During the reconstruction period a mass of 6.8 kN/m² (overall 200 t) was added to the attic floor. The dynamic parameters (natural frequency, mode shapes) before and after the reconstruction were identified and compared.

Additionally numerical simulations were performed using the experimental data to update the model. In the second step the additional mass was added to the model (without increasing the structural stiffness) and the dynamic parameters were computed. The results of both investigations can be seen in Table 1.

As expected the experimentally derived natural frequencies of the building after the reconstructions were considerably higher than those from the numerical simulations.