Comparison of velocimeter and coherent lidar measurements for building frequency assessment

Over recent years there has been a growing interest in the building frequency analysis for earthquake and structural engineering fields using ambient vibrations. Simultaneously, velocity measurements with LASER remote sensing techniques have gained more interest for several applications. This paper details the comparison of the frequency analysis obtained using sensitive velocimeter sensor and coherent LIDAR (Light Detection and Ranging) sensor, and applied to one RC existing building. Ambient vibrations recordings were processed using the Frequency Domain Decomposition method for defining the frequencies and mode shapes of the building target, while LASER remote sensing approach used coherent LIDAR method for velocity and frequency measurement. The results of the two systems are discussed. A good agreement is observed, which let us conclude on the ability of the coherent LIDAR to assess the frequency of existing buildings for structural and earthquake engineering fields at long range and without any retroreflector on the structure.