高温后新Ⅲ级钢筋力学性能的试验研究

通过对37组共111根(?)16和(?)12新Ⅲ级钢筋高温后的力学性能试验,研究了经历不同受火温度和受火恒温时间 后的屈服强度、极限强度、弹性模量、延伸率和受拉应力-应变关系等力学性能的变化规律。试验表明。新Ⅲ级钢筋在经历 高温作用后,其屈服强度、极限强度和弹性模量在400℃以前变化不大,之后随所经历温度的升高而逐渐下降,降幅一般在 15％左右,实测的受拉应力-应变关系曲线,仍然出现明显的屈服台阶和强化段。根据试验结果,本文建议了高温后新Ⅲ 级钢筋屈服强度、极限强度、弹性模量、延伸率和受拉应力.应变全曲线计算公式。本文研究成果可作为火灾后混凝土结 构的损伤评估和非线性有限元全过程分析的依据。

Experimental research on material properties of new Ⅲ grade steel bars after fire

The material properties of new Ⅲ grade steel bars after fire are studied experimentally through 111 specimens of 37 groups with diameters 16mm and 12mm respectively. The laws of variation of yield strength, ultimate strength, elastic modulus, elongation percentage and tensile stress-strain curves after enduring different fire temperatures and constant temperature time are obtained. The experiments indicated that the yield strength, ultimate strength and elastic modulus change little after enduring the fire temperature less than 400℃, and then depress gradually with elevating of fire temperature, and the extent are about 15%. The tensile stress-strain curves of the steel bars change also, and still there are obvious yield plateau and strain-hardening range. Based on the experimental results, the paper proposes the calculation formulas of yield strength, ultimate strength, elastic modulus and tensile stress-strain curves of the new Ⅲ grade steel bars after fire. The conclusions of the paper supply a basis for evaluating damage and the further non-linear finite element analysis of reinforced concrete structures after fire.