不同拉压应力水平对混凝土超声波波速的影响

Influences of Different Tensile and Compressive Stress Levels on Ultrasonic Wave Velocity of Concrete

为了研究应力水平对混凝土超声波波速的影响,本文设计并浇筑了素混凝土轴心抗拉试件、素混凝土轴心抗压试件、素混凝土立方体抗压试件、钢筋混凝土受弯构件,并分别对素混凝土试件、钢筋混凝土构件进行不同应力水平下的超声波波速检测试验。结果表明:拉、压应力水平对混凝土试件超声波波速影响较小,可以忽略不计。低应力水平对钢筋混凝土构件超声波波速影响较小,高应力水平导致混凝土构件出现裂缝时对超声波波速影响较大。混凝土构件拉应力-超声波波速关系曲线可分为无损伤期、损伤发展期、损伤稳定期、构件破坏期。当拉应力达到极限拉应力的15%~25%时,构件从无损伤期进入损伤发展期,此时超声波波速没有变化;当拉应力达到极限拉应力的35%~55%时,构件从损伤发展期进入损伤稳定期,此时超声波波速降低了5%左右;当拉应力到达极限拉应力的60%~75%时,构件从损伤稳定期进入构件破坏期,此时超声波波速降低了8%左右。

In order to study the influence of stress level on ultrasonic wave velocity of concrete,plain concrete axial tensile specimens,plain concrete axial compressive specimens,plain concrete cube compressive specimens and reinforced concrete flexural members were designed and poured in this paper.The ultrasonic wave velocity tests of plain concrete specimens and reinforced concrete members under different stress levels were carried out respectively.The results show that the tensile and compressive stress levels have little effect on ultrasonic wave velocity of concrete specimens,which can be ignored.The low stress level has little effect on ultrasonic wave velocity of reinforced concrete members,and the high stress level has a great influence on ultrasonic wave velocity when cracks appear in concrete members.The tensile stress-ultrasonic wave velocity relationship curves of concrete members can be divided into four stages,including no damage period,damage development period,damage stability period and component failure period.When the tensile stress reaches 15%~25%of ultimate tensile stress,the component enters damage development period from non-damage period,and the ultrasonic wave velocity does not change at this time.When the tensile stress reaches 35%~55%of ultimate tensile stress,the component enters damage stabilization period from damage development period,and the ultrasonic wave velocity is reduced by about 5%.When the tensile stress reaches 60%~75%of the ultimate tensile stress,the component enters failure period from damage stable period,and the ultrasonic wave velocity is reduced by about 8%.