Behaviour of Reinforced Concrete Frames under Various Load Conditions with Pre-Applied Elevated Temperature

The structural stability of reinforced concrete buildings exposed to fire is gaining very high significance in the design process, as there is increased demand and requirement for fire safe solutions.In a reinforced concrete building, the most critical section is the beam column joint and enhancing its structural behavior was found to be of great significance at ambient and elevated temperatures.This paper reports the behavior of a simple (single bay single storied) reinforced concrete frame under various loading conditions after exposure to elevated temperature (28°C to 800°C).Various loading conditions were applied on the frame specimens after exposing them to higher temperatures to stimulate the actual behavior of the frame after a real fire exposure.The specimens were cast with three different grades of concrete (M20, M45 and M60), representing the normal, standard and high strength concrete as per IS 456: 2000.Performance of the specimens are evaluated and presented in terms of load-deflection hysteresis loop.The results and observations of the study reveal that the frames made with high strength concrete are more prone to earlier failure than the frames cast with standard and normal strength concrete.At a temperature of 400⁰C, the load carrying capacities of the frame cast with M20, M45 and M60 grades of concrete are 80%, 71% and 58% of the capacity at 28⁰C respectively.