This study proposes a simplified method for evaluating the seismic energy input ratio in low- to mid-rise buildings with shallow foundations. The ground–foundation system is modeled using equivalent mechanical properties that incorporate both translational and rotational motions. Without relying on time-history analysis, the method enables efficient estimation of input energy. Comparison with numerical simulations shows good agreement, with deviations within 2%. In addition, nonlinear effects such as stiffness degradation and increased damping in the soil and superstructure can be considered. The method is suitable for practical design applications under various ground and structural conditions.
