Slide 18 of 24
- Seismic forces accumulate downward in a building
- Seismic forces in the building are greatest at the base of the building.
- The seismic force at base of the building is called the base shear.
- Earthquakes often damage buildings at this level
- The figure shows base shear damage in a building
- Weight of the building above the cracking is the shear force that broke the building
- Typically earthquake damage occurs at base of building
- For buildings with cripple walls, the weakest part of the building must resist the greatest force.
- This is why retrofit standards require strengthening of the cripple walls.