Flexural behavior of the hollow slab girders strengthened with ultra-high performance concrete: Field full-scale experiment and analysis

Due to high strength and well durability, ultra-high performance concrete (UHPC) can be designed to strengthen damage hollow slab girder. The main objective of this study is to evaluate reinforcement feasibility of compression zone of hollow slab girder via field full-scale experiments and finite element (FE) analysis. To this end, UHPC layer was firstly proposed to reinforce top plate of damaged hollow slab girder. Then, four -point bending tests were conducted to investigate flexural behavior of hollow slab girder with/without UHPC layer. FE models were developed to simulate bending failure process of hollow slab girders. The deflection, crack propagation and stress distribution of hollow slab girders were analyzed as well as failure modes. The results show that UHPC layers can significantly improve flexural stiffness of hollow slab girder, and it results in an increase of 11.5% in cracking load and 23.7% in ultimate load, respectively. Moreover, reinforced girder exhibits well ductility and relatively high flexural bearing capacity. Furthermore, the parameter analyses were performed to investigate the effects of the thickness of UHPC layer and prestress on flexural behavior of reinforced girder. The results show that the prestress significantly affects the ductility and cracking load. Whereas, it seems to be independence of ultimate load. Finally, theoretical analysis was performed to obtain calculation formulas, which determine cracking and ultimate loads of reinforced hollow slab girder. Overall, this study has verified effectiveness of proposed reinforcement method in improving stiffness and flexural bearing capacity of hollow slab girder.