Evaluation of residual stress in pre-stressed concrete material by digital image processing photoelastic coating and hole drilling method

A digital discrete image processing photoelastic coating and hole drilling combined system was developed to determine the magnitude of the residual stress in a pre-stressed concrete specimen subjected to a uniform uniaxial compression load. In the digital image processing fringe analysis, the optical data contained in the reflection photoelastic isochromatics were converted into values of residual stress. The evaluation was conducted through the measurement of the in-plane stress field generated by the introduction of the small hole. The stress field was determined from the calculation of the photostress distribution by means of digital discrete image processing method. The magnitude of the applied stress was calculated and compared with the initial applied stress value in the concrete specimen.