Experimental and Numerical Investigation on Flexural Behaviors of a 30 m Full-Scale Prestressed UHPC-NC Composite Box Girder

Ultra-high-performance concrete (UHPC) exhibits significantly superior compressive and tensile properties compared to conventional concrete, demonstrating substantial application potential in bridge engineering. This study conducted full-scale bending tests on a 30 m prestressed UHPC-NC composite box girder within an actual engineering context. The testing flexural capacity Mt=34,469.2 kN·m exceeded the design requirement Md=18,138.0 kN·m, with Mt/Md=1.90. Finite element modeling (FEM) was employed to analyze and predict experimental outcomes, revealing a simulated flexural capacity of approximately 37,597.1 kN·m. The finite element models further explored failure mode transitions governed by the loading position while the concentrated load-to-support distance exceeds 9.62 m (shear span to effective depth ratio λ = 6.3), and the box girder fails in flexure; while less than 9.62 m, the box girder fails in shear. The flexural capacity of the test girder was also estimated using Response-2000 software and the recommended formulas from the Chinese code T/CCES 27-2021 (Technical specification for ultra-high-performance concrete girder bridge). The Response-2000 software yielded a flexural capacity estimate of Mr=30,816.1 kN·m. The technical specification provided two estimating results: (with safety factors) Mu1=25,414.4 kN·m and (without safety factors) Mu2=33,810.9 kN·m. All estimated values of Response-2000 and Chinese code were rationally conservative (Mr, Mu1, Mu2<Mt). Comparative analysis demonstrates that Abaqus FEM accurately simulates the flexural behavior of the prestressed UHPC-NC composite box girders. Both Response-2000 calculations and the Chinese code T/CCES 27-2021 provide critical references for similar applications of prestressed UHPC-NC composite box girders.