Behavior and design of eccentrically compressed hybrid steel and GFRP reinforced concrete columns at elevated temperature

This study presents analytical model for the analysis of hybrid (steel and fiber reinforced polymers (FRP)) reinforced concrete (RC) columns at elevated temperature under eccentric compressive loads. The bending moment resistance of the (RC) columns at elevated temperature is formulated based on force equilibrium and strain compatibility of the concrete column section under combined bending moment and axial force. Deterioration the mechanical properties of concrete, steel, and FRP bars due to the rise of temperature has been taken into account using equations proposed by previous studies. Validating the suggested model was carried out by comparing the analytical results with corresponding experimental and numerical results in terms of axial load-lateral displacement relationships, axial load-bending resistance interaction diagrams, and failure modes. Validation results have shown the accuracy of the suggested analytical model. A parametric study has also been conducted using the proposed analytical model to investigate the effect of some parameters on the axial load-bending resistance interaction diagrams of hybrid steel and FRP-RC columns under elevated temperature. These parameters include the effect of higher temperature values, the effect of reinforcement material, and the effect of reinforcement configuration. Parametric study results have revealed some interesting conclusions that may be implemented in the design of hybrid RC columns at fire.