A New Approach to Determine the Effective Flexural Stiffness of Doubly-Reinforced Beams According to Nonlinear Behavior

Determining the effective stiffness of structural elements made of reinforced concrete with reliability has always been an important subject of research since it provides a reliable estimate of a building's capacity in the case of a seismic event. The load-bearing element's design parameters, such as the longitudinal reinforcement ratio and concrete compressive strength, influence the effective stiffness of the cracked section in reinforced concrete structures, even if it is not always constant. In this study, a secure and efficient approach covering all important design parameters is proposed to determine the stiffness coefficient of cracked sections of doubly-reinforced beam models. The proposed equation for the effective stiffness coefficient has been verified by comparisons with moment–curvature relationships and data provided by various researchers and standards, based on numerical results. For beam sections, the suggested equation provides values of the effective stiffness coefficient that are reasonably accurate and consistent. Therefore, it is possible that the results of analytical solutions may differ from each other according to different researchers and standards. Analysis results have shown that an important parameter influencing the nonlinear behavior of the sections and the effective stiffness in beams is the reinforcement ratio, which includes concrete strength and compression reinforcement ratios.