A number of simple models containing frequency‐independent elements have been presented to simulate unbounded soil in dynamic soil‐structure interaction problems. Most of the existing models were established through a traditional top‐down strategy with significant computational complexities. This study develops an alternative method based on a bottom‐up strategy, in which the optimal element layout is determined by an adaptive refinement procedure considering finite modularized units. This innovation eliminates the need for lengthy procedures to establish simple models. The proposed three‐parameter model is used to simulate the layered soil for rigid foundations undergoing vertical vibration. The accuracy of the model is validated by comparing the magnified responses obtained when a foundation is subjected to harmonic forces with those obtained via theoretical solutions and advanced numerical simulations. The proposed model is found to effectively simulate a layered half‐space and a soil layer on rock. Compared to two existing models, the proposed model performs better and has fewer parameters and a higher degree of adaptivity. Therefore, the adaptivity of simple models obtained using the proposed method may allow simulation of a variety of layered soil systems.