Behaviour of superficial foundations of a building under dynamic excitation

The survey led in the setting of this work permitted to make an analysis on the behaviour of the superficial foundations submitted to a dynamic excitation at the basis of the soil profile (bedrock). We are interested, mainly, by the horizontal displacements of the continuous foundations. The superstructure has not been taken in the simulation model. The behaviour of the foundations in terms of displacements differs when one passes from two to four lines of footings. The frequency content of the accelerograms used plays an important role in the footings displacements. The substratum being situated at 25m depth, the displacements in surface of soil are practically identical to those of the substratum. The accelerations, as for them, are amplified through the layers of soil.
An earthquake can be simulated while using a coefficient of acceleration Kh of the site. We used a harmonic function for the horizontal loading.

We established a calculation of reference by finite elements model for a given project. This calculation of reference is a reasonable approximation of the reality. One made varied individually; the magnitude (represented by the Kh coefficient) then the frequency, of the dynamic excitation, and to study their influence on the behaviour of the foundations.

The increase of Kh (magnitude of the earthquake) influences in an explicit manner the behaviour of the superficial foundations. The frequency of the harmonic loading influences inversely the horizontal displacements of the superficial footings.