Effect of Confining Reinforcement on Fire Behavior of Reinforced Concrete Columns: Experimental and Numerical Study

This paper studies the role of confining reinforcement on the compression behavior of axially loaded reinforced concrete (RC) columns at elevated temperatures. To demonstrate, experimental tests are conducted on 10 RC stub columns, each with a cross-sectional dimensions of $230\times 230\mathrm{mm}$ and a length of 860 mm. Two different concrete mixes (M30 and M50) exposed to varying combinations of two different heating durations (140 and 200 min) and two different volumes of confining reinforcement (0.25% and 2.14% by volume) are used in these tests. A length of approximately 500 mm at the middle of the column is heated for the desired duration and then loaded concentrically in compression until failure. The tests reveal that an increase in the amount of confining reinforcement significantly improves the axial load–carrying capacity of RC columns at elevated temperatures. These tests are also simulated using finite element (FE)–based heat transfer and stress analyses. The numerical simulations predict the time-temperature ($t\text{-}T$), axial load-deformation behavior, and the failure mode reasonably well. The numerical simulations are further used to understand the role of the confining reinforcement on the confinement pressure in the RC columns.