闭口肋加劲板屈曲临界应力计算方法

采用能量法, 推导了单向均匀受压四边简支闭口肋加劲板屈曲临界应力计算方法, 考虑加劲肋扭转刚度的影响, 按照截面实际形心位置计算了加劲肋和母板的抗弯刚度。以苏通大桥钢箱梁中采用的梯形闭口肋加劲板为例, 采用Timoshenko方法、小西一郎方法、板壳有限元法及提出的能量法进行了屈曲临界应力比较。分析结果表明: 加劲板长宽比β小于1时, Timoshenko方法和小西一郎方法计算的临界应力与钢材屈服强度比值λ大于能量法计算值; β在1~6之间时, Timoshenko方法和小西一郎方法计算的λ值小于能量法计算值; β在3~6之间时, 能量法计算值与有限元分析结果最接近, 偏差在9%~25%之间。可见, 采用能量法进行正交异性钢箱梁顶、底板弹性稳定分析可行。

Calculation method of critical buckling stress for stiffened plate with closed ribs

A calculation method of critical buckling stress for stiffened plate with closed ribs was proposed by using energy method under unidirectional uniform pressure and simply supported on four sides. The influence of torsional rigidity of stiffened ribs was considered, the whole flexural rigidity of mother board and stiffened ribs was calculated according to the centroid of actual section. The stiffened plates with closed trapezoidal ribs in the steel box girder of Suzhou-Nantong Bridge were taken as example, the critical buckling stresses calculated by Timoshenko method, Ichiro Konishi method, shell finite element method and the proposed energy method were compared. Analysis result shows that when the length-width ratio β of stiffened plate is less than 1, the ratio λ values of critical buckling stress to steel yield strength calculated by Timoshenko method and Ichiro Konishi method are greater than the calculation value of energy method. When β is between 1 to 6, the λ values calculated by Timoshenko method and Ichiro Konishi method are less than the calculation value of energy method. When β is between 3 to 6, the calculation value of energy method is most approaching with the result of finite element analysis, their difference is between 9% to 25%. So the proposed energy method is feasible to analyze the elastic stabilities of top and bottom plates for orthotropic steel box girder.