Tension Force Detection of Short Suspender by Using Laser Doppler Vibrometer

Abstract

In this study, the vibration frequency of steel rod-type short suspenders simulated by three types of prestressed steel rebars with aspect ratios of 14, 20.8, and 37.8 was detected accurately and remotely by using Laser Doppler Vibrometer (LDV); then the tension force state of short suspenders was evaluated through the quadratic regression relationships between vibration frequency and tension force. The results showed that the vibration frequency of steel rod-type short suspenders increases with the increase in tension force, and there is a good correlation between vibration frequency and prestress. Furthermore, when the prestress applied is the same, the vibration frequency of short suspenders decreases with the increase of their aspect ratios, indicating aspect ratio plays a decisive role on the change of vibration frequency. The errors between the tension force obtained by experiment and tension string theoretical calculation for short suspenders are large, due to the nonrigid boundary condition. The establishment of quadratic regression relationships between vibration frequency and tension force effectively avoids the influence of various factors on the existing calculation model such as mass, stiffness, and constraint type, and makes the detection accuracy of tension force achieve 98%.