Theoretical and experimental modal analysis of a cantilever steel beam with a tip mass

Abstract

The need of a better understanding of the dynamic behavior of systems has been showing the importance of the use of reliable methods to determine modal properties through the knowledge of output-only measurements. This article begins describing the theoretical bases of an efficient method for output-only system identification and an application example is demonstrated further. The studied system is a steel cantilever beam with a tip mass, which was tested at the Group of Applied Mechanics/Federal University of Rio Grande do Sul. Through free vibration tests, the response of the beam is acquired, and using the stochastic subspace system identification method (SSI), its dynamic properties are determined. Next, the beam is analysed by finite-element method and also through the theory of vibrations of continuous systems, determining its spectral properties. Thus, the results obtained through SSI are compared with the numerical and theoretical results, showing that the dynamic properties obtained through the procedure of system identification are reliable.