Precast Pretensioned Trapezoidal Box Beam for Short Span Bridges

This paper describes a new trapezoidal precast, pretensioned beam that can span up to 100 ft (.30.5 m). The beam has a maximum weight of 55 tons (50 f). The new beam is presented in two different shapes: a closed totally precast concrete shape and an open-top shape requiring a cast-inpiace composite topping. To maintain continuity between adjacent beams and to eliminate the potential of reflective cracks, both shapes have shear keys and continuity reinforcement in the transverse direction. The new beam has a high span-to-depth ratio, ranging between 30 and 40, in comparison to an I-beam system, which makes it suitable for low clearance sites. It can cover a large surface area with fewer beams than the adjacent AASHTO box beams, reducing erection time and cost. The new beam also produces an aesthetically pleasing closed superstructure soffit.