UHPC中PBL剪力键力学性能试验研究

Experimental Study on Mechanical Properties of PBL Shear Connectors in UHPC

PBL剪力键的力学行为与键周边混凝土材料特性密切相关,UHPC良好的材料性能有望与PBL键配合进一步提高其力学性能。进行两组UHPC中PBL剪力键的推出试验,得到UHPC中PBL剪力键的破坏模式、荷载-滑移曲线、荷载-应变曲线等,评定了剪力键的主要力学性能指标,与普通混凝土中PBL剪力键的力学行为进行对比,并评估了既有PBL承载力计算公式的适用性。研究结果表明:UHPC中PBL剪力键的破坏模式为贯穿钢筋剪切破坏;UHPC可提高PBL剪力键的承载能力30%以上,抗剪刚度60%以上;UHPC中PBL剪力键的力学性能较普通混凝土更稳定,但集簇布置时荷载分配不均匀系数更高;现有规范或研究成果中,仅个别计算式适用于UHPC中PBL剪力键的单孔承载力值计算。

The mechanical behavior of PBL shear connectors is closely related to the material properties of their embedding concrete. Using PBL connectors with UPHC is expected to further improve their mechanical properties. Two groups of push-out tests of PBL shear connectors in UHPC were introduced in this paper. The failure mode, load-slip curves, and load-strain curves of the PBL shear connectors in UHPC were obtained to evaluate their mechanical properties and compare them with those of PBL shear connectors in normal concrete. Meanwhile, the applicability of the existing calculation formula of PBL bearing capacity was evaluated. The research results show that the failure mode of PBL shear connectors in UHPC is caused by the shear fracture of the perforating rebar. Using UHPC can increase the bearing capacity of the PBL shear connectors by more than 30% and the shear stiffness by more than 60%. The mechanical properties of the PBL shear connector in UHPC are more stable than in normal concrete, but load distribution between connectors is more uneven. In the existing codes or research results, only a few formulas can be used to calculate the bearing capacity of PBL shear connectors in UHPC.