Structural repair of damaged old bell towers based on dynamic measurements

For structural repair, the measurement of the dynamic behaviour of the structural unit tower nave and its numerical simulation are an important basis. By identifying the numerical model on the basis of measured data and by subsequent parametric studies the best method of repair can be found. On the basis of measured results it will be decided whether the horizontal displacements of the tower are too big. It will also decided if the displacements have to be reduced by tuning the pendulum frequency of the bells in such a manner that the natural bending frequency of the tower does not coincide with the third harmonic of the pendulum frequencies of the bells or if the installation of counter pendulums is necessary. In case of cracks, the masonry of the tower has to be consolidated by cement injections and prestressed by steel bars in horizontal direction.