Restoration of dynamic characteristics of RC T-beams exposed to fire using post fire curing technique

Abstract This paper presents experimental results of structural performance and dynamic characteristics of fire-damaged reinforced concrete (RC) T-beams subsequently repaired using the technique of post-fire curing. A total of six specimens were cast, two were unheated specimens, four specimens were exposed to 900 °C furnace temperature for 1 h. Two of the heated specimens were re-cured in water for 28 days. The dynamic characteristics such as frequency and damping were determined by exciting the beams using the free fall impact test. The beams were also subjected to load tests for strength and stiffness evaluation. Experimental results from load tests showed that T-beams lost approximately 40% strength and 33% stiffness when exposed to elevated temperatures. After post-fire curing, the beams regained almost 90% of their strength and stiffness. The loss of frequency in percent was found to be very similar to the stiffness values from load tests. The analytical modelling of the frequencies for undamaged, fire-damaged and repaired beams was carried out using lumped mass approach. The analytical and experimental results were found to be in good agreement. The change in dynamic characters due to fire damage is found to be an important factor, ignored in previous studies. All the beams exhibit failure in flexure during the third point loading test.