钢板组合单边螺栓钢筋机械连接件抗拉性能试验

Experimental study on tensile properties of steel plate composite blind bolts as rebar mechanical connectors

为实现无湿作业、无焊接条件下将单向预制板横向钢筋拉通受力并形成双向板,考虑施工效率和可操作性,提出钢板组合单边螺栓钢筋连接件。为研究连接件抗拉性能,对22个试件进行单调拉伸试验,研究参数为钢板强度、螺栓个数、预紧力大小和锚固长度,重点考察破坏形态、极限承载力、荷载-位移曲线及变形能力。试验研究表明:此类连接件存在钢筋拉断、钢筋犁沟式拔出两种破坏模式;对于调质45#钢盖板,连接件的钢筋临界锚固长度在2d~3d之间,低于临界锚固长度时钢筋犁沟式拔出,高于临界锚固长度时钢筋拉断;连接螺栓数为4时,连接件即可实现钢筋等强连接;连接件的盖板宽度减小时,临界锚固长度增加;在锚固长度相同条件下,连接件抗拉强度随螺栓预紧力增大而增大;对于Q460C高强钢盖板,均为齿钉挤压变形、钢筋拔出破坏;在相同试验条件下,带肋钢筋与光圆钢筋试件的破坏模式相同;提出了这种钢筋连接件的抗拉承载力的计算公式,与试验结果吻合较好,可为小直径钢筋机械连接设计提供参考。

In order to achieve pull-through of transverse rebar of one-way precast slab to form two-way slab without wet operation or welding,considering the operability and efficiency of construction,steel plate composite blind bolts as rebar mechanical connectors were proposed.To study the tensile properties of the connectors,a monotonic tensile test was performed on 22 specimens.The research parameters were steel plate strength,number of bolts,pre-tightening force,and anchorage length,and the failure form,ultimate bearing capacity,load-displacement curve,and deformation capacity were investigated.Research results show that there were two failure modes of the specimens including fracture and pull-out of rebar.For the quenched and tempered 45#steel cover plate,the critical anchorage length of the reinforcing bar of the connector was between 2 d and 3 d.When it was less than the critical anchorage length,the rebar experienced scraping plough type pull-out;when it was larger than the critical anchorage length,the rebar would fracture.When the number of the connecting bolts was four,the specimens realized equal-strength connection of rebars.With the decrease in the width of the connecting cover,the critical anchorage length increased.Under the same anchorage length,the tensile strength of the joints increased with the increase in the pre-tightening force of the bolts.For the Q460C high-strength steel cover plate,the failure modes were deformation of the tooth nails and pull-out of the rebar.Under the same experimental conditions,the failure modes of the specimens with ribbed bars and rounded steel bars were the same.The formula for calculating the tensile bearing capacity of the proposed connector was proposed,and the analytical values agreed well with the experimental results,which could provide references for relevant design and research.