高原高寒地区H形混凝土桥塔日照温度效应

分析了混凝土结构温度场边界条件计算方法, 以青海省海黄大桥H形混凝土桥塔为工程背景, 计算了高原高寒地区四季典型气象条件下的桥塔温度场分布, 对比了四季的桥塔表面温差和塔壁局部温差, 确定了桥塔的最不利温度荷载, 建立了桥塔整体有限元模型, 分析了四季桥塔的偏位、竖向应力、横向应力和纵向应力等温度效应。分析结果表明: 桥塔表面温差与桥塔局部温差均在冬季最大, 最大值分别可达11.88℃、20.79℃, 在夏季最小, 最大值分别可达5.15℃、15.25℃; 横桥向和纵桥向桥塔表面温差最大值分别达到9.15℃、11.88℃, 远大于《公路斜拉桥设计细则》 (JTG/T D65-01—2007) 推荐值±5℃; 接近正南方向的塔壁局部温差最大, 沿壁厚方向的温差分布接近指数形式, 冬季和夏季温度衰减系数最大值分别为4.50、5.01, 故冬季桥塔壁板局部温度分布较夏季更不均匀; 桥塔温度效应同样在冬季最大, 1天中最大桥塔偏位超过40mm, 白天桥塔偏位变化值超过15mm, 不利于施工过程中的桥塔偏位监测; 桥塔根部竖向最大拉应力达到2.2MPa, 桥塔根部同样产生较大水平向拉应力, 纵桥向和横桥向最大拉应力分别为1.82、0.82 MPa, 均发生在桥塔内侧, 在与其他作用组合时可能会造成桥塔开裂, 建议在桥塔塔壁内侧布置一定量的钢筋网片来控制裂缝; 在进行高原高寒地区桥塔设计和施工控制时, 应充分考虑温度效应带来的不利影响。

Temperature effects of H-shaped concrete pylon in arctic-alpine plateau region

The boundary condition calculation method of concrete structure temperature field was analyzed. The H-shaped concrete pylon of Haihuang Bridge in Qinghai Province was taken as engineering background, and the temperature field distributions of pylon under typical meteorological conditions during all seasons in arctic-alpine plateau region were calculated. The temperature differences between pylon surfaces and parts of tower wall in all seasons were compared, and the most adverse temperature load of pylon was determined. The whole finite element model of pylon was established, the temperature effects of pylon such as the displacements, vertical stresses, horizontal stresses and longitudinal stresses in all seasons were analyzed. Analysis result shows that the temperature differences of surface and local of pylon reach maximum in winter, and the maximum values are 11.88 ℃ and 20.79 ℃, respectively. The temperature differences reach minimum in summer, and the maximum values are 5.15 ℃ and 15.25 ℃, respectively. The maximum transverse and longitudinal temperature differences of pylon surface are 9.15 ℃ and 11.88 ℃, respectively, and are much larger than ±5 ℃ recommended in Guidelines for Design of Highway Cable-stayed Bridge (JTG/T D65-01—2007). The local temperature difference of tower wall near the south direction is largest, and the temperature difference distribution along thickness direction is close to exponential form. The maximum temperature attenuation coefficient is 4.50 in winter and 5.01 in summer, so the local temperature distribution of pylon wallboard in winter is more nonuniform than in summer. The maximum thermal effect also appears in winter, the maximal displacement of pylon is more than 40 mm in a day, and the variation value of displacement is more than 15 mm during daytime, which is adverse to monitoring pylon displacement in construction. The maximum vertical tension stress of pylon root reaches 2.2 MPa, pylon root also has large horizontal tensile stresses, the maximum longitudinal and transverse tension stresses are 1.82 and 0.82 MPa, respectively, and both occur inside pylon. When the tensile stresses combined with other actions may cause pylon cracks, so a certain amount of reinforced net should be arranged inside pylon wall to control the cracks. In the design and construction control of pylon in arctic-alpine plateau region, the adverse temperature effects should be considered.