Methods and Practices of One-Time Tensioning of Buckle Cables: Fid-Bau Portal

Methods and Practices of One-Time Tensioning of Buckle Cables

Zheng, Jielian

CFST arch bridges have been rapidly developing and widely used in China owing to many advantages, including their economy, aesthetics, convenient construction and good durability. As of January 2015, more than 400 CFST arch bridges have been built, and their construction spans as well as the arch ring segment numbers have continuously created new records. Particularly, the effective span of the Wushan Yangtze River Bridge and the Bosideng Bridge hit 460 m and 530 m, respectively. Meanwhile, the number of arch ring segments reached 22 and 18, respectively. Besides, the number of arch ring segments of Matan Hongshui River Bridge during the construction stage was 24, which had a higher requirement for the control of structural alignment and cable force uniformity during construction. So far, the calculation method used for determining the CFST arch bridge cantilever assembly construction cable force mainly includes analytical and numerical methods. The analytical method is based on the principle of moment balance, which is also known as the “zero moment method”. The numerical method mainly includes the positive assembly analysis method, the inverted disassembly analysis method, the fixed length buckling method, etc. Currently, the analytical method is primarily applicable to rib structures with small spans alongside a small number of arch ring segments, which challenges and limits its application in analyzing the center of gravity location and effective length of large-span truss CFST arch under complex force conditions. However, the numerical method, particularly the finite element method, effectively addresses the abovementioned drawbacks of the analytical method. It also has been widely utilized in engineering practice through various finite element software. Nevertheless, the traditional fixed-length buckling method employed in the numerical approach relies on a "controlled process and optimal result" methodology that often imposes multiple state variables as constraints, including the arch rib stress, buckling tension and displacement. This leads to numerous constraints and poor uniformity of cable force during the construction. Therefore, further research is needed to develop a more precise method for optimizing diagonal buckling suspension construction. In response to issues of excessive constraints, uneven cable forces, and the challenge of alignment control when applying the traditional fixed-length buckling method during the construction of CFST arch bridges, this chapter introduces a one-time tensioning method based on an "optimal process and controllable results" for the first time. This method has been successfully utilized to analyze a CFST arch bridge with a span of 265 m, i.e. the Matan Hongshui River Bridge, and another arch bridge with a span of 575 m, i.e. the Pingnan Third Bridge (the largest span arch bridge under construction). It is confirmed that such a method offers a couple of advantages including the less constraint condition, uniform cable force distribution, high calculation efficiency and precise construction alignment.