Design Guide for Modelling Damping in Reinforced Concrete Coupling Beams Under Cyclic Loading

Damping is a measure of energy dissipation, and while coupling beams contribute to this through yielding and nonlinear behaviour, conventional structural design software does not assign a specific damping ratio to these members. Reinforced Concrete coupling beams protect the shear walls or cores by absorbing and dissipating seismic energy through cracking and rotation, making their damping estimation crucial in lateral design. This technical note introduces two complementary power-law models for estimating damping in Reinforced Concrete coupling beams subjected to the deemed effects of cyclic loading. The first model relates damping (D) to stress amplitude (σₐ), and the second model expresses D as a function of plastic hinge rotation (θ). Both models are rooted in Khanna’s earlier ICE (Institution of Civil Engineers-1976) work and are demonstrated using a 20-storey structural example. To enhance practical relevance, the methodology employs an equivalent static approach, avoiding full time-history or Finite Element Method (FEM) -based hysteretic modelling. The note also introduces the role of soil–structure interaction (SSI) and compares damping predictions from both models across elastic, cracked, and yielded states. Normalized design curves and manual worked examples illustrate that the stress amplitude model is more responsive to early-stage material cracking, while the rotation-based model reflects overall deformation. This combined framework offers structural designers a transparent, physics-based guide to assessing damping in coupling beams and is useful for performance-based seismic design, retrofit evaluation, and simulation benchmarking. This technical note presents two complementary power-law models for quantifying damping behavior in reinforced concrete (RC) coupling beams under cyclic loading. The first model relates damping (D) to stress amplitude (σₐ), while the second relates damping (D) to plastic hinge rotation (θ). Together, they offer a practical framework for estimating hysteretic damping without full-scale Finite Elelement Method (FEM) analysis. The note also introduces the role of soil–structure interaction (SSI) and compares damping predictions from both models across elastic, cracked, and yielded states. Normalized design curves and manual worked examples illustrate that the stress amplitude model is more responsive to early-stage material cracking, while the rotation-based model reflects overall deformation. This combined framework offers structural designers a transparent, physics-based guide to assessing damping in coupling beams and is useful for performance-based seismic design, retrofit evaluation, and simulation benchmarking.