Effective flexural rigidities for ordinary reinforced concrete columns and beams



Current effective flexural rigidities proposed for use in design and analyses of reinforced concrete structures have been examined. The level of accuracy in the estimation of section rigidity plays a very important role in determining realistic values for the structural stiffness and hence the seismic forces imposed. The most significant parameters influencing the effective rigidity, which reflects the effect of cracking as well as the theoretical yielding of reinforced concrete sections, have been determined through comprehensive moment–curvature analyses of various reinforced concrete sections. The geometry, axial load level, concrete strength and the amount of compression and tension reinforcements have been identified as the most important factors affecting the effective rigidity. New relationships that are believed to represent the effective stiffness of reinforced concrete members have been adequately developed. Efficiency of the code-specified and proposed values has been investigated through experimental data and parametric studies. It has been observed that the relationships developed herein have provided the most accurate results in prediction of the effective rigidity of older-type structural elements with low-strength and longitudinal reinforcement ratio. They can be used for assessment of ordinary buildings. Copyright © 2012 John Wiley & Sons, Ltd.