考虑焊接残余应力的钢桥面板U肋焊接处局部应力分析

为研究正交异性钢桥面板的顶板与U肋焊缝连接处残余应力及与外荷载组合作用下的局部受力特征,针对宽体钢箱梁工程实例,基于热弹塑性有限元法对该焊缝的施焊过程进行了数值模拟,分析了焊接过程中温度场和应力场的变化;以初应力的方法实现了焊接残余应力与外荷载作用的组合。研究结果表明：面板下缘垂直于焊缝方向的残余拉应力峰值接近材料的屈服强度,远离焊缝的区域应力急剧减小,焊趾处的横向残余应力要明显大于焊根处;由面板上缘至下缘,纵向残余应力由压应力变为拉应力,横向残余应力呈现出“拉应力-压应力-拉应力”的交替变化趋势;以初应力的方式考虑残余应力,稳定应力场的相对误差可控制在5.0%以内;自重与二期恒载对焊缝区局部应力场的分布特征和焊根及焊趾处的应力极值的影响不大(1.7%以内);外荷载中考虑局部对称轮载作用且未考虑焊接残余应力在外荷载作用下的消散情况时,焊根及焊趾处垂直于焊缝的横向应力极大值最大分别可增大10.7%、17.6%;焊接残余应力及与外荷载组合作用下,焊趾及焊根位置处沿面板厚度应力的分布符合“直线+抛物线”的规律。

Local Stress Analysis in Welding Area of U-rib of Steel Deck Considering Welding Residual Stress

In order to study the local strress characteristics at weld joints between the top plate and U-rib of Orthotropic steel deck under welding residual stress and the combination of external loads and welding residual stresses, taking a wide body steel box girder as an example, the numerical simulation of welding process of the welding seams was carried out based on thermo elastic-plastic finite element theory. The changes of temperature field and stress field in welding process were analyzed. The combination of welding residual stress and external loads was realized by the method of initial stress. The results show that the peak value of the residual tensile stress perpendicular to the direction of the weld at the bottom of the steel deck is close to the yield strength of the material, and the stress in the area far away from the weld seam decreases sharply. The transverse residual stress at the weld toe is obviously greater than that at the weld root. From top surface to bottom surface of the steel deck, the longitudinal residual stress changes from compressive stress to tensile stress, and the change trend of the transverse residual stress is "tensile stress to compressive stress to tensile stress". Considering the residual stress in the way of initial stress, the relative error of stable stress field can be controlled within 5.0%. The influence of self weight and secondary dead load on the distribution characteristics of local stress field and the extreme value of stress at weld root and weld toe is not significant (within 1.7%). When the local symmetrical wheel loads is considered in the external load but the dissipation of residual stress under the external loads is not considered, the maximum value of transverse stress perpendicular to the weld at the weld root and weld toe can be increased by 10.7% and 17.6% respectively. Under welding residual stress and the combination of external loads and welding residual stresses, the distribution of the stress along the thickness of the top plate at the weld toe and weld root are in accordance with the rule of "straight line and parabola".