-10℃下超高性能混凝土的弯曲疲劳性能

Flexural Fatigue Properties of Ultra-High Performance Concrete at-10℃

为了解负温时超高性能混凝土(UHPC)的弯曲疲劳性能,对20℃和-10℃两种温度下的UHPC进行了不同应力水平下的弯曲疲劳试验。结果表明:随着温度的降低,由于试件开裂截面钢纤维的冷脆特征,使得循环荷载作用下UHPC弯曲疲劳性能的退化明显加剧,疲劳强度也明显降低。与20℃的结果相比发现,-10℃UHPC的疲劳强度降低了15.6%;虽然低温试件的疲劳强度低于常温试件,但两类试件与各自疲劳强度对应的疲劳变形模量比En/E0相近,均在0.48左右;无论是常温试件还是低温试件,经历200万次循环而未发生弯曲疲劳破坏的UHPC试件,其疲劳后的剩余强度均与单调加载时的静力强度接近。基于试验结果,提出了20℃和-10℃两种温度下UHPC的疲劳寿命方程。

The fatigue properties of ultra-high performance concrete(UHPC)at 20℃and-10℃were investigated via flexural fatigue tests under different stress levels.The results show that,the degradation of UHPC flexural fatigue performance and the fatigue strength decrease under a cyclic load with the decrease of temperature due to the cold brittleness characteristics of steel fibers at the cracked section.Compared with the test results at 20℃,the fatigue strength of UHPC at–10℃is decreased by 15.6%.Although the fatigue strength of the specimens at a low temperature is lower than that of the specimens at normal temperature,their fatigue deformation modulus ratios(En/E0)corresponding to their fatigue strengths are similar,which are 0.48.The residual strength of UHPC specimens undergoing 2 million cycles without flexural fatigue failure is close to the static strength under monotonic loading,at normal temperature or low temperature.Based on the results,a model of predicting the fatigue life of UHPC at 20℃and–10℃was proposed,and the predicted results could be used as reference in the practical application.