Simplified approach for evaluating residual strength of fire-exposed reinforced concrete columns

An approach for evaluating residual strength of reinforced concrete (RC) columns is presented in this paper. The approach is based on the maximum temperature attained in the concrete core and rebars, and associated reduction in strength of steel and concrete. For validating the proposed approach, post-fire residual strength tests were carried out on five high strength concrete columns. The test variables included type of concrete, presence of fibers (polypropylene and/or steel) in concrete and load ratio. The columns were loaded and exposed to a design fire, allowed to cool, and then residual strength tests were carried out. Results from these fire tests indicate that high strength concrete columns retain most of their room-temperature load carrying capacity after exposure to a design fire. A comparison of residual strength predictions with measured values from tests indicates that the proposed approach is capable of predicting the residual strength of fire-exposed RC columns.