Height / Weight Relationship

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Slide 11 of 24

Notes:

Height and weight
- The effects of earthquake forces on buildings are related to both the weight and height of the building.
- The higher the building’s weight is above its support base, the further the top of the building will move under the same earthquake force.
- Using the left side of the figure, imagine a one-story building with a height of 14 feet.
  - Inertia force of the earthquake moved the top of the building 1-inch (HD1).
  - If you put additional weight on that building, the top of the building will move more, for example 1-½ inches (HD2).
- Using the right side of the figure, imagine the same type of building that is two stories and 24 feet high.
  - The top of the building may now move 2 inches at the lighter building (HD3) and 3 inches at the heavier building (HD4).
  - The greater the height, and/or the greater the weight of a building, the more the building will move during an earthquake.
- This makes it clear why you need more plywood, more strength, on a 3-story house than a 1-story house.