Zhuojin Pipe Fitting Co., LtdTemperature Field Distribution in CFST Members Under Solar Radiation
Literature Overview
The paper by Chen Baochun and Liu Zhenyu, published in Journal of Highway and Transportation Research in 2008 (Vol. 25, No. 12, pp. 117-122), presents an experimental investigation of the cross-sectional temperature field in steel tube concrete (CFST) members subjected to solar radiation. The research was supported by the Fujian Provincial Key Science and Technology Project (2003F007) and conducted at the College of Civil Engineering, Fuzhou University. This work is directly relevant to the thermal design of CFST bridge members, where solar radiation induces non-uniform temperature distributions that generate thermal stresses and secondary effects.
Experimental Observations and Temperature Distribution Patterns
The temperature field measurements revealed that the cross-sectional temperature distribution under solar radiation is inherently non-uniform. The temperature variation at the center point of the section is more influenced by the east-west direction (the direction of solar radiation) than by other factors. Away from the center, the temperature variation along the radial direction exhibits progressive lag relative to atmospheric temperature, with the lag increasing as the measurement point moves toward the center.
| Observation Category | Key Finding |
|---|---|
| Temperature field uniformity | Non-uniform across the section |
| Center point influence | Dominated by east-west solar direction |
| Radial temperature lag | Increases toward section center |
| Orientation effect | Horizontal members show larger amplitude than vertical |
| Sun-facing vs. shaded face | Sun-facing face has larger variation |
| Maximum temperature difference | Horizontal members exceed vertical members |
| Radial distribution model | Representable by cubic polynomial |
Thermal Response Characteristics
Horizontal (transverse) members exhibited larger temperature variation amplitudes compared to vertical members under identical solar conditions. The sun-facing surface experienced significantly larger temperature changes than the shaded surface, and the maximum cross-sectional temperature difference in horizontal members exceeded that in vertical members. The radial temperature difference distribution could be adequately represented by a cubic polynomial, providing a convenient mathematical tool for thermal stress analysis.
For vertical members, the maximum radial temperature difference in the morning was approximately equal to that in the afternoon, indicating a symmetric thermal response pattern. This symmetry is important for fatigue assessment, as the daily thermal cycling pattern is predictable and can be incorporated into fatigue life estimation models.
Engineering Practice Implications
For CFST bridge design, particularly for long-span cable-stayed bridges and arch bridges where temperature effects are significant, the non-uniform temperature field induces both axial thermal forces and bending moments. The cubic polynomial representation of the radial temperature difference enables efficient thermal stress analysis in finite element models. Engineers should account for the orientation-dependent thermal response when designing CFST members for different structural positions within a bridge system.
Study Insights
This research underscores the importance of considering solar radiation as a primary thermal load for CFST bridge members, not merely as a secondary effect. The non-uniform temperature field creates thermal gradients that can induce significant secondary stresses, particularly in restrained members. The finding that horizontal members experience larger temperature variations is consistent with the greater exposure area to solar radiation. For practical design, the cubic polynomial fit provides a computationally efficient means of applying realistic temperature profiles in structural analysis. The symmetry of morning and afternoon temperature differences in vertical members simplifies the thermal loading model for daily cyclic analysis. This work contributes to the ongoing refinement of thermal load models in bridge design codes, particularly for regions with significant solar exposure.