CFRP加固X型圆钢管相贯节点焊缝极限承载力研究

Study on ultimate bearing capacity of CHS X-joints strengthened with CFRP

为研究碳纤维增强塑料(CFRP)对X型圆钢管相贯节点的影响,对ABAQUS有限元软件进行二次开发,运用Fortran语言将VGM模型编译成VUSDFLD子程序对90个节点模型进行有限元分析,并研究支主管外径比β、主管径厚比γ、CFRP黏贴长度与主管直径之比L、CFRP黏贴层数n对节点承载力的影响.结果表明:CFRP可以减小节点的应力集中,提高节点的承载力,节点开裂会发生在相贯线鞍点焊缝内侧与支管相交的焊根处,随着荷载增加,裂纹会从焊缝鞍点沿着相贯线向冠点发展.对节点进行参数分析可以发现:随着γ的增加,节点极限承载力逐渐减小;随着β的增大,节点极限承载力逐渐增加;随着n和L的增加,节点极限承载力会有所提高.本文节点的破坏发生在焊缝,提出CFRP加固X型圆钢管相贯节点焊缝承载力建议公式,对比有限元结果可以发现,节点主管壁厚较小,支管外径较大时,拟合公式的结果存在不安全.

In order to study the influence of carbon fiber reinforced plastic(CFRP)on the X-shaped circular steel tubular joints,the ABAQUS finite element software was redeveloped.The VGM model was compiled into the VUSDFLD subroutine by Fortran language.The finite element analysis of 90 joint models was carried out,and the effects of the ratio of the outer diameter of the branch to the main pipeβ,the ratio of the diameter to the thickness of the main pipeγ,the ratio of the length of CFRP to the diameter of the main pipe L,and the number of CFRP layers n on the bearing capacity of the joints were studied.The results show that CFRP can reduce the stress concentration of the joint and improve the bearing capacity of the joint.The cracking of the joint will occur at the weld root where the inner side of the saddle point weld of the intersecting line intersects with the branch pipe.With increasing of the load,the crack develops from the weld saddle point along the intersecting line to the crown point.Parameters analysis of the joint show that with the increasing ofγ,the ultimate bearing capacity of the joint decreases gradually,with the increasing ofβ,the ultimate bearing capacity of the joint increases gradually,with the increasing of n and L,the ultimate bearing capacity of the joint will increase.For the failure of the joint occured in the weld,the formula for the weld bearing capacity of the CFRP strengthened X-shaped circular steel tube intersecting joint was proposed.Compared with the finite element results,it can be found that the results of the formula fitted are unsafe when the wall thickness of the main pipe of the joint is small and the outer diameter of the branch pipe is large.