Response of a Column in Random Vibration Tests

Laboratory experiments were conducted to observe and measure the response amplitude and frequency of a simply supported column. The column was excited by axial forces generated from sinusoidal and random (bandwidths of 3 Hz, l0 Hz, 30 Hz, and l00 Hz) signals. The column will vibrate near its natural frequency if the excitation contains a sufficiently high level power spectral density within the parametric resonance zone of the column. The variance of the response amplitude decreases with increasing bandwidth of excitation. A zero amplitude of response is found during a considerable portion of the excitation time; this indicates there is a discrete component in the probability distribution at zero amplitude.