Applications of bi-directional evolutionary structural optimization technique and its extension to transient dynamic problems
Creators: name: Ling, Ee
Publisher: name: RMIT University
Year: 2024

description: This thesis first investigates various applications of the bi-directional evolutionary structural optimization techniques (BESO) and then extends the technique to structural optimization problems with transient dynamic loading. The BESO technique allows material to be simultaneously removed from and added to a structure. Research on static response optimization using BESO technique is extensively explored, while research on dynamic response is scarce due to the complex phenomena that are however likely to happen in reality. The first application of BESO method is the optimization of footbridge design that is initiated by a footbridge project in Melbourne. The bridge is constructed as a cylinder and is modeled based on the boundary conditions provided to ensure it is closest to reality. The optimized cylinder footbridge is created with different cross section configurations such as rectangular section and circular section. A demonstrative optimized circular twisted cross-section design is casted in the lab. The prototype is casted with concrete where a reinforcing steel cage is put in the middle and steel fibers are added to provide more strength. The circular prototype is assembled through six pieces of identical carefully arched parts and the connections of every piece are bolted with steel bolts. The casting of the prototype is carried out in collaboration with an architect from BKK Architect. The second application of the BESO method is the optimization of deep-sea sponge. Nature never fails to fascinate researchers with its exceptionally strong structure patterns, especially deep-sea sponge that exhibits potentially strong building pattern to withstand both internal and external forces. Literature on physical properties of deep-sea sponge is reviewed to have the model to be as accurate as possible. Several different loading configurations on the deep-sea sponge model are demonstrated such as pressure, twisting, bending and point loads and the optimized designs are discussed. The optimization of deep-sea sponge with different loading configurations are carried out to show that the optimum designs achieved from BESO method could be similar to real deep-sea sponge structure. Structures are very likely to undergo dynamic loading in reality due to the mobility of forces in all directions. Extensions to the current BESO method are proposed to deal with dynamic response problems. Under stiffness optimization for dynamic response problems, structural optimization is performed aiming to reduce the mean compliance during the loading history. Dynamic analysis output a series of strain energies of the structure in the history and the highest strain energy values are selected for optimization. This is to ensure the structure to possess the stiffest design against the worst scenarios in the loading history when large deformations are present. Various numerical examples are tried in order to prove the effectiveness of the proposed approach. The results show that the final optimal solutions respond to the dynamic loading more smoothly than the original designs during the history, with the peak mean compliances reduced. The findings shown in this thesis corroborated the BESO method is applicable in various applications for designing and optimizing structures subjected to both static and dynamic loading.