Research In Construction Simulation Analysis For Large-span Steel-truss Bridge Based On The Step-by-step Model Method

In recent years, large-span steel-truss structures are more and more widely applied in practical projects for their advantages. On one hand, the construction of this kind of structure is complex, and influenced by many uncertain factors. On the other hand, the traditional structures design research in complete structure but construction is a time-varying process from non complete structure to complete.Meanwhile, the construction and design of the structure inevitably are out of touch sometimes for kinds of reasons and this may make the structural internal force designed according to the normal used standard may not meet the construction requirement. All of these will make the actual construction more difficult. So,it is necessary to make tracking simulation analysis on its construction process, find out the variation of the displacements and internal forces of the structure immediately during the construction period, and ensure the whole construction process in a controllable scope.This paper uses segmentation cantilever construction in a large-span steel-truss as the research background, and discusses about the construction simulation for the large-span structure and related nonlinear problems in the construction. the whole construction process of the large-span structure is include large displacement, supports settlement as well as a variety of structural systems conversion and other factors which make the actual shape and location of the installed structure and the structure to be installed newly change constantly. All of this make the construction process have boundary nonlinear characteristics. In view of the problem that the results of the traditional method to simulate the construction process with the element birth and death function in ANSYS cannot reflect the actual location of the installed and to be installed structure, this paper uses the step-by-step model method(or named step-by-step model technology) to simulate the whole process of the segmentation cantilever construction of large-span bridge,and solves the nonlinear problem in the construction process very well. The main research includes:(1)Introducing the key problems in construction mechanical analysis, the construction simulation methods and the Step-by-step model method:this method is base on the element birth and death function of finite element program ANSYS.The different is that it models meanwhile calculates step by step. This method considers the influence of the location changeing of the installed structural on the newly installed structure in each construction step, that is that the newly installed structure in each construction step is built based on the installed structure after deformation.(2) This paper is in view of the geometry nonlinear problem and boundary nonlinear problem in the process of construction simulation for a large-span structure. With finite element program ANSYS, this paper use the step-by-step model method to simulate the construction process of the large-span steel-truss bridges. Meanwhile, combined with the actual measured data, it proved the rationality of the method and solve the geometry nonlinear problem in the segmentation cantilever construction for the large-span steel structure;(3)By comparing the design with construction about internal force and linear of bridge model, this paper puts forward the construction optimization scheme and simulation. Then the paper compares the simulation results before and after the optimization again, and analysis the influences that the construction to internal forces and linear of final bridge.(4)Through the above analysis, the paper provides many constructive suggestions to the process of construction, and provides a reference for the other similar projects.