OPTIMAL DESIGN OF MULTI-PURPOSE STRUCTURAL ELEMENTS.

The paper presents the optimal (minimum-weight) design of a simple supported elastic member that is to serve as a beam for a part of its design life and as a tie for the rest but not both at any given time. Constraints were prescribed on the maximum elongation in tie action and on the maximum transverse deflection under a uniformly distributed load in beam action. The necessary optimality condition was derived using variational calculus. An iterative procedure was employed to arrive at the optimal solution for members of solid cross-section, and the efficiency of the optimal design was judged against a prismatic member. The solution of a related optimal design (maximum bending stiffness design) problem was also obtained.