Structural Dynamic Parameter Identification and the Effect of Test Techniques

Abstract

Ambient and forced excitation test techniques are both widely used to dynamically identify civil engineering structures. Two floor levels of a newly constructed building, the Charles Institute at University College Dublin, were tested using both techniques. Both floor designs were identical although the layout of partitions above and below each were different. The objective of the tests was to determine the most appropriate test procedure and also to identify whether the layout of partitions contributes in a significant manner to dynamic response. It was found that at low levels of excitation, ambient test levels, the dynamic response of both floors was identical. In contrast, at higher vibration excitation levels, during forced vibration testing, the floor responses were substantially different. The differing modal parameters identified are attributed to an amplitude dependent response resulting from engagement, or not, of the partitions in the dynamic response of the system. The practical significance of this finding is that it is imperative to consider, and test at, the in-service vibration amplitude expected for a floor system.