Unbalanced oil filled sphere as rolling pendulum on a flat surface to damp horizontal structural vibrations

The passive damping of horizontal structural vibrations by means of an unbalanced oil filled sphere as a tuned mass damper (TMD) is examined. Due to the unbalance contained in the TMD, a pendulum-like motion is produced. The TMD lies unconstrained on the structure. As a result, forces are only transferred through the static friction between the TMD and the structure. The TMD is filled with oil to enable energy dissipation. This paper investigates the mechanical system of the proposed TMD and calculation methods for its tuning. Furthermore, experimental results of the TMD are presented. To determine the advantages and disadvantages of the proposed TMD, it will be compared to other passive tuned mass dampers. The advantages of the presented TMD are its robust design, simple mounting/demounting onto the main system and its adjustability after mounting. The oil filling makes the damper construction simple, as an additional container for the oil is no longer needed. Furthermore, the energy dissipating effect of breaking waves is used when the oil level inside the TMD is shallow. The disadvantages of the presented TMD when compared to a conventional tuned mass damper (linear spring-mass-damper-system) are its slightly lower performance and its complex tuning. (C) 2016 Elsevier Ltd. All rights reserved.