Simulated Annealing Optimization Of Walls,Portal And Box Reinforced ConcreteRoad Structures

Abstract

This paper deals with the economic optimization of reinforced concrete walls, portal and box frame structures typically used in road construction. It shows the efficiency of heuristic optimization by the simulated annealing algorithm. The evaluation of solutions follows the Spanish Code for structural concrete. Stress resultants and envelopes of framed structures are computed by an external finite element program. Design loads are in accordance with the national IAP Code for road bridges. The algorithm is first applied to RC retaining walls with 26 continuous design variables of geometry, materials and reinforcement. Results on this topic show the importance of limiting the deflection of walls. No restriction leads to slender solutions with deflections of up to 1/40 the height of the wall. Such elements are unfeasible and, hence, a limitation of 1/150 of the height is adopted for the design of these structures. The second structure analysed is a 10 m horizontal span RC portal frame. This example has 28 discrete variables, 5 geometrical, 3 types of concrete and 20 types of reinforcement bars of fixed length. The evaluation module includes the limit states that are commonly checked in design: flexure, shear, deflections, etc. Results of this research are again quite slender, i.e. a slab of 0.375 m (1/26.67 slab/span ratio), not complying with the rarely checked fatigue of concrete. The last type of structure analysed is a 13 m horizontal span RC box road frame. This example has 44 discrete variables, 2 geometrical, 2 types of concrete and 40 reinforcement bars and bar lengths. The evaluation module includes fatigue plus other limit states. Results are now reasonably slender, i.e. a slab of 0.65 m (1/20 slab/span ratio). Finally, run times indicate that heuristic optimization is a forthcoming option for the design of real RC structures.