2019 CSCE Annual Conference - Laval (Greater Montreal)

2019 CSCE Annual Conference - Laval (Greater Montreal) Conference

Strength Modeling of GFRP-Reinforced Concrete Deep Beams with Web Openings

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Dr. Brahim Benmokrane, Universite de Sherbrooke (Presenter)
Mr. Jacob Frappier, University of Sherbrooke
Dr. Khaled Mohamed, University of Sherbrooke
Dr. Ahmed Farghaly, University of Sherbrooke

Reinforced concrete deep beams are usually used when designing transfer girders or bridge bents. In deep beams, openings are placed in the web area to facilitate fundamental services, such as conduits, and network system access. The use of web openings often interrupts the load transfer by concrete struts forming between the loading point and the. This interruption causes an acute decrease of strength and serviceability of the deep beams. Design previsions recommend the design of steel- and FRP-reinforced deep beams using the strut-and-tie model (STM). The accuracy of STM in determining the strength of glass fiber reinforced polymer (GFRP)-reinforced deep beams without web openings was examined and revealed adequate estimations. The STM provides a conceptually simple design methodology and easy visualization of the flow of forces; however, its implementation is usually complicated for more complex truss models such as in deep beams with web openings. Therefore, an alternative analytical method is essential to predict the shear strength of GFRP-reinforced concrete deep beams with web openings. The current study aims at developing an analytical model to calculate the resistance of GFRP-reinforced deep beams with openings while considering deformation compatibility, equilibrium, and laws of constitutive materials. The developed model is based on a previously adopted model for steel-reinforced deep beams with web openings; however, taking into consideration the difference in material behavior between steel and GFRP reinforcement. Experimental results of GFRP-reinforced deep beams with web openings were used to calibrate the suggested model. Accordingly, strain limitations for the GFRP bars were suggested as a lower-bound limit and implemented in the model to mitigate the excessive strains on concrete struts resulted from softening of concrete surrounding the GFRP bars. Additionally, limiting the strains in GFRP bars ensures adequate amount of FRP bars to avoid failure due to rupture of the GFRP bars. The applied limitation allowed for conservative, yet, consistent results over the original model and can be used for designing GFRP reinforced deep beams with web openings with adequate level of conservatism.