Rectangular high-strength concrete columns confined with carbon fiber-reinforced polymer (CFRP) under eccentric compression loading

Abstract

A total of 16 rectangular high-strength columns were constructed and 14 of them were strengthened with carbon fiber reinforced polymer (CFRP) strips externally along the column. All these columns were tested under eccentric compression loading with the eccentricity range from 50 mm to 100 mm. The main variables in this study included CFRP layout, the number of CFRP sheets and pre-damaged condition. The failure modes, axial load-midspan deflection curves, ductility factors and the strain distribution of CFRP were analyzed. The test results show that the ductility and ultimate capacity of columns were obviously increased by wrapping CFRP sheets around the columns. Specifically, for the eccentricity equal to 50 mm, the horizontal fully wrapped CFRP exhibited the most extraordinary mechanical performance than other strengthened specimens. When the eccentricity increased to 100 mm, the ductility and energy absorption ability were enhanced significantly on the specimens strengthened with longitudinal CFRP and wrapped with horizontal CFRP strips simultaneously. However, as for the specimens which were pre-damaged before retrofitting, the strengthened effect was largely weakened regardless of the value of eccentricity. Finally, a new stress-strain model was proposed for the FRP confined concrete according to a large database, which can be either applied to the normal strength concrete or high strength concrete. Based on the proposed model, the axial ultimate capacity of all the strengthened columns in the present study and other researches were calculated and compared to the test data. It is evident from the results that satisfactory accuracy and good agreement can be found between the theoretical predictions and test observations.