考虑钢-砼接触特征的CFST管节点热点应力分析

为研究不同钢-砼界面接触特征下钢管混凝土桁架焊接管节点局部应力分布及热点应力集中系数，以钢管混凝土桁架Y型焊接管节点（主管与支管夹角θ=60°）为研究对象，利用ANSYS有限元软件，选择其Solid45、Mass21、Targe170和Conta173单元建立管节点有限元模型，引入非线性面-面接触关系模拟局部变形导致钢管与内填混凝土之间发生相互挤压或脱离，计算得到钢管与内填混凝土接触间隙、侵入深度、法向接触应力和切向摩擦应力等局部接触变形及应力状态。分析了3种摩擦系数下(0，0.35，0.60)，主管及支管的热点应力集中系数（SCF）分布。研究结果表明：主管焊趾处热点应力SCF在冠跟处出现最小值，在鞍点和冠趾之间的中点出现最大值；与主管相比，支管SCF总体较小，冠跟处出现最小值，鞍点和冠趾之间出现最大值。支管轴向拉力作用下Y型管节点焊缝附近钢、砼相互脱开，冠点附近比鞍点附近脱空区域大，鞍点脱空区域外围是钢管和混凝土接触挤压最剧烈区域，接触法向压力最大，混凝土对钢管支撑作用最明显。摩擦系数对管节点热点应力集中系数分布趋势影响很小，对SCF最大值有一定影响。

Hot Spot Stress Analysis of CFST Joints Considering Steel-Concrete Contact Characteristics

In order to investigate the local stress distribution and hot spot stress concentration factors(HSCF) of welded tubular joints of concrete filled steel tube(CFST) truss under different contact characteristics of steel-concrete interfaces, the Y-shaped welded tubular joints of CFST truss (the angle between the chord and the branch is 60°) are used as the research object. Based on finite element software ANSYS, finite element model of the tubular joint was established by using Solid45, Mass21, Targe170 and Conta173 elements. Considering nonlinear surface-surface contact relationship between the steel tubular wall and the filled concrete, internal squeezing or detachment caused by local deformation were simulated. Local contact deformation and stress state such as the contact gap, penetration depth, normal contact stress and tangential friction stress between the steel tubular and the filled concrete were obtained. The HSCF distribution of the chord and branch under three friction coefficients (0, 0.35, 0.60) is analyzed. The research results show that the HSCF at the weld toe of the chord has a minimum value at the crown heel and a maximum value at the midpoint between the saddle point and the crown toe. Compared with the chord, the HSCF of the branch is generally smaller and the minimum value appears at the crown heel. The maximum appears between the saddle point and the crown toe. Under the action of the axial tension of the branch, the steel and concrete near the welding seam of the Y-shaped tubular joint are separated from each other, and the void area near the crown point is larger than that near the saddle point. The periphery of the void area of the saddle point is the most violent contact and compression area between the steel tubular and the concrete. The pressure is the greatest, and the concrete supports the steel tube most obviously. The friction coefficient has little effect on the distribution trend of the HSCF of tubular joint, and has a certain effect on the maximum value of HSCF.