The paper presents the results of a study on the performance of Glass Fiber-Reinforced Polymer (GFRP) wrapped High Strength Concrete (HSC) columns under uniaxial compression. The columns had slenderness ratios of 8, 16, 24 and 32. Three types of wrap materials (chopped strand mat GFRP, unidirectional cloth GFRP, and woven roving GFRP) were used with 3 mm and 5 mm thickness. The columns were tested under monotonic axial compressive loading up to failure. The deflections and axial strain were noted for each load increment. The HSC columns with GFRP wrapping exhibited improved performance in terms of ductility and energy absorption capacity. Adaptive Neuro-Fuzzy Inference System (ANFIS) modeling was proposed for predicting the performance parameters. A better correlation was observed between the test results and those predicted through the proposed modeling.

In any structural system, columns stand out as significant structural elements, and weakness or failure of a column hampers the structural integrity. Improving adequate strength and ductility to such critical elements is a sine qua non. This important issue can be addressed both through traditional and innovative methods. In recent years, Fiber-Reinforced Polymer (FRP) wrapping technique has gained importance towards the purpose of qualifying the structural elements for unanticipated events like those of seismic and wind-induced effects. In particular, FRP wrapping is found to be very much beneficial for column members. The strength, deformation capacity and ductility of a column can be significantly improved through FRP confinement procedure.

Ahmed and Fattah (1991) and Ahmed and Mallase (1994) have carried out analytical studies and suggested models for predicting the stress-strain behavior of normal strength and High Strength Concrete (HSC) columns. Saaman et al. (1996) have carried out analytical investigations on the behavior of concrete confined by Glass Fiber-Reinforced Polymer (GFRP) and came out with a confinement model of their own. They observed that many existing models failed to predict the behavior of GFRP confined concrete because they ignore the stiffness of the confining mechanism provided by the GFRP. Nonlinear finite element (FE) investigations to model the stress-strain behavior of FRP found that the strength of concrete, shape of the cross-section and ratio of diameter of concrete to thickness of FRP had a significant impact on the performance of confined concrete (Shams and Saadeghvaziri, 1999).

Seismic performance of GFRP confined bridge piers was investigated by Saadatmanesh et al. (1996), and they concluded that GFRP confinement provided in potential plastic hinge region leads to significant improvement in both strength and displacement ductility. Mirmiran et al. (1998) studied the effect of shape of column cross-section, length of column adhesive and mechanical bond between concrete surface and FRP on more than 100 concrete specimens under uniaxial loading. The investigation found that square sections are less effective compared to circular sections, the effect of length to diameter reaches in the range of 2 to 5 did not have any significant impact on strength and ductility, and mechanical bond of FRP to the concrete surface affects the load-carrying capacity of confined concrete rather than adhesive bond.

The present paper compared with the experimental results and modeling in terms of load-carrying capacity and ductility, obtained from tests on circular concrete columns, reinforced with external E-glass fiber composite. The study parameters included the material and stiffness of FRP confinement wraps.

Structural Engineering Journal, ANFIS, Deformation, GFRP, High Strength Concrete, Ductility.