Behavior of Slender RC Columns Bent in Single and Double Curvature at Elevated Temperatures

In this study, a numerical model for tracing the behavior of eccentrically loaded slender reinforced concrete (RC) columns bent in single and double curvature, and subjected to elevated temperatures is presented. The developed model incorporates the high-temperature material properties, the nonlinear behavior of concrete sections, time dependent effects, and the nonlinear responses of slender RC columns. Based on Newton–Raphson method, an iterative technique, wherein strain and curvature are concurrently iterated, is used to find the strain distribution on the cross-section. By proposing a simple and reliable calculation procedure, the lateral deflection is calculated using numerical and searching techniques. The compatibility between forces and deformations at a joint in the column is established by another iterative technique, which involves the analysis of the whole column. The validity of the analytical model is established by comparing its predictions with results obtained from laboratory tests found in literature. A parametric study is conducted to investigate the effect of end eccentricity conditions on columns bent in single and double curvatures. It was found that lateral deflection plays an important role on column responses when subjected to fire. This finding confirms the usefulness of lateral deflection as a powerful tool in validating eccentrically loaded slender RC columns. It was also found that unwinding at elevated temperature has detrimental effect on columns bent in double curvature. It was observed that for all columns, there exists a critical eccentricity after which column responses to fire change.