Study On The Analysis And Optimization Of Ellipsoid Hybrid Form Cable Dome Structure

The demand for buildings with large space especially the long-span sports facilities is growing as the development of economy and society.Cable dome structure is one of the most efficient and state-of-the-art structural systems.Cable dome structures are based on the concept of tensegrity that consists of continuous tension members and isolated compression members.The scale of largest cable dome in the world had already surpassed 200 m,while in China it has just reached 100 m.In the design and construction of cable dome,several problems need to be solved: structural systems adapting to irregular architectural scheme,form and force finding method for irregular cable domes,behavior of the new cladding forms and controlling of the construction error,etc.Focusing on these problems,this thesis studies the method to judge the geometric feasibility and form finding,optimization of prestress,behavior of rigid-flexible roof,influence and controlling method of construction error.The results are as follow:The method to judge the geometric feasibility of irregular cable domes directly is proposed.The unbalanced force is redistributed based on equilibrium matrix and stiffness matrix.The feasibility is judged by whether the unbalanced force converge to zero.The efficiency of calculation is increased by avoiding the obtaining and serving feasible combinations of self-stress modes.Independent self-stress modes can be obtained directly with random initial value.When the initial geometry is infeasible,the form finding is conduscted by moving the free node step by step.The form finding method for ellipsoid hybrid form cable dome is proposed.This method consists of three main steps: geometric adjustment,obtaining partition results and assembling.The partial solutions are assembled by adding horizontal auxiliary cables and optimization of coordinates of lower node of struts.The integral feasible prestress and geometry complying to constraints that the architectural surface keeps unchanged and prestress of each hoop distributes evenly are obtained with less calculation.Based on multi-objective optimization and multiple criterion decision making method,the method to obtain optimal prestress for cable domes with multiple self-stress modes is given.The combination of self-stress modes is optimized by NSGA-II.The objective functions are material cost,structural stiffness,number of sectional types and sensitivity to cable length error.The unique solution for the practical object is given by filtering and ranking of Pareto solutions.The multiple objective optimization method for prestress design that is adaptive to practical engineering and is able to consider more structural demands is established,which gives guidance to the scheme comparison and structural design of cable domes.Ellipsoid hybrid form and Geiger form cable domes are compared,the advantage of hybrid form over Geiger form is given.Two types of modal shape are found and the method to judge the type of modal shape is given.Influence of rigid-flexible roof on ellipsoid hybrid form cable dome is studied.The ellipsoid hybrid form cable domes with different boundary conditions are analyzed,the influence of lower structures on cable dome is obtained.A scaled model of ellipsoid hybrid form cable dome is constructed and the analysis results ars verified by conducting static experiments on the model.The influence of cable length error on cable dome structures is analyzed via Monte Carlo method.The results show that the main impact of cable length error is prestress deviation.The active error controlling method based on improved genetic algorithm is proposed.The tensioning force of active cables are optimized to minimize the prestress deviation induced by the cable length error.It is verified by a large number of examples that the method is valid to reduce the prestress deviation and make the erected structure more close to the design scheme.