Mechanical responses of high-performance concrete beam reinforced with CFRP/GFRP tendons based on nonlinear shell beam mixed element

For high-performance concrete (HPC) beams reinforced with hybrid Carbon Fiber Reinforced Polymer/Glass Fiber Reinforced Polymer (CFRP/GFRP) tendons, the nonlinear shell beam mixed element is studied and the whole mechanical process is analyzed. The CFRP/CFRP tendons are simulated with spatial beam element and the HPC beam is modeled with the layered shell element. With the coordination of nodal linear displacement and rotational displacement of CFRP/GFRP tendons element, the contribution of CFRP/GFRP element to stiffness matrix of nonlinear shell beam mixed element is deduced. Then, Jiang’s yielding criterion, Hinton’s crushing criterion, and so on, are used to describe the material nonlinearity of concrete. The new kind of nonlinear shell beam mixed element is achieved and the three-dimensional nonlinear calculation program is developed. The calculative results are consistent with the development trend of test results, which shows the correctness of the nonlinear shell beam mixed element and the reliability of the development program. The mixed element can accurately simulate the geometric configuration of CFRP tendons and realize the tension-compression-bending-shearing performance of CFRP tendons, which is helpful to fully reflect the reinforcement effect of reinforcement in the structure. The computational stiffness is defined and the stiffness degradation experiences three change processes. During the whole processes in the proposed typical load cases, the CFRP/GFRP tendons are still kept in the elastic stages.