Shear design of precast prestressed concrete NEXT beam bridges: A critical assessment

Abstract

Northeast extreme tee (NEXT) precast prestressed concrete beams have recently emerged as a promising solution to accelerate bridge construction and enhance the sustainability of bridges. To date, several studies on the live load distribution factor (LLDF) for moment and shear in NEXT F beam bridges have been reported, which indicated that using the AASHTO LRFD LLDF for moment in NEXT F beam bridges could provide a sufficient safety margin; however, a 20% increase in the LRFD LLDF for shear was recommended for the safety of shear design. This paper intended to investigate the required transverse shear reinforcements in NEXT F beam bridges by using a factor of 1.2 for the LRFD LLDF for shear. A comprehensive study was carried out by considering various parameters, including concrete strength, beam section, bridge section, and span length. Results from this study showed that providing the minimum transverse shear reinforcement could offer a sufficient safety margin for the shear design of NEXT F beam bridges, even with an increase of 20% on the LRFD LLDF for shear. It is recommended that a factor of 1.2 be used for the LRFD LLDF for shear to ensure a safe design of NEXT F beam bridges, though the minimum transverse reinforcements will be likely to control the shear design.