LONG TERM PERFORMANCE OF REHABILITATED CONCRETE BEAMS STRENGTHENED FOR TORSION USING CFRP

Abstract

The paper presents long term performance of reinforced concrete floor beams that were rehabilitated in 2007 for torsion using carbon fiber reinforced polymer (CFRP). The two rehabilitated beams were members of the concrete beam and slab floor system of a new parking garage near Boston in Massachusetts, USA. Without this rehabilitation, the new garage could not be accepted. The paper recapitulates the causes that led to the cracking and the rehabilitation of the beams for torsion, and the choice between strengthening by reinforced concrete jacket and by CFRP wrap. It was probably the first time and ahead of the Codes of Practice that CFRP was used to resist torsion in real as-built concrete structure and for total torsion. In previous practices, CFRP was ever used for flexure and shear strengthening in partial supplement to the original strength, not for total strength. The methodology for CFRP for torsion was given. Pictures depicting the rehabilitation in 2007 are illustrated. The recent pictures of the beams taken in December 2021 are given. The long term monitoring and observation, on the author’s own time and duty of care, for the past 14 years on this real structure confirms the reliability, durability and efficiency of CFRP wrap for torsion of concrete beams under sustained dynamic live loading and vibration from motor vehicles. The paper concludes with discussion of the advantages of CFRP wrap over the reinforced concrete jacket strengthening.