Taye, Shifferaw(PhD)HaileMichael, Samuel2018-06-202023-11-112018-06-202023-11-112002-06http://etd.aau.edu.et/handle/12345678/2125This thesis concerned with optimization of simply supported prestresed concrete box girder bridge. Usually, the design of prestressed concrete bridges is done based on codes on prestressed concrete bridges. The code requirement is generally concerned with the safety of the structure in its lifetime. Apart from satisfying the code requirement, the design should be economically chosen. For a given condition, there might be a large number of alternatives that satisfy the requirements imposed by codes. But the designer must be in position to choose the one, which is optimal against certain measure of optimality. Therefore, the designers have to do some optimization to arrive at such design. The objective of this thesis work is to show how the optimal design of a prestressed concrete boxgirder bridge can be obtained. It will established a general relationship among different design variables at optimum and will recommend a simple procedure to identify an the optimum design. The presentation is divided in to six chapters. In chapter one, a detail discussion on the theory of prestressed concrete is presented. Great emphasis is given for analysis of sections for flexure both in elastic and plastic ranges. It also explains the usual trends to be followed in the design of a pre stressed concrete section under service and over loads. In chapter two, application of pre stressed concrete on bridge is discussed. Conditions favoring pre stressed concrete application for such type of structural systems Chapter three discusses about optimization theory and general formulation of an optimization problem. Emphasis will be given numerical optimization theory and techniques. Chapter four deals with the methods used to solve an optimization problem. An extended complete coverage is given on linear programming and feasible direction methods, as they will be used later in chapter six to solve an optimal design problem for box-girder bridge. In chapter five, an optimal design problem is formulated for simply supported rectangular box-girder bridge based on AASHTO 96 Code. 2 In chapter six, the optimal design problem formulated in (chapter five) is solved for 40m span bridges using a Fortran program written for the method of Feasible Direction. The program is developed for this particular purpose. Concluding remark is also given The source code of developed program along with a flow chart outlining the program logic to this work is included in an appendix.enGirder ;BrigdeThesis