Module 19
Structural control
Passive, semi-active and active control at an accessible level, with tuned mass dampers given the strongest practical treatment; sensors, actuators, feedback, robustness and fail-safe behaviour.
What this module covers
- Explain how a tuned mass damper works and why one resonance becomes two
- Apply Den Hartog's optimum tuning and say what it optimises
- Quantify the effect of mistuning and explain why it is the practical limit
- Distinguish passive, semi-active and active control by what supplies the force
- State what an active system needs and how it must fail
- Say when a TMD is the right device and when it is not
Lessons
A second mass that moves out of phase, the tuning that makes it work, and the mistuning that undoes it.
Start lesson →What supplies the force, what each needs to work, and why fail-safe behaviour decides which is buildable.
Start lesson →
Module checkpoint
Check what you have taken in
4 questions
Question 1
A tuned mass damper has a mass ratio of 3%. What is Den Hartog's optimum tuning ratio?
Question 2
For the same 3% mass ratio, what is the optimum damper damping ratio?
Question 3
With a 3% mass ratio at the optimum, what peak magnification does the undamped theory predict?
Question 4
A structure's safety in the design earthquake would depend on an active control system operating. Is that acceptable?