A Study on Ultimate Strength of Folded Steel Plate Girders.

本文研究了由折边腹板和折边翼缘板组合而成的钢板梁在等端弯矩作用下的稳定强度。本文对腹板展开的工字形钢梁和腹板折叠的工字形钢梁的屈曲抗力进行了试验比较。试验结果表明，腹板折曲梁的屈曲抗力比普通工字形梁的屈曲抗力要高。为分析腹板折曲梁的极限承载力，采用基于几何和材料非线性等参壳单元的弹塑性有限元方法，对腹板折曲梁进行了初始挠度和焊接残余应力引起的初始缺陷分析。假设材料本构关系遵循Von Mises屈服准则和Plandtl-Reuss塑性流动法则，并结合材料和几何不变性定律、应变硬化定律和线性卸载定律。非线性矩阵 ...更多信息 或者根据Newton-Raphson和Updated Lagrangian公式进行数值求解，其中位移逐步增加。采用实测的方法对初始缺陷的残余应力和初始挠度进行了分析。极限承载力试验结果与分析结果的比值在0.98 ~ 1.028之间，平均值为0.996。采用非线性有限元方法研究了折板角度、板宽厚比、梁长细比、残余应力和屈服应力比对折板梁极限承载力的影响。在参数研究的基础上，提出了折板梁的失稳分类。确定了三种屈曲模式，即，非弹性弯扭屈曲模式、非弹性局部屈曲模式以及两者的交互屈曲模式。通过参数分析，得出折叠腹板单元对折叠钢板梁极限承载力的影响。少

In this research, the stability strength of steel plate girders assembled by folded web plates and flange plates under equal end moments about their strong axis are investigated. This paper compares experimental buckling resistances of I-shaped steel girders having unfolded web plates with those of the folded plates. The tests show that the buckling resistances of the girders with folded webs can be higher than those of conventional I-shaped girders.To analyze the ultimate carrying capacity of folded steel plate girders with initial imperfections due to initial deflections and residual stresses caused by welding, an elasto-plastic finite element analysis was used based on geometric and material non-linear isoparametric shell elements. It was assumed that material constitutive relationship follows the Von Mises yield criterion and the Plandtl-Reuss plastic flow rule, combined with material and geometric invariance law, strain hardening law and linear unloading law. The non-linear behavi … More or is solved numerically according to both the Newton-Raphson and the Updated Lagrangian formulations where the displacements increase step-by-step. Actual measurements were used for the initial imperfections of residual stress and initial deflection. The ratio of the test results to analysis results for the ultimate carrying capacity is between 0.98 and 1.028, with an average of 0.996. Thus, it may be concluded that this analysis is quite accurate in evaluating the ultimate load carrying capacity of folded steel plate girders.A parametric study using nonlinear finite element approach is also conducted to evaluate the effects of folded angle, width thickness ratio of plate, slenderness ratio of beam, residual stress and yield stress ratio on the ultimate strength of folded steel plate girders. This paper also presents the instability classification of folded steel plate girders based on the parametric study. Three buckling modes are confirmed, i.e., an inelastic lateral-torsional buckling mode, an inelastic local buckling mode and an interactive buckling of the two. From a parametric study, it appears that the effects of folded web element on the ultimate strength of folded steel plate girders. Less