Structural damage evaluation of reinforced concrete beams exposed to high temperatures

The objective of this study is to investigate the effect of temperature distribution, concrete strength, cover thickness, and heating time on the structural behavior of reinforced concrete beams. Toward this goal, reinforced concrete beams with different concrete compressive strength and cover thickness are fabricated and subjected to furnace heating for 60, 90, and 120 min under a loaded state. In order to analyze structural behavior based on the thermal behavior of the beams, transient temperature distribution is measured during the furnace heating. After furnace heating, spalling is observed. From loading tests performed on the damaged reinforced concrete beams, residual strength, maximum loads, and beam deflections are measured and examined. The experimental results show that significant damage occurs in the reinforced concrete beams under high temperatures. In addition, it is found that thermal and structural behavior of damaged reinforced concrete beams is dependent on cover thickness and concrete strength and that most structural damage occurs in a relatively short period of heating time. Using these experimental findings, an equation is proposed that can be used to predict maximum load capacity and stiffness reduction ratio of the damaged reinforced concrete beams.