钢-UHPC组合结构中PBL剪力键力学性能研究

为探究钢-UHPC组合结构与普通钢-混组合结构中PBL剪力键力学性能的差异性，通过推出试验和有限元分析相结合的方法对其展开详细研究。首先，对9个UHPC试件和9个普通混凝土试件进行推出试验，根据2种混凝土试件中PBL剪力键的破坏形态、荷载-滑移曲线及应变分布规律揭示其失效机制及力学性能的差异，分析贯穿钢筋直径和钢板开孔数对PBL剪力键力学性能的影响；然后，采用试验结果验证的有限元模型开展参数分析，详细探讨UHPC强度、钢板开孔孔径、贯穿钢筋屈服强度和钢板厚度对PBL剪力键极限抗剪承载力的影响；最后，基于试验和有限元分析结果，提出考虑钢纤维的PBL剪力键极限抗剪承载力计算公式。结果表明：受钢纤维的影响，UHPC的裂缝发展受到限制，且较普通混凝土裂缝数量少、宽度小；UHPC试件中贯穿钢筋发生明显屈服,以剪切破坏为主；单孔PBL剪力键的极限抗剪承载力主要取决于贯穿钢筋直径，而受混凝土强度影响较小;多孔PBL剪力键的极限抗剪承载力主要取决于贯穿钢筋直径和混凝土强度；与普通混凝土试件相比，UHPC试件的抗剪刚度提升了2~3倍，双孔剪力键极限抗剪承载力约提高41%，三孔约提高56%；钢板开孔孔径、贯穿钢筋屈服强度和钢板厚度均是影响PBL剪力键抗剪承载力的因素；提出的PBL剪力键极限抗剪承载力计算公式计算结果与试验结果吻合度高。

Study on Mechanical Properties of PBL Shear Connectors in Steel-UHPC Composite Structures

To explore the differences in the mechanical properties of PBL shear connectors between steel-UHPC composite structures and ordinary steel-concrete composite structures, the mechanical properties of PBL shear connectors were studied through push-out tests and numerical simulations. First, push-out tests were conducted on nine UHPC specimens and nine normal concrete specimens. According to the failure modes, load-slip curves, and strain distribution of the PBL shear connectors in the two types of concrete specimens, the differences in the failure mechanism and stress characteristics were revealed. The effects of the diameter of penetrating rebar and the number of hole in the steel plate on the mechanical properties of PBL shear connectors were analyzed. Then, finite element models, which were confirmed by the tested results, were employed to perform the parametric analysis. On this basis, the effects of UHPC strength, hole diameter, the yield strength of penetrating rebar, and the thickness of steel plate on the ultimate shear capacity of PBL shear connectors were discussed. Finally, based on the experimental and numerical simulation results, a formula considering the contribution of steel fibers for calculating the ultimate shear capacity of PBL shear connectors was proposed. The results show that the extension of cracks on UHPC is limited owing to the influence of steel fibers, and the number and width of cracks are smaller than those of normal concrete specimens. The penetrating rebars yield obviously and shear failure in the UHPC specimens. The ultimate shear capacity of single-hole PBL shear connectors depends on the diameter of penetrating rebar, which is less affected by concrete strength, and the ultimate shear capacity of multi-hole PBL shear connectors depends on the diameter of penetrating rebar and concrete strength. Compared to normal concrete specimens, the shear stiffness of the UHPC specimens increases 2-3 times, and the ultimate shear capacities of the two holes and three holes increase by 41% and 56%, respectively. The diameter of steel plate opening, yield strength of penetrating rebar, and thickness of steel plate are the factors affecting the shear capacity of PBL shear connectors. The proposed ultimate shear capacity formula has high precision, and the calculated results are in good agreement with the experimental results.