Spectrum Broadening

When a response spectrum is generated from a time history it can be have sharp peaks.  A response spectrum analysis may have modes which are just off these peaks and so the response may be underestimated.

Definition

Reference spectrum

The spectrum to be broadened

Broadening factor (Δf)

Each peak is smeared across bu the broadening factor to avoid unrealistic dips.

Overwrite reference / create new spectrum

The existing spectrum can be updated with the broadened spectrum or a new spectrum can be generated from the reference spectrum.