Flexural behavior analysis of U-shaped UHPC and recycled aggregate concrete composite beams
The precast technology is used to compound ultra-high performance concrete(UHPC)around the recycled aggregate concrete(RAC)to form a U-shaped UHPC-RAC composite cross section beam to improve the mechanical properties.The U-shaped UHPC-RAC composite beams are designed with the reinforcement ratio in U-shaped UHPC.The four-point flexural performance test is carried out to analyze the fracture morphology and failure mechanism,the strain of the UHPC and the reinforcements and load-displacement curves.The results show that the beams with reinforced composite section have small width,uniform distribution and small spacing of bending cracks,forming 1-2 cracks with the largest width as failure showing ductile failure finally.The U-shaped UHPC shell can significantly increase the cracking load by 72.1％,and the reinforcement ratio can increase the yield load and ultimate load by 25.4％and 35.7％,which improve the initial stiffness,ductility and energy dissipation coefficient of the recycled concrete beam.RAC,UHPC and reinforcement in the composite section work collaboratively,and the strain change linearly,which conforms to the assumption of plain section.According to the superposition principle,the stress distribution curve is simplified and the calculation formula of flexural bearing capacity of U-shaped UHPC-RAC composite cross section beam is established.The calculated results are in good agreement with the experimental values.
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