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.