Zhuojin Pipe Fitting Co., LtdConstruction Control of 500-Meter Class Steel Tube Concrete Arch Bridges
Literature Overview
The paper by Hao Niebing and Gu Anbang from Chongqing Jiaotong University, published in the Journal of Southwest Jiaotong University (2015, Vol. 50, No. 4, pp. 635-640), addresses the practical challenges of construction control for large-span steel tube concrete (STC) arch bridges in the 500-meter class. This is a significant engineering topic given the growing trend of large-span arch bridges in Chinese infrastructure development.
The Challenge of Construction Control
Construction control of STC arch bridges involves managing the evolving structural state from segmental assembly through concrete infilling to the final composite structure. Key challenges include:
- Geometric control: Ensuring the erected arch rib geometry matches the design profile within acceptable tolerances.
- Stress control: Managing internal stresses during the various construction stages to prevent yielding or excessive deformation.
- Cable force adjustment: In cable-stayed arch bridges, the stay cable forces must be precisely controlled to maintain equilibrium.
Traditional construction control methods often require frequent cable force adjustments, leading to high labor costs and potential cumulative errors. The authors propose the "Adjustable Domain Method" (可调域法) as an alternative approach.
The Adjustable Domain Method
| Feature | Traditional Method | Adjustable Domain Method |
|---|---|---|
| Adjustment frequency | Frequent, at most stages | Only at critical stages |
| Control philosophy | Target values | Acceptable ranges (domains) |
| Cable adjustment count | High | Reduced |
| Implementation complexity | Moderate | Requires domain definition |
The Adjustable Domain Method defines acceptable ranges (domains) for structural geometry, stress, and cable forces. Rather than forcing the structure to match precise target values at every stage, the method allows the structure to remain within predefined acceptable domains, only requiring adjustment when values approach domain boundaries.
Application to Bosideng Bridge
The method was applied to the Bosideng Bridge, a 500-meter class STC arch bridge. The results demonstrated:
- Post-closure geometry errors remained within the limits specified by JTG/T F50-2011
- Stress errors after closure were also within code-specified tolerances
- The number of cable force adjustments was significantly reduced compared to conventional methods
Technical Analysis from a Pipe Fabrication Perspective
For engineers involved in the supply of steel tubes for arch bridge ribs, this paper highlights several important considerations:
- Segmentation and joint design: The arch rib is assembled from prefabricated steel tube segments. The quality of butt-welded or bolted joints between segments directly affects the final geometry and stress distribution. Weld distortion control during fabrication is therefore critical.
- Tube straightness and dimensional accuracy: The adjustable domain method assumes that the inherent geometry of each segment is predictable. Any manufacturing deviations in tube straightness or cross-sectional dimensions will propagate through the assembly sequence.
- Welding sequence and residual stress: In arch rib segments with complex geometries (curved tubes), the welding sequence must be carefully planned to minimize residual stresses that could cause post-fabrication deformation beyond acceptable construction tolerances.
- Concrete infilling control: The transition from steel tube arch to composite STC arch involves a significant change in structural behavior. The infilling sequence and rate must be coordinated with the construction control plan.
Standards and Quality Control
The reference to JTG/T F50-2011 (Technical Specifications for Construction of Highway Bridge and Culvert) underscores the importance of adhering to Chinese highway bridge standards. For the steel tube components specifically, relevant standards include:
- GB/T 14975 for seamless steel tubes
- GB/T 8163 for fluid transport welded tubes
- SY/T 5037 for spiral welded tubes (where applicable)
- Welding procedure qualifications per GB/T 19866 or ISO 15614
Study Insights
This paper demonstrates that a domain-based control philosophy can be more practical and economical than target-value-based control for large-span arch bridges. The reduction in adjustment frequency translates directly to lower construction costs and shorter construction schedules. For the steel tube supply chain, this means that while manufacturing tolerances remain important, the overall system has more built-in tolerance, potentially allowing for slightly relaxed inspection criteria on individual segments provided the cumulative effect is monitored and managed.