Abstract
Although the use of carbon fibre reinforced polymer (CFRP) materials is considered as a very effective retrofitting technique for reinforced concrete columns, still it is the identification of cost reduction strategies that draws most of the attention since the use of CFRP materials is considered as more expensive than any other retrofitting method. Providing partial confinement in place of full confinement which is the current practice may be a viable option that allows for considerable cost savings while maintaining the required structural capacity. Although CFRP technology has been in use for several decades, some countries still do not have adequate technical know-how to use this technique effectively. As there are several design guidelines available globally, it is quite unclear which design guideline will provide an economical design while maintaining the required factor of safety. This paper presents an experimental study conducted using 17 specimens to investigate the strength increments due to external CFRP confinement of reinforced and unreinforced concrete columns. Reinforced concrete columns were provided with both full and partial confinement to study their strength and ductility increments. The volumetric ratio of CFRP was kept constant for partially confined columns to study the effect of the jacket arrangement pattern. The experimental failure loads obtained were reviewed against the theoretical values calculated using ACI and fib guidelines, to investigate the overall safety factors available when using each design guideline. The experimental results showed considerable strength and ductility increments in all of the fully and partially confined specimens. Although the volumetric ratio of CFRP was kept same for all partially confined columns, it was observed that depending on the jacket location, the strength and ductility increments would vary. It was also observed that both design guidelines give for fully confined reinforced concrete columns, a factor of safety exceeding 1.5.
Highlights
In the modern world, the sustainability of built environments has become a key issue
There are a considerable number of studies that have been carried out on reinforced concrete column strengthening with carbon fibre reinforced polymer (CFRP)
Failure mode is the characteristics of the failure observed at ultimate load, failure load is the maximum load that the specimen can undergo up to the time of the failure, and the ductility ratio used to study the ductile behaviour is the ultimate displacement at the time of failure divided by specimen height
Summary
The sustainability of built environments has become a key issue. One of the main strategies available for improving the sustainability of the existing built environment is the prolonging of the life of the structure while modernizing it. There are many techniques such as steel plate bonding, external post tensioning, section enlargement and fibre reinforced polymer systems (FRP systems) for retrofitting concrete structures. It was observed that circular sectioned columns gain the highest strength increment, while those of square section with sharp corners displayed no significant improvement in their load carrying capacities, and that strength gain is increased when corner radius is increased. The same observation has been made in studies done by Carlos and Silva [2] and Tamer[3] which indicated that columns with circular cross sections can have greater ductility and strength increments. Carlos and Silva [2] have studied the effect of the number of plies, effect of steel
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