Flexural Behavior of Concrete Box Girders Reinforced with Mixed Steel and Basalt Fiber-Reinforced Polymer Bars

Abstract

This paper presents an experimental study about the effect of the ratio between the area of Basalt Fiber Reinforced Polymer (BFRP) bars to the total area of steel and BFRP bars (Af/At) on the behavior of Reinforced Concrete Box (RCB) girders. Also, it displays the effectiveness of the mixed steel and BFRP (MSBFRP) bars as the main reinforcement to enhance the behavior of RCB girders in flexure. Moreover, the ultimate flexural capacity of the tested girders was evaluated analytically. The experimental program consisted of five RCB girders. The first two girders were reinforced in the tension side with either steel or BFRP bars, while the other three ones were reinforced with both steel and BFRP bars with different Af/At ratios. The effect of Af/At ratio on the initiation and propagation of cracks, mode of failure, ultimate and cracking loads, the corresponding deflection, and ductility was investigated. It was found that increasing the Af/At ratio improved both the ultimate load and the deflection at failure, while the ductility index decreased. Comparing the obtained RCB test results with those found in the literature of the ordinary beams revealed that the behavior is almost identical. The Af/At ratio of about 50% to 70% is recommended in the design of hybrid RCB girders as it provides enough post elastic strength and stiffness for meeting the ductility requirement.

Keywords

• reinforced concrete box girders
• reinforcement ratio
• mixed steel and bfrp bars
• ductility index
• analytical design