Experimental and numerical investigations on the mechanical behavior of reinforced concrete arches strengthened with UHPC subjected to asymmetric load

Ultra-high Performance Concrete (UHPC) has been widely applied for strengthening old and dangerous bridges. Related theory and design methods have been intensively studied. However, the influence of pre-damage on the UHPC reinforcement structures remains unclear. This paper investigates the mechanical behavior of pre damaged reinforced concrete (RC) arch strengthened with UHPC, considering two reinforcement positions (arch extrados and arch intrados) and various pre-damage levels. Comprehensive and comparative analyses of experiments, calculations and finite element methods (FEM) of the RC and UHPC arches are carried out to verify the numerical model. The pre-damage levels are defined according to the formation of hinges in the RC arch. A traction-separation model is used to simulate the bond behavior between the UHPC layer and the RC arch. Load deflection curves, failure modes and reinforcement efficiency of the strengthened arches are obtained. Results indicate that the concrete damaged plasticity (CDP) can well reflect the crack patterns of the RC and UHPC arch. The bearing capacity and ductility of arch intrados strengthened with UHPC are respectively increased by 85.25% and 84.76%. Strengthening at arch extrados or intrados can prevent the formation of hinges in different regions. Moreover, interfacial debonding both appears at arch extrados or intrados. Strengthening at arch extrados is demonstrated to be the most efficient method for strengthening heavily damaged RC arch. This research can provide a reference for the further applications of UHPC in strengthening arch bridges.