The measurement of the structural dynamic characteristics of floors with installed machines

Abstract Dynamic characteristics of receiving structures can be determined from mobility measurements which have important applications in structure-borne sound transmission analysis, in particular, the prediction of the dynamic response of connected and supporting structures when subject to machine excitation. Measurement, with the machine installed, provides data useful for the investigation, evaluation, and comparison of machine performance. However, the study of installed machines is often hampered by the uncertainties in in situ measurement of the mobility of the supporting floor due to the mass of the machine acting at the contact points. On the other hand, it is recognised that removing the machines is generally not possible in most circumstances. This study is aimed at ascertaining the requirements for enabling reliable in situ measurement of floor mobility based on the concept of source and receiver mobility mismatch at the contact points. Theoretical beam models are examined along with experimental measurements on a concrete floor. It is found that the influence of dynamic loading is not significant if the source (machine) mobility is more than 10 dB greater than the receiver (floor) mobility at the contact points.