APPROXIMATION OF YOUNG MEASURES BY FUNCTIONS AND APPLICATION TO A PROBLEM OF OPTIMAL-DESIGN FOR PLATES WITH VARIABLE THICKNESS

Given a parametrised measure and a family of continuous functions (phi(n)), we construct a sequence of functions (u(k)) such that, as k --> infinity, the functions phi(n)(u(k)) converge to the corresponding moments of the measure, in the weak * topology. Using the sequence (u(k)) corresponding to a dense family of continuous functions, a proof of the fundamental theorem for Young measures is given. We apply these techniques to an optimal design problem for plates with variable thickness. The relaxation of the compliance functional involves three continuous functions of the thickness. We characterise a set of admissible generalised thicknesses, on which the relaxed functional attains its minimum.