This thesis concerned with optimization of simply supported prestresed concrete box girder bridge.rnUsually, the design of prestressed concrete bridges is done based on codes on prestressed concreternbridges. The code requirement is generally concerned with the safety of the structure in its lifetime.rnApart from satisfying the code requirement, the design should be economically chosen. For a givenrncondition, there might be a large number of alternatives that satisfy the requirements imposed byrncodes. But the designer must be in position to choose the one, which is optimal against certain measurernof optimality. Therefore, the designers have to do some optimization to arrive at such design.rnThe objective of this thesis work is to show how the optimal design of a prestressed concrete boxgirderrnbridge can be obtained. It will established a general relationship among different designrnvariables at optimum and will recommend a simple procedure to identify an the optimum design.rnThe presentation is divided in to six chapters. In chapter one, a detail discussion on the theory ofrnprestressed concrete is presented. Great emphasis is given for analysis of sections for flexure both inrnelastic and plastic ranges. It also explains the usual trends to be followed in the design of a pre stressedrnconcrete section under service and over loads.rnIn chapter two, application of pre stressed concrete on bridge is discussed. Conditions favoring prernstressed concrete application for such type of structural systemsrnChapter three discusses about optimization theory and general formulation of an optimization problem.rnEmphasis will be given numerical optimization theory and techniques.rnChapter four deals with the methods used to solve an optimization problem. An extended completerncoverage is given on linear programming and feasible direction methods, as they will be used later inrnchapter six to solve an optimal design problem for box-girder bridge.rnIn chapter five, an optimal design problem is formulated for simply supported rectangular box-girderrnbridge based on AASHTO 96 Code.rn2rnIn chapter six, the optimal design problem formulated in (chapter five) is solved for 40m span bridgesrnusing a Fortran program written for the method of Feasible Direction. The program is developed forrnthis particular purpose. Concluding remark is also givenrnThe source code of developed program along with a flow chart outlining the program logic to this workrnis included in an appendix.