Stiffness degradation analysis of recycled aggregate concrete beam on Kerr-type foundation: Force-based approach

This study proposes a new beam–foundation model for analyzing the static behavior of recycled aggregate concrete (RAC) beam resting on Kerr-type foundations. The novelty of the approach lies in the integration of three distinct damage models—the Voigt parallel model, the Reuss serial model, and the generalized self-consistent model—into a force-based framework. These models are employed to capture stiffness degradation in RAC beams under isotropic and homogeneous conditions, addressing the need for more realistic damage representation in sustainable concrete structures. The Kerr-type foundation model accounts for interaction between the beam and its underlying foundation, while the Euler–Bernoulli beam theory governs the beam's deformation behavior under small displacements. The governing equations are formulated using the virtual force principle. Through a series of numerical simulations, the study investigates how damage mechanisms and system parameters influence the bending response of the RAC beam–foundation system. The results demonstrate that both the type of damage model and foundation characteristics significantly affect the structural stiffness, leading to either softening or stiffening responses.