16.7. Seismic Excitation in MDOF Systems

Try these first

1. 1.

   What is the influence vector?

   Hint

   Think about how the ground motion can be represented mathematically.

2. 2.

   What is seismic excitation?

   Hint

   What do we observe in buildings during an earthquake?

3. 3.

   What does the influence vector usually consist of during uniform ground motion?

   • Zeroes
   • Ones
   • Random numbers

   Hint

   Think about how ground motion affects each mass point.

4. 4.

   True or False: Modal analysis allows you to analyze all modes simultaneously without uncoupling them.

   • True
   • False

   Hint

   Consider how modes are separated in dynamic analysis.

5. 5.

   Given a 5-story building with a mass matrix [M] made up of 1000 kg for each story, and a stiffness matrix [K] summed as 2000 N/m per story, derive the influence vector if subjected to a uniform ground acceleration of 0.5 m/s².

   Hint

   Consider how masses and stiffness relate to seismic forces.

6. 6.

   Discuss the impact of ignoring damping in the analysis of seismic response for an MDOF structure.

   Hint

   Reflect on how damping naturally limits responses to dynamic forces.