This thesis introduces an optimization software system which supports two separate optimization approaches to solve structural optimization problems with small and large-scale finite element models. The approach for solving the structural optimization problems of small-scale finite element models consists of the gradient-based optimization method and input file regeneration program. The small-scale structural optimization system, requires users only to put in the parameters of the initial design, the system will run the optimization process and generate new models automatically until the solutions are obtained. The approach for solving structural optimization problems of large-scale finite element models combines parametric finite element modeling methods executed by Python scripts with response surface optimization methods (RSM). This approach reduces the number of finite element analyses as well as reduces the optimization process time. The optimization module of the system is performed by the MATLAB optimization toolbox and the Abaqus finite element program with scripts implemented in Python. A benchmark hollow-tube weight-minimization problem is conducted to test the optimization software system. The percent difference between the solution found by the graphical optimization method and the solution found by the 3D beam finite element model with Sequential Quadratic Programming (SQP) solver and the graphical optimization method is 1.99%. The percent difference between the results from the 3D beam finite element model with SQP solver and the result from 3D brick finite element model with response surface method is 8.16%. The percent difference between the results from the 3D brick finite element model with RSM and the result from the graphical optimization method is 10.31%. / Master of Science / Commercial structural optimization software packages which integrate modeling tools, optimization and extensive computational tools such as a finite element solver were developed and pushed to the market. However, some commercial approaches to structural optimization are not very general. In addition, the commercial codes are designed for a specific-purpose, and they may not be suitable in many cases. If the commercial codes do not properly represent the structural optimization problem, users have to write custom Python scripts to assist the software system in retrieving data from the .odb files generated by FEA software. This thesis introduces an optimization software system which supports two separate optimization approaches to solve structural optimization problems with small and large-scale finite element models. The optimization module of the system is performed by the MATLAB optimization toolbox and the Abaqus finite element program with scripts implemented in Python. This optimization software system allows users to extract and manipulate data for optimization without limitations. Furthermore, once the required parameters are input in the system, the scripting software creates the finite element model and proceeds with the optimization automatically.

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Many commercial finite element programs support piezoelectric modeling and composite modeling to some extent. The popular program ABAQUS, however, has piezoelectric modeling capabilities only for continuum and one-dimensional truss elements. In situations where aspect ratio constraints and computational inefficiencies become a significant issue, such as modeling very large thin structures, alternate modeling techniques are sometimes required. Much of the focus of this thesis was to introduce equivalent methods for modeling laminated piezoelectric beams and plates. Techniques are derived based on classical beam and plate theory, classical lamination theory, and the linear theory of piezoelectricity. Finite element approximations are used with the principle of minimum potential energy to derive the static equilibrium equations for piezoelectric laminated structures. Equivalent loading techniques are derived based on the constitutive equations of piezoelectricity to simulate actuation forces within the piezoelectric layers. Finite element models using equivalent modeling techniques as well as equivalent loading techniques for piezoelectric laminated structures are developed and compared to ABAQUS models using piezoelectric elements to evaluate the error in theoretical assumptions. The analysis will prove that equivalent structural models and equivalent loading techniques provide excellent means for simplifying the analysis of thin piezoelectric laminated structures. / Master of Science

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Thesis (MScEng)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The role of the computer has changed from a calculation tool to a tool that supports human thinking. In this thesis fundamental aspects of the Finite Element method are mapped to an object model with a well defined structure which provides for local and distributed analysis work. To achieve this the following was investigated: • An object-oriented framework for the Finite Element analysis method • An associated graphical user interface that enables the user to create and modify Finite Element models in an effective way • Requirements for the sharing of analysis information in a communication network Proposed solutions are implemented in a pilot application which indicates their potential. / AFRIKAANSE OPSOMMING: Die rol van die rekenaar het verander vanaf 'n gereedskapstuk wat berekening doen na 'n gereedskapstuk wat menslike denke ondersteun. In hierdie tesis word die fundamentele aspekte van die Eindige Element metode oorgedra na 'n objek model met 'n goed gedefinieerde struktuur wat lokale en verspreide analisering werk ondersteun. Om dit te bereik is die volgende ondesoek: • 'n Objek orienteerde raamwerk vir die Eindige Element metode • 'n Geassosieerde grafiese raamwerk wat die gebruiker in staat stelom objekte te skep en te verander • Vereistes vir die deel van analise inligting in 'n kommunikasie netwerk Die voorgestelde oplossing is geimplimenteer in 'n loodsimplementering wat die voordele van die benadering uitlig.

published_or_final_version / Civil and Structural Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy