Edinburgh Napier University

  This study presents an optimization procedure based on the modified Bi-directional evolutionary structural optimization (BESO) approach to optimize both location and orientation of discrete reinforcing steel bars within concrete structures, while satisfying the prescribed realistic volumetric ratio of steel amount into the continuum concrete. Opposed to the strut-and-tie model (STM) mechanism, both tension and compression are taken into account in reinforcing bars. The optimization variables are only applicable to steel reinforcements that are modelled as discrete truss bars embedded into a concrete domain. The flexible orientation of each reinforcing bar is achieved by employing a heuristic orientation finding scheme according to principal strain direction into a two-dimensional (2D) BESO algorithm. Also, apart from ranking the sensitivity number of each reinforcing bar, an update scheme for design variables is developed due to the asymmetric property of concrete in tension and compression. The capability of the proposed optimization method is shown through two cases. It can be concluded that the proposed method obtains a rational reinforcement layout under a volume constraint on steel used in reinforced concrete (RC) structures. Reinforcing bars playing high contribution to the structural behavior are remained within a constant concrete domain, which provides a valuable suggestion for the distribution of steel reinforcements.