Research On Modeling Method Of Free-form Space Grid Structure And Program Development Based On Rhino Software

With the development of computer aided geometric design technology and the gradual improvement of people's pursuit of architectural aesthetics,the modellings of regular surface such as spherical surface,cylindrical surface,hyperboloid,ellipsoid,etc.in space grid structure have gradually failed to meet the growing architectural expression requirements.The free-form surface is increasingly favored by architects because it is free and diverse in form and visually beautiful and smooth.It is constantly applied in various types of buildings such as airport terminals,stadiums,and commercial centers.However,how to quickly and efficiently design a high-quality space grid structure on a free-form surface is always a difficult and complicated problem.Some research on this problem is performed in this paper,and the corresponding results are obtained.According to the characteristics of the free-form surface,three kinds of mesh generation method-mapping method,isoparametric curve equal chord length dividing method and projection method are proposed.And based on Rhino+Grasshopper platform,several commonly used types of free-form space grid structure parametric modeling programs have been developed.They mainly include two-way orthogonal quadrilateral mesh,two-diagonal oblique quadrilateral meshe,triangular cone meshe,ribbed mesh,Schwedler single-layer shell,Lamella single-layer shell,Kiweitt single-layer shell,and Kiweitt-Lamella single-layer shell.By calling these parametric modeling programs,a space grid structure model can be quickly and easily created on a free-form surface,and the modified model can be dynamically generated in real-time through modification of program parameters.In the design of free-form space grid structure,it is often difficult to obtain high-quality mesh just by meshing due to the complexity of the surface.Therefore,further optimization is always required.To solve this problem,a grid optimization method is presented,and the program of uniformity optimization is compiled based on the Rhino&Grasshopper software.This program takes the minimum standard deviation of the rod length as the optimization goal,and optimize the mesh by adjusting the mesh node to the optimal position on the surface one by one,so as to obtain a space grid with better uniformity.In order to import the space grid structure model established in Rhino software into to the structural analysis software for calculation and analysis,a plug-in program of Rhino software is developed to realize data interaction between Rhino software and USSCAD software,SAP2000 software through txt file(.Cuss file and.s2k file),and it greatly improves the efficiency of architectural design and structural analysis.Through this plug-in program,the study models were successfully imported from Rhino to US SCAD and SAP2000 for calculation and analysis,which verifies that the plug-in program is practical and efficient.