Simplified Analysis of RC Beams Exposed to Fire

With performance-based design becoming more prevalent in today’s standards, practical and simplified methods are needed to model and analyze reinforced concrete (RC) structures. These methods must meet the time and cost constraints for the practitioners, while maintaining a high degree of accuracy. Fire incidents are initiated by the ignition of combustible materials and can spread vertically and horizontally based on the specific compartment boundary conditions. RC elements, which are exposed to fire, develop a time-dependent three-dimensional temperature gradient. The developed temperatures cause the element’s stiffness to degrade and result in thermal induced deformations. This research introduces two simplified numerical methods to analyze continuous RC beams during fire exposure. The first method divides the beam into predefined segments and uses iterations to define the stiffness for each segment. An automated program was developed to conduct the iterations and redistribute the moments until convergence is achieved. The second approach assigns nonlinear plastic hinges to the predefined segments. The moment–curvature diagrams for these hinges account for the effect of fire exposure. Predictions of both methods were validated using published research by others.