6.6.1. Free Body Diagram Analysis

Try these first

1. 1.

   What is a free body diagram?

   Hint

   Think about visualizing forces.

2. 2.

   What does base excitation refer to?

   Hint

   Remember earthquakes and their effects.

3. 3.

   What does the right-hand side of the equation mu¨(t) + cu˙(t) + ku(t) = -mu¨g(t) represent?

   • Applied force
   • Pseudo-force due to ground motion
   • Restoring force

   Hint

   Think about forces that affect the mass due to ground shaking.

4. 4.

   True or False: The mass's inertia is irrelevant in the analysis of structures under earthquakes.

   • True
   • False

   Hint

   Consider how an object behaves when moving.

5. 5.

   Consider a system where a mass is subjected to ground motion. Analyze how modifying the stiffness of the system changes its response to seismic loads.

   Hint

   Think about the relationship between stiffness and response frequency.

6. 6.

   Sketch a free body diagram for a mass experiencing both gravitational and inertial forces during ground motion. Indicate all forces acting on the mass.

   Hint

   Remember to draw arrows to signify the direction and magnitude of each force.