Does strut-and-tie modelling benefit from topology optimization?

Strut-and-Tie modelling (STM) has proven to be a powerful method to design D-regions of reinforced concrete structures. STM uses truss analogy models to represent the stress field within the D-regions of concrete elements. Schematizing a suitable truss model is one of the most important aspects in the STM. Over the past decades, the use of Topology Optimization (TO) methods has been explored to inspire efficient truss models for the STM. However, it is at present still unclear whether these TO-based truss models benefit the STM. In order to investigate this question, this paper presents a case study based on a deep beam with an opening. Firstly, a TO-based STM model is generated which satisfies requirements of the axial force equilibrium and stress constraints of the STM method. Secondly, different STM designs are analysed by Nonlinear Finite Element Analysis (NFLEA), based both on classical STM models and TO-based models. The resulting steel usage, ultimate capacity and failure mode are used as measures to evaluate the designs. Finally, based on the generated STM model, two practical steel designs considering construction complexity are proposed and evaluated by NLFEA. The effectiveness of the TO-based STM model for this deep beam case has been demonstrated based on the evaluation results.