Diaphragm Effects on Ultimate Strength of Horizontally Curved Thin-Walled Box Girders.

1.提出了一种预测平面弯曲、中间隔板加劲薄壁焊接钢箱梁极限强度和非线性性能的解析方法。该方法采用非线性有限元法进行挠曲分析，考虑了有限变形、弯曲和圣维南扭转复合作用下材料的屈服、应变反转引起的卸载、屈服区、卸载区和再加载区在截面和沿梁的分布、焊接残余应力等因素的影响。提出了在非线性屈曲分析中如何考虑构件板的局部屈曲和变形翘曲。对极限强度的分析结果与试验结果进行了比较，令人满意。所提出的考虑板屈曲的应力-应变曲线模型如图3所示，可用于构件板的局部屈曲分析，该模型可用于非线性屈曲分析。屈曲板的宽度可理解为梁截面的抗压凸缘宽度，等于腹板的抗压区深度。本构模型对局部屈曲的预测结果与试验结果吻合较好。在非线性弯曲分析中，畸变翘曲的影响可以在初始应变状态下以增量的方式模拟，其中畸变翘曲的应变增量以逐步的程序应用，直到达到外部扭曲力矩。从较低的荷载水平上，实验证实了腹板受压部分的弯曲变形具有凸形特征。这种现象可以认为是曲线梁中受压截面部分充当了具有初始弯曲度的柱的非线性行为。以上结论中关于模型试验的结果是基于有限的实验工作。显然，需要研究更大规模的模型试验的实验方案。如果所提出的考虑局部板屈曲的本构模型要应用于同样由水平和/或垂直加强筋加固的梁，尽管需要进行一些验证，但假设的屈曲板宽度通常是保守的。少

1.An analytical procedure is proposed to predict ultimate strength and nonlinear behavior of thin-walled, welded steel box-girder curved in plan and stiffened by intermediate interia diaphragms. In the approach, the effects of finite deformation, yielding of material under combined bending and St. Venant's torsioning, unloading caused by strain reversal, spreads of yielding, unloading and reloading zones in the cross-sections and along the gider, and residual stress due to welding are all taken into account in flexure analysis by nonlinear finite element method. How to consider local buckling of component plates and distortional warping in the nonlinear flexure analysis is also proposed.2.The comparison of the analytical with the experimental results on the ultimate strength was judged satisfactory.3.The local buckling of component plates can be evaluated by the proposed model of stress-strain curve allowing for plate buckling as shown in Fig. 3 and this model can be incorporated into … More the nonlinear flexure analysis.4.The breadth of buckling plate can be taken to be width of the compressive flanges of the cross-section of the girder and equal to the depth of the compressive zone of the web plate.5.The constitutive model predicted the local buckling compared well with the experimental results.6.The effect of distortional warping can be simulated in an incremental way at the initial strain-state in the nonlinear flexure analysis, where the strain increments for distortional warping are applied in a step-by-step procedure until an external distortional moment is reached.7.From lower level of loading, bowing deformation which is characterized by covnex form was experimentally confirmed at the compressive part web plate. This phenomenon might be considered to be that the cross-sectional part in compression in the curved girder acts as so-called nonlinear behavior of column with initial crookedness.The above results on the model tests in the conclusions are based on a limited amount of experimental work. Research is clearly needed on the experimental program of larger amount of the model-tests. Though some verification is necessary if the proposed constitutive models allowing for local plate-buckling is to be applied to the girder also stiffened by horizontal and/or vertical stiffeners, the assumed breadth of buckling plate is generally conservative. Less