Modern Systems for Wind and Seismic Induced Vibrations

This contribution examines the application of modern systems for increasing damping in regard to protect structures against wind and seismic induced vibrations. The Tuned Mass Control System, presented as the first of two systems, consist of an additional mass, elastically connected to the main structure—in general quite similar to the well-known tuned mass systems that are applied at high rise structures against wind-induced effects. Dampers are installed in parallel to the elastic devices to widen the operating frequency band of the system and to reduce the relative displacements between mass and main structure. This passive seismic protection system yields a significant reduction of induced acceleration, displacement levels as well as internal stresses, support reactions and interstory drift. An important advantage is the possibility to use the inside of the building as there is no disturbance by the upgrade activities, if these systems are used as retrofitting systems. Corresponding project examples are presented and results of numerical investigations are described to verify the effectiveness of the mitigation measures. Just as these systems are suitable for new buildings and for existing structures, viscous wall dampers are also appropriate for both cases. They are using the shear resistance force of a highly viscous fluid. The devices consist of an outer steel dashpot, filled with liquid and an internal shearing piston. The extension of a two-story building by seven new floors is presented as corresponding example, where the increase of structural damping was required to protect the existing structure against seismic demands.