Form-finding And Load State Analysis Of ETFE Cushions Based On The Vector Form Intrinsic Finite Element

With the application of ETFE cushion structure to National Swimming Centeras the envelope structure for the first time in our country, its many advantages havegained much recognition and verification, and the application and development inbuilding field of our country have been promoted which has made itself appearsuccessively in Guangzhou South Railway Station and Dalian Stadium and otherlarge-span spatial structures as a new type of building cladding system. However, asthe rapid development of building technology, compared to the tensiond membranestructure, the application of the ETFE pneumatic membrane structure is still at theprimary stage, deeper recognition and research, and formal specification are reallynecessary. At present, the analysis of ETFE cushion is mainly based on thenonlinear finite element method. The air cushion as a flexible structure wouldproduce large deformation and rotation under load, where rigid body displacementand elastic deformation are coexistent. The traditional finite element method indealing with such issues may have some restrictions, which would lead toinaccurate results.The Vector Form Intrinsic Finite Element Method (VFIFE) as a new numericalanalysis method, based on vector mechanics, is adapted to deal with stronglynonlinear problems or discontinuous behaviors effectively, such as mechanismmotion, elastic-plastic, large deformation, large displacement, fracture, collisionand collapse so on.In this thesis, based on the above research background, VFIFE is introducedinto the form-finding and load analysis of ETFE cushions, then the feasibility andeffectiveness of VFIFE are discussed. The three stage analysis of membranestructure are summarized in detail and three common numerical methods ofform-finding and load analysis are compared. Through the derivation of theoreticalformula of bar element, the basic principle and analysis procedure of VFIFE aredetailed, then a program of bar element is compiled and used for analysis of a truss,mechanism motion and form-finding of cable net structure, which have verified thefeasibility and accuracy of the bar element formula and program of VFIFE.Then the basic theoretical formulas of3-node constant strain triangularmembrane element of VFIFE have been derived, and a membrane element programhas been compiled. The feasibility and effectiveness of the membrane elementformulas and program have been verified through simulating an airbag inflation.After that, they are applied to form-finding analysis of triangular, rectangular and hexagonal ETFE cushions, some useful results have been obtained and comparedwith that analyzed by ANSYS, which well validates the applicability and validity ofform-finding analysis of ETFE cushions by VFIFE.Based on the form-finding analysis, VFIFE has been applied to load analysis ofrectangular ETFE cushion with five common loading conditions, some beneficialresults have been obtained and compared with that analyzed by ANSYS, whichadequately reflects the practicability and validity of load analysis of ETFE cushionsby VFIFE.