Title:
Flexural rigidity of circular reinforced concrete sections
Author(s):
Gregory R. Sigmon and Shuaib H. Ahmad
Publication:
Structural Journal
Volume:
87
Issue:
5
Appears on pages(s):
548-557
Keywords:
building codes; columns (supports); computer programs; flexural strength; high-strength concretes; models; reinforced concrete; rigidity; slenderness ratio; Structural Research
DOI:
10.14359/2639
Date:
9/1/1990
Abstract:
The use of circular slender columns in the design of buildings and bridge substructures makes it necessary to adequately determine the flexural rigidity or stiffness parameter EI. In this paper, the ACI Building Code (ACI 318-83) expressions for estimating the stiffness parameter are examined for circular reinforced concrete sections. Results show that ACI Building Code Eq. (10-10) consistently overestimates the stiffness parameter. This suggests that the method of determining the stiffness parameter per ACI 318 needs to be reexamined. Based on the results of a parametric study, expressions are developed for estimating the stiffness parameter EI for circular columns at the stage of cracking and at ultimate. The proposed expressions for estimating the stiffness parameter include the effect of axial load P and the reinforcement index ({omega} = {rho}fy / f'c). A computerized model is developed to produce the results needed for the parametric study. The distribution of stresses along the length of the legs of stirrups was found to be nonuniform, even at failure. The inclination of the diagonal cracks also had a significant effect on the behavior of stirrups.