Residual response of fire-damaged high-strength concrete beams

This paper presents results from an experimental study on residual capacity of fire-damaged high-strength concrete (HSC) beams. Four reinforced concrete (RC) beams, fabricated with HSC, were first subject to structural loading and fire exposure with a distinct cooling phase and then loaded to failure upon cooldown to ambient conditions to evaluate residual capacity. Temperatures, deflections, and spalling in the beams were monitored during heating and cooling phases of fire exposure. Further, residual capacity, strains at critical section, and crack patterns (failure mode) of fire-damaged beams were recorded during residual capacity tests. Results from experiments indicate that the load level during fire exposure, duration of heating phase, rate of cooling, extent (type) of spalling, and duration of postcooling storage influence residual deformations and also residual capacity of RC beams. Further, fire-damaged HSC beams can recover 40% to 70% of their flexural capacity with respect to their room temperature design capacity provided they survive the entire duration of fire exposure.