Modeling Effect of Biaxial Stresses on Average Stress-Strain Relationship of Reinforcing Bar in Reinforced Concrete Panels

The load versus deformation behavior of a reinforced concrete (RC) panel element under membrane stresses can be predicted by the modified compression field theory (MCFT) and the softened truss model (STM). In these theories, the stress-strain relationships for reinforcing bars are derived from tests under uniaxial tension. When these relationships are applied to an element under biaxial stresses, the Poisson’s effect is usually neglected. This leads to an overestimate of the shear resistance offered by the element. The present research investigated Poisson’s effect in RC panels subjected to biaxial stresses. To incorporate Poisson’s effect in the analysis of panels, an orthotropic formulation was developed, based on the concept of apparent Poisson’s ratio (APR). The APRs were quantified by testing panels under biaxial tension-compression. Poisson’s effect is incorporated in the STM to rectify the overestimate of the shear resistance of a panel element.