Topology optimization of strut-and-tie models in reinforced concrete structures using an evolutionary procedure

This paper presents a performance based evolutionary topology optimization method for automatically generating optimal strut-and-tie models in reinforced concrete structures with displacement constraints. In the proposed approach, the element virtual strain energy is calculated for element removal, while a performance index is used to monitor the evolutionary optimization process. By systematically removing elements that have the least contribution to the stiffness from the discretized concrete member, the load transfer mechanism in the member is gradually characterized by the remaining elements. The optimal topology of the strut-and-tie model is determined from the performance index history, based on the optimization criterion of minimizing the weight of the structure while the constrained displacements are within acceptable limits. Several examples are provided to demonstrate the capability of the proposed method in finding the actual load transfer mechanism in concrete members. It is shown that the proposed optimization procedure can produce optimal strut-and-tie models that are supported by the existing analytical solutions and experimental evidence, and can be used in practice, especially in the design of complex reinforced concrete members where no previous experience is available.