When eccentric live loads are applied on the deck overhang of steel-box girder bridges, torsional moments, comprising pure torsional and distortional moments are generated on the box sections. The torsional moment on the bridge girders distorts the box girder cross-sections, inducing additional normal stress components and causing instability of the box girder sections in severe cases. Hence, it is essential to install intermediate diaphragms in the box sections to minimize distortional behaviors. Although the applied live loads are critical parameters that influence intermediate diaphragm spacings, the effects of live load combinations have rarely been addressed in the design of intermediate diaphragm spacings. Thus, load combinations should be evaluated to design the intermediate diaphragm spacing of the box girder bridges more thoroughly. In this study, the load combination effects on the distortional behavior and adequate intermediate diaphragm spacing were evaluated through a finite element analysis (FEA). Composite rectangular box girder bridges with different cross-sectional aspect ratios () and spans () were analyzed in the parametric study. It was found that the truck load, which represents the concentrated load, significantly influences the distortional warping normal stress, normal stress ratio, and intermediate diaphragm spacing. In addition, the FEA results showed that the controlling load combinations could be varied with the span.

中文翻译：

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荷载组合对简跨钢箱梁桥变形行为的影响

当偏心活荷载施加在钢箱梁桥的桥面悬垂上时，在箱形截面上会产生扭矩，包括纯扭矩和扭曲扭矩。桥梁上的扭矩使箱梁截面变形，引起额外的法向应力分量，严重时会导致箱梁截面不稳定。因此，必须在箱形截面中安装中间隔膜以最大程度地减少失真行为。尽管施加的活荷载是影响中间隔板间距的关键参数，但在中间隔板间距的设计中很少涉及活荷载组合的影响。因此，应评估荷载组合以更彻底地设计箱梁桥的中间隔板间距。在这项研究中，通过有限元分析 (FEA) 评估了载荷组合对变形行为和足够的中间隔膜间距的影响。在参数研究中分析了具有不同横截面纵横比（ ）和跨度（ ）的组合矩形箱梁桥。结果表明，代表集中荷载的卡车荷载显着影响扭曲翘曲法向应力、法向应力比和中间隔膜间距。此外，有限元分析结果表明控制荷载组合可以随跨度而变化。在参数研究中分析了具有不同横截面纵横比（ ）和跨度（ ）的组合矩形箱梁桥。结果表明，代表集中荷载的卡车荷载显着影响扭曲翘曲法向应力、法向应力比和中间隔膜间距。此外，有限元分析结果表明控制荷载组合可以随跨度而变化。在参数研究中分析了具有不同横截面纵横比（ ）和跨度（ ）的组合矩形箱梁桥。结果表明，代表集中荷载的卡车荷载显着影响扭曲翘曲法向应力、法向应力比和中间隔膜间距。此外，有限元分析结果表明控制荷载组合可以随跨度而变化。