Discussion on “A bidirectional and homogeneous tuned mass damper: A new device for passive control of vibrations” by Jose L. Almazan, Juan C. De la Llera, Jose A. Inaudi, Diego Lopez-Garcia, Luis E. Izquierdo [Eng Struct 29 (2007) 1548–1560]

The aforementioned paper proposes a new type of pendulum tuned mass damper with unidirectional friction damper. The proposed tuned mass damper is novel. However, the authors use the inappropriate examples to illustrate their device. In their example, the length of pendulum is too small, and then the angle of pendulum is very large. The aim of this discussion is to point out that the examples are impractical.