Transverse Post-tensioning Design of Precast Concrete Multibeam Deck

Precast concrete multibeam deck systems are widely used to replace deteriorated bridge decks. The system's rapid erection substantially reduces traffic disruptions. The transverse precompression force provided by the posttensioning tendons is an important design consideration to ensure adequate load transfer between contiguous beams and to reduce potential differential cracking at shear key joint locations. This paper presents an analysis method, based on grillage analogy, for calculating the required transverse posttensioning stress for a deck built with precast concrete multibeams. The effects of skew--as well as other influencing factors, such as deck width, thickness, and span length--on the required posttensioning stress were studied. Results of the study indicate that the effect of skew is significant when the skew angle is greater than 30 deg. Results compare well with the AASHTO's LRFD specifications for right-angle decks; however, the required posttensioning stress is decreased with an increase in skew angle.