空心板桥新型粗骨料UHPC铰缝抗剪性能试验

为研究空心板桥新型粗骨料超高性能混凝土(UHPC)铰缝的抗剪性能，对14个铰缝试件进行了静力抗剪试验，试验参数包括铰缝混凝土材料类型、界面处理方式、抗剪钢筋构造形式、抗剪钢筋强度等级和配筋率。分析了试件的裂缝发展过程和分布规律、破坏模式以及各试验参数对铰缝抗剪性能的影响；同时，基于铰缝典型的荷载-位移曲线分析了铰缝的抗剪机理。试验结果表明：铰缝的裂缝宽度从下至上呈现逐渐减小的规律，由于传统配筋方式上部抗剪钢筋的位置靠近顶部，导致上部抗剪钢筋在铰缝抗剪承载力极限状态时尚未屈服，对抗剪承载力的贡献小。试件破坏模式分为2种：传统铰缝的界面剪切破坏；UHPC铰缝的预制混凝土块剪切破坏。UHPC材料、界面预留槽处理方式、抗剪钢筋新配筋方式以及提高抗剪钢筋的强度等级和配筋率，均能不同程度地提升铰缝的抗剪性能。与传统铰缝相比，新型粗骨料UHPC铰缝的开裂荷载、抗剪承载力和名义抗剪刚度提升幅度分别可达42.8%、185%和218.3%。当达到抗剪承载力极限状态时，UHPC铰缝主要依靠抗剪钢筋屈服提供的剪切摩擦抗力以及预制混凝土块剪断提供的剪切抗力来抵抗外荷载。提出了UHPC铰缝开裂荷载及抗剪承载力计算公式。计算结果表明：开裂荷载、抗剪承载力试验值与计算值比值的均值分别为1.47、1.19，变异系数分别为0.05、0.12，所提出的计算公式可以较精确和稳定地预测UHPC铰缝的开裂荷载及抗剪承载力。

Experimental Study on Shear Behavior of New Coarse Aggregate UHPC Hinge Joint of Hollow Slab Bridge

To study the shear behavior of a new type of coarse aggregate ultra-high-performance concrete (UHPC) hinge joints of a hollow slab bridge, static shear tests were carried out on 14 hinge joint specimens. The test parameters included the concrete material, interface treatment, shear reinforcement layout, shear reinforcement strength grade, and reinforcement ratio. The crack development and distribution, failure mode of the specimens, and influence of the test parameters on the shear behavior of the hinge joints were analyzed. The test results showed that the crack width of the hinge joints gradually decreased from the bottom to the top. The position of the upper shear reinforcement in the traditional reinforcement layout is too close to the top, resulting in the upper shear reinforcement not yielding in the ultimate shear capacity state of the hinge joints, which contributes little to the shear capacity. There were two failure modes of the specimens: interface shear failure in the traditional hinge joint and shear failure of the precast concrete block in the UHPC hinge joint. Meanwhile, the shear mechanism of the hinge joints was analyzed based on the typical load-displacement curve of the hinge joints. UHPC material, interface groove treatment, new reinforcement layout of shear reinforcement, and increasing the strength grade and reinforcement ratio of shear reinforcement can improve the shear performance to different degrees. Compared with the traditional hinge joint, the cracking load, shear capacity, and nominal shear stiffness of the new coarse aggregate UHPC hinge joint in this study increased by 42.8%, 185%, and 218.3%, respectively. When the ultimate state of shear capacity is reached, UHPC hinge joints mainly rely on the shear friction resistance provided by the yield of the shear reinforcement and the shear resistance provided by the shearing of the precast concrete block to resist the external load. Formulas for calculating the cracking load and shear capacity of UHPC hinge joints are proposed. The calculation results show that the average ratios of the experimental and calculated values of cracking load and shear capacity are 1.47 and 1.19, respectively, and the coefficients of variation are 0.05 and 0.12, respectively. The proposed formulas can accurately and stably predict the cracking load and shear capacity of UHPC hinge joints.