪力键,用于增强基础环式风力机基础中基础环与混凝土间的界面抗拔能力。通过对1:3缩尺模型进行了3组共9个静力拔出试验,研究了UHPC薄层厚度对新型栓钉组合剪力键的荷载-滑移曲线、破坏形态及极限承载能力的影响。结果表明,整个受力过程可经历4个阶段,即界面间摩擦传力弹性阶段、栓钉受剪弹性和弹塑性阶段、混凝土受拉破坏阶段。UHPC薄层的加入,栓钉不仅在钢板与UHPC薄层界面(简称第一界面)即栓钉根部出现了塑性,同时在UHPC薄层-普通混凝土交界面(简称第二界面)上亦出现了明显的塑性,使得新型栓钉组合剪力键抗剪刚度及承载力均较普通栓钉剪力键有显著提高。同时栓钉根部剪应力峰值明显降低,有效提高了剪力键的抗拔性能。基于试验结果,提出了基于双界面栓钉屈服的新型栓钉组合剪力键抗拔承载力计算公式。对比结果表明,该公式能较好反映UHPC薄层厚度对承载力的贡献。

Based on great mechanical performance of ultra-high performance concrete(UHPC),a new type of stud combined shear connector composed of steel plate,UHPC thin layer and ordinary concrete was proposed to strengthen the interface pulling ability between foundation ring and concrete.The effects of UHPC thin layer thickness on load-slip curve,failure modes and ultimate bearing capacity of the new stub composite shear connector were studied by using 3 sets of 9 static pull-out tests on the 1:3 scale model.The results show that the whole loading process can be divided into four stages,namely the elastic stage of friction force transfer between interfaces,the elastic and elastoplastic stages of stud shear,and the tensile failure stage of concrete.With the addition of UHPC thin layer,the studs not only appear plastic at the interface between steel plate and UHPC thin layer(referred to as the first interface)namely the root of the studs,but also appear obvious plastic at the interface between UHPC thin layer and ordinary concrete(referred to as the second interface),which makes the shear rigidity and bearing capacity of the new stub composite shear connector improve significantly than the ordinary stud shear stud.Meanwhile,the peak value of shear stress at the root of stud decreases obviously,which effectively improves the shear performance of the new stud composite shear connector.Based on the results of test,a formula according to the yield criterion for double interface studs for calculating the shear capacity of the new stub composite shear connector was put forward.The comparison results show that the formula can reflect the contribution of thickness of UHPC thin layer to the bearing capacity,and can be used for reference in practical engineering.