Fail-Safe Optimal Design of Structures.
Interim technical rept. no. 19, Sep-Dec 75,
IOWA UNIV IOWA CITY DIV OF MATERIALS ENGINEERING
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A general fail-safe optimal design problem for structures with fixed geometry is formulated in this report. Structural weight or some other performance index can be used as a cost function. Member stress, buckling load, nodal displacement, and natural frequency constraints on the complete and damaged structures are considered. The design variables are size, moment of inertia, or other mechanical properties of structural members. The structure is descretized and a finite element method is used for structural analysis. An iterative algorithm, based on a generalized steepest descent method, is developed to search for optimum designs. In this optimization process, the cost function, state equations, and inequality constraints are linearized and the dependence of these equations on the state variables is eliminated by solving adjoint equations. A fail-safe optimal design problem for a three member truss is solved analytically, to study the properties of fail-safe optimal design problems. A FORTRAN computer program is implemented to solve the fail-safe, minimum weight truss design problem. Structures with three, four, twenty-five, and seventy-two members are treated.
- Civil Engineering
- Structural Engineering and Building Technology