Vibrations of building elements and spectra of main modes

Vibration measurements inside buildings and structures are performed to assess the occurrence of resonant vibrations of parts of the structure under the influence of external influences.
Three-component displacement sensors (geophones) or accelerometers installed in different parts of buildings are used for measurements. The dominant frequencies of the vibration spectra recorded during shock, periodic impacts, or transport noises are compared with the calculated resonant frequencies of the structures.

Oscillations of soil foundations under the influence of road transport

Transport noises are the most common type of vibration. The spectral composition of vertical and horizontal oscillation components in the soil massif varies significantly during the passage of waves from road transport.
The spectra of horizontal components are substantially enriched by low frequencies, the most dangerous for the foundations of structures. However, the amplitude of displacements in horizontal components is usually several times lower than the vertical component.

The vibrations in the ground from the railway transport

The spectrum of vibrations from passing freight and electric passenger trains in comparison with the spectrum of vibrations from the highway significantly shifted towards low frequencies. The most dominant frequencies are in the band from 6 to 40 Hz. The enrichment of the spectra of horizontal components with low and ultra-low frequencies (from decimal parts of Hz up to 3-4 Hz) is also noted.
Several distinct narrow modes are distinguished on the spectra due, apparently, to the peculiarities of the structure of the railway track and the passage of the wheels at the joints of rails.
The greatest intensity of vibrations is observed during braking and acceleration of the trains.