SEISMIC BEHAVIOUR OF SQUARE CONCRETE COLUMNS RETROFITTED WITH CARBON FIBRE REINFORCED POLYMERS

摘要

Columns within structures must resist severe ground motion to prevent failure during a major earthquake. The seismic resistance of deficient steel reinforced concrete columns can be improved through the use of structural materials that increase confinement, thereby enhancing ductility and energy absorption capacity. Compared to conventional retrofit options, using carbon fibre reinforced polymers (CFRP) provides a faster and more economical alternative since structures can often remain in service with little disruption during the procedure. This paper investigates the seismic performance of a select group of deficient columns strengthened with CFRP. Each 305-mm square column was 1.47-m long and was integrally cast with a 0.81-m long stub representing a beam-column joint or footing. Each specimen was tested under a constant axial load and simultaneously applied lateral cyclic displacement excursions simulating earthquake forces. Results show that responses of columns with inadequate seismic steel reinforcement detailing can be greatly improved through retrofitting with CFRP. Ductility, toughness and strength are progressively enhanced as the number of CFRP layers increases. Seismic behaviour of strengthened specimens can be superior to responses of comparable columns designed according to earthquake provisions of design codes. Columns subjected to higher axial loads require more CFRP reinforcement for the same improvement in performance demonstrated by lightly loaded columns.