Effect of heated areas on thermal response and structural behavior of reinforced concrete walls exposed to fire

The purpose of this study was to investigate variations in the thermal and structural behavior of reinforced concrete (RC) walls according to the fire exposure time, compressive strength of the concrete, and the heated area. To this end, fire and axial loading tests were performed to obtain the temperature distributions and residual strengths. Heat was applied to the walls according to the ISO 834 standard time-temperature curve for 1 or 2 h. The fire test results demonstrated significant dependence of the heat propagation through the wall along the thickness on the moisture clog formed during heating. In order to show the effect of moisture clog on the heat propagation, heat transfer analyses were performed, and the results of temperature distributions obtained from the finite element (FE) model including the moisture clog zone were in good agreement with experimental results. The axial loading test results also indicated that the structural behaviors of the fire-damaged walls were affected by the fire exposure time, concrete strength, and heated area. In particular, the wall heated only on the front surface showed eccentricity, which reduced the residual strength considerably. Numerical studies for the structural behaviors of the fire damaged concrete walls were also conducted considering the eccentric loading effect due to fire. As results from the validation, the proposed simplified modeling approach was able to predict the asymmetric behaviors of fire damaged concrete walls owing to fire damage.