Research On Deformation Monitoring And Key Issues In Section Hoisting Construction Of Steel Box Girder

Steel box girder is widely used in large span bridge, but restricted by transportation, hoisting and construction condition, subsection hoisting construction method becomes the most commonly used method. For this reason, the closed whole cross section is divided into open asymmetric cross section, which will cause significant changes in stress and deformation in the process of hoisting and erecting construction. Taking a single steel box beam engineering project as the background, some problems in the subsection hoisting construction are discussed in this paper, including torsional deformation, reinforcement measures, dynamic deformation monitoring.Using the finite element numerical method and mathematical analysis method, this paper analyzes the difference of stress and deformation between the closed whole cross section and the open section. And it is concluded that the open asymmetric thin wall steel relative to the closed whole section, torsional stiffness will greatly abate, besides, under the action of gravity, there will be a large torsion deformation, which leads to the vertical deformation and stress increasing.Considering the significant vertical deformation caused by the lateral torsional deformation of the open steel box girder, producing large vertical deformation, this paper comes up with a reinforcement scheme, which uses shape steel forming shear brace and cross brace, and the reinforcement effect is verified by using finite element numerical method. The paper also concludes that the torsional deformation, stress and vertical displacement of steel box girder after reinforcement are having made a lot of improvement, indicating that this method can have immediate effect.For the large deformation measurement, this article discusses the tilt-angle method, using cubic spline interpolation function and the least square method to fit the deformation curve respectively, and the results of the two methods are compared and analyzed in detail. We can find that under the simple loading condition, it is best to set up four monitor sites for the simply supported beam bridge with constant stiffness, and compared with the least square method has a higher accuracy.Tilt-angle method is used to make the application analysis for the surface with lateral torsional deformation. We can draw a conclusion that for simply supported girder bridge with constant stiffness, seven inclinometers are enough to measure the deformation surface under the action of deadweight, and it is able to reach very high accuracy.