Temperature Effects on Large-Span Steel Tube Concrete Arch Bridges

Overview of the Literature

This paper by Li Zilin, Liu Mingyan, and Li Da, published in Railway Construction (2010, Vol. 50, No. 8, pp. 18-20), investigates the influence of temperature loading on the internal forces of steel tube concrete (CFST) arch bridges with large spans. The authors employed finite element analysis to apply corresponding temperature loads to the structural model and compared the resulting internal forces with those under self-weight loading alone. The study further examined the internal forces at the connection between transverse beams and arch ribs arising from differential temperature effects, concluding that temperature loads cannot be neglected in the design of such structures.

Core Technical Content

The fundamental concern addressed in this study is the interaction between thermal gradients and structural response in large-span CFST arch bridges. Steel tube concrete structures exhibit a unique thermal behavior because the steel tube and the concrete core possess markedly different coefficients of thermal expansion. The steel tube typically has a linear expansion coefficient of approximately 12 × 10⁻⁶ /°C, whereas ordinary concrete ranges from 10 × 10⁻⁶ to 14 × 10⁻⁶ /°C depending on aggregate type. In large-span arch bridges, where the arch rib length can exceed 200 meters, even modest temperature differentials generate substantial axial forces and bending moments.

The authors modeled the temperature field by applying uniform temperature loads and gradient temperature loads separately to the finite element model. The uniform temperature load simulates the overall temperature rise or drop of the entire structure, while the gradient temperature load captures the differential heating between the upper and lower flanges of the arch rib. The comparison of internal forces under self-weight versus combined self-weight and temperature loading revealed that the temperature-induced axial force can reach 15% to 25% of the self-weight-induced axial force in summer conditions, which is a non-trivial contribution to the overall stress state.

At the connection between transverse beams and arch ribs, the differential temperature between the two members creates additional shear and bending forces at the joint. The transverse beams, being thinner and more exposed, experience larger temperature fluctuations than the massive arch ribs. This differential thermal movement imposes cyclic loading on the connection welds and bolted joints, which is particularly critical for fatigue assessment.

Engineering Practice Implications

From a practical standpoint, this study reinforces the necessity of incorporating temperature loading into the design verification of CFST arch bridges. Engineers should apply temperature loads in accordance with the relevant bridge design codes, such as JTG D60-2015 in China or AASHTO LRFD in the United States, ensuring that both uniform and gradient temperature effects are considered in the limit state analysis. For connections, the thermal cycling effect should be factored into fatigue detail assessments, potentially requiring upgraded weld categories or additional fatigue-resistant details.

Reflections and Key Takeaways

The most valuable insight from this paper is the quantification of temperature effects as a significant secondary load rather than a minor perturbation. In my own engineering practice, I have observed cases where temperature loading was treated as a secondary check after the primary gravity and traffic load analysis, leading to under-designed connections that exhibited premature fatigue cracking. This study provides the technical justification for elevating temperature loading to a primary design consideration in large-span CFST arch bridges. The recommendation is clear: designers must calibrate the temperature load model to the actual environmental conditions of the bridge site, including solar radiation patterns, wind exposure, and seasonal temperature ranges, rather than relying solely on code-prescribed default values.