A proof-of-concept study on a proposed ambient-vibration-based approach to extract pseudo-free-vibration response

• Published in: Engineering structures 2020-06, Vol.212, p.110517, Article 110517
• Main Authors: Moghadam, Amin, Melhem, Hani G., Esmaeily, Asad
• Format: Article
• Language: English
• Subjects: Accelerometers; Ambient-vibration-based approach; Change detection; Computer simulation; Damage detection; Data collection; Excitation; Feature extraction; Finite element method; Free vibration; Frequency-domain; Fundamental frequency; Mathematical models; Numerical models; Properties (attributes); Pseudo-free-vibration response; Resonant frequencies; Steel frames; Stiffness; Structural damage; Vibration; Vibration response
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2020.110517

•This random-vibration-based approach extracts a structure free-vibration response.•Two steel frames with different stiffness are tested and numerically modeled.•The structure may subject to any ambient vibration regardless of the excitation.•Reduction in the structure stiffness causes a decrease of fundamental frequencies.•Fundamental frequency is the same under different vibrations for constant stiffness.•Detecting a reduction of the fundamental frequency can be an indication of damage.•Forced vibration and the use of complex equipment and instrumentation are not needed. This paper reports the results of an analytical, experimental and a numerical study (proof of concept study) on a proposed method for extracting the pseudo-free-vibration response of a structure using ambient vibration, usually of a random nature, as a source of excitation to detect any change in the dynamic properties of a structure that may be caused by damage. The structural response contains not only a random component but also a component reflecting the dynamic properties of the structure, comparable to the free vibration for a given initial condition. Structural response to the arbitrary excitation is recorded by one or several accelerometers with a desired data-collection frequency and resolution. The free-vibration response of the structure is then extracted from this data by removing the random component of the response by the method proposed in the paper. The features of the free-vibration response of the structure extracted by a suitable method, namely FFT in this study, can be used for change detection. Possible change of the pattern of these features is dominantly linked to the change in dynamic properties of the system, caused by possible damage. To show the applicability of the concept, besides an analytical verification using Newmark’s linear acceleration method, two steel portal frames with different flexural stiffness were made in the steel workshop of the structural laboratory for an experimental study. These structures were also numerically modeled using a finite element software. A wireless accelerometer with a sampling frequency rate of 2046 Hz was affixed on the top of the physical structure, at the same location where the acceleration was recorded for the corresponding numerical model. The physical structure was excited manually by an arbitrary hit and the response of the structure to this excitation, in terms of the acceleration on the top of the structure, was r