# Refined 3D Solar Temperature Field and Effect Simulation of Ultra-High Steel Bridge Pylon
## 1 Introduction  
Bridges exposed to the open environment have an uneven temperature field due to the influence of solar radiation, ambient temperature, and wind [1; 2; 3]. The considerable temperature-related structural deformation and additional thermal stress greatly increase the difficulty of controlling the alignment shape and internal force during construction [4; 5; 6], especially for large steel bridge structures. In order to reduce the influence of temperature effects on steel segment splicing, the morning period before sunlight is usually chosen as the construction time due to the stable air temperature. However, because of the large size of the steel bridge segment and the protracted installation stage, the precision of assembly and shape control is inevitably affected by the rapid change in temperature caused by solar radiation. Because the steel surface temperature is constantly rising in the sunlit areas and is relatively low in the shaded areas, an obvious difference in temperature deformation exists on the steel surface under different solar conditions. If the solar radiation-related deformation error cannot be eliminated during the splicing process, the subsequent segment assembly will be more difficult, causing the actual internal force of the bridge to deviate significantly from thatof the original design [7; 8; 9; 10]. In Xining, Qinghai Province, China, during the main girder construction process of a single-pylon cable-stayed bridge, many wedge welds were used in the steel box girder splicing position, causing serious bearing disengagement due to the solar temperature effect [11]. A steel pylon is similar to a vertical cantilever beam but has a lower structural stiffness before transversal beam construction. Under this structural state, the temperature effect is more obvious and greatly increases the construction difficulty [12]. For H-shaped and A-shaped bridge pylons, at some moment, the temperature effect of one side of the pylon column significantly decreases because of the shelter provided by the other side of the pylon column, which leads to different deformations on both sides of the pylon column, further increasing the difficulty of construction control. Thus, accurately assessing the bridge pylon's shadow and calculating the temperature effect are the basis of controlling the alignment shape of a bridge pylon. The temperature field of a bridge structure Is mainly affected by solar radiation and convection, and these two kinds of heat exchange are generally mutually influential. Thus, the accurate simulation of solar radiation and the convective coefficient have a significant impact on the calculation of the bridge temperature effect. At present, most temperature field studies are based on the calculation assumption that the longitudinal temperature difference of a bridge pylon can be neglected. Based on this assumption, the 3D temperature field can be simplified into a 2D temperature field, which is regarded as the input temperature action with which to calculate the thermal effect of the bridge pylon. [PERSON] et al. calculated the thermal stress and deformation of an H-shaped concrete bridge pylon from Haihuang Bridge under the 2D temperature field and found that the inner side of the bridge pylon may crack under the action of the solar temperature field [13]. [PERSON] et al. analyzed the spatial stress distribution under the most unfavorable temperature difference in the thickness direction of the suspension bridge pylon walls using measured data and a finite element simulation. The inner and outer walls of the bridge pylon experienced high tensile stress under the positive and negative temperature difference, respectively [14]. [PERSON] and [PERSON] used the thermal-mechanical indirect coupling method and analyzed the temperature effect of an H-section concrete bridge pylon. They concluded that cracks may occur on the pylon surface [15]. Based on the measurement and simulation of the temperature effect of Xiantao Hanjiang highway bridge, [PERSON] et al.