Confinement effect of CFRP and/or steel ties in circular RC columns 35 MPa concrete strength

Carbon Fiber Reinforced Polymer (CFRP) has long been used to retrofit Reinforced Concrete columns (RC columns). Since confining RC columns with CFRP enhances its carrying load capacity, it has become a subject for many studies. In this study, RC columns were made to simulate short compressive members having a dimension of 180mm diameter by 500 mm in height. The RC columns were grouped according to the spacing of the steel ties and the number of ply of CFRP. The cylinders were subjected to compressive axial loads and the deformations for longitudinal and lateral were measured. The result of the analysis showed that the 40 mm and 80 mm spacing were able to increase the load carrying capacity of the cylinder unlike the 120 mm spacing, which has a statistically equivalent compressive stress with the columns that had no steel reinforcements. Furthermore, the 40 mm spacing was the most effective spacing among the three since it was able to obtain the highest compressive stress. The results also showed that as the volumetric ratio of CFRP increased, the load carrying capacity and ductility of the column increased. Moreover, the absence of the sulfur or rubber capping during testing resulted to eccentricity in loading therefore resulting to two observed deformation. The first observed deformation was when the column bulged at both sides and the second deformation of the column was the concaving inward of the other side while pushing the other side outward. Lastly, existing (Mander et al 1988, Saadatmanesh et al 1994, Li and Fang 2004, Oreta et al 2005) models were used to predict and compare the computed theoretical compressive stress (f⁾ cc) with the actual compressive stress (f⁾ cc exp). Although a large difference between f⁾ cc and f⁾ cc exp was observed the behavior resulted from the model was the same behavior observed from the experiments