Application of the finite element method to the conservation of old foundations

The elastic plastic finite element analyses of two case histories are illustrated. They concern, re-spectively, the underpinning of the pier of an old bridge and the effects of the faulting process that could take place during a seismic event below an existing building. In both cases, the data are de-scribed first which were obtained from the in situ investigations carried out at the sites. Then the calculations are discussed showing that they lead to quite different conclusions in the two cases. For the first problem, in fact, the available geotechnical data were sufficient to calibrate the numerical model and led to a proper evaluation of the pier conditions. On the contrary, the soil data for the second problem were not sufficient to calibrate the strain softening material model necessary to analyse the faulting process. As a consequence, some uncertainties remain on the effects of the possible development of a fault in the soil underneath the foundation. To overcome them, the back analysis of in situ load tests is suggested and commented upon.