The Structural Design Considerations for the Long-Period Ground Motions in Taiwan
Structural responses are affected by the hypocenter mechanism, the wave propagation route, the site specific magnifying effect of ground motion, the soil-structure interaction effect, and the vibration response of the structure. Until now, the seismic code of most countries considered only vertical soil profile for the design acceleration spectrum. The factors regarding hypocenter mechanism, wave propagation route are not considered in the design spectral acceleration. However, the responses of high-rise buildings were significantly affected by long-period ground motions based on the observation of 2011 Tohoku Earthquake. The effects of long-period ground motions being affected by the hypocenter mechanism and wave propagation route has seldom been taken into account by the current seismic codes worldwide. Previously, the acceleration response spectrum specified in the Taiwan Seismic Code usually followed Japanese and American codes. After the magnitude 6.8 Haulian Earthquake in November 15th, 1986, the design seismic loads were modified for resonance effects of the Taipei Basin. The design characteristic period was changed and became greater than the Chinese and Japanese codes. From the observation results of the 921 Chi-Chi Earthquake, the basin area and the coastal area of alluvial plain are sensitive to the long-period ground motions. Some areas will be magnified at the period of 4-5 seconds. These long-period ground motions will significantly impact the high-rise buildings and the isolated buildings.
This study is based on the strong ground motion data gathered from 921 Chi-Chi Earthquake in 1999. Firstly, the factors caused by the long-period ground motion in the basin and alluvial plain of Taiwan were discussed. Secondly, the seismic hazard analyses between different countries were compared. The differences of the design response spectrum between different codes are also explained. Finally, the impact caused by the long-period ground motions to the structural design and the design considerations are elaborated.
This study is based on the strong ground motion data gathered from 921 Chi-Chi Earthquake in 1999. Firstly, the factors caused by the long-period ground motion in the basin and alluvial plain of Taiwan were discussed. Secondly, the seismic hazard analyses between different countries were compared. The differences of the design response spectrum between different codes are also explained. Finally, the impact caused by the long-period ground motions to the structural design and the design considerations are elaborated.