自钻自攻螺钉与不同基材连接节点抗拉拔承载力试验与理论研究

EXPERIMENTAL AND THEORETICAL STUDY ON PULL-OUT CAPACITY OF JOINTS BETWEEN SELF-TAPPING SELF-DRILLING SCREWS AND DIFFERENT SUBSTRATES

螺钉与基材连接节点的力学性能是大跨金属屋面研究的关键问题之一,可靠的连接节点是确保屋面抗风安全的重要组件之一。开展了碳钢螺钉与铝基材(CSA节点)、不锈钢复合螺钉与铝基材(SSA节点)、不锈钢复合螺钉与钢基材(SSS节点)三类节点共360组样本试验研究,分析了三类节点的损伤失效模式,揭示了抗拉拔承载力的参数影响规律,建立了节点承载力设计计算公式。结果表明:两种钻入方式下三类节点均呈现螺钉与基材共同承载、到二者咬合处产生损伤变形行为、再到螺钉被拔出基材的失效模式,节点抗拉拔能力依次为SSS节点、CSA节点、SSA节点;基材厚度、螺钉直径和螺距均对节点承载力产生影响,尤以基材厚度和螺距最为显著,同等条件下改变螺距对三类节点承载力的影响最高达94.54%;所提三类节点承载力设计计算公式与试验结果吻合度良好。

The mechanical properties of screw-substrate joints have become one of the key issues in the research of long-span metal roofing systems.Reliable connections are one of the important components to ensure the wind resistance of metal roofs.The mechanical properties of carbon steel screw and aluminum substrate(CSA joint),of stainless steel composite screw and aluminum substrate(SSA joint),and of stainless steel composite screw and steel substrate(SSS joint)were tested in details through totally 360 experimental samples.The damage failure modes of these three joint types are analyzed,the influence law of parameters on the pull-out capacity of joints is revealed,and the design and calculation equation of joint bearing capacity is established.The study results show that:under the two drilling modes,the three joint types show the failure mode that the screw and the substrate are loaded together,the damage and deformation behavior occur at the occlusal place,and then the screw is pulled out from the substrate.The pull-out resistances of the joints are the SSS joint,CSA joint and SSA joint in turn.The substrate thickness,screw diameter and pitch have the influences on the pulled-out capacity of the joints,especially for the substrate thickness and pitch.Under the same conditions,the influence of changing pitch on the bearing capacity of three types of joints is up to 94.54%.The proposed equation for calculating the bearing capacity of the three types of joints are in a good agreement with the experimental results.