钢-UHPC结合段PBL连接件和钢梁端面承压联合作用研究

Joint Action of PBL Connectors and Steel Beam End Bearing in Steel-UHPC Joint Section

钢-混结合段作为钢梁和混凝土连接为整体的核心部件,传力构件的受力性能对钢-混凝土结合段至关重要。为提高结合段的力学性能,进行了仅有钢梁端面承压、PBL连接件和两者联合作用3组推出试验。结果表明:3组试件最终破坏裂缝分布均为钢梁端面侧“八”字形分布;钢梁端面组(D组)试件破坏模式主要为UHPC的开裂破坏而失效,PBL连接件组(P组)和联合作用组(PD组)试件主要是贯穿钢筋的剪切破坏而失效;3组试件的荷载-滑移曲线均包含弹性、裂缝开展和屈服3个阶段,由于贯穿钢筋和UHPC榫具有抑制裂缝开展和提高试件延性的作用,P组和PD组试件裂缝开展阶段较D组更短,屈服阶段更长,延性更好。对荷载-滑移曲线进行拟合,提出了钢梁端面承压和PBL连接件承载力随滑移量变化的计算公式。引入滞后滑移差Δs_(j),当Δs_(j)=0~0.67 mm时,联合作用计算结果偏于安全。计算得到钢梁端面承压传力比例约为43%,PBL连接件传力比例约为57%,两者传力效果基本相当。利用UHPC作为外包混凝土时,建议采用承载能力更高的贯穿钢筋,以充分发挥UHPC的高强性能,从而提高结合段的承载能力。

The steel-concrete joint section is the core component to connect the steel beam and concrete as a whole,and the force performance of the force-transfer member is very important for the steel-concrete joint section.In order to improve the mechanical properties of the joint section,three groups of deduced tests were carried out,including only the steel beam end bearing,only the PBL connection and the combined action of the above two.The results show that the distribution of final failure cracks in the three groups of specimens is the“figure-eight”distribution on the end face side of the steel beam.The failure mode of the specimens of the steel beam end group(Group D)is mainly the failure of UHPC cracking failure,and that of the specimens of PBL connector group(P group)and combined action group(PD group)is mainly due to the shear failure of the penetrating steel bar.The load-slip curves of the three groups of specimens all include three stages such as elasticity,crack development and yield.And because the penetrating steel bar and UHPC mortise have the effect of inhibiting crack development and improving the ductility of the specimen,the crack development stage of the P group and the PD group specimens is shorter than that of the D group,while the yield stage is longer,and the ductility is better.The load-slip curve is fitted,and the calculation formula of the steel beam end bearing and the bearing capacity of the PBL connector with the slip amount is proposed.The hysteresis slip differenceΔs_(j) is introduced,when theΔs_(j) is 0~0.67 mm,the combined action calculation results are biased towards safety.It is calculated that the force transmission ratio of the steel beam end bearing is about 43%,and the force transmission ratio of the PBL connector is about 57%,and the force transmission between the two is basically the same.When UHPC is used as outsourced concrete,it is recommended to use penetrating steel bars with higher bearing capacity to fully utilize the high strength performance of UHPC,so as to improve the bearing capacity of the joint section.