In this paper, a mathematical model of large amplitude vibration of a uniform cantilever beam arising in the structural engineering is proposed. Two efficient and easy mathematical techniques called variational iteration method and He's variational approach are used to solve the governing differential equation of motion. To assess the accuracy of solutions, we compare the results with the Runge-Kutta 4th order. An excellent agreement of the approximate frequencies and periodic solutions with the numerical results and published results has been demonstrated. The results show that both methods can be easily extended to other nonlinear oscillations and it can be predicted that both methods can be found widely applicable in engineering and physics. The Structural engineering theory is based upon physical laws and empirical knowledge of the structural performance of different landscapes and materials. Many engineering structures can be modelled as a slender, flexible cantilever beam carrying a lumped mass with rotary inertia at an intermediate point along its span; hence they experience large-amplitude vibration (Wu, 2003;Herisanu and Marinca, 2010;Cveticanin and Kovacic, 2007;Hamdan and Shabaneh, 1997;Hamdan and Dado, 1997).
Key wordsIn general, such problems are not amenable to exact treatment and approximate techniques must be resorted to. So, many new techniques have appeared in the open literature such as: variational iteration method (He, 2007a;Barari et al., 2011), homotopy perturbation method Saravi et al., 2013), homotopy analysis method (Liao, 2003;Khan et al., 2012)and some other methods Ghasempoor et al., 2102;Akbarzade and Khan, 2012;Alinia et al., 2011;Ganji, 2012;Torabi et al., 2012;