REINFORCEMENT LAYOUT DESIGN OF RC STRUCTURES UNDER MULTIPLE LOAD CASES USING TRUSS-LIKE MATERIAL MODEL

Abstract

THIS PAPER PROPOSES A METHOD TO OPTIMIZE THE REINFORCEMENT LAYOUT OF RC STRUCTURES UNDER MULTIPLE LOAD CASES (MLCS) USING THE PLANAR TRUSS-LIKE MATERIAL MODEL. IT IS ASSUMED THAT CONCRETE IS FILLED WITH TRUSS-LIKE MATERIALS. TWO FAMILIES OF ORTHOTROPIC MEMBERS IN THE TRUSS-LIKE MATERIALS ARE USED TO SIMULATE STEEL BARS. THE DENSITIES AND ORIENTATIONS OF STEEL BARS AT NODES ARE CONSIDERED AS DESIGN VARIABLES. THE OPTIMIZATION PROBLEM IS TO MINIMIZE THE TOTAL VOLUME OF STEEL BARS WITH STRESS CONSTRAINTS. FIRST, UNDER EACH LOAD CASE, THE DISTRIBUTION OF STEEL BARS IS OPTIMIZED AS PER THE FULLY STRESSED CRITERION. SECOND, BASED ON THE RESULTS OBTAINED ABOVE, THE DIRECTIONAL STIFFNESS AT NODES UNDER MLCS, DESCRIBED BY A CLOSED QUADRATIC CURVE, IS OBTAINED USING THE LEAST SQUARES METHOD. FINALLY, BY SOLVING THE EIGENVALUES PROBLEM OF THE COEFFICIENT MATRIX OF THE QUADRATIC CURVE, THE OPTIMAL DISTRIBUTION OF STEEL BARS UNDER MLCS IS OBTAINED.