Development of a low cost system for modal parameters identification under ambient vibration: A low rise building as a case study

The dynamic behavior analysis of the existing buildings is a subject of great importance for seismic risk and vulnerability evaluation. The difficulty consists in the accurate determination of the parameters characterizing the main modes of a structure. Recently, research studies have been oriented towards the use of ambient vibrations to extract such parameters. Indeed, this method allows extracting modal parameters such as natural frequencies, damping and mode shapes without using any artificial excitation. Based on this approach, acquisition and processing systems can be found on the market. However, these systems remain relatively expensive and are more adapted to high-rise structures. In the case of low-rise building, such systems might not be an optimal solution. In this work, we have developed a low-cost acquisition and processing system which is more appropriate to low-rise buildings. This system can measure the response of this kind of structure under ambient solicitations and extract its modal parameters with high precision. Dynamic parameters are extracted using different operational modal analysis (OMA) based methods and finite element modelling. The experimental results show good agreement with the numerical data. The error percentages for the 1st, 2nd, 3rd, 4th and 5th modes are 0%, 2%, 1.7%, 4% and 0.1%, respectively. Consequently, it was concluded that ambient vibration is a confident approach for identifying the modal parameters of structures.