Parametric Design And Optimization Of Superellipsoid Long-span Spatial Gridshells

Structural design is now within the sphere of the influence of digital architecture which has been reshaping the architectural construction with computer technology,parametric deisgn serving as one of the means.Parametric design is the product of computer-aided design as it evolves upwards,changing not only the traditional architectural design but also the cooperation between architecturals and structural engineers.Large-span spatial gridshell,whose structural form is closely related to its architectural morphology,is a good object for studying the collaboration of structural and architectural designers on a parametric design form.In order to investigate the interaction between structural design and architectural design in design practices,the superellipsoidal large-span spatial gridshells is targeted on in this thesis and the hierarchical design is adopted.The main work done is as follows:(1)Cross-platform design was achieved by using C # computer programming language connecting a mainstrain parametric design platform and a commercial finite element structural analysis software.The available studies on the co-work of structural design and parametric design is summarized firstly,followed by the connection of Grasshopper and SAP2000 through Grasshopper KDP and SAP2000 API.(2)The shape optimization design of the superellipsoidal gridshell was studied.The shape of the superellipsoidal grid shell was firstly modelled with the visual programming of Grasshopper and then encapsulated as add-on battery.A mathematical model for the shape optimization design of the superellipsoidal gridshell was constructed considering architectural constraints and structural constraints.Efforts and discussions were made to achieve the adjustment of shape controlling parameters of superellipsoidal gridshell according to the structural performances.The multi-objective optimization genetic algorithm NSGA-II was improved per structural characteristics of the superellipsoidal gridshells.The following example shows that the improved algorithm can successfully capture the optimal solution in the multi-state structure analysis.(3)The topology optimization of superellipsoidal spatial grid shell investigated in context of civil engineering structures.To shun the high computational cost of topology optimization of long-span spatial gridshell by traditional structural topology optimization methods,whether discrete or continuum one,parametric topology optimization was put forward.Grid patterns or topologies for ellipsoidal long-span spatial gridshell were constructed in Grasshopper for further usages.A mathematical model for the topology optimization of superellipoidal long-span spatial gridshell was established,too.Afterwards,a genetic algorithm combination multi-population genetic algorithm and multi-objective genetic algorithm was proposed for the selection of grid topologies so as to ensure the accessible space of algorithm in its searching during the parametric topology optimization.The fitness space analysis ensued in the example demonstrates the capability of the proposed algorithm to give the Pareto solutions.(4)The section optimization design of superellipsoidal long-span spatial gridshell was researched.As the enormous number of members carried by a long-span spatial gridshell could bring massive computational cost in direct parameterization of the sections and decrease the engineering practicability of optimization results,a section library with steel sections specified by Chinese codes was constructed for member grouping by stress-level under multiple loadcases.The mathematical model for section optimization design of superellipsoidal long-span spatial grid shell was build,too.Subsequently,in analogy of present design in design institutes,the mutator in simple genetic algorithm is improve,whose feasibligy were proved by the example.(5)The result plan after the hierarchical design was compared with a real engineering project,the National Grand Theater of People's Repulic of China.The architectural shape,grid toplogy and section of the two plans were compared and the causes of the differences were discussed.It is shown that tht result plan is much more superior in architectural shape and grid topology while the section,due to the limitation of section types considered.The results show that the optimization results are better than the reference plan.All in all,it is found that structural parametric design can well connect the architectural deisgn and structural design to provide a better design options.