Experimental study on reinforced concrete columns partially confined with carbon fiber reinforced polymer (CFRP)

The requirement of strengthening of reinforced concrete structures may emerge not only due to timed degradation but also due to various reasons like construction faults, increased loads and changes in utilization purpose etc. Rehabilitation of reinforced concrete structures using Carbon Fibre Reinforced Polymer materials is recognized as a very effective retrofitting method. The current practice on strengthening reinforced concrete columns with external CFRP jacketing is to provide full wrapping all over the column with less care on the required strength increment As CFRP is a costly material, providing partial wrapping may be a viable option for cost reduction rather than providing full confinement. An experimental study was carried out with 17 specimens to study the partial confinement effect. The test specimens consist of 6 plain concrete columns with 3 control specimens and 3 fully confined columns. 11 reinforced concrete columns with 3 control specimens, 3 columns with full confinement and 5 columns with partial confinement. Two wrapping patterns were used for partially confined columns with 75mm and 50mm laminate width, keeping the volumetric ratio of CFRP constant to study the effect of wrapping pattern and jacket location for strength and ductility increment. The results of experimental study revealed that the load carrying capacity increment for fully wrapped reinforced concrete columns were 100% while for plain concrete columns it was 47% and for partially confined columns, the specimens with two 75mm wraps showed a capacity increment of 59% while specimens with three 50mm wraps showed an increment of 83%. It was observed that, by only changing the jacket location 15% ultimate load carrying capacity increment can be obtained. When ductility increment is considered it was observed that ductility increment is proportional to the strength increment