以921集集地震之建築物強震紀錄探討大樓高層震度的放大效應

Intensity Amplification of Seismic Excitation for 28 Buildings during the 1999 Chi-Chi Earthquake, Taiwan

本研究分析1999 年集集大地震中央氣象局28 棟建築物的強震紀錄，探討大樓高層震度的放大效應，並分析造成放大效應差異的原因。結果所得之建築物頂樓樓高放大倍率，水平方向平均值為3.12，標準差為1.22；垂直方向平均值為1.68，標準差為0.52。上述結果大於國內目前的規定，值得下次修訂法規時加以重視。此外，建立了樓高加速度放大係數對樓高及樓層數的關係式後，顯示出三個軸向加速度放大係數皆隨著樓高及樓層數增加而增加。另值得注意的是，樓高12 層的建築物（TAP4B）在週期1 秒左右有明顯的共振現象，而造成頂樓之短向與長向的加速度放大倍數高達7.31 與5.81 倍。若未考慮基本週期之共振效應，超高層建築物因位於軟弱地盤，會比低層建築物或中高層建築物有較高的加速度放大倍率。本研究結果，有助於設計者對建築內設備物於大地震下的震動特性，有進一步的瞭解，並可提供氣象局作為往後建立高樓震度發布的參考。

Strong seismic data obtained by the Taiwan Strong Motion Instrumentation Program (TSMIP) are used to derive new relationships for peak floor acceleration and floor height and floor number of building. A total of 28 sets building array each with 30-channel accelerograms recorded from the 1999 Chi-Chi earthquake, Taiwan have been analyzed to study the acceleration amplification of seismic excitation on the roof storey of buildings. The results show the amplification factors are 3.12 with one standard deviation of 1.22 and 1.68 with one standard deviation of 0.52 in the horizontal and vertical component, respectively, greater than the building code values. We further found that, for both horizontal and vertical component, the amplification factor increase with the floor height and floor number increase. In addition, it is notable that the amplification factor of building TAP4B of a 12-story building reaches the significantly high values of 7.31 and 5.81 in the lateral and longitudinal axis, respectively, due to the resonance of seismic excitation.