复合型开孔板连接件抗剪性能试验

为提高开孔板连接件(PBL)的抗剪性能，提出了带柔性套筒的复合型PBL连接件，并对其抗剪性能进行试验研究，建立复合型PBL承载力计算方法。基于贯穿钢筋弯拉受力模型，推导其抗剪作用表达式，得到PBL孔内应力扩散角对贯穿钢筋抗剪作用的影响规律。设计制作8个PBL推出试件并进行破坏试验，探究柔性套筒壁厚对复合型PBL抗剪刚度、承载能力、延性、破坏模式及孔内钢筋混凝土榫传力机制的影响。研究结果表明：极限状态下，复合型PBL的贯穿钢筋弯拉变形较大，荷载-滑移曲线呈现明显的强化特征，且连接件延性得到显著改善；与无柔性套筒的常规PBL比较，贯穿钢筋周围包裹2 mm壁厚套筒的复合型PBL极限承载力和相应滑移分别提高了40.0%和42.6%；继续增大柔性套筒壁厚，由于孔内混凝土榫的有效剪切面积削弱，且两侧混凝土对贯穿钢筋的局部支撑作用减小，连接件承载力有所降低，但延性得到持续改善。将试验结果与已有常规PBL承载力计算公式进行对比分析表明，以钢筋混凝土榫剪切变形为主的常规PBL承载力计算公式对复合型PBL抗剪承载力计算误差较大，相关公式计算值均小于试验实测值。结合复合型PBL传力机理，给出了考虑混凝土榫剪切作用、贯穿钢筋作用和混凝土板局部支撑作用的PBL承载力计算公式。与试验结果对比发现，所提承载力公式计算值与试验结果吻合良好，可用于复合型PBL抗剪承载力的确定。

Experiment on Mechanic Behavior of Perfobond Rib Connectors with Rubber Rings

In order to improve the performance of perfobond rib connectors (PBL), an innovative type of composite PBL with soft rubber rings surrounding transverse rebars was developed. Structural behavior of the composite PBL was experimentally explored, and prediction method for the PBL was introduced. Based on the deformation compatibility of transverse rebar under tension and bend actions, equations to predict the effect of transverse rebar in PBLs was developed. Characteristic value for stress diffusion angle in concrete dowel was obtained using the MATLAB software. Eight in total, push-out specimens, aiming at the influence of rubber ring on shear stiffness, bearing capacity, ductility, failure mode, and load transferring mechanism of reinforced concrete dowel, were fabricated and tested. The results indicate that transverse rebar in composite PBLs failed in tension-bending modes, and the measured load-slip curves are shown in typical multi-lines. Comparing to the normal PBLs without rubber rings, the resistance and relative slip of composite PBL using rubber rings with a wall thickness of 2.0 mm increase by 40.0% and 42.6%, respectively. Although ductility of composite PBL gradually improves with the rubber wall thickness, due to the reduced cross-section area of concrete dowel, the PBL resistance presents a continual drop after the wall thickness larger than 2.0 mm. Comparisons between the resistances from current tests and those predicted by existing PBL formulas reveal the low accuracy of the models. Moreover, equations to predict the composite PBL resistance, which composed of the effects of concrete dowel, transverse rebar and local supporting concrete, were theoretically derived and experimentally calibrated. It is concluded that the proposed equation could be potentially used for the prediction of composite PBL resistance.