Eccentric Behavior of Full-Scale Reinforced Concrete Columns with Glass Fiber-Reinforced Polymer Bars and Ties

Recent years have witnessed noticeable advances in evaluating the behavior and contribution of fiber-reinforced polymer (FRP) bars in concrete columns under concentric loading. In contrast, there is a scarcity of investigation available in the literature on full-scale concrete columns reinforced with FRP bars and ties under combined axial and flexural loads. This paper reports experimental data on the behavior of square concrete columns reinforced with deformed and/or sand-coated glass FRP (GFRP) bars and ties. A total of 12 full-scale concrete columns 16 x 16 in. (405 x 405 mm) in cross section and 80 in. (2000 mm) in height were constructed and tested up to failure. The columns were loaded under four different levels of eccentricities to develop axial load-moment (P-M) interaction diagrams. The influence of different GFRP bars of comparable quality on the performance of the columns and their P-M interaction diagrams were assessed. In addition, columns reinforced with conventional steel bars and ties were introduced into the test matrix as references. The load-strain behavior for the concrete, bars, and ties; load-deformation curves (axial and lateral); and experimental P-M interaction diagrams are presented herein. The impact of the compressive behavior of longitudinal GFRP bars versus steel bars was assessed. The test results indicate that the specimens reinforced with two comparable types of GFRP bars (deformed and/or sand-coated) under different levels of eccentricity behaved similarly to their steel reinforced concrete counterparts. Design strain limits were proposed to define the failure-mode mechanisms of the GFRP specimens on the P-M interaction diagram.