小半径九十度弯曲钢箱梁桥空间受力特性研究

Study on Spatial Mechanical Behavior of Steel Box Girder Bridges with Small-Radius and 90-Degree Curvature

摘要: 城市立交匝道因红线、既有构筑物或景观限制，有时需采用极小平曲线半径的钢箱梁桥，该类桥梁的弯–扭耦合效应、剪力滞、畸变翘曲与支座横桥向不均匀受压并存，使得挠度、应力及反力分布与直线梁差异显著。本文以某小半径九十度弯曲钢箱梁为例，采用板壳单元进行了全桥空间精细化仿真，主要结论如下：1) 该桥空间效应显著，恒载下的中跨跨中截面外侧挠度达到内侧的1.48倍，预拱度设计时应予以注意；静活载作用下，上述差异进一步放大；2) 应重视对支座处钢箱构件的局部强化设计，从而降低底板厚度需求而节约钢材用量；3) 同一桥墩处的支反力不均现象明显，支座选型时应有所差异；4) 在立交设计中，必要时可采用90˚弯曲钢箱梁，曲线半径可小至40 m，但需依据全桥精细化模型和空间影响面结果进行设计，尤其应避免出现支座脱空甚至上构倾覆风险。

Abstract: Due to constraints such as right-of-way limits, existing structures, or landscape requirements in urban interchange ramps, steel box girder bridges with extremely small horizontal curve radii are sometimes adopted. In such bridges, combined bending-torsion coupling effects, shear lag, distortional warping, and transverse uneven compression at supports coexist, leading to significant differences in deflection, stress, and reaction distributions compared to straight girders. Taking a small-radius 90-degree curved steel box girder bridge as an example, a refined spatial simulation of the full bridge was conducted using shell elements. The main conclusions are as follows: 1) The spatial effects of the bridge were notable. Under dead load, the deflection at the outer side of the mid-span section reached 1.48 times that at the inner side, which should be considered in camber design. Under static live load, this difference was further amplified. 2) Local strengthening of steel box components at supports should be emphasized to reduce the required bottom plate thickness and save material. 3) Significant uneven distribution of support reactions was observed at the same pier, indicating that different bearing types should be selected. 4) In interchange design, 90-degree curved steel box girders with radii as small as 40 m may be used when necessary. However, design should be based on refined full-bridge models and spatial influence surface results, with particular attention to avoiding bearing uplift or even superstructure overturning risks.