Influence of Temperature Load on Tendon Deviation Angle During Segmental Erection of Concrete-Filled Steel Tube Arch Bridges

Literature Overview

This paper by Li Xiumei, Lai Lian, and Xie Xiaoli from Guangxi University, published in 2004 in the Central-South Highway Engineering (Vol. 29, Issue 4, pp. 29-30), investigates the effect of temperature loads on the deviation angle of hanger tendons during the segmental erection process of concrete-filled steel tube (CFST) arch bridges using hydraulic jack and steel strand inclined hanger technology. Supported by the National Natural Science Foundation of China (Grant No. 50068001), the Guangxi Science and Technology Commission (Grant No. 0135008), and the Guangxi Department of Education Research Fund (Grant No. 316 of 2002), the study derived an analytical expression for the tendon deviation angle under temperature changes and examined its practical significance.

Core Technical Content

The segmental erection of CFST arch bridges using inclined hanger tendons is a complex construction process in which the geometry and force distribution of the tendons must be precisely controlled. Temperature variations during construction can affect the length and tension of the steel strands, potentially altering the tendon deviation angle and, consequently, the force distribution in the arch rib and the hanger system. The authors derived a mathematical expression relating the change in tendon deviation angle to temperature variations and evaluated the magnitude of this effect under realistic construction conditions.

Key Technical Parameters

Principal Finding

The study concludes that the influence of temperature loads on the tendon deviation angle is very small, such that during temperature variations, the direction of the tendon force can be considered essentially unchanged. This finding has practical significance for construction planning, as it means that temperature-induced changes in tendon geometry do not require significant adjustments to the construction methodology or force control procedures.

Engineering Practice Implications

The finding that temperature effects on tendon deviation angle are negligible is practically valuable for the construction management of CFST arch bridges erected using inclined hanger tendons. It simplifies the construction planning process by indicating that temperature variations do not require real-time adjustments to the hanger tendon geometry or the jack positioning.

Practical Recommendations

1. Construction planning: Temperature variations can be treated as secondary effects in the construction planning of segmental CFST arch bridges, simplifying the scheduling and force control procedures.
2. Force monitoring: While the deviation angle is not significantly affected, the tendon force itself may still be influenced by temperature through thermal expansion of the steel strand. Force monitoring during construction should account for temperature effects on strand tension.
3. Erection sequence optimization: The construction sequence should be optimized to minimize the duration of exposure of erected segments to large temperature differentials, particularly during the final closure stage when geometric precision is critical.
4. Closure temperature control: The final closure of the arch, which determines the as-built geometry and force state of the completed structure, should be performed at a controlled temperature to minimize residual stresses and geometric deviations.

Methodological Assessment

The analytical approach adopted in this study, deriving a closed-form expression for the tendon deviation angle under temperature changes, is appropriate for a relatively focused engineering question. The simplicity of the analysis is matched by the simplicity of the conclusion, which is that the effect is negligible. However, the study's short length (two pages) and the limited scope of the analysis suggest that it may not fully address the combined effects of temperature, construction sequence, and material aging on the long-term performance of the hanger system. The practical value of the study lies in its clear conclusion, which provides engineers with confidence that temperature-induced geometric changes in the tendon system are not a critical concern during construction.

Study Insights and Reflections

This paper addresses a specific and practically relevant question in the construction of CFST arch bridges: whether temperature variations during segmental erection significantly affect the geometry of the hanger tendon system. The conclusion that the effect is negligible is reassuring for construction engineers and simplifies the construction planning process. However, it is important to recognize that while the geometric effect on the deviation angle is small, temperature variations can still influence the tension in the steel strands through thermal expansion, which may require compensation in the jack force control. The study serves as a useful reference for construction engineers working on CFST arch bridge projects, confirming that temperature-induced changes in tendon direction are not a critical concern, while also highlighting the need for careful force control during construction to account for temperature effects on strand tension. For the broader community of bridge engineers, this paper contributes to the body of knowledge on construction-phase effects in composite steel-concrete structures and reinforces the importance of understanding the interaction between construction methodology and structural behavior.