In structural engineering, lateral displacement is a key factor in ensuring the stability and safety of buildings, particularly in seismic-prone areas. Conventional structural design often assumes that column stiffness is independent of beam stiffness. However, the beam-column connection is rigid, meaning that beam stiffness significantly affects column behaviour. This study evaluates the impact of beam stiffness on column stiffness using the Muto Stiffness and Flexural Stiffness approaches and validates the findings with ETABS simulations. The analysis is conducted on two critical portal frames, Portal Frame C-6 and Portal Frame 3-F, commonly found in multi-story reinforced concrete structures. The results reveal that lateral displacement obtained through Muto Stiffness is greater than that from Flexural Stiffness, with an average difference of 72.179% for Portal Frame C-6 and 65.289% for Portal Frame 3-F. ETABS simulations yield displacement values between the two analytical methods, suggesting that the analytical approaches provide conservative structural response estimates. To reduce lateral displacement, beam dimensions were adjusted. This modification successfully minimized the displacement difference to 1.554% for Portal Frame C-6 and 7.575% for Portal Frame 3-F, improving overall structural stiffness. This study confirms that Muto Stiffness better captures the interaction between beam and column stiffness compared to Flexural Stiffness. Therefore, it is recommended that high-rise building design enhance the accuracy of lateral displacement predictions, ensuring improved structural performance under lateral loads.