Mechanical Analysis And Monitoring On The Key Construction Process Of Large-span Space Steel Structure

With the development of society,large-span space steel structure is widely used,and its construction technology is developed rapidly.For example,the large sports venues of the Beijing Olympic Games,whose construction scale and technical level lead the world,has become a milestone in the development of space structure in China.Because of the complexity of the structure form of large-span space steel structure,the construction process is also more complicated.In the construction process,multiple stress redistribution can occur in the whole structure,and the stress some components should happen large variation.So the stress state of spatial structure in the construction process is more complicated than the use stage.Reasonable construction steps and completion of each step according to the requirements are crucial to the perfect formation of the final structure,therefore stress analysis and structural monitoring in the construction process is very important.For different construction environments and structural forms,different installation methods will be used to apply different engineering needs.For the engineering of using overall lifting method,its main construction process is divided into installation,lifting and unloading,and generally the lifting frame for auxiliary lifting is needed when using overall lifting method.There are generally many lifting points to the engineering which using overall lifting method,so the study of asynchronous lifting of the structure in the overall lifting process has become the key to ensure the safety of the structure.On the other hand,the completion of unloading means that the space steel structure is formed,and the simulation of unloading boundary conditions is related to the influence on the structure under the action of late temperature load,so that the unloading process is the key link in the construction of large-span space steel structure.In this thesis,the research status of large-span space steel structure construction process is analyzed and summarized.An engineering example is taken as the research object.The method of combining analysis of finite element method with the site experiment is used,which provide reference for the research of construction process analysis and monitoring means of large-span space steel structure.The safety and analysis methods of key construction steps of large-span space steel structure are also studied.The main research work and results are as follows.(1)Aiming at the large-span space steel structure of a gymnasium,in the present thesis,a reasonable mechanical model is established for the construction process of the large-span space steel structure according to the overall lifting construction technology of the project structure.Then the mechanical analysis of the construction process of the structure is carried out by using the finite element method,and the safety of the large-span space steel structure in the construction process is evaluated according to the analysis results.(2)The stress status of structural key components and the displacements of key joints are tracked and monitored by the site test during construction.Based on the FE analysis of the stresses of the components during the construction process,the composition of the monitoring system and the arrangement of the measuring points are given.The stress test values of the key components are compared with ones of the finite element analysis.It is shown that the numerical simulations of the structural stresses and deformation states are in agreement with the experimental measured values,which presents the rationality of the established mechanical model in the construction stage of the large-span steel structure and the efficientness of the finite element analysis.(3)In addition,the influence of unsynchronized lifting for the structure under the overall lifting construction method is studied.Through the comparison and analysis of three mechanical parameters of lifting point support force,node displacements and component stresses and the high difference limit value of lifting point controlled by the lifting process are determined by comprehensive comparison selection,which was used to guide the actual construction of the structure.(4)In the process of the preliminary unloading construction,the large span space steel structure and lifting frame support are proposed as the whole mechanical model instead of the jack suspension to support the large-span space steel structure.The stress states of the structure under the two unloading construction schemes subjected to the temperature changes are analyzed by using the finite element method and iterative technique.Through the analysis and comparison of the calculation results of two unloading construction schemes,the established lifting frame support scheme is more reasonable and economic than one of the jack suspension to support.As a result,the construction equipment occupancy and cost expenditure are reduced.The research results in the present thesis can provide reference for the construction technology and monitoring of similar large-scale engineering projects.