Study On Theory Of Self-adaptive Stress-free Shapes Control Method For Super Long-span Cable-stayed Bridge

With the development of cable-stayed bridge striding to super long span,cable-stayed bridge on the design, construction and construction control have put forward higher requirements. With reference to SuTong Yangtze River Highway Bridge, based on the self-adaptive stress-free thought, this paper carries on a more thorough discussion to construction control theory for super long-span cable-stayed bridge. The concrete research work is as follows:(1) Basic thought of self-adaptive stress-free shapes control method is elaborated. Necessity and feasibility of self-adaptive stress-free shapes control method is analyzed. And a reasonable construction control system of self-adaptive stress-free shapes control method to cable-stayed bridge is put forward. This system includes six sub-systems, prefabricated system, test system, error processing systemâ… , judgment analysis system, error processing systemâ…¡and forward analysis system .(2) Based on the geometric nonlinear finite element theory, the nonlinear iteration arithmetic of forward-construction is studied,which is about the computation of cable-stayed bridge stress-free shapes. Its main contents cover the determination of cable unstressed lengths, the determination of assembled geometry and manufacture geometry for steel girders. And through stress-free shapes of example, it confirms that each component's unstressing condition (mainly including cable unstressed lengths, unstressed curvature of main girders and towers) throughout maintains invariable in the installation process, which is in reasonably completed bridge condition.(3) The parameter sensitivity analysis of the SuTong Yangtze River Highway Bridge is carried on, thus the sensitive degree of the main design parameter is distinguished. The main design parameter to the girder geometry sensitive degree from larger to smaller is, cable rigidity, girder weight, girder stage length, cable length, girder rigidity, cable weight, main tower rigidity. To the main tower displacement sensitive degree from larger to smaller is, cable rigidity, girder weight, cable length, girder rigidity, girder stage length, main tower rigidity, cable weight.To the girder internal force sensitive degree from larger to smaller is, cable rigidity, girder weight, girder stage length, cable length, cable weight, girder rigidity, main tower rigidity.(4) Emergence of stayed cables'twist is described, mechanism of stayed cables' twist is studied ,and the revised formula of cable unstressed lengths of stayed cables'twist is proposed. Basic reason of stayed cables'twist is analyzed theoretically, which is caused by the unbalanced torque at the cable end, and three possibly kind of reasons causing stayed cables'twist is analyzed from the practice.(5) The cantilever installation technique of steel box girder is studied.The valuation method of local survey ascertaining the installation position of steel box girder and global survey ascertaining the global profile in the process of the cantilever installation of steel box girder,is put forward. And this method has been applyed to actual project. And construction measure to assure steel box girder welding smoothly is put forward, and this indicates the method is effective and available for long-span bridge of the same kind.