Analytical Approach for Flexural Capacity of FRP Prestressed Concrete T-Beams with Non-Prestressed Steel Bars

Available flexural strength formulas mainly focus on rectangular concrete beams exclusively prestressed with fiber-reinforced polymer (FRP) tendons. Moreover, an iterative procedure is required when FRP rupture governs the design. This paper presents a simplified and yet rational analytical approach for flexural capacity of prestressed concrete T-beams with bonded FRP tendons and non-prestressed steel bars. First, a sectional analysis assuming balanced failure is conducted to distinguish tension and compression failure. In conjunction with a statistical analysis of an experimental database of 87 beams, a new transition region between tension- and compression-controlled sections is proposed in terms of ratio of provided-to-balanced reinforcement (1.0 < rho(ep)/rho(ep,b) <= 1.5) instead of the traditional net tensile strain limits in current American design guidelines. Then, a numerical sectional analysis of tension-controlled sections is was used to perform a detailed parametric study of more than 120,000 sections. Based on a multiple regression analysis of the numerical results, simplified equations are developed for the flexural capacity of the sections. Then equations are presented for flexural capacity of compression-controlled sections. Finally, the accuracy of the proposed approach is verified based on the experimental database from 87 beam tests. (c) 2018 American Society of Civil Engineers.