Quantifying mass changes with ambient vibration measurements. (1st March 2022)

• Record Type: Journal Article
• Authors: Wynne, Zachariah; Stratford, Tim; Reynolds, Thomas P.S.
• Is Part Of: Engineering structures. Volume 254(2022)
• Publication Date: 2022-03-01
• Subjects: Static loading -- Operational modal analysis -- Ambient vibration testing -- Non-linear structural dynamics -- Mass estimation -- Time-domain modal analysis; Structural engineering -- Periodicals; Structural analysis (Engineering) -- Periodicals; Construction, Technique de la -- Périodiques; Génie parasismique -- Périodiques; Pression du vent -- Périodiques; Earthquake engineering; Structural engineering; Wind-pressure; Periodicals; 624.105
• DOI: 10.1016/j.engstruct.2021.113745
• Languages: English
• ISSNs: 0141-0296

Abstract

Abstract: The static loading is one of the key unknowns in the structural design process. While weigh in-motion stations and load cells allow load to be measured over small areas or small structures, they are not viable for more complex structures such as long-span bridges or larger buildings, and can be prohibitively expensive. Operational modal analysis can reveal changes in the dynamic behaviour of civil structures measured with accelerometers, potentially offering a low-cost, durable technique for estimating changes of mass in-service. In order to do this, the dynamic parameters of the structure must be estimated with sufficient accuracy, and then processed using a mass change estimation method robust enough to accommodate noise and measurement error. In this paper a new technique for estimating changes in mass, random sampling mass estimation (RSME), is introduced and applied to experimental data for a laboratory-scale beam structure. RSME incorporates the uncertainty in the estimates of the dynamic parameters and allows least-squares estimation of the total change in mass applied to a structure if the locations of the changes in mass are known, or prediction of both the magnitude and location of a single concentrated change in mass through a novel graphical implementation. For individual masses added to the beam, 92.0% of mass location predictions have errors smaller than 2% of the length of the span and 69.4% of added mass magnitude predictions are within ± 10 g, approximately 0.05% of the mass of the beam. For concurrent added mass locations, the mean error of the estimates for the total change in mass where 2 or more added masses are present on the beam is -2 g, approximately 0.011% of the mass of the beam. Highlights: Changes in dynamic structural behaviour tracked using ambient vibrations. A novel method incorporates uncertainty in the modal parameters. Mass and location estimated using changes in multiple modes of vibration. Changes in stiffness could also be estimated this way. Methods demonstrated using laboratory tests on a steel beam.