Pendulum type liquid column damper (PLCD) for controlling vibrations of a structure – Theoretical and experimental study

Tuned liquid column dampers (TLCDs) or tuned mass dampers (TMDs) are attached to structures to suppress their vibrations, which are normally excited by dynamic environmental loadings. In this paper, a study is reported on a passive hybrid type damper derived from the configurations of a pendulum type TMD and a TLCD, which can be attached to a primary structure as a compound pendulum (herein called a PLCD). One main advantage of such a system is that the source of damping is the liquid damping at an orifice as in a typical TLCD. As this concept increases complexity in the analysis by introducing an extra degree of freedom, the focus in this paper is kept limited to formulate a mathematical model for a two-dimensional case and to prove its validity through an experimental study; furthermore, the basic characteristics of the system are identified for the benefit of its design. All mathematical models presented here are derived from the energy expression by using the Lagrange’s equation. A cantilever beam orientated vertically and attached with a mass at the free end, which can vibrate in a two-dimensional plane, is fabricated as a primary structure. Initially, the primary structure fitted with a general compound pendulum type mass damper is numerically studied to approximately optimize the mass of the PLCD. Following that, a model of the PLCD is fabricated to carry out the experimental study. Finally, the theoretical and the experimental results for the combined structure-damper system are compared; this validates the mathematical model used here and demonstrates that implementation of such a concept is possible.

► A new passive damper concept which is a hybrid of a TMD and a TLCD is studied. ► Mathematical model of the damper mounted on a cantilever structure is presented. ► Test results from a fabricated model are used to validate the mathematical model. ► It is shown that such a damper can also effectively reduce structural vibrations. ► Detailed optimization is not included, but a general optimizing procedure is followed.