中文摘要：

采用红外热像技术,给出高温后HRB 500级钢筋红外热像平均温升随时间的变化曲线,建立钢筋红外热像平均温升与钢筋过火温度及强度损失的回归方程.结果表明,HRB 500钢筋的屈服强度、抗拉强度随着受火温度的升高而下降,在400℃以下,其变化不大,在800℃时达到最小值,但900℃时有所回升;钢筋的热像平均温升随着受火温度的升高而升高,500℃以下持续上升,600℃时突然下降,之后又持续上升.

英文摘要：

Using infrared thermal image technique,the curves of average temperature rising of infrared thermal images of steel bars（HRB 500） versus time after fire are obtained.The regressive equations of the average temperature rising of infrared temperature and strength degradation of steel bars（HRB 500） are established.The results show that the strength decreases with increasing temperature,the strength changes little when temperature is less than 400 ℃,the strength decreases to minimum when temperature is 800 ℃;but when temperature reaches 900 ℃,the strength rebounds a little.The average temperature rising of infrared temperature increases when the temperature of fire increases,but the average temperature rising drops at 600 ℃.