INFLUENCE OF LIMIT STATES ON THE OPTIMIZATION OF REINFORCED CONCRETE PLANE FRAMES
Marcela Alejandra Juliani1; Wellison José de Santana Gomes1
1 Federal University of Santa Catarina
doi:10.20906/CPS/CILAMCE2017-0219
Resumo
Most current structural design codes are based on the concept of limit states, that is, when a structure fails to meet one of its purposes, it is said that it has reached its limit state. According to the Brazilian code ABNT NBR 6118 (2014), in the design of reinforced concrete structures, the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS) must be checked. Therefore, this paper presents an optimization scheme for reinforced concrete structures, based on the lowest cost, considering ULS and SLS constraints. The optimal characteristics of the structures subject to each limit state, individually, as well as to both limit states simultaneously, are discussed. The methodology is applied to a plane frame using genetic algorithms (GA) to solve the optimization problem, since this problem involves several local minima. The objective function employed corresponds to the cost of the structural elements, which includes the consumption of concrete, steel and formwork. For the case studied, it is noted that the optimal sections for the ULS are preponderant to the optimal sections for the SLS, so that when considering both limit states simultaneously the solution found is equal to the ULS.
Palavras-chave: Optimization; Reinforced concrete; Limit states; Plane frames