FORM-FINDING OF MEMBRANE STRUCTURES BY DYNAMIC RELAXATION
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摘要: 张拉膜结构中应力的分布既可以是处处相等的等应力分布,也可以是满足平衡条件的不均匀分布的应力,膜内各点处处相等的膜内应力分布将得到最小曲面,而平衡应力分布则得到平衡曲面。动力松弛法是常用的膜结构找形方法之一,它的缺点是所需要的迭代次数较多。在找形过程中根据结构位形的变化不断调整计算参数,从而加快了计算的收敛,大大减少了迭代次数。由于忽略膜内剪切刚度,找形过程中单元变形较大,可通过节点坐标多步提升到位来解决问题。Abstract: Stress distribution in membrane structures can be either homogeneous and isotropic resulting in a minimum surface or inhomogeneous and anisotropic resulting in a equilibrium surface.As one of the most frequently used form-finding method for membrane structures,dynamic relaxation features the facility of no need to assemble and solve structure stiffness equations,whereas its defect is the relatively numerous iterations.Dynamic relaxation was modified to accelerate the convergence.During the form-finding procedure the calculating parameters were continuously adjusted according to changing of the structure,and the iteration steps to convergence were greatly reduced as compared with those without parameter adjusting.The excess distortion of elements,which may occur due to omitting of the in-plane shear stiffness and can be overcome by sequential designation of node coordinates.
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Key words:
- membrane structure /
- minimal surface /
- form-finding /
- dynamic relaxation
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