Fire Resistance of RCC T-beam Under Cyclic Load: A Numerical Study

Fire hazards of RCC bridges and their failures in recent years have warned to check the effect of fire on the structural members, which is very often overlooked in popular design codes. Bridge fire occurring below the superstructure can severely hamper its strength, durability, and further stability. Hence, it is very essential to study the fire resistance of the RCC structural members of bridge-like lifeline structures. This present study aims to develop a thermomechanical model of a simply supported RCC T-beam representing real-life bridge girders. The model is based on a transient heat-transfer analysis and a coupled temperature–displacement analysis. The cross-sectional temperature of the RCC T-beam is determined following the heat transfer analysis. Higher temperature changes inside structures demonstrate stress redistribution; leading to a rapid deterioration in strength, stiffness, and service life. The second part of this paper aims to analyze the variations in stress on the material fibers due to fire exposure. The changing nonlinear cross-sectional temperature distribution of a bridge girder during the fire exposure may cause it to experience distress in form of thermal cracks. This study also includes the effects of repetitive loading on the T-beam subjected to concrete damage adopting the Concrete Damaged Plasticity (CDP) model for illustration of flexural damage pattern. The entire Finite Element Analysis (FEA) has been carried out using the commercial FEA package ABAQUS. The present study assumes importance as one of the first attempts made to assess the fire resistance of RCC bridge girders.