Importance Evaluation Method For Cables And Struts In The Loop-Free Suspen-Dome

The suspen-dome is mainly composed of a top single-layer reticulated shell and a bottom prestressed cable-strut system.It has the advantages of beautiful shape and good stability,and belongs to a rigid-flexible combined structure.The loop-free suspen-dome analyzed in this article is a special type of the suspen-dome.The bottom part of it has a good continuous collapse resistance due to the use of a loop-free prestressed cable-strut system.However,the prestressed cable-strut system is relatively redious,which not only affects the overall mechanical performance of the structure,but also causes certain difficulties in construction.At the same time,due to the unique geometric configuration of the prestressed cable-strut system,the importance of the cables and struts at different positions is still unclear.The effect of structural performance is also unclear.Based on this,this paper uses a 100m-span loop-free suspen-dome with a four-layer loop-free prestressed cable-strut system as the initial analysis model,and optimized the number of layers of the prestressed cable-strut system and grid-jumping the struts to determine its the final optimization scheme,and the static performance parameter analysis of the structure using the final optimization scheme;based on the peak value of the total strain energy change of the top reticulated shell before and after the brace and the standard deviation of the strain energy change rate of the reticulated shell members An improved strain energy method that evaluates the importance of cables and struts for the structure that adopts the final optimization scheme,and determines the importance of cables and struts at different positions.In the model optimization of the loop-free suspen-dome,firstly,optimized the number of cable-strut system layers for the structure.Eight schemes of cable-removing are proposed for the number of cable-strut system layers,and the eight schemes of cable-removing are compared with the initial analysis model.For the difference in steel content,static force and stability performance,the optimal cable-removing scheme is determined to remove the innermost cable-strut system;secondly,the struts grid-jumping optimization is performed on the structure using the optimal cable-removing scheme,and27 types of schemes of struts grid-jumping are compared.The difference in steel consumption,static force,and stability between the grid-jumping of struts scheme and the optimal cable-removing scheme is determined to be the final optimization scheme to remove the second layer of struts in first and second-layer cable-strut systems,the first and second layer of struts in the third-layer cable-strut system on the basis of removing the innermost cable-strut system（a total of four layers of struts）;finally,analyzed the static performance parametric of the structure using the final optimization scheme,The influence of the height of the struts,the pretension of the cables and the initial geometric imperfections on the static performance of the structure: the influence of the cable pretension and the height of the struts in different layers of the cable-strut system on the static performance of the structure continuously decreases from the outside to the inside.Geometric imperfections have a greater impact on the bearing capacity of the structure.In the evaluation of the importance of the cables and struts of the loop-free suspen-dome,the finite element analysis model is established with the structure of the final optimized plan as the research object,and the modified lagrangian incremental solution of the central difference mode is adopted the time history curve of total strain energy and the standard deviation of the strain energy change rate of the upper reticulated shell of the loop-free suspen-dome with broken cables and struts are solved,and the influence of the size of the cable prestress and the cross-sectional area on the evaluation results is studied.The research results show that the importance evaluation method of cables and struts based on the change rate index of the total strain energy of the reticulated shell is not suitable for the loop-free suspen-dome.The improved strain energy method proposed in this paper is the peak change of the total strain energy of the reticulated shell value is taken as the main evaluation index,and the standard deviation of the strain energy change rate of the reticulated shell member is taken as the auxiliary evaluation index.The evaluation results obtained will not change with the change of the cable pre-tension and the cross-sectional area,and the impact of the decrease in strain energy of the prestressed cable-strut system is avoid,this method can effectively distinguish the importance of cables and struts in different parts of the loop-free suspen-dome.Based on the analysis of the improved strain energy method,it is found that the importance of cables and struts between different layers of prestressed cable-strut systems decreases from the outside to the inside;the rupture of a single cable and strut only has a certain impact on the nearby reticulated shell members.The overall impact on the structure is small,and the structure has excellent resistance to continuous collapse.The analysis and research of the loop-free suspen-dome can promote people’s cognition of the structure system,and provide reference for the application of the loop-free suspen-dome in actual engineering.