UHPC中MCL形组合销的抗剪性能

改进螺旋线（Modified Clothoide，MCL）形组合销是抗剪性能优异的一类新型剪力连接件，在组合结构桥梁中具有广阔的应用前景。为探究MCL形组合销在超高性能混凝土（Ultra-high Performance Concrete，UHPC）中的抗剪性能，依据新型波形组合桥面板结构中MCL形组合销的纵向和横向受力特征，设计并开展了纵向和横向2类推出试验；建立了考虑材料与界面接触等非线性因素的2类推出试验有限元模型，基于试验结果验证了有限元模型的适用性；采用有限元模型开展了结构的全过程受力分析，阐明了2类推出试验的荷载传递历程与破坏机理；依据受力特征和破坏模式，推导了适用于钢销失效破坏模式的MCL形组合销纵向极限抗剪承载力计算式；通过现有公式对比，确定了适用于UHPC压溃破坏模式的MCL形组合销横向极限抗剪承载力计算式。结果表明：UHPC中MCL形组合销的纵向和横向抗剪性能差异显著，纵向抗剪性能表现出良好的延性特性，而横向抗剪性能表现出较高的抗剪刚度和抗剪承载力；主要力学指标的有限元计算值与试验结果符合较好，验证了有限元模型的适用性；MCL形组合销的纵向破坏模式主要表现为钢销产生较大的塑性变形，其根部截面进入屈服状态，而横向破坏模式主要表现为钢销下侧UHPC压溃；纵向和横向极限抗剪承载力计算值与试验值之比的均值分别为1.18，1.06，标准差分别为0.13，0.01，计算值与试验值吻合良好。

Study on Shear Behavior of MCL-shaped Composite Dowels in UHPC

MCL-shaped composite dowels are innovative shear connectors with excellent mechanical properties and have wide application prospects in composite structure bridges. To explore the shear behavior of MCL-shaped composite dowels in UHPC, longitudinal and transverse push-out tests were designed and conducted according to their mechanical characteristics in the innovative corrugated composite bridge decks. Finite element models of two types of push-out tests were established considering nonlinear factors such as the materials and interface contact, and they were verified against the test results. The load transfer process and failure mechanism of two types of push-out tests are expounded by conducting stress analysis of the structure based on the finite element models. Based on the mechanical characteristics and failure mode, a formula was developed to calculate the longitudinal ultimate shear capacity of MCL-shaped composite dowels with the failure mode of steel dowel failure. Based on a comparison with the existing formula, a formula was determined to calculate the transverse ultimate shear capacity of MCL-shaped composite dowels with the failure mode of UHPC crushing. The results indicate that the longitudinal and transverse shear behaviors of the MCL-shaped composite dowels are significantly different. The longitudinal shear behavior of the MCL-shaped composite dowels showed good ductility, while the transverse shear behavior showed high shear stiffness and ultimate shear capacity. The main mechanical indexes calculated by the finite element models are in good agreement with the test results, and the applicability of the finite element models was verified. The longitudinal failure mode of the MCL-shaped composite dowels shows that the steel dowels produce large plastic deformation causing its root section to enter the yield state, while the transverse failure mode shows that the UHPC under the steel dowels is crushed. The mean and standard deviation of the ratios between the calculated values and test values of the longitudinal and transverse ultimate shear bearing capacities are (1.18 and 1.06) and (0.13 and 0.01), respectively, which indicate that the calculated values agree well with the test values.