Research On Closure And Unloading Of Long Span Steel Structure

In recent decades, the research of design and construction of long span steel structure has attracted wide attention by the experts of steel structure, it has become a hot spot of studying and many calculable theories and methods have emerged. Some of the research results have been included in standards, such as the United Kingdom standards and Germany industrial standards. A number of new ideas and new theories about design and construction of steel bridges, industrial plants, commercial buildings and sports facilities have been put forward by many inland scholars, and the new ideas and new theories have supported with a lot of experiments in actual projects and-also have some achievements and solve some practical problems. This paper has mainly taken a long span steel stadium project as background, According to the actual stadium construction, as well as the technical problems and key issues encountered in the process of construction, a certain amount of research is made, mainly about closure technology and unloading technology and other key issues in the construction of long span steel structure. Besides, temperature changes also have different temperature stress and displacement of the closure, and the unloading method and step-by-step process of unloading has been researched.Big stride over the Long span steel structure is obtained and the formative technology is complicated. Structure installation needs to experience longer time span , structure forming process and using process to there exist bigger difference in temperature in meeting. It may produce bigger temperature deformation and temperature strain in the process of usage in structure. Temperature deformation and temperature stress are directly related to the temperature differences in structure forming process and using process. To control the deformation of installation process, and reduce the ultimate deformation temperature and temperature stress in using process, in the process of installing the main truss, the general method is the installation of a piecewise block, that each piecewise structure joint in proper order for symmetrical , homogeneous arrangement in high altitude plate followed by independent block, then to connect every independent block as a entity. The ultimate problem is the closure of steel structure. Generally, accuracy calculation must be prior to the closure, to ensure accurate component taking its place and fitting in. This involves a simplified model, the reasonable value of such loads and constraints conditional. The different closure division may produce different temperature strain and initial strain at the same time, and effect closure deviation thereby. Closure of the each installation block has large difference in temperature, the temperature changes will have greater impact, the different temperatures will produce different temperature stress. considering various factors causing Temperature changes, calculating up the temperature deformation of each component. In this paper, a finite element analysis method will be adopted for the simulation of structural closure. Analysis of different closure division temperature and the effects of temperature stress of different closure division on the closure are also involved. With the simulative calculation of closure ostium different state of the finite element model of stadium, more accurately calculate the value of the displacement and temperature stress are thus aquired. By reserving a gap in order to closing the section for sure, under such circumstances, calculating the different temperature stress values of closure unit under the maximum temperature and minimum temperature include the value changed in axial force, shear force, torque, displacement and moment. Based on these values, the interim board cards is designed for the role of connecting up.It is a the state of using into a state of the construction process from the supporting structure forces characteristics of Unloading, a process that the load of temporary support gradually reduced to zero load, so the main structure gradually began to bear the load. By the academic calculation of Cantilever Beam and Simple and we may make out the different load step producing different results, more accurately simulate the unloading process of construction through nonlinear load step calculation. Truss structure from simple cantilever beam structure into a step-by-step structure for unloading, theoretically proves that the real value of the feasibility. Analysis of the results, to ascertain the unloading amounts of every step and unloading step number with the principle of little change in load, using Excel for loading - unloading curve. With this the theoretical a more detailed calculation of unloading step value of the entire stadium is calculated. providing a theoretical basis for the unloading of the long span steel structure, which works to provide more convenient and effective method of unloading. Summing up the law will eventually be used to guide practice.