Damage Detection of Wood Beams Using the Modal Flexibility Curvatures

2012 ◽  
Vol 538-541 ◽  
pp. 1815-1820
Author(s):  
Chuan Shuang Hu ◽  
Wei Wen ◽  
Hong Yun
Keyword(s):  
Modal Testing ◽  
Mode Shapes ◽  
Damage Scenarios ◽  
Statistical Algorithm ◽  
Wood Construction ◽  
Modal Flexibility ◽  
Wood Beams ◽  
Before And After ◽  
Damage Indicators ◽  
Axial Moment

Local damages such as knots, decay, and cracks can be translated into a reduction of service life due to mechanical and environmental loadings. In wood construction, it is very important to evaluate the weakest location and detect damage at the earliest possible stage to avoid the future catastrophic failure. In this study, modal testing was conducted on wood beams to generate the first two mode shapes. A novel statistical algorithm was proposed to extract the damage indicator by computing the modal flexibility curvature before and after damage in timbers. Different damage severities, damage locations, and double damages were simulated by removing mass from intact beams to verify the algorithm. The results have shown that the proposed statistical algorithm is effective and suitable to the designed damage scenarios. The proposed algorithm can qualitatively identify the damage existence and its location although there is no linear correlation between damage indicators and damage severities. The peak values of the damage indicators increase when the losses of the second axial moment of area increases. It is also reliable to detect multiple damages.

scholarly journals Damage Detection in Different Types of 3D Asymmetric Buildings Using Vibration Characteristics

2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Yi Wang ◽  
Ziru Xiang ◽  
Zhenyuan Gu ◽  
Chenhui Zhu ◽  
Wangping Qian
Keyword(s):  
Damage Index ◽  
Vibration Characteristics ◽  
Mode Shapes ◽  
Reinforced Concrete Structure ◽  
Modal Strain Energy ◽  
Damage Scenarios ◽  
Asymmetric Buildings ◽  
Modal Strain Energy Method ◽  
Modal Flexibility ◽  
Different Types

This paper treats the vibration characteristics of three different types of asymmetric buildings and investigates the feasibility of applying an innovative vibration-based multicriteria approach-based damage index (MCA-DI) technique to detect the damage. This technique combines a modified form of the traditional modal strain energy method (MSEM) developed by decomposing the mode shapes into lateral and vertical components together with a modified form of the modal flexibility method to define a new damage indicator. Lastly, the dynamic behavior of three asymmetric building instances, including a 10-storey L-shaped structure, a 10-storey setback structure, and a 6-storey reinforced concrete structure with an unsymmetrical distribution of columns, was studied under five different damage scenarios. The results showed that despite different vibration characteristics of these three asymmetric buildings, the proposed method was able to accurately and effectively locate all damages and eliminate the confusion when more than one index is simultaneously used by using only the first a few modes.

FEM Free Damage Detection of Beam Structures Using the Deflections Estimated by Modal Flexibility Matrix

2021 ◽  
pp. 2150128
Author(s):  
Wen-Yu He ◽  
Wei-Xin Ren ◽  
Lei Cao ◽  
Quan Wang
Keyword(s):  
Damage Detection ◽  
Structural Damage ◽  
Damage Index ◽  
Element Model ◽  
Mode Shapes ◽  
Beam Structures ◽  
Flexibility Matrix ◽  
Damage Quantification ◽  
Modal Flexibility ◽  
The Cost

The deflection of the beam estimated from modal flexibility matrix (MFM) indirectly is used in structural damage detection due to the fact that deflection is less sensitive to experimental noise than the element in MFM. However, the requirement for mass-normalized mode shapes (MMSs) with a high spatial resolution and the difficulty in damage quantification restricts the practicability of MFM-based deflection damage detection. A damage detection method using the deflections estimated from MFM is proposed for beam structures. The MMSs of beams are identified by using a parked vehicle. The MFM is then formulated to estimate the positive-bending-inspection-load (PBIL) caused deflection. The change of deflection curvature (CDC) is defined as a damage index to localize damage. The relationship between the damage severity and the deflection curvatures is further investigated and a damage quantification approach is proposed accordingly. Numerical and experimental examples indicated that the presented approach can detect damages with adequate accuracy at the cost of limited number of sensors. No finite element model (FEM) is required during the whole detection process.

