REDUCTION OF STRUCTURE-BORNE SOUND USING TUNED MASS DAMPERS COMPRISED OF GRANULAR MATERIALS

摘要

Reducing structure-borne sound in concrete buildings is difficult, because concrete has low internal damping. We tried to reduce concrete slab vibrations in their lower frequencies using granular materials. The granular materials are retained in polyethylene bags, which are placed in the cavities of voided concrete slabs. They act as Tuned Mass Dampers (TMDs), with the bags working as springs, and the granular materials as masses. Lower frequency vibrations in concrete slabs are reduced by the granular materials in the bags. As a result, structure-borne sound, such as floor impact sound, is reduced. In this study, laboratory experiments were conducted into reducing the vibration of a concrete slab. The vibration characteristics of a voided slab both with and without granular materials in the cavities were compared. Vibrations were significantly reduced across a specific range of frequencies. The frequency range shifted as the mass of granular materials or thickness of the polyethylene bags changed. As a result, it was presumed that vibrations were reduced by a TMD mechanism. Numerical analysis was also conducted using the Finite Element Method. The vibration characteristics of a slab model with and without TMDs were calculated. The results from the calculations and experiments demonstrated good agreement. It is concluded that granular materials in polyethylene bags act as TMDs and reduce vibrations in concrete slabs.