An advanced investigation of the core-drilling method (CDM) for direct application in bridge assessment is conducted. In the CDM, a small hole is drilled into concrete and the displacements that result are measured and related to the in situ stress. Knowledge of the stress profile within the concrete of a girder would allow determination of the magnitude and location of force in its prestressing steel. The programme described in this paper and its companion paper had two objectives - to demonstrate the effectiveness of the CDM in determining concrete stresses when using small-diameter holes and to demonstrate feasibility, accuracy and appropriateness of the CDM for the assessment of prestressed concrete bridge girders and for determining the existing prestress in their tendons. The method had never been applied to a prestressed beam. After verifying the method in concrete slabs in part I of this work, the technique was used with 75 mm holes to investigate the stresses in a prestressed beam and to determine the force in its prestressing steel. The tendon forces determined by drilling any single hole using the CDM are accurate, with an average error of 58.5 kN and a relative error of 15.94%. They are also consistent, with a standard deviation in error of 75.2 kN. The tendon force in a prestressed concrete beam can be determined to within +/- 8% if three holes are drilled.
展开▼
