The use of image correlation photogrammetry in investigating the performance of fire-damaged circular RC columns strengthened with CFRP

Over the past few decades, circumferential wrapping with externally-bonded carbon fibre-reinforced polymer (CFRP) fabrics has proven to be a promising method for enhancing both the strength and ductility of reinforced concrete (RC) columns. This is particularly useful when repairing columns that have been damaged due to heating in a fire. In this ongoing study, digital image correlation (photogrammetry) is used to investigate the residual behaviour of heat-damaged RC columns that have been repaired with CFRP sheets. A total of six 204 × 750mm circular RC columns and six 100 × 200mm plain concrete cylinders were fabricated and tested to failure. The photogrammetry technique was considered for use since this should be able to provide strains at many locations compared with conventional strain gauges, which are limited to measuring strain at a number of discrete points. The strain efficiency of the CFRP wraps could be better assessed using a full-field surface measurement technique up to peak load and beyond. To enable such measurements, the RC column’s surface area was used for strain measuring purposes using a Vic-3D digital image correlation system camera. This paper presents the test results and highlights the differences in the strain data measurements using photogrammetry and conventional strain gauges