Semi-analytical solution for elastoplastic deflection of prismatic fixed-end beams with circular cross-section

Prismatic fixed-end beams with circular cross-section are often used in engineering. Therefore, there is a need for a solution of an elastoplastic deflection of prismatic fixed-end beams with circular cross-section loaded by lateral displacement at one end of the beam, which is suitable for practical use. The elastoplastic deflection beam theory does not provide a solution in a closed form for such a problem. Hence, a semi-analytical solution is proposed in this paper. Homogenous and isotropic beams with the bilinear elastoplastic strain hardening behaviour are covered in the proposed solution. The elastic deflection of a beam is determined by the Bernoulli–Euler formula. However, differential equation of beam bending in the plastic domain of material behaviour does not have a solution in a closed form. Therefore, an incremental procedure for determining the curvature of the plasticised region of the beam is suggested. The proposed semi-analytical solution is validated by comparing to the finite element analysis results of 16 different fixed-end beam models with varying geometric and material characteristics. Also, validation is done with experimental results of the bar damper device, available in the literature, which has been selected as a sample of a real engineering system where the proposed solution can be applied. A satisfying agreement between the proposed semi-analytical results and the subsequent numerical and experimental results is herein achieved, confirming the solution’s reliability. Finally, a parametric study is conducted using the proposed semi-analytical solution in order to determine the influence of geometrical parameters and material characteristics on the mechanical properties of prismatic fixed-end beams with circular cross-section loaded by lateral displacement at one end of the beam.