并列异形PBL-钢纤维增强混凝土组合剪力键受剪性能研究

Shear Behavior of Parallel Special-shaped PBL-steel Fiber Reinforced Concrete Composite Shear Connection

为解决PBL连接件在装配式组合梁中应用困难的问题,提出了一种并列异形PBL-钢纤维增强混凝土(SFRC)组合剪力键。以连接件内贯穿钢筋数量为参数,进行了5个简化单边推出试验,得到试件的破坏模式与荷载-位移曲线,对比分析关键受剪变形特征的变化规律。基于试验结果,建立与试验结果吻合较好的有限元模型,并分析了不同材料部件的应力、应变发展及分布特点;对异形钢板剪力键的断裂机制进行了初探性研究。研究结果表明:并列异形PBL-SFRC组合剪力键具有初始剪切刚度大和延性好的特点;贯穿钢筋可有效防止SFRC的纵向劈裂破坏,减小连接件的拔出效应;组合剪力键的整体性随贯穿钢筋数量的增加而提高;有限元分析较好地揭示了该类剪力键从PBL屈服到SFRC损伤再到PBL断裂的破坏过程,PBL剪力键断裂点的钢材应变较大,与钢材颈缩应变吻合较好。

To promote application of PBL connectors in fabricated composite beams,a parallel special-shaped PBL-steel fiber reinforced concrete(SFRC)composite shear connection is proposed.Taking the number of steel bars in the connection as a parameter,5 simplified unilateral push-out specimens are tested,and their failure modes and load-displacement curves are obtained.The key deformation characteristics of the shear performance of the specimens are compared and assessed.Based on the test results,a finite element(FE)model is established after a careful calibration against the test results.The"stress and strain"development and distribution of various material components in the FE models are analyzed.A preliminary study on the fracture mechanism of the special-shaped steel connector is carried out.Through this study,it is found that the parallel special-shaped PBL-SFRC composite shear connections have the advantages of large initial shear stiffness and high ductility.The configuration of steel bars can effectively prevent the longitudinal splitting damage in the SFRC,and reduce the pull-out effect of the connectors.Integrity of the composite connection increases with an increase in the number of steel bars.The failure mechanism of these connections is well simulated by the FE analyses,i.e.,the failure of the connection is initiated the yielding of PBL connector,then the damage of SFRC,and ultimately the fracture of PBL connector.The fracture point of the PBL connector is found to have a large steel strain in the FE model,and it agrees well with the steel necking strain.