NATURAL FREQUENCIES OF STRUCTURES FOR DESIGNERS.

The author describes how by separating a vibration problem into two distinct parts, one concerned only with the spring forces in the structure and the other only with the inertial forces imposed by the mass carried, easy calculations can be used to solve fairly complex structures. The method is based on the simple formula for the frequency of vibration of a mass hanging on a spring and shows that it is possible to reduce the difficulty of structural problems until mere hand calculations will give sufficiently accurate values for use in design. The method finds the lowest natural frequency, or the frequency of any other mode shape chosen by an engineer, including the cases of partial or sway vibrations.