Earthquake & vibration calculation

When the subsoil is shaken, e.g. by earthquakes, earthworks or machine vibrations, waves propagate throughout the subsoil, acting on buildings and being reflected and refracted by them. This mutual influence of soil and building is called soil-structure interaction (SSI).

Where is the SSI needed?

  • Earthquake verification of dams
  • Verification of nuclear power plants, their components and pipe systems for earthquakes
  • Propagation calculation of vibrations, e.g. as a result of pile-driving work

Our tool - ACS SaSSI

In the field of soil-structure interaction, ACS SaSSI is currently the leading software package from Ghiocel Predictive Technologies Inc.

Generation of spectrum-compatible time histories

Earthquake loads are given for a location in the form of free-field excitations. Time histories are required for the SSI calculation. These can either be generated artificially or derived from real earthquake events.

SSI calculation model

  • Building model with the most important fixtures and soil near-zone (HOUSE)
  • Soil layer model of the upper soil layers and the infinite half-space (LAYER)

House model

Modeling of the building and possibly the near-ground area. The level of detail of the FE model for the SSI calculation significantly determines the calculation time. Subsequent transfer of the calculation model and the boundary conditions from the SSI to ANSYS with the option of model refinement and stress evaluation.

Soil layer model

Soil parameters per soil layer up to the half-space:

  • Layer thickness
  • Weight
  • S-wave velocity
  • P-wave velocity
  • Attenuations

Iteration of the dynamic soil properties:

  • Shear modulus
  • Damping

SSI calculation


SV waves in X direction

SH waves in Y direction

P-waves in Z-direction


Frequency-dependent stiffness (impedance)


Mass and stiffness matrix


SSI calculation


  • Output of the accelerations
  • Paths and voltages

Spectrum processing

  • RSS superposition of the responses in each spatial direction due to the excitations of the individual spatial directions
  • Averaging of the spectra from the excitation with different time histories
  • Capping of peaks
  • Broadening of the spectra
  • Enveloping the calculations of different ground models