Analysis and Parametric Study of Partially Composite Precast Concrete Sandwich Panels under Axial Loads

This paper presents a numerical model developed to predict the response of partially composite load bearing concrete sandwich panels under axial loads applied to the structural wythe at any eccentricity. The model accounts for material nonlinearity, second-order effects, and cracking of concrete and plasticity of steel reinforcement, and can also model fiber-reinforced polymer (FRP) connectors. The analysis uses a bond-slip model to simulate partial composite action between the two wythes resulting from various configurations of insulation and shear connectors. A variety of failure modes can be detected, including concrete crushing, flexural yielding, connectors yielding, pullout or rupture, and stability failures. Progressive failure of connectors is also modeled. The degree of composite action (${\kappa }_u$) can be calculated for a given design. The model was verified against experimental data and used to conduct a comprehensive parametric study. It was shown that ${\kappa }_u$ increases with panel length. Connectors’ diameter and spacing greatly affect ${\kappa }_u$ and give similar gains in strength and stiffness at the same connector’s reinforcement ratio (${\rho }_v$). Connectors inserted at an angle are considerably stronger than those inserted normal to panel face. The insulation bond alone provides a 31% ${\kappa }_u$ without any connectors, but this contribution decreases as ${\rho }_v$ increases.