Comparison of seismometer and radar measurements for the modal identification of civil engineering structures

The vulnerability of structures subjected to dynamic actions has been a very active field of research in recent years. In particular, the use of ambient response recording aims to improve our knowledge about the dynamic behaviour of structures, and the interferometric Real Aperture Radar (RAR) technique has recently emerged as a promising tool for the identification of modal properties such as natural frequencies and mode shapes through ambient vibration measurements of structures. To evaluate the modal characteristics of a reinforced concrete wall building, measurements of ambient vibrations of the building were carried out using a RAR and a network of velocimeters.The paper, after introducing the functioning principle of the two techniques, describes and analyses the obtained experimental results, thereby evaluating the capability of the RAR technique to identify the modal properties accurately. Comparisons between the two measurement techniques and between a numerical model of the structure and real observations are presented.Finally, the conclusion can be drawn that the radar technique used for the identification of modal properties of the structure by ambient excitation yields results that are in good agreement with those obtained using the velocimeter and numerical model.

► Interferometric Real-Aperture Radar (RAR) technique was used for record ambient noise in a building.
► The first five frequencies of the structure have been identified by RAR.
► RAR frequencies were validated with velocimeter results.
► RAR instrument can measure vibration amplitudes around the micron.