铁道建筑

针对铁路钢桥焊接构造在循环荷载作用下易产生应力集中与疲劳损伤的问题，本文以Q345qD钢平板对接焊构造和十字熔透焊构造为研究对象，采用有限元软件建立精细化三维有限元模型，分析焊趾区域应力分布规律与热点应力特性，同时开展疲劳试验对数值模型进行验证，并进一步拟合得到两类构造的疲劳S-N曲线。结果表明：对接焊构造在165 MPa、十字熔透焊构造在105 MPa拉伸载荷作用下，两类焊接构造均在焊趾区域产生明显应力集中，焊趾X向应力均呈“升-降-升”三段式变化规律，与国际焊接协会（IIW）热点应力理论一致；两类构造热点应力最大值均位于距边缘1 cm的焊趾处，有限元计算结果与试验实测值偏差均小于5%。十字熔透焊构造受几何偏置影响，疲劳寿命离散性明显增大。

To investigate the stress concentration and fatigue damage of welded structures in railway steel bridges under cyclic loading, Q345qD steel butt-welded joints and cruciform full-penetration welded joints were selected as the research objects.Refined threedimensional finite element models were established using finite element software to analyze the stress distribution and hot spot stress characteristics in the weld toe region. Fatigue tests were further conducted to validate the numerical models, and the fatigue S-N curves of the two welded structures were obtained. The results show that under a tensile load of 165 MPa for butt welds and 105 MPa for cruciform full-penetration welds, both types of welds exhibit significant stress concentration at the weld toes. The X-direction stress at the weld toes follows a three-stage ‘rise-fall-rise' pattern, which is consistent with the hotspot stress theory of the International Institute of Welding(IIW).The maximum hot-spot stresses of both structures are located at the weld toe 1 cm away from the edge, and the deviations between finite element results and experimental measurements are within 5%. In addition the geometric misalignment of cruciform full-penetration welded joints significantly increases the scatter of fatigue life.