VIBRATION CHARACTERISTICS OF HIGH-RISE STEEL BUILDING IN SHINJUKU SKYSCRAPER DISTRICT BEFORE AND AFTER THE 2011 OFF THE PACIFIC COAST OF TOHOKU EARTHQUAKE

Abstract

This paper presents and analyzes the identified vibration characteristics of steel high-rise building built at Shinjuku. The vibration characteristics, i.e.; natural periods, damping coefficients and participation functions, are identified from the measured acceleration during some earthquakes including the mainshock of the 2011 off the Pacific coast of Tohoku Earthquake. The curve-fitting method using the transfer function is applied in the identification. The change in natural period before and after the earthquake and the dependency on the modal amplitude are clear. The damping coefficients for the 1st and 2nd modes are found to be unexpectedly smaller than 0.02, that has been conventionally assumed in design of steel buildings.