Experimental Study of Blade Vibration in Centrifugal Compressors

2011 ◽  
Author(s):  
Andrew H. Lerche ◽  
J. Jeffrey Moore ◽  
Timothy C. Allison
Keyword(s):  
High Cycle Fatigue ◽  
Axial Flow ◽  
Modal Testing ◽  
Mode Shapes ◽  
Cyclic Symmetry ◽  
Centrifugal Compressors ◽  
Compressor Blades ◽  
Blade Vibration ◽  
Phase Cancellation ◽  
Blade Failure

Blade vibration in turbomachinery is a common problem that can lead to blade failure by high cycle fatigue. Although much research has been performed on axial flow turbomachinery, little has been published for radial flow machines such as centrifugal compressors and radial inflow turbines. This work develops a test rig that measures the resonant vibration of centrifugal compressor blades. The blade vibrations are caused by the wakes coming from the inlet guide vanes. These vibrations are measured using blade mounted strain gauges during a rotating test. The total damping of the blade response from the rotating test is compared to the damping from the modal testing performed on the impeller. The mode shapes of the response and possible effects of mistuning are also discussed. The results show that mistuning can affect the phase cancellation which one would expect to see on a system with perfect cyclic symmetry.

Infrastructure Sustainability

2011 ◽  
pp. 186-201
Author(s):  
Hoi Wai Shih ◽  
David Thambiratnam ◽  
Tommy Chan
Keyword(s):  
Energy Method ◽  
Strain Energy ◽  
Health State ◽  
Modal Strain Energy ◽  
Structural Health ◽  
Modal Strain Energy Method ◽  
Modal Flexibility ◽  
Before And After ◽  
Composite Bridges ◽  
Strain Energy Method

Assessing the structural health state of urban infrastructure is crucial in terms of infrastructure sustainability. This chapter uses dynamic computer simulation techniques to apply a procedure using vibration-based methods for damage assessment in multiple-girder composite bridges. In addition to changes in natural frequencies, this multi-criteria procedure incorporates two methods, namely, the modal flexibility and the modal strain energy method. Using the numerically simulated modal data obtained through finite element analysis software, algorithms based on modal flexibility and modal strain energy change, before and after damage, are obtained and used as the indices for the assessment of structural health state. The feasibility and capability of the approach is demonstrated through numerical studies of a proposed structure with six damage scenarios. It is concluded that the modal strain energy method is capable of application to multiple-girder composite bridges, as evidenced through the example treated in this chapter.

scholarly journals Vibration-Based Damage Assessment in Gravity-Based Wind Turbine Tower under Various Waves

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Cong-Uy Nguyen ◽  
So-Young Lee ◽  
Heon-Tae Kim ◽  
Jeong-Tae Kim
Keyword(s):  
Wind Turbine ◽  
Damage Assessment ◽  
Natural Frequencies ◽  
Modal Identification ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Damage Scenarios ◽  
Wind Turbine Tower ◽  
Induced Variation ◽  
Wave Induced

In this study, the feasibility of vibration-based damage assessment in a wind turbine tower (WTT) with gravity-based foundation (GBF) under various waves is numerically investigated. Firstly, a finite element model is constructed for the GBF WTT which consists of a tower, caisson, and foundation bed. Eigenvalue analysis is performed to identify a few vibration modes of interest, which represent complex behaviors of a flexible tower, rigid caisson, and deformable foundation. Secondly, wave-induced dynamic pressures are analyzed for a few selected wave conditions and damage scenarios are also designed to simulate the main components of the target GBF WTT. Thirdly, forced vibration responses of the GBF WTT are analyzed for the wave-induced excitation. Then modal parameters (i.e., natural frequencies and mode shapes) are extracted by using a combined use of time-domain and frequency-domain modal identification methods. Finally, the variation of modal parameters is estimated by measuring relative changes in natural frequencies and mode shapes in order to quantify the damage-induced effects. Also, the wave-induced variation of modal parameters is estimated to relatively assess the effect of various wave actions on the damage-induced variation of modal parameters.

