Novel Optimization-Based Method for Three-Dimensional STMs Considering Thermoelastic Effects

The strut-and-tie model (STM) is an idealized representation of force flow in disturbed regions (D-regions) of reinforced concrete, offering a conservative estimate of load-bearing capacity. The major challenge lies in constructing suitable trusslike models, for which topology optimization offers an innovative solution. However, although pixel-based optimized designs offer valuable design inspiration, they require manual STM extraction with struts and ties identification. This significantly increases the difficulty of postprocessing, particularly in complex three-dimensional (3D) D-regions in realistic engineering applications. This paper presents an explicit 3D topology optimization method of multimaterial bimodulus thermoelastic structures based on the node-driven moving morphable components (MMC) method. Under the proposed framework, optimized STMs with explicit geometry composed of concrete compressive struts and steel tensile ties can be obtained directly. Other advantages of the design method include automatic identification of struts and ties with explicit geometry parameters, and consideration of thermomechanical coupling effects. Benchmark examples validate the effectiveness of the proposed optimization framework, illustrating the influence of temperature variation on the STM design.