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

Abstract

This paper presents the flexural behavior of reinforced concrete box (RCB) girders reinforced with both steel and fiber-reinforced polymer (FRP). An experimental study was conducted on five RCB girders. The first two girders were reinforced in the tension side with either steel or basalt FRP (BFRP) bars, while the other three ones were reinforced with both steel and BFRP bars with various BFRP-to-total reinforcement ratios (Af/At). The RCB girders were tested under four-point monotonic static loading and the main fundamental characteristics of the proposed reinforcement were investigated. The experimental results showed 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. With the range of the experimental investigations conducted in this study, a value of about 50% to 70% for Af/At ratio is recommended in the design of hybrid RCB girders as it provides enough post elastic strength and stiffness for meeting the ductility requirement. Ultimately, the application of the analytical structural approach available in the literature was adopted to predict the flexural capacity of mixed RCB girders and good agreement with the experimental results was proved.