Measurement of the vibration reduction index between concrete masonry walls and precast hollow core floors

Measurements of the vibration reduction index (Kij ) were made in full accordance with the standard, ISO 108048 on junctions constructed from 190 mm thick hollow concrete block masonry walls connected to 203 mm (8”) thick precast prestressed hollow core slabs, with the objective to collect the data required to determine the Apparent Sound Transmission Class (ASTC) rating of building constructions which use these elements. The vibration reduction index measured in the laboratory was equal to or higher than that predicted using the theory outlined in Annex E of the standard, ISO 15712-1 over the frequency range of interest. Based on the distribution of the velocity levels measured on the concrete masonry walls and the precast hollow core floors, it was determined that these elements behave as homogeneous elements for the purpose of calculating the ASTC rating of this construction. Therefore, the results of this study suggest that theoretical calculations of the vibration reduction indices found in Annex E of ISO 15712 can be used to predict the vibration reduction index of other junctions between concrete masonry walls and precast hollow core floors with a mass per area greater than or equal to 323 kg/m2. Based on the findings from this study, it is expected that constructions of hollow concrete block masonry walls with a mass per unit area greater than 238 kg/m2 connected to precast hollow core floors with a mass per unit area greater than 323 kg/m2 will achieve ASTC ratings which are equal to or greater than 47. This report includes examples of calculations of the ASTC ratings for constructions consisting of bare concrete masonry walls connected to bare precast hollow core floors. The examples using the simplified and detailed methods show that constructions of bare (no liners, unpainted) normal weight 190 mm thick hollow concrete block masonry walls connected to bare 203 mm (8”) thick precast prestressed hollow core slabs can achieve an ASTC rating of 48 for side-by- side rooms (horizontal transmission) and an ASTC rating of 55 for one-above-the-other rooms (vertical transmission). The installation of linings on the floor, ceiling or walls would increase the ASTC ratings. Although the values of the vibration reduction index which were measured for this study were for junctions with the continuous voids of the hollow core planks oriented perpendicular to the concrete masonry walls, the results may also be used for the case where the voids are oriented parallel to the walls. The vibration reduction indices are expected to be higher for the case where the continuous voids are oriented parallel to the concrete masonry walls and so using vibration reduction index values for the case of voids oriented perpendicular to the concrete masonry walls may yield more conservative values than may be found in practice. The benefit of using the same results for both cases is that it eliminates the risk of using the wrong set of data for the calculation of the ASTC rating.
On title page: Canadian Concrete Masonry Producers Association