14. Natural Frequencies

Try these first

1. 1.

   Define natural frequency.

   Hint

   It relates to how a structure would vibrate naturally.

2. 2.

   What happens in free vibration?

   Hint

   Think about what happens when you pluck a string.

3. 3.

   What is natural frequency?

   • Frequency of external forces
   • Frequency at which a system oscillates naturally
   • Frequency of forced vibrations

   Hint

   Think of it as the frequency the structure prefers.

4. 4.

   True or False: Damped systems exhibit continuous vibrations indefinitely.

   • True
   • False

   Hint

   Remember what damping does to energy over time.

5. 5.

   A building has a mass of 2000 kg and a stiffness of 80000 N/m. Calculate its natural frequency.

   Hint

   Apply the formula step by step, starting with stiff and mass values.

6. 6.

   Discuss the impacts of resonance during the 1985 Mexico City earthquake with respect to natural frequencies.

   Hint

   Think about the relationship between building designs and the characteristics of the earthquake.