Geometrically nonlinear Heterosis combined shell element of concrete beam with high performance composite rebar

In order to study the mechanical properties of concrete beam with high performance composite rebar (CFRP rebar) during the whole course, a geometrically nonlinear combined shell element analytical model of the beam with CFRP rebar was presented. The Von Karman theory was introduced and the Piola-Kirchhoff st ress matrix and geometrical stiffness matrix were deduced in the local coordinative system. The prest ressed CFRP rebar and the GFRP rebar were respectively modeled by the combined shell element and the layered shell element and then the cont ribution stiffness matrix of the prest ressed CFRP element to the combined shell element was completed.Based on Heterosis selecting integral technology, the shearing lock and the zero energy pattern were both avoided. The nonlinear analytical procedure was compiled, with which the computational results were obtained. The calculations including displacement variation regularity and strain variation regularity of CFRP rebar are in good agreement with those in the experiment results, which show the efficiency of the studied nonlinear element and the correctness of the finished nonlinear procedure. CFRP rebars are still in elastic status when the beam reaches the ultimate loads because of high strength property. The stiffness degraded regularity of the beam was studied by using the strain redistribution coefficient of CFRP rebar , and the result showes that in the final stage of adding loads, the stiffness degradation is decreased when the GFRP rebar substitutes the common steel.