小半径曲线连续箱梁桥恒载应力的空间分布特性分析

为研究混凝土曲线箱梁桥的空间受力特性，以某主梁宽9.75m、桥长5×18.76 m的城市立交匝道桥为工程背景，利用ANSYS有限元软件计算几种标准跨径的桥梁模型，通过对截面应力进行积分运算获取截面不同区域所承担的内力比例，并以内力比值系数、应力差值和应力比值为评价指标讨论了同跨径下曲线箱梁桥与直线箱梁桥在一期恒载作用下各控制截面弯矩、剪力和应力的差异。研究发现:一期恒载作用下，曲线箱梁顶、底板法向正应力分布不均匀，剪力滞系数最大可达1.35；外侧腹板承担剪力值最大可达内侧腹板的2.65倍；圆心角超过8°时，边跨跨中截面剪力比值系数大于1.1，圆心角超过13°时，边跨支点截面剪力比值系数大于1.13；在恒载作用下，曲线箱梁桥中性轴“倾斜”，在边跨跨中截面外侧出现正应力卸载现象，边跨支点截面内侧出现应力卸载现象。现行普遍使用的梁系有限元法计算结果不能真实反应曲线箱梁的空间受力分布，箱梁各腹板受力和顶底板弯曲正应力的分布在工程设计中应引起足够的重视。

Spatial characteristics of stress in curved box-sectional bridge with minor radius

In order to study the spatial mechanical characteristics of concrete curved box girder bridge, taking an urban interchange ramp bridge with 9.75 m main beam width and 5 × 18.76 m bridge length as the engineering background, ANSYS finite element model is used to calculate several bridge models with standard span. The internal force ratios of different regions of the section are obtained by integral calculation of the section stress. The internal force ratio coefficient, stress difference and stress ratio are used as evaluation indexes to discuss the differences of bending moment, shear force and stress of each control section between curved box girder bridge and linear box girder bridge under one-stage dead load. It is found that under the first-stage dead load, the normal normal stress distribution of the top and bottom plates of the curved box girder is uneven, and the maximum shear lag coefficient can reach 1.35 ; the maximum shear force of the lateral web is 2.65 times that of the medial web ; When the center angle exceeds 8°, the shear ratio coefficient of the middle section of the side span is greater than 1.1, and when the center angle exceeds 13°, the shear ratio coefficient of the side span fulcrum section is greater than 1.13. Under the action of constant load, the neutral axis of curved box girder bridge is inclined, and the positive stress unloading occurs outside the middle section of side span, and the stress unloading occurs inside the section of side span fulcrum. The calculation results of beam finite element method commonly used currently cannot truly reflect the spatial stress distribution of curved box girder. The stress distribution of each web of box girder and the bending normal stress distribution of roof and floor should be paid enough attention to in engineering design.