Optimized Calculation Method for Hoisting Process of Large-Span Concrete-Filled Steel Tube Arch Bridge

Literature Overview

Published in Bridge Construction in 2002 (Vol. 32, No. 1, pp. 52-54), this paper by Zhang Jianmin from South China University of Technology, Zheng Jialian from the Guangxi Communications Department, and Qin Rong from Guangxi University presents an innovative application of optimization theory to the hoisting process of large-span concrete-filled steel tube (CFT) arch bridges. The research addresses a practical construction challenge that I have encountered in my own engineering practice: the complex tensioning sequence and jack adjustment required during the assembly of large arch ribs.

Technical Methodology

The authors introduced optimization calculation theory into the arch rib hoisting calculation, employing a first-order analysis method to determine the reasonable construction state. The key outputs include the cable tension forces and arch rib hoisting heights at each construction stage.

The optimization approach effectively addresses the challenges of the jack tensioning and hanging system, specifically:

The first-order analysis method determines the optimal construction state by minimizing a defined objective function, typically the deviation between the actual and target arch rib geometry. This approach transforms a complex multi-variable problem into a tractable optimization problem.

Key Findings and Technical Analysis

The study demonstrates that the optimized calculation method effectively solves the problems of jack tensioning iteration count and method limitations in the jack tensioning and hanging system. By simulating the CFT arch rib assembly process, the authors provide a systematic framework for planning the construction sequence.

From a structural engineering perspective, the hoisting process of a large-span CFT arch bridge involves several critical phases:

1. Segment fabrication and storage: Individual arch rib segments are fabricated from CFT pipe sections, typically with butt-welded joints.
2. Temporary support erection: Temporary towers and cables are erected to support the arch during assembly.
3. Segment hoisting and positioning: Each segment is lifted and positioned at its target location.
4. Tensioning and adjustment: Cables and jacks are adjusted to bring the arch to its final geometry.
5. Concrete filling: The steel arch ribs are filled with concrete to create the composite CFT structure.
6. Temporary support removal: The temporary supports are carefully removed, transferring the load to the permanent structure.

The optimization of the tensioning sequence is particularly critical because improper tensioning can induce excessive stresses in the arch ribs, potentially causing permanent deformation or even failure. The first-order method provides a systematic approach to avoid these risks.

Engineering Practice Integration

For engineers involved in the fabrication and welding of CFT arch bridge components, this paper has several practical implications:

• Segment fabrication tolerances: The optimized hoisting calculation assumes precise segment geometry. Fabrication tolerances must be tight enough to ensure that the as-built geometry matches the design geometry within acceptable limits.
• Weld quality at segment joints: The butt welds joining arch rib segments must be of the highest quality. These welds are subject to complex stress states during and after the hoisting process, and any weld defects can initiate cracks under the cyclic loading of the construction process.
• Construction sequence planning: The optimized tensioning sequence provides guidance for construction planning, but the actual implementation requires skilled operators who can interpret the calculated tension values and make real-time adjustments.

The paper also highlights the importance of construction monitoring. During the hoisting process, the actual geometry and stress state of the arch should be continuously monitored and compared with the predicted values from the optimization model. Any significant deviation should trigger a re-analysis and adjustment of the tensioning plan.

Study Insights and Reflections

This paper is a prime example of how optimization theory can be applied to practical construction problems. The transformation of the jack tensioning problem from an experience-based trial-and-error process to a systematic optimization problem represents a significant advancement in construction engineering methodology.

For the steel pipe fabrication industry, this research underscores the importance of precision fabrication in large-scale construction projects. The optimized hoisting calculation assumes that the fabricated segments meet design specifications, and any deviation can compromise the optimization results. This means that fabrication quality control must be integrated with construction planning, not treated as an independent activity.

The paper also reminds us that construction engineering is not merely about executing design drawings—it is about managing a complex, dynamic process where material properties, geometric tolerances, and environmental conditions all interact to determine the final outcome. The optimized calculation method provides a framework for managing this complexity, but successful implementation requires skilled engineering judgment and experienced construction teams.