Abstract:
A geometrically exact beam element suitable for dual nonlinear analysis is developed based on the BFGS update method of second kind. The high order Hermite function and Lagrange function are adopted to approximate the displacement field of Euler-Bernoulli beam element and Timoshenko beam element. The nonlinear sectional behavior without shear deformation, with shear deformation but not considering shear effect of stirrup, with shear deformation and shear effect of stirrup was studied. The first-order variation and the second-order variation of the sectional deformation of Euler-Bernoulli beam element and Timoshenko beam element are deduced based on the geometrically exact beam theory, and the finite element procedure is presented based on the two-level consistent secant operator. The beam element developed based on UEL interface of software ABAQUS is employed to conduct the geometrical nonlinear analysis of elastic cantilever beam, and material nonlinear and dual nonlinear analysis of reinforced concrete beam column components. The proposed beam element is suitable for large deformation and rotation analysis. The Timoshenko beam element considering the shear effect of stirrup has good applicability to analysis the nonlinear behavior of reinforced concrete columns with different failure modes. The BFGS update method of second kind has better numerical stability than that of BFGS update method of first kind.