Tendon Profile layout Impact on the Shear Capacity of Unbonded Post-Tensioned Prestressed Concrete Bridge I-Girders

The primary objective of this research is to investigate the impact of tendon profile layout on the shear strength of unbonded, post-tensioned prestressed concrete bridge I-girders. This study involves an experimental investigation where ten un-bonded, post-tensioned bridge girders are cast and subjected to four-point loads. The focus of the investigation is on the effect of different tendon profile layouts, including trapezoidal, parabolic, and harped shapes. The experimental results reveal that the shear behavior of the specimens progresses through three distinct stages: the elastic stage, the elastic–plastic stage, and the plastic stage, with all specimens ultimately failing due to shear. The findings show that tendon profiles with an eccentricity at the end of the beam = -80mm (80 mm above the neutral axis) exhibited the highest ultimate load capacity, coupled with the largest deflection. Conversely, profiles with an eccentricity of = 80mm (80 mm below the neutral axis) demonstrated the lowest load capacity and minimal deflection. Among the various configurations tested, the specimen with the harped tendon profile (GF-1 HA) showed the highest ultimate load capacity. On the other hand, the trapezoidal tendon profile specimen (GF-2 TR) exhibited the lowest deflection. These improvements in stiffness, load capacity, and deflection are attributed to enhanced resistance, particularly at the supports. Consequently, the optimized tendon layouts offer a reduction in deflection and an increase in the overall structural efficiency, leading to potential cost savings in bridge girder production.