5.12. Concept of Modal Mass and Modal Stiffness

Try these first

1. 1.

   Define modal mass in the context of structural dynamics.

   Hint

   Focus on its role in dynamic analysis.

2. 2.

   What is modal stiffness?

   Hint

   Connect its definition to modal mass and frequency.

3. 3.

   What does modal mass represent?

   • The total mass of the structure
   • Mass associated with a specific mode
   • The weight of the foundation

   Hint

   Think about the participation of mass in vibration.

4. 4.

   True or False: Modal stiffness is independent of circular frequency.

   • True
   • False

   Hint

   Review how stiffness is defined.

5. 5.

   A structure has a mass of 200 kg and its first mode frequency is 10 rad/s. Calculate the modal stiffness and explain its significance.

   Hint

   Focus on how frequency plays into the stiffness equation.

6. 6.

   In a multi-story building, if the modal mass of the first mode is 150 tons and the modal stiffness is calculated to be 2500 kN/m, discuss how these values impact the building's seismic design.

   Hint

   Consider how higher modal mass might affect design criteria.