Flexural behavior of embedded GFRP grid framework-UHPC composite plate without steel rebar

A novel embedded GFRP grid framework-UHPC composite plate without steel rebar was proposed to solve the problems of conventional reinforced concrete plate, such as heavy weight, easily cracking and poor durability. The composite plate is expected to be superior in mechanical mechanism and durability benefiting from the combination of UHPC and GFRP, and only minimal construction process was needed. The flexural properties of the novel composite plate, varying in centroid height of GFRP grid and loading shear span ratio, were investigated via four-point loading tests. The failure mode, load-deflection curve, sectional strain and ductility of the composite plate were analyzed. Experimental results showed that the flexural failure process of the composite plate could be divided into three stages: elastic stage, working stage with cracks and descent stage. The flexural failure of the composite plate was characterized by the tensile fracture of GFRP grid. The flexural bearing capacity and stiffness of the composite plate can be significantly improved, since the GRFP grid was more completely tensioned as the centroid of the embedded GFRP grid framework fell. The maximum bearing capacity of composite plates could reach 317.9 kN when the distance between GFRP grid and the plate bottom was 25 mm and the shear span ratio was 1.5. Shear failure was only observed in the composite plate with the distance between GFRP grid and the plate bottom of 0 mm and the shear span ratio of 1.5. Finite element (FE) models were established considering both geometric and material nonlinearities to further analyze the flexural failure mechanism of the composite plate. The reliable connection between GFRP grid and UHPC without additional shear connector was proved, and the numerical results coincided well with the experimental ones. Finally, the calculation method introducing the stress distribution non-uniformity coefficient of the GFRP grid plate was proposed to predict the flexural capacity of the composite plate.