3.9.3. Base Shear and Force Distribution

Try these first

1. 1.

   Define base shear in seismic design.

   Hint

   Think about what happens to a structure during shaking.

2. 2.

   What does the seismic coefficient represent?

   Hint

   It relates to the dynamic behavior of structures.

3. 3.

   What does an increase in damping typically do to base shear values?

   • Increase base shear
   • Decrease base shear
   • No effect

   Hint

   Think about the relationship between damping and spectral acceleration.

4. 4.

   True or False: Base shear is only determined by the weight of the structure.

   • True
   • False

   Hint

   Consider what affects seismic forces.

5. 5.

   A new building weighs 2000 kN and has a damping ratio of 25%. Calculate the expected base shear if the seismic coefficient for its location is determined to be 0.12. What design strategies should you keep in mind to further reduce seismic forces?

   Hint

   Focus on the relationship between damping and seismic responses.

6. 6.

   If increasing the damping of a structure from 10% to 30% reduces its base shear from 300 kN to a new value, calculate the reduction in kN and percentage decrease in base shear.

   Hint

   Calculate both the actual kN reduction and then the percentage based on initial values.