Study And Improvement Of Dynamic Relaxation Method For Cable-reinforced Membrane Structures

Being a new kind of special tension structure, cable-reinforced membrane structures are universally accepted and developed rapidly during the past decades for its fully and aesthetical variation, high structure efficiency and long span. Efficient and accurate analysis of form-finding and load-behavior is the kernel part of cable-reinforced membrane structures design. Among the current analyzed method, dynamic relaxation method used a linear way to solve the nonlinear process, the accurate and reliable equilibrium surface can be obtained by a simple algorithm. So this thesis focuses on the dynamic relaxation method.Firstly, in this thesis the characteristics of cable-reinforced membrane structures and the current analysis methods were discussed and the basic theories of traditional dynamic relaxation method were introduced in detail. After proceeding the form-finding analysis with the dynamic relaxation method and studying two parametersΔt , S /M in the algorithm, meanings of these parameters and their convergence range were defined, and the other parameter influence the iterate performance was found– initial velocity. Through theory analyze and deduce, parameters simplification was promoted, by synthesizing the two parameters into single parameter, the algorithm calculate simply. With the assistance of ANSYS surface approximate ability, fulfill the algorithm by ANSYS programming can decrease the iteration dramatically. Moreover, the friendly Graphical User Interface can display the real time location of every node, that make the observation and programming very convenient. Then, by calculating several examples and comparing the results, some conclusions were obtained: The improved simplified method was accurate enough, and the iteration was stable; the form-finding process of membrane structures was independent with the initial stress; the equilibrium surface of cable-reinforced membrane structures is correlative with the stress ratio of cable and membrane. Finally, on the basic of form-finding, process the load analysis on membrane structures with dynamic relaxation method, conclusions can be obtained by examples: initial stress, ratio of rise to span and boundary restraint influence the deformation of membranes under load.Parameters simplification of dynamic relaxation method is an improvement of the traditional method, and the increment of iteration is so small that this promoted method is worthy of further studying. Meanwhile, for convenient, the program's versatility and the entirety with ANSYS should be improved.