Post on 23-Feb-2016
description
RESONANCE & DAMPING
SPH 3U
Resonance & Damping Think of life on the swings:
How do you go faster?
How do you slow down?
Resonance & Damping Swings are examples of resonance and
damping
Damping: a reduction in the amplitude of a wave as a result of energy absorption or destructive interference
The amplitude is minimized
Resonance & Damping All things have a resonant frequency –
this is the ‘natural’ frequency
Resonance occurs when the frequency of the waves affecting the object are equal to the resonant frequency
The amplitude is increased
Waves & Structures Mechanical Resonance: When energy
transfers from one source to another with the same natural resonance
Aeroelastic Flutter: When more energy is added by vibrations then can be lost by natural damping
Often caused by wind interacting with the aerodynamics of an object
Waves & Structures
Tacoma Narrows Bridge
Waves & Structures Structures are susceptible to wind and
earthquakes
Narrow streets increase wind speed
Wind can cause buildings to sway up to 1 m; earthquakes can cause buildings to exceed this
Waves & Structures Before WWII, tall buildings were
constructed with thick concrete walls, with steel bars
The concrete resisted compression, but was not flexible
The steel bars added some flexibility
Waves & Structures After WWII, tall
buildings were constructed using girders these are better able to withstand waves
The walls were not for support, but merely weather-proofing
Waves & Structures Earthquake Dampers
Taipei Mass Damper
Discovery Taipei 101 (3/5)