Abstract
This paper describes the dynamic characteristics based on microtremor measurement data concerning a middle rise steel building. The object building which was completed in March 2004 is 44 m height and rectangular plan. Microtremor measurement is periodically continued in the building. The acceleration of measurement data in two horizontal directions and torsional direction are analyzed for natural frequencies and damping ratios on 1st mode to 3rd mode. The changes along passages and the dispersions of those dynamic characteristics in microtremor are studied. And the relations between vibration amplitude and damping ratios in free vibration waves employing manpower excitation, large vibration waves in strong wind and severe vibration waves during earthquakes are discussed.
