The paper presents the theoretical analysis of a variable stiffness beam. The bending stiffness EI varies continuously along the length of the beam. Dynamic equation yields differential equation with variable coefficients based on the model of the Euler-Bernoulli beam. Then differential equation with variable coefficients becomes that with constant coefficients by variable substitution. At last,the study obtains the solution of dynamic equation. The cantilever beam is an object for analysis. When the flexural rigidity at free end is a constant and that at clamped end is varied,the dynamic characteristics are analyzed under several cases. The results demonstrate that the natural angular frequency reduces as the flexural rigidity reduces. When the rigidity of clamped end is higher than that of free end,low-level mode contributes the larger displacement response to the total response. On the contrary,the contribution of low-level mode is lesser than that of high-level mode.
