Natural frequencies and buckling of compressed non-symmetric thin-walled beams

Piana, Gianfranco; Lofrano, Egidio; Manuello, A.; Ruta, Giuseppe

doi:10.1016/j.tws.2016.11.021

Cited by 17 publications

(14 citation statements)

References 23 publications

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“…In two cases, a globally unstable behavior was registered in the softening branch; this character is reflected by the acoustic emission energy analysis. We also remark that piezoelectric pickups typical of music technology, recently adopted by some of the authors to extract modal parameters of slender metallic elements in the lab [8][9][10], were successfully used here, as long as the natural frequencies of stubby concrete specimens are extracted. The main remarks, related to the results of the present study, can be summarized as follows.…”

Section: Discussionmentioning

confidence: 94%

“…The natural frequencies were detected by piezoelectric pickups (PZT buzzers), sensitive in the range 0-20 kHz, placed along the beam surface. These sensors, typical of music technology, were recently applied to modal testing by some of the authors and found to be effective and robust in extracting natural frequencies and mode curvatures/shapes of straight and curved beams [8][9][10]. Their main advantages are high accuracy, small dimensions, low weight, easy usage, and low cost; they proved to have the same reliability of common laser sensors (but offering a much wider operating frequency range at a very low cost) and of piezoelectric accelerometers.…”

Section: Introductionmentioning

confidence: 99%

“…Their main advantages are high accuracy, small dimensions, low weight, easy usage, and low cost; they proved to have the same reliability of common laser sensors (but offering a much wider operating frequency range at a very low cost) and of piezoelectric accelerometers. They can also be conveniently coupled to audio acquisition devices without requiring calibration and filtering [8,9]. PZT buzzers were thus adopted in this work aiming at (i) testing their possible use on concrete specimens (so far they were only tested on metallic elements) and (ii) taking advantage of an existing experimental apparatus and the relevant know-how.…”

Section: Introductionmentioning

confidence: 99%

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Acoustic Emission and Modal Frequency Variation in Concrete Specimens under Four-Point Bending

2017

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Abstract:The Acoustic Emission (AE) and Dynamic Identification (DI) techniques were applied simultaneously, in an original way, to examine the stress dependent damage progress in pre-notched concrete beams tested in four-point bending. The damage mechanisms were characterized by analyzing the AE signals registered during the tests, conducted by increasing the specimen's vertical deflection. In particular, the dominant fracture mode was identified, and correlations between dissipated and emitted energies were investigated. Moreover, variations in the natural bending frequencies, produced by the crack advancement under loading, were detected and put in relation with the cumulated AE energy. Two different types of piezoelectric (PZT) sensors, operating in well distinct frequency ranges, were used to measure AE and modal signals. This study may be of interest with an outlook on possible correlations between a multi-parameter structural monitoring and the solution of inverse problems by numerical models.

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Section: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Acoustic Emission and Modal Frequency Variation in Concrete Specimens under Four-Point Bending

2017

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“…In principle, a permanent monitoring system, as well as occasional measurements, could be set up on the most stressed elements in order to prevent buckling instability. For example, among other methods, resonant frequency measurements can be used to make experimental predictions on the buckling load of compressed elements [15][16][17].…”

Section: Resultsmentioning

confidence: 99%

Robustness of an airport double layer space truss roof

Piana

Biagi

Chiaia

2021

Curved and Layered Structures

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Robustness analyses are very well referenced for concrete or steel frame structures but less for spatial structures; in particular for truss roofs. Here, we present a robustness analysis of an existing airport space structure. A finite element model was implemented based on the original design documents, where the structure is modeled as a spatial truss composed of elastic, perfectly hinged bars. With respect to five main design loading conditions, the most stressed bars among the top layer, the bottom layer and the diagonals, were alternately removed, and the stress variations in the remaining bars monitored. A total of fifteen analyses with removal of either the most stretched or the most compressed bar were run. Also, reductions of the most stressed bars’ axial stiffness were considered to investigate the effects of such local reductions on the global structural flexibility. Linearized global buckling analyses were also conducted to point out again the effect of a global loss of stiffness, due to local losses. The study gives basic information about the general behavior of the structure in case of failure, or damage, of a key element. Results show that this kind of lightweight and efficient structures are very sensitive to local losses, since their redistribution capabilities are not large.

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“…With the recent advances in electronics, new types of sensors for structural health monitoring and modal analysis are being manufactured and utilized [17]. Wired communication is being replaced using wireless communication sensors, as they significantly reduce the cost of the health monitoring system [18] and have reached a level where they can be implemented on full-scale structures [19].…”

Section: Introductionmentioning

confidence: 99%

Ambient Vibration Testing of a Pedestrian Bridge Using Low-Cost Accelerometers for SHM Applications

2019

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Damage detection and structural health monitoring have always been of great importance to civil engineers and researchers. Vibration-based damage detection has several advantages compared to traditional methods of non-destructive evaluation, such as ground penetrating radar (GPR) or ultrasonic testing, since they give a global response and are feasible for large structures. Damage detection requires a comparison between two systems states, the baseline or “healthy state”, i.e., the initial modal parameters, and the damaged state. In this study, system identification (SI) was carried out on a pedestrian bridge by measuring the dynamic response using six low-cost triaxial accelerometers. These low-cost accelerometers use a micro-electro-mechanical system (MEMS), which is cheaper compared to a piezoelectric sensor. The frequency domain decomposition algorithm, which is an output-only method of modal analysis, was used to obtain the modal properties, i.e., natural frequencies and mode shapes. Three mode shapes and frequencies were found out using system identification and were compared with the finite element model (FEM) of the bridge, developed using the commercial finite element software, Abaqus. A good comparison was found between the FEM and SI results. The frequency difference was nearly 10%, and the modal assurance criterion (MAC) of experimental and analytical mode shapes was greater than 0.80, which proved to be a good comparison despite the small number of accelerometers available and the simplifications and idealizations in FEM.

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Natural frequencies and buckling of compressed non-symmetric thin-walled beams

Cited by 17 publications

References 23 publications

Acoustic Emission and Modal Frequency Variation in Concrete Specimens under Four-Point Bending

Acoustic Emission and Modal Frequency Variation in Concrete Specimens under Four-Point Bending

Robustness of an airport double layer space truss roof

Ambient Vibration Testing of a Pedestrian Bridge Using Low-Cost Accelerometers for SHM Applications

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