Upgrading Reinforced Concrete Columns by Jacketing with Carbon Fiber-Reinforced Plastic (CFRP) Sheets

摘要

Experimental studies are reported on upgrading the load carrying capacity of reinforced columns by jacketing with carbon fiber reinforced plastic (CFRP) flexible wraps. Several square columns with medium high strength concrete (cube strength = 64 MPa) were tested under concentric compression. The studied variables include: different upgrading configurations (continuous wrapping all over the height, discontinuous straps, straps concentrated at end zones); volume of wraps; and pre-loading prior to wrapping to simulate insitu strengthening process in practice. Effective wrapping provided lateral confinement to enhance the concrete compressive strength and the load capacity of the columns, in addition to the improvement of the ductility. With higher levels of confinement the axial capacity was further enhanced. Besides, effective retrofitting of preloaded columns restored and even increased their load carrying capacity over that of the original columns. It seems better to use effective full height wraps for enhancement of both strength and ductility and to help restrain against buckling of longitudinal bars, however the effect of confining the columns' ends cannot be overlooked. The confined concrete strength from tests was compared with those estimated by certain empirical models and the comparisons were favorable in many cases. Other conclusions are also drawn.