Nonlinear beam-shell composite element of HPC beam mixed with CFRP/GFRP rebars

To study the mechanical performances of HPC beam mixed with CFRP/GFRP rebars during the whole course, a new three-dimensional nonlinear beam-shell composite element was derived. After the degraded shell element theory was introduced, the prestressed CFRP rebar was modeled by a spatial beam element and then based on the compatibility of displacements and rotations of the nodes of CFRP rebar element, the contribution in the stiffness matrix by the prestressed CFRP element to the beam-shell composite element was completed. The GFRP rebar and HPC beam were both modeled by the layered shell element. Combined with Jiang-yielding and Madrid-hardening criteria which were used to depict the material nonlinearity of concrete, a new nonlinear beam-shell composite element was put forward. The nonlinear analytical procedure was compiled. The calculations are in good agreements with experiment results, which shows the efficiency of the studied nonlinear beam-shell composite element and the reliability of the gained nonlinear procedure and the correctness of the adopted criteria of material nonlinearity of concrete. By the composite element, the configuration of CFRP rebar is precisely expressed and the performances such as tension, suppression, torsion and bending are comprehensively considered, which helps to synthetically embody the reinforcement of assembled rebars to the structure.