Optimal design of elastic trusses by approximate equilibrium

Abstract Optimal design of elastic trusses is formulated as an approximate linear programming problem. Using the displacement method of analysis it is shown that the system equilibrium equations represent the only nonlinear functions of the variables. The linear programming formulation is obtained by ignoring temporarily the nonlinear terms in the latter equations. The solution of this approximate problem can be viewed as an exact optimum for a set of different loadings. An iterative procedure of solution, based on a sequence of linear programs, is proposed. In each iteration cycle both the design variables and a set of imaginary loadings are modified. The latter loadings can be introduced from those loadings corresponding to the exact optima at preceding iteration cycles. The proposed procedure provides more flexibility in the solution process compared with the usual algorithms based on a sequence of linear programs and may improve the convergence to the optimum.