(3) Vibration Generator Test
In the case of actual buildings, a vibration generator is often used to apply harmonic
external forces. A vibration generator is usually set up on the top of the target structure as
shown in Fig. 2. A simple vibration generator consists of two sets of weights rotating in the
opposite directions mutually. Consequently, the force in the X-direction is canceled and the
cyclic force is generated in the Y-direction. The rotating speed is changed step by step and
steady-state response at each step is measured. Finally the vibration generator test brings the
resonance curve of the target structure.
The harmonic force generated by the equipment shown in Fig. 2 is given by the
following equation: