The main purpose of this study is to analyze the natural frequencies of space frames using dynamic stiffness matrix method. The paper is going to present how to establish the dynamic stiffness matrix of the linear frame element bearing axial, torsion and bending in two planes on the basic of inertia to find the exact root of the dynamic balance equation using Euler - Bernoulli beam theory. Then, the matrix above was employed to establish the dynamic stiffness matrix of space frame elements and applied to analysis the natural frequencies of space frames. Comparing the analysis results of the dynamic stiffness method with those of the finite element method showed the accuracy of the dynamic stiffness method. The dynamic stiffness method gave accurate results as soon as the frame was viewed as a single element while the finite element method failed to perform the similar task.

Keywords: Dynamic stiffness matrix, natural frequencies, space frame, vibration