OPTIMUM DESIGN OF COMPOSITE HYBRID PLATE GIRDERS

A general formulation using the generalized geometric programming (GGP) technique is presented for the optimum design of unstiffened and stiffened composite hybrid plate girders. It is based on the load factor design method of the American Association of State Highway and Transportation Officials standard specification for highway bridges. A mathematical formulation is developed for the optimization of the composite hybrid plate girder problem, using the weight of the girder as the objective function and the section properties and strengths for the problem constraints. The independent and dependent variables are defined for the optimization problem, and the design constraints are formulated in both equality and inequality forms. The nonlinear objective function and the nonlinear design constraints are expressed in suitable form for application of the GGP technique to find the optimum design. A computer program is written in FORTRAN 77 to implement the design procedure, and examples are presented to demonstrate the validity of the mathematical model.