In order to assess the biaxial or multi-axial fatigue behavior of some particular structure details of steel bridges, the stress field intensity method was applied to establish a field diameter solving model of steel bridge components. Based on that, the concept of effective field diameter was put forward by reference to the railway steel bridge design code, and an analysis model for solving the biaxial fatigue strength was built. Furthermore, the biaxial fatigue strength of the steel bridge gusset plate was predicted by the analysis model, and the quantitative relation among the input loads in each direction was obtained. Taking the steel bridge gusset plate as example, its fatigue strength can be calculated through the field diameter solving model, in an error of less than 15％. The results show that to keep the same fatigue life, when the load in the main direction increases, the load in the secondary direction should decrease in a magnitude -0.5 times less than the load increment in the main direction.%为对桥梁结构中一些特殊构造细节进行双轴或多轴疲劳强度评估,运用应力场强法,建立了钢桥构件场径求解模型.结合铁路钢桥规范,提出了有效场径概念,建立了应力场强法计算钢桥构件双轴疲劳强度的分析模型,并以钢桥节点板为例进行模拟验证.用分析模型预测了钢桥节点板在双轴受力情况下的疲劳强度,得到了双向荷载之间的定量关系.研究结果表明,用钢桥构件场径求解模型计算的疲劳强度误差小于15%;在疲劳寿命相同的情况下,主方向荷载增加,次方向荷载将减小,次方向荷载增量为主方向荷载增量的-0.5倍.
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