Cracking and Crack Control in Circular Concrete Bridge Members Reinforced with Fiber-Reinforced Polymer Bars

Abstract

Serviceability requirements are crucial in the design of fiber-reinforced-polymer (FRP) RC bridge members. Permissible crack width under service loads is one of the requirements that can control design. Crack-control models have been included in the Canadian and American design codes based on experimental work on FRP-RC members with rectangular cross sections. In this study, the applicability of these models to RC bridge members with a circular cross section was assessed experimentally. A total of nine full-scale, circular RC specimens measuring 0.5 m in diameter and 6 m in length were constructed and tested up to failure under a four-point bending load. The test parameters included the longitudinal-reinforcement ratio and the longitudinal-reinforcement type, including glass FRP, carbon FRP, basalt FRP, and steel bars. The experimental results were reported in terms of crack patterns, crack spacing, and crack width versus flexural tension-bar strain and the applied moment. Crack-control models in the current FRP codes and design guidelines were re-examined, extended, and applied to circular FRP-RC members. Design equations for estimating the service stress in the FRP reinforcement and the cracked moment of inertia were theoretically derived and presented for the circular FRP-RC members. Crack-width predictions were compared with the experimental results. The comparison indicated that the crack-control formulae developed for rectangular FRP-RC members can be used for the cracking control of circular FRP-RC members by using the redefined parameters developed and proposed in this study to take into account the geometry, bar spacing and distribution, and effective tension stiffening area.