Research On Optimizing Synchronously Both Construction And Completion Cable Force Of The Cable-Stayed Bridge

The cable-stayed bridge, which is known for its long span, beautiful formative and simple structure, has been widely used all around the world. As a highly redundant structure, the cable-stayed bridge is composed of cable, tower and girder, of which cable is tensioning member, tower and girder are bending components. The cable forces have greatly tremendous influence on the distribution of internal stress in the structure system, and it has become the key to control the reasonable internal forces of the whole bridge. The existing cable force optimization theory of cable-stayed bridge is generally divided into two steps: the first step is usually to determine reasonable state of the completed bridge; the second step, based on the former, is to determine all construction target states according to the construction phase, so that the final state of a bridge approaches the reasonable state of the completed bridge as close as possible.On the basis of studying and summarizing the existing theories, this paper proposes a method of optimizing synchronously both construction and completion cable force of the cable-stayed bridge. Based on the influence matrix theory of construction phase and superposition principle, the forward analysis is done taking construction cable forces as design variables, according to the divided construction phases; Selecting bending energy as the objective function, optimal solution is obtained by using the constrained nonlinear optimization methods, taking construction and completion cable force within the specified limits as the constraint condition; Using of the generated influence matrix, the completion cable force is acquired by taking construction cable force to assemble the cable-stayed bridge step by step.The analysis of a concrete cable-stayed bridge proves that the method theory is correct. The successful application of the theory in a cable-stayed bridge test model proves the practicality of the method. The results show that taking construction cable forces, which are optimized by using the synchronous optimization method, as pre-tensioning forces, the cable forces change slightly in the construction process, which meets the requirements of the construction safety. The optimized completion cable forces distribute reasonably, and the bending moment are uniform with high safety storage. Synchronous optimization method has guiding significance value to some extent for cable force optimization and construction controlling of the cable-stayed bridge.