Compression behavior of concrete confined by FRP- ECC composites layers: Experiments and modeling

초록

Fiber-reinforced composite (FRP)-engineered cementitious composite (ECC) composite layers are widely used to strengthen concrete structures. This reinforcement method is a passive constraint, and the reinforcement effect is significantly affected by the ductility and stiffness of the composite layer. However, its influencing mechanism is still unclear. This paper prepares composite layers with ECC and different FRP meshes and uses them to confine concrete columns. Through compression experiments, the influence of composite layer ductility, stiffness and matrix type on the compressive performance of confined concrete columns is analyzed, hoping to reveal the compression characteristics and failure mechanism of composite layer reinforced concrete. Referring to the existing stress-strain model of FRP-confined concrete with large fracture strain and considering the strength contribution of the constraining layer, a design-oriented model suitable for FRP-ECC composite layer-confined concrete is established to provide a reference for the reinforcement application of FRP-ECC composite layer. The results show that increasing the ductility and stiffness of the constraining layer can disperse concrete cracks and provide greater confining pressure, respectively, thereby improving the reinforcement efficiency. Compared with unconfined concrete, the strength of concrete confined by FRP-ECC can be increased by up to 80 % and the ductility can be increased by 90 %, which shows the effectiveness of FRPM-ECC confinement. Since ECC has excellent crack dispersion ability, the hoop stress can be evenly and effectively transferred from the core concrete to the textile mesh, so that the FRP can play a confining role. The established bilinear linear model has good consistency with the experimental curve, and can provide theoretical guidance for the application of FRP-ECC composite layers.

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