Identification of the Vistula Mounting tower model using measured modal data

This paper discusses the problem of parametric identification of a historic masonry tower model. The tower tends to lean and its foundation stiffness is a concern to authorities. The authors identified a few modal characteristics of the tower, natural frequencies and mode shapes. Based on the first mode shape identified it is known that the structure behaves like a stiff solid on elastic foundation. Thus, a simple, five parameter plane model is taken into consideration. The unknown parameters are identified to be the solution to an optimisation problem, which involves using the sensitivity analysis and scatters of the modal identification. A hierarchical process is formulated, where two natural frequencies are assumed to be the input data. In this approach, the number of unknown parameters increases incrementally, and the process changes from even-posed to under-posed successively. Such approach allows one to control the final under-posed identification problem and leads to an increasingly better solution.