A response spectrum is a diagram giving the response of a structure forced into motion in function of its natural frequency. The response can be given in terms of displacement, velocity or acceleration,

The acceleration response spectrum is a very useful tool for the seismic design of structures.

Normally the acceleration response spectrum is given by the relevant seismic codes and provides to the designer all the useful information allowing designing the structure.

In the response spectrum in particular are given the information about the intensity of the earthquake and the effect of the soil properties

In the following figures are shown as an example the response spectra given by the European standard in function of the damping.

Looking at the typical feature of a response spectrum it appears quite evident which strategy shall be used to reduce the seismic action in a structure:

  • Increase the natural period
  • Increase the damping, or the energy dissipation

Sliding pendulum isolators apply a combination of the 2 strategies

Base isolation
Base isolation