Topology Optimization of Strut-and-Tie Models in Non-Flexural Reinforced Concrete Members

This paper deals with the topology optimization of strut-and-tie models in non-flexural reinforced concrete members by using the Evolutionary Structural Optimization (ESO) method for plane stress continuum structures with displacement constraints. By means of systematically removing elements that have less contribution to the stiffness from the discritized concrete member, the actual load paths within the member are 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 displacement is within an acceptable limit. Two examples are provided to illustrate the effectiveness of the present procedure in automatically finding the actual load paths in a reinforced concrete deep beam with web openings and a corbel. It is demonstrated that the ESO method and the performance index are capable in generating reliable optimal strut-and-tie models that are supported by analytical solutions and experimental evidence, and can be used in practice especially in the design of complex structures where no previous experience is available.