AbstractIn many cases, structural damping of lightweight structures is quite low. Therefore, additional damping systems have to be applied. These systems are, in most instances, passive ones. Concerning lightweight structures, live loads become decisive with respect to the eigenfrequencies of the system affected. Resultant changes in dynamic behavior lead to a loss of the optimal adjustment of the passive systems, which is often followed by disturbing vibrations. This in turn leads directly to an impairment of serviceability. Semiactive damping systems can solve these problems by actively reacting to changes of the system. The following article focusses on the development of a semiactive friction damper using piezoelectric stack actuators in order to reduce the vibrations of a large-scale model of a pedestrian bridge.