Shaking Table Test on Effects of Combination of Soil and Building Properties on Seismic Response of Building

To clarify seismic force to buildings and foundations, an effect of dynamic soil and structure interaction is very important. The seismic force to buildings and foundations is influenced by characteristics of both soil deposits and buildings. To investigate the effects of vibration of soil deposits and buildings, a scaled model of building, foundation, and soil deposit is set up on a shaking table. Through analyzing difference between response of foundation without buildings, and surface grounds under the steady state excitation, the horizontal response of foundation is less that of ground surface. This tendency is large with frequency. As one of parameters, there are three kinds of buildings that are 8, 11 and 15 stories models. Under combinations of soil deposits and building properties, seismic forces are compared. The building response is very large when a resonant frequency of building is near to that of soil deposit. The bending moment of piles are affected by not only a base shear of buildings but a displacement of surface ground

Response of a tall building far from the epicenter of the 11 March 2011 M9.0 Great East Japan earthquake and aftershocks

The 11 March 2011M 9.0 Great East Japan earthquake generated significant long-duration shaking that propagated hundreds of kilometers from the epicenter and affected urban areas throughout much of Honshu. Recorded responses of a tall building at 770 km from the epicenter of the mainshock and other related or unrelated events show how structures sensitive to long-period motions can be affected by distant sources. Even when the largest peak input motions to the building is about 3% g, the strong-shaking duration was about 140 s. The 300- to 1000-s prolonged responses of the building are primarily due to a combination of site resonance (e.g. structural fundamental frequency ~0.15 Hz and site frequency ~0.13–0.17 Hz) and low damping (~1–2%) of the structure. Response modification technologies can improve the response of the building during future earthquakes. The need-to-consider risks to such built environments from distant sources are emphasized