The ground and the building influence each other

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Unformatted text preview: d transmitting them to the ground. The ground and the building influence each other through the foundation, and this is called the Dynamic Soil-Structure Interaction (hereafter abbreviated to SSI) 2) Degree of Influence of SSI on Response of Building depends on: (a) Stiffness of Ground (b) Dynamic Characteristics of Building itself, that is, Natural Period, Damping Factor (c) Foundation Types 3) Foundation Type (a) Spread Foundation (b) Pile Foundation without Basement (c) Basement without pile (d) Basement with piles The position where the SSI takes place. (a) Spread Foundation: through the bottom surface of the foundation (b) Pile Foundation without Basement: through the pile foundation (c) Basement without pile: not only at the bottom surface, but also on the side wall surface (d) Basement with piles: through the basement surface and the piles The influence of the SSI becomes remarkable and more complicated, as the amount of contact area between the ground and the foundation increases sequentially in the order from (a) to (d). 4) Interaction between Ground and Building during Earthquake Top F1 F2 E1 Building Foundation G.L F0 R1: Radiation Wave E0 : Seismic Wave Soil Earthquake Fault When the seismic wave EO generated by the earthquake fault reaches the bottom of the foundation, they are divided into two types: the waves E1 entering into the building and the waves FO being reflected back into the ground. The wave E1 are called the transmission waves, while the wave FO are called the reflection waves. And then, they are reflected at the top and travel back down to the foundation. Here, a crucial phenomenon occurs for consideration of the SSI. Top F1 F2 E1 Building Foundation G.L F0 R1: Radiation Wave E0 : Seismic Wave Soil Earthquake Fault The transmission waves E1 entering into the building travel towards the top of the building with subjecting the building to vibration. When the waves that are reflected at the top of the building and traveling downwards (F1 in this figure) reach the foundation, a part of them is transmitted into the ground, while the rest is reflected back again and once starts to move upwards through the building. The former waves, escaping into the ground, are called “ Radiation waves”. Top F1 F2 E1 Building Foundation G.L F0 R1: Radiation Wave E0 : Seismic Wave Soil Earthquake Fault When the amount of these radiation waves are small, the seismic waves once transmitted into the building continue to remain in the building, and the building continues to vibrate for a long time. The apparent vibration condition becomes the same that of the small damping of the bui...
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