Analytic models for high-strength concrete square columns confined by carbon fiber reinforced polymer

In order to study the performances and the basic born capabilities of high strength concrete members bonded with CFRP (carbon fiber polymers), stress-strain relationship should be determined. Experiments on the relationship between stress-strain of high strength concrete columns are carried out through nine group members with different strengthening schemes, which have taken several factors into account, such as the amount of CFRP, bonding methods, space between CFRP strips. Based on the analysis of the experiments, the stress-strain relationship of high strength concrete columns bonded with CFRP is given, together with some conclusions being drawn as follows. Compressive strength of high strength concrete columns externally bonded with CFRP has increased to a certain extent, whether they are bonded with CFRP strips or sheets, and enhances with the increasing amount of CFRP. Simultaneously, the scheme of strengthening with CFRP sheets has much more distinct effect than that with CFRP strips. The stress-slip relation of CFRP strengthened members is gently descending, behaving in a much more ductile way but still with a great deal of brittleness at failure.