Displacement- and drift-based formulas for estimating the fundamental period of reinforced concrete buildings

In this study, analytical formulations are developed to estimate the fundamental periods of reinforced concrete buildings based on the roof (peak) displacement and the maximum interstory drift ratio. Unlike existing empirical equations reported in the literature, the proposed formulations are derived using equivalent shear and flexural beam models, ensuring a more rational representation of the lateral stiffness and deformation characteristics of building structures. Furthermore, an original formulation has been developed to enable the application of the proposed approach to shear-type building systems. Additionally, a complementary approach has been developed to enhance the applicability of the proposed method to reinforced concrete frames with infill walls. Comparative analyses using SAP2000 show that the proposed equations provide more accurate and comprehensive fundamental period estimates than existing seismic code relationships.