Study On Morphogenesis Technique For Reticulated Shells Based On Genetic Algorithm

As a kind of layout plan, reticulated shell structures are widely applied in the filedof spatial structures due to their good mechanical behavior and beautiful appearance,but there still lie the defect in terms of simple structural forms and fixed mesh.Thus, ithas a great significance to obtain reticulated shells with novelty form and goodmechanical behavior by structural morphosis methods.This thesis studied the morphogenesis technique for reticulated shells based ongenetic algorithm. The basic principle of genetic algorithm was introduced and amorphogenesis technique for reticulated shells based on genetic algorithm was putforward. First, a base structure was created according to the plane projection of thestructure. Then,though topology, shape and sizing optimization,structures with newforms would be created. For the topology optimization, a stable triangular unit was setas the code. Through choosing the triangular codes, different connections of bars wereformed. For the shape optimization, the nodes in the structure were the operation targets.The vertical coordinates of the nodes were changed by selecting one coordinate valuefrom a series of discrete coordinate values in the z-direction. For the sizing optimization,a table containing a set of bars with different cross sections was established. Each bar inthe structure was selected form the table. For different variables, different encodingswere used, where the cross-section variables and the node coordinate variables usedinteger coding, while the topological variables used binary coding.Minimizing structural quality and minimizing the product of the structure mass andwork of external forces were used as optimization objectives. Though topology andsizing optimization and topology,sizing and shape optimization, new structures withsquare planar projection and hexagonal planar projection were created. The load caseswere vertical concentrated load and vertical uniformly distributed load. Constraints suchas member strength, slenderness ratio, stability of bending bars, the overalldisplacement of the structure were taken into account in the form of the penaltyfunction.The methods of ensuring the structural integrity and reasonably distributinguniform load were put forward. The structural integrity refered to the topological codeproduce a structure rather than a institution, with no isolated bars, in order to avoidstructural stiffness matrix singular. The load needs to be assigned to the appropriatenode under the uniform load. The method was dividing the planar projection of thestructure into a number of identical, sufficiently small load lattices. Each load latticewas the basic unit, and was assigned to the closest nodes.According to the diversity of the actual structure evaluation, a morphogenesis technique though multi-objective optimization had been studied. Both minimisingstructural quality and minimising the product of the structure mass and work of externalforces were used as the optimization objectives. Two target model of structuraloptimization design was established. Structural morphosis for structures with squareplanar projection under vertical concentrated load and vertical uniformly distributedload were studied, and a series of good Pareto solution were obtained.