Numerical Simulation of Temperature Stress in Concrete-Filled Steel Tube Tie-Arch Bridges

Literature Overview

This paper by Xiong Hongxia and Liu Muyu from Wuhan University of Technology presents a finite element analysis of temperature-induced stresses in concrete-filled steel tube (CFST) tie-arch bridge arch ribs. Published in 2007 in the Journal of Wuhan University of Technology, the study employs ANSYS software to evaluate internal forces and stress distributions at critical cross-sections under thermal loading conditions. The research was supported by the Hubei Provincial Natural Science Foundation (Grant No. 2003ABA016) and focuses on how design parameters—specifically the rise-to-span ratio and the arch axis coefficient—influence structural response to temperature differentials.

Core Technical Content and Methodology

The authors adopt a three-dimensional finite element approach to model the arch rib structure of a CFST tie-arch bridge. The numerical model accounts for the composite behavior of the steel tube and the infilled concrete, which is essential because temperature gradients can induce differential expansion between the steel shell and the concrete core. The temperature load cases likely include uniform temperature changes, radial temperature gradients (inner versus outer surface), and possibly longitudinal temperature variations along the arch axis.

The key design parameters investigated are:

The study compares results at three critical locations: the crown section, the quarter-span section, and the springing (arch foot) section.

Key Findings and Interpretation

The most significant finding is that variations in the rise-to-span ratio and arch axis coefficient have a pronounced effect on the axial force and bending moment at the crown section, while their influence on the quarter-span and springing sections is comparatively minor. This observation aligns with classical arch mechanics: the crown section is the most sensitive to geometric changes because it is the point of maximum curvature and typically experiences the largest bending moment under asymmetric or non-uniform loading.

From a practical standpoint, this means that thermal stress design checks should be prioritized at the crown section, particularly for bridges with shallow rise-to-span ratios (e.g., f/L < 1/8) where thermal bending effects can be amplified. The tie-arch system provides a horizontal restraint that partially mitigates thermal expansion effects, but the interaction between the tie rods and the arch rib under temperature differentials remains a critical design consideration.

Engineering Practice Implications

For steel pipe fabrication and bridge construction, several practical implications emerge from this study:

1. Pipe thickness and material selection: The steel tubes used in CFST arch ribs must accommodate thermal strains without excessive residual stress accumulation. For typical bridge applications, the temperature range can span from -20°C to +60°C or higher, resulting in differential strains of approximately 0.006 between steel and concrete.
2. Welding considerations: Longitudinal welds in the arch rib steel tubes are particularly susceptible to thermal fatigue. The cyclic temperature loading can accelerate crack initiation at weld toes, especially in the HAZ where microstructural changes reduce toughness.
3. Quality control emphasis: The crown section, being the most thermally sensitive location, warrants enhanced non-destructive testing (NDT) coverage, including ultrasonic testing (UT) and magnetic particle inspection (MT) of all welds in this region.
4. Design optimization: The study suggests that optimizing the arch axis coefficient to approximate the funicular shape under combined dead and temperature loads can significantly reduce thermal bending moments at the crown.

Key Questions and Reflections

One important question that arises from this study is how the thermal stress findings translate to the fatigue life of the structure. The paper focuses on static temperature stress but does not address the cumulative fatigue damage from repeated thermal cycling over the bridge's design life. In practice, bridges in regions with large diurnal and seasonal temperature swings—such as those in northern China or high-altitude locations—may experience thousands of thermal cycles annually.

Another reflection concerns the modeling assumptions. The study uses a linear elastic finite element model, which is appropriate for serviceability checks but may underestimate peak stresses at stress concentrations such as weld details and connections. A nonlinear analysis incorporating plasticity and creep effects would provide a more conservative assessment of long-term thermal performance.

Summary and Reference Value

This paper provides a valuable baseline understanding of how geometric design parameters influence thermal stress distribution in CFST tie-arch bridges. For steel pipe manufacturers and bridge engineers, the findings underscore the importance of tailoring pipe specifications—particularly wall thickness, material grade, and weld quality—to the specific thermal environment of the bridge site. The emphasis on the crown section as the critical location for thermal stress design offers a clear priority for quality control efforts during pipe fabrication and erection. The study's methodology using ANSYS remains relevant and can be extended to more complex scenarios involving combined temperature and wind loading, or to analyze the effects of different concrete grades on thermal stress mitigation.