In this thesis, a theory for optimal design of beam-truss built-up structures is developed. A cable-stayed bridge is optimized with the theory as an example.
For design sensitivity analysis, all the equations and functions appearing in the optimization problem are first transformed to functional form. To transform the system equilibrium equation to variational form, a kinematically admissible displacement set of the system is defined and extensively used later on through the procedure. Then an adjoint variable is employed, to remove state variable dependence of the first variations of the functions.
With the design sensitivity analysis results, an interative optimization is utilized to obtain an optimum. In this research the gradient projection method is taken.
Results of the research fully demonstrates validity and generality of the procedure, and it is expected that the procedure can be readily applicable to optimization of built-up structures with other types of structural elements.