Mechanical Characteristics And Stability Analysis In The Construction Of Large-span Grid

In recent years,Spatial grid structure has been widely used in large public buildings such as exhibition halls,steel factory buildings and railway platforms because of its good mechanical performance,large overall stiffness and elegant shape,it has gradually become a mainstream trend.Therefore,a large number of scholars at home and abroad are attracted to engage in the theoretical research of large-span spatial structure.However,most of the current researches mainly focus on the overall structure after construction,and there are few research results on the mechanical properties and stability analysis during the construction process.The construction period of the large-span space structure is long and it is a process of change.The structure geometry,stiffness,load and constraint of the grid under each construction stage are different,Therefore,the mechanical properties of the grid during construction are different from the structure after completion,Especially in the construction process,the stability of the grid structure is poor,and once it encounters the dynamic wind load,it is easy to appear safety accidents.According to statistics,it is found that the safety accident rate of space structure in the construction process is as high as 49.2%.Therefore,the mechanical characteristics and stability of the long-span grid structure in the construction process is an important research topic.This article takes a building Workshop roof structure under construction as the research object;The statics analysis,vibration characteristic analysis and transient dynamic analysis of the roof truss structure under dangerous working conditions are carried out.Based on the results of the analysis,assisting construction unit to identify the most dangerous moment in roof truss construction,and solving the overall stress and deformation at the moment,and guide the construction unit to avoid risks,it provides theoretical guidance for the safe construction of roof truss and achieves the purpose of safe production.The main research contents of this paper are as follows:（1）Designing the construction scheme of the roof truss.According to the site construction of this project,formulate the roof trusses in the welding and assembly process requirements;According to the construction conditions and construction difficulties of the project,the construction plan of the roof truss structure was designed.Firstly,Ground pre-assembly.then,Lift the block grid unit into blocks to the corresponding position for installation.finally,highaltitude bulk.（2）Solving the mechanical properties of roof trusses during construction.Analyzing the whole construction process of the roof truss,so as to determine the dangerous conditions in the construction.and analyze the constraints and loads of the roof truss under various working conditions.Utilizing Ansys software to establish the parametric model of the roof truss structure under each working condition,and perform statics analysis on the roof truss structure under each working condition respectively.（3）Solving the natural frequency and vibration mode of the roof truss structure.The basic theory is based on modal harmonious response analysis.solve the first 30 natural frequencies of the roof truss under the most unfavorable conditions and its corresponding mode shape,and calculate the frequency that is most likely to cause the structure to resonate.（4）Simulating fluctuating wind load,Kaimal spectrum was used as the target power spectrum,using MATLAB software,linear filter method and modified Fourier method are used to simulate the time history of fluctuating wind speed at key nodes within 900 s,and compare the pros and cons of the two methods.In a addition.Simulating the fluctuating wind load time history curve of key nodes（5）Dynamic analysis.Using Ansys software,the dynamic wind load and static load are applied to the roof truss structure,through transient dynamic analysis,the displacement response time history curve of dangerous members is solved,at the same time,finding the most dangerous moment in construction,and further solve the stress and deformation of the roof truss at this moment.Guiding the construction unit to avoid risks and provide theoretical guidance for the safe construction of roof trusses.