Deformation measurement based on high resolution distributed optical fiber sensing and conjugated beam method

Abstract

Structural deformation is in general an effective indicator of unforeseen damage accumulation. It is difficult to monitor deformation distribution by traditional single point measurement methods. Based on a high strain sensing resolution technique of optical frequency domain reflectometry (OFDR), this paper presents a hybrid method for structural deformation measurement. The main advantage is the explicit relationship between structural deformation and monitored strain data thus the calculation process can be conducted free from load identification and stiffness measurement. The accuracy of this method is investigated via both theoretical and experimental study. In lab experiments, simple support beam with fix supports and spring supports was designed. Compared with classical double integration method, the accuracy of the conjugated beam method (CBM) improved 5%. In concentrated and uniform distributed load conditions, the average relative error ranges from 4% to 7%. Furthermore, the average relative errors for several points are no more than 3% in complex load conditions.