Performance of GFRP-Reinforced Concrete Circular Short Columns under Concentric, Eccentric, and Flexural Loads

This paper presents test results of seven large-scale circular concrete columns reinforced with either steel or glass fiber-reinforced polymer (GFRP) reinforcement. The columns measured 355 mm in diameter and 1,750 mm in length and were tested to failure under concentric, eccentric, or four-point bending configuration. Test parameters included the reinforcement type (GFRP and steel), the GFRP spiral pitch (50 and 85 mm), and varying ratios of eccentricity-to-column diameter (e/D= 0, 0.085, 0.17, and 0.34). The obtained axial capacity of the GFRP-reinforced concrete (RC) column was approximately 17% less than that of the steel-RC counterpart. However, fore/D= 0.085, the GFRP-RC column with a lesser spiral pitch exhibited approximately 10% more axial capacity than the column with a larger pitch. As thee/Dratio increases from 0 to 0.34 the axial capacity reduced by 32%, 39%, and 70% from the axial capacity of the concentric column. A "knee"-shaped interaction diagram for circular GFRP-RC columns was developed and compared with the predictions of available codes and guidelines for GFRP-RC structures.