Evaluation of minimum flexural reinforcement for precast prestressed concrete NEXT beam bridges.

This article focuses on evaluating the minimum flexural reinforcement requirements for bridges constructed with the newly developed northeast extreme tee (NEXT) precast/prestressed concrete beams, as specified in the AASHTO LRFD Bridge Design Specifications. Through an analytical parametric study of 48 NEXT beam bridges varying in beam width (8 ft and 12 ft), beam depth, concrete strength (6, 8, and 10 ksi), and span length, the study found that all examined bridges met the minimum reinforcement criteria, with the ratio of factored flexural resistance (Mr) to cracking moment (Mcr) exceeding the required threshold of 1.2. Results indicated that bridges with 8 ft wide NEXT beams generally exhibited higher Mr/Mcr ratios than those with 12 ft wide beams, and that higher concrete strength and longer spans increased this safety margin. The study suggests that 12 ft wide NEXT beams may be less suitable for short-span bridges with concrete strengths below 8 ksi, providing practical insights for bridge engineers in the design of NEXT beam bridges.