圆管混凝土T型焊接节点热点应力试验研究

Experimental Study on Hot Spot Stress of Welded Concrete Filled CHS T-joints

摘要:

作为疲劳评估的基础性工作，试验研究了由圆钢管支管与圆钢管混凝土主管组成的焊接桁架T型节点(CFCHS)在支管轴向拉力、压力和平面弯矩作用下的热点应力分布及应力集中系数(SCF)特性.讨论了CFCHS节点的热点应力测试方法和试验结果，并与支管和主管均为圆钢管的T型焊接节点(CHS)进行比较,考察两种节点的性能差异.研究表明：CFCHS节点的热点应力，对主管可采用线性外推方法，对支管需采用二次外推方法；相比CHS节点，CFCHS节点的热点应力分布趋于均匀，SCF显著减小；CFCHS节点支管轴向受拉比受压不利，SCF增大；CFCHS节点几何参数β,τ,γ对主管SCF的影响效应与CHS节点基本一致，但是对支管SCF的影响效应与CHS节点有些差异；混凝土的作用主要是改善CFCHS节点刚度，从而降低SCF，并预期可提高疲劳强度，但混凝土自身强度等级的高低没有显著影响节点的SCF.

Abstract:

The hot spot stress distributions and stress concentration factors (SCF) of welded truss T-joints made of circular hollow section braces and concrete-filled circular hollow section chords (so-called CFCHS joints) under axial tension and compression and in-plane bending on the braces were investigated experimentally,which is a foundation for fatigue assessments of the joints.The measuring method and results of hot spot stresses on the CFCHS joints were discussed and compared with those on the welded T-joints made of circular hollow section braces and chords (so-called CHS joints) to examine the difference in behavior of the two kinds of joints.The current research points out that for the CFCHS joints the linear extrapolation method can be used for chords,whereas the quadratic extrapolation method must be used for braces.The hot spot stress distributions on the CFCHS joints tend to be more uniform and their SCFs become smaller significantly,compared with the CHS joints.Axial tension on the brace puts the CFCHS joints at a disadvantage,which produces higher SCFs than axial compression.The effects of nondimensional geometric parameters β, τ and γ on SCFs of the chords of the CFCHS joints are basically the same as those of the CHS joints,but for the braces,there is a bit difference in the effects of parameters β,τ and γ between the two kinds of joints.Concrete has the function of improving the CFCHS joint rigidity and then decreasing SCFs which is expected to increase fatigue strength,but concrete strength grade does not exert significant influence on SCFs.