Morphology Study Of Cable-strut Structures Based On Mechanism Displacement Analysis

Since its appearance,the cable-strut tension structure has been characterized by its light weight and high efficiency.It has become a hotspot in the field of space structure.Morphological analysis is an indispensable part in the study of cable-strut tension structure,which is composed of cables and struts.Traditional finite element method based on displacement variable becomes invalid in the study of cable-strut tension structure,because of its indeterminate attribute.Based on mechanism displacement analysis,Morphological analysis of cable-strut tension structure has been done in this paper,which includes shape optimization and forming process,displacement adjustment after forming,path planning in displacement adjustment,collapse and failure of cable tension structure.The equilibrium equation of the structure has been established by the potential energy function of the system and its first order variation.In order to solve the mechanism displacement problem of different types of structures,the mechanism displacement solution strategy is proposed,which includes mechanism displacement with and without considering the length variation of bars.A program by MATLAB is developed to analyze and calculate the actual application.In addition,the Jacobian method is used to study the bifurcation of structural equilibrium path and the bifurcation of mechanism motion.The similarities and differences between the two are summarized.Based on the genetic algorithm and Vector Form Intrinsic Finite Element(VFIFE),A program to do the optimal design of cable-strut tension structure is proposed.Taking the cable-dome structure as an example,three design variables of the cable-member section,prestress and shape parameters in the cable-dome structure are selected as optimization variables to optimize the structure.The program can be used to achieve the goal of minimum steel amount per unit area.The mechanism displacement analysis method is used to simulate the forming process,and the whole process of the structure from shape optimization to forming process is realized.An active control algorithm for structural morphological adjustment of cable-strut tension structure is proposed based on genetic algorithm and mechanism displacement analysis.The prestressed structure is taken as the research object,the configuration analysis of the structure with small configuration adjustment and big configuration adjustment was carried out through the self-made MATLAB program.When the displacement of the structure is small,the analysis process of its adjustment is considered to be linear.When large displacement adjustment occurs in the structure,the analysis process of its adjustment needs to be iterated,and by introducing VFIFE in the iterative process,the unbalanced force of free nodes can be eliminated and the convergence speed of the program can be accelerated.With the introduction of genetic algorithm,the active control algorithm can optimize the number of actuator installation and location while meeting the structural adjustment target.Based on Rapidly-exploring Random Tree(RRT),the path planning method of cable-strut tension structure in morphological adjustment is established.A collision detection program is introduced in each step,which is used to determine that there is no collision between structural elements and between the structure and the external environment during the deformation of the structure.After giving each step by RRT,VFIFE is introduced to eliminate the unbalance force of free nodes and ensure that the structure is in self-equilibrium state in every step of configuration.The path planning algorithm has been proved to be valid in the path planning of planar and spatial cable-strut tension structure through the self-made MATLAB program.On the basis of mechanism displacement analysis and VFIFE,an algorithm to solve the buckling path of structures is proposed.The mechanism displacement analysis method is used to calculate the possible displacement of a structure under a certain load,while VFIFE is used to eliminate the unbalance force of free nodes after possible displacement.Then the equilibrium configuration of the structure can be obtained,and the external load that the structure can resist is calculated by the elastic deformation of each member.The load-displacement curve of the structure can be obtained by repeated above steps.The proposed algorithm has been used to simulate the buckling path of the rigid structure,and the collapse failure of the cable dome structure is analyzed.The results of numerical examples verify the validity of the algorithm in the analysis of buckling behavior of spatial strut structures and collapse failure analysis of cable dome structures.A series of effective algorithms of cable-strut tensile structures have been developed in the research work based on the mechanism displacement analysis.And the research work have been used to do the analysis of cable-strut tensile structures from zero state to load state,and then collapse failure state.The algorithms provide theoretical support for the design,optimization and construction of such structures in practical engineering applications.