Abstract
This paper describes natural frequencies and damping ratios in a high-rise steel building. The object building which was completed in October 1998 is 120m height and rectangular plan. The microtremor has been measured periodically for more than 100 months since completion. The acceleration data and the velocity data in two horizontal directions and torsional direction are analyzed on 1st mode to 4th mode. It is studied the changes along passages of natural frequencies and damping ratios in microtremor and relation between amplitude and damping ratios in free vibration waves by manpower excitation.
