Fundamentals of Time Domain Modal Identification

Ibrahim, S. R.

doi:10.1007/978-94-011-4503-9_11

Cited by 14 publications

(12 citation statements)

References 9 publications

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“…One, the matrix pencil algorith, (Hua and Sarkar, 1990), is a single-channel technique, developed to extract natural frequencies and damping ratios from the free-decay response of a structure at a single point, in a single direction. The second, the Ibrahim time domain (ITD) method (Ibrahim, 1999), was developed to analyse a matrix formed from the free-decay response of a series of measurement channels, and can therefore extract natural frequencies, damping ratios and mode shapes from the data.…”

Section: Modal Analysis Techniquesmentioning

confidence: 99%

Ambient vibration tests of a cross-laminated timber building

Reynolds

Harris

Chang

et al. 2015

Proceedings of the Institution of Civil Engineers - Constructio

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Cross-laminated timber has, in the last 6 years, been used for the first time to form shear walls and cores in multi-storey buildings of seven storeys or more. Such buildings can have low mass in comparison to conventional structural forms. This low mass means that, as cross-laminated timber is used for taller buildings still, their dynamic movement under wind load is likely to be a key design parameter. An understanding of dynamic lateral stiffness and damping, which has so far been insufficiently researched, will be vital to the effective design for wind-induced vibration. In this study, an ambient vibration method is used to identify the dynamic properties of a seven-storey cross-laminated timber building in situ. The random decrement method is used, along with the Ibrahim time domain method, to extract the modal properties of the structure from the acceleration measured under ambient conditions.The results show that this output-only modal analysis method can be used to extract modal information from such a building, and that information is compared with a simple structural model. Measurements on two occasions during construction show the effect of non-structural elements on the modal properties of the structure.

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Section: Modal Analysis Techniquesmentioning

confidence: 99%

Ambient vibration tests of a cross-laminated timber building

Reynolds

Harris

Chang

et al. 2015

Proceedings of the Institution of Civil Engineers - Constructio

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“…This is achieved by a numerical method of parameter identification which determines the frequency and dampening of the free vibration response. In this case a modified Ibrahim time domain method was used [6], [7]. With the aforementioned parameters is possible to construct the terms of the matrixes.…”

Section: Application To a Solar Trackermentioning

confidence: 99%

Inclusion of Mechanical Dampers in the Multimodal Flutter Analysis of Slender Structures

Suárez

Jurado

Ponte

et al. 2020

WIT Transactions on Engineering Sciences

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Sometimes slender structures are reinforced with mechanical dampers to reduce the vibrations caused by aeroelastic phenomena like flutter. However the formulation of flutter analysis only considers the classical damping ratio to take into account the structural damping. This paper explains the procedure used for adding mechanical dampers with a known constant to the analysis software FLAS. This code was developed at Universidade da Coruña to calculate the critical wind speed for flutter instability. An example of a solar tracker with two rows of flat panels is shown. In this slender structure two mechanical dampers are used to reduce the vibrations caused by the wind in structure interaction. The solar tracker has been studied for five different positions of the angle of attack. Results of flutter speed for several values of the dampers constant and global structural damping ratio are presented.

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“…1. carrying out aerodynamic tests of sectional models, obtaining the time history of the forces and moment, and the value of the aerodynamic coefficients; 2. carrying out aeroelastic tests with three degrees of freedom, giving the 18 flutter derivatives by numerical methods [30,31]; and 3. carrying out vortex shedding tests, giving the time history of the forces or accelerations and the range of the lock-in phenomenon.…”

Section: Experimental Studies Of the Solar Tracker In Thementioning

confidence: 99%

Experimental and computational studies on the performance of solar trackers under vortex shedding, torsional divergence, and flutter

Quintela¹,

Jurado²,

Rapela³

et al. 2020

Int. J. CMEM

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The current development of renewable energies has originated a number of new structural typologies that are the physical support of the energy production systems. Photovoltaic energy is a very mature source and it is obtained using rows of panels implemented in a longitudinal grillage. Many studies have been carried out in the past with an aim to improve the capacity to obtain electrical power, but another important issue is the need to guarantee the performance of these industrial facilities under the phenomena induced by the turbulent wind flow, taking into account the fact that they are usually built in wide open spaces. This paper describes an extensive research carried out on two configurations of solar trackers by experimental and computational methods. The former was composed of a number of tests of reduced models of segments of the solar trackers, which were carried out in an aerodynamic wind tunnel. The latter consisted of a series of structural analyses worked out through a finite element model of the full panel subjected to aerodynamic and aeroelastic loads. Several angles of attack of the wind flow and a wide range of wind speeds were included in the study. This approach allowed to clearly evaluate the structural and dynamic performance of both the configurations of solar trackers under the most important wind-induced phenomena such as vortex shedding, torsional divergence, and flutter. The paper relates the phases of the study and informs about the more relevant numerical results obtained in the experiments and the computer analysis.

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Fundamentals of Time Domain Modal Identification

Cited by 14 publications

References 9 publications

Ambient vibration tests of a cross-laminated timber building

Ambient vibration tests of a cross-laminated timber building

Inclusion of Mechanical Dampers in the Multimodal Flutter Analysis of Slender Structures

Experimental and computational studies on the performance of solar trackers under vortex shedding, torsional divergence, and flutter

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