MODAL ANALYSIS OF FRICTION BASED-ISOLATED STRUCTURES

In friction pendulum isolation systems the structure is decoupled through a special teflon layer from its foundation. Because of the special geometrical form of the set, i.e. concavity of the base plate, a recentering force is induced in the system which leads to restricted permanent displacements after severe shakings. By the applying classical modal analysis to such a non-linear problem between different possible phase changes, i.e. all possible combination of sticking and sliding phases, and also using an adaptive time incrementation algorithm it is possible to simulate the behavior of such complex sets. Considering just the first few modes of vibration guarantees the desired accuracy and reduces the numerical costs of such a simulation drastically.