大尺寸混凝土试样动态参数的试验研究

Experimental study on the dynamic parameters of concrete samples with large dimension

根据超声波在混凝土介质中传播的声速、首波幅值、波形,分析了大尺寸混凝土试样的内部缺陷和均匀性,并对其弹性模量、衰减系数、松弛时间等动态参数进行求解。为了与超声波检测结果对比,采用改进的Hopkinson压杆技术对同配比的圆柱形混凝土试样进行实验研究来测定其相应动态参数,并对比分析了两种方法的不同之处。实验结果表明:两种方法测定的动态弹性模量基本一致;HPB试验测得的衰减系数比超声波试验测得的值大,这说明HPB试验中存在动态损伤的影响;HPB试验测得的松弛时间比超声波测得的增加了近一倍,这表明了在高应变率下,混凝土试样的脆性得到了明显的增加。试验数据可以为工程应用提供借鉴。

According to the experimental data of the ultrasonic wave propagating in concrete samples with large dimension,the internal defect and uniformity of concrete is analyzed and the dynamic parameters such as modulus of elasticity,attenuation coefficient and relaxation time are obtained.Meanwhile,the cylindrical samples of concrete with the same mix ratio as the large size samples are molded.Using Hopkinson Pressure Bar(HPB) test,the dynamic parameters are obtained and compared with the results from ultrasonic testing.Experimental results obtained show that the dynamic modulus of elasticity measured by ultrasonic wave is generally consistent with HPB test ones.The attenuation coefficient obtained from HPB test is larger than that from ultrasonic testing due to the dynamic mechanic damages.Moreover,the relaxation time derived by HPB test is about two times of that derived by ultrasonic testing.It implies that the samples in high strain rate tests seem more brittle.Simultaneously,the data of test can provide reference for engineering application.