Axial-Flexural Performance of High-Strength-Concrete Bridge Compression Members Reinforced with Basalt-FRP Bars and Ties: Experimental and Theoretical Investigation

The forthcoming editions of the American and Canadian design codes will include complete sections with provisions on designing nonprestressed-concrete compression members (columns, piles, and piers) reinforced with fiber-reinforced polymer (FRP) bars subjected to combined axial and flexural load. This article presents the results of a research program investigating the use of newly developed sand-coated basalt-FRP (BFRP) bars and ties in axial-flexural members made with high-strength concrete (HSC). Eight full-scale concrete columns 400 x 400 mm in cross section and 2,000 mm in height were constructed and tested. The test variables were eccentricity-to-depth ratio and reinforcement type (BFRP and steel bars and ties). The test results indicate that the specimens reinforced with BFRP bars and ties under different levels of eccentricity behaved similarly to their steel-reinforced counterparts. An analytical study was conducted to predict the axial-flexural capacity. A parametric study was introduced to examine the effect of increasing the reinforcement ratio and concrete strength. Moreover, the effective flexural stiffness was estimated and plotted at different load levels and compared with design-equation results. The findings of this investigation can be considered as a fundamental step toward developing code provisions for the use of BFRP bars and ties as internal reinforcement in bridge pier and pile applications.