Experimental Modal Testing of the Elastic Tube Bundle

2013 ◽  
Vol 718-720 ◽  
pp. 1816-1819
Author(s):  
Ji Zhou Zheng ◽  
Jia Lin Hou ◽  
Yan Zhang
Keyword(s):  
Complex Shape ◽  
Tube Bundle ◽  
Dynamic Properties ◽  
Elastic Tube ◽  
Modal Testing ◽  
Mode Shapes ◽  
Constraint Condition ◽  
Heat Transfer Efficiency ◽  
Reduce Energy Consumption ◽  
Experimental Modal Testing

The elastic tube bundle is a new-style heat exchange element that can enhance heat transfer efficiency and reduce energy consumption. It is difficult to obtain exact analytical solutions because of the complex shape and constraint condition. An experimental modal testing technique is applied to get the dynamic properties. Some issues to which one should pay attention during the experiment are emphasized. Natural frequencies and mode shapes are identified from the test and compared to numerical results. Agreement is found for most frequencies of interest. But, some discrepancies exist for the vibration in-plane due to the inevitable operation error.

Shaking Table Tests on Multi-Leaf Stone Masonry Structures: Analysis of Stiffness Decay

2010 ◽  
Vol 133-134 ◽  
pp. 647-652 ◽  
Author(s):  
Nicola Mazzon ◽  
Cano M. Chavez ◽  
Maria Rosa Valluzzi ◽  
F. Casarin ◽  
Claudio Modena
Keyword(s):  
Dynamic Behaviour ◽  
Shaking Table ◽  
Stone Masonry ◽  
Mode Shapes ◽  
Masonry Structures ◽  
Shaking Table Tests ◽  
Grout Injection ◽  
Hydraulic Lime ◽  
Natural Hydraulic Lime ◽  
Before And After

The influence of the natural hydraulic lime-based grout on the dynamic behaviour of injected multi-leaf stone masonry elements is discussed in the paper. Shaking table experiments on two stone masonry buildings, tested before and after grout injection, have been performed. The paper focuses on the analysis of both the recorded accelerations and related displacements, at the bottom and at each further storey. This leads to evaluate the stiffness of the unstrengthened and injected structures. The input at increasing PGA allowed the stiffness decay to be studied, simulating a gradual damaging of the structures. These results were also interpreted in the light of both computed frequencies and mode shapes. Finally, the comparison among these results, obtained from all the models, allows to deepen the knowledge concerning the effects induced by the lime-based grout injection and on its capability to modify the dynamic behaviour, when intervening on a damaged (repairing) or on an undamaged (strengthening) structure.

A Damage Identification Method Using Vibration Modal Parameters Through Finite Element Discretization

2003 ◽  
Author(s):  
Xiaoping Zhou ◽  
Abhijit Gupta
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Damage Identification ◽  
Least Squares Method ◽  
Modal Testing ◽  
Mode Shapes ◽  
Element Formulation ◽  
Element Discretization ◽  
Damage Indices ◽  
Actual Damage

Natural frequencies and mode shapes of a structure will change whenever the structure has any kind of damage. This paper introduces a technique to quantify and locate the damage when the natural frequencies and mode shapes of undamaged and damaged structure are known. Aluminum beams (with and without damage) are used for numerical simulation and experimental verification. To establish the theoretical basis of this method, finite element formulation is used. A set of undetermined equations involving damage indices and natural frequencies and mode shapes of undamaged and damaged structures are obtained. The damage indices are computed using non-negative least squares method. Impact modal testing was conducted with three aluminum beams and damage indices based on experimental data are compared with actual damage cases to establish the effectiveness of this method to identify the damage.

scholarly journals Damage Detection in Plates with the Use of Laser-Measured Mode Shapes

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Ziemowit Dworakowski ◽  
Kajetan Dziedziech ◽  
Pawel Zdziebko ◽  
Krzