To counter resonance effects on bridges and buildings, engineers build them in such a way as to reduce the amplitude of resonance. Bridge designers make bridges more streamlined so that the wind passes over without imparting much energy. Damping reduces the effect of resonance.

Key terms

• Forced oscillation: oscillation in which external driving force is applied.
• Resonance : a phenomenon that takes place when the natural frequency of oscillation matches with the frequency of driving force.
• Resonance frequency: the frequency at which resonance happens

Skyscraper designers employ many strategies to lessen resonant vib-ration. One very effective approach is to use a large mass at the top of the building, called a “tuned mass damper,” which is free to oscillate back and forth (Figure 55). Controlled by computers, it can be made to vibrate at the resonant frequency of the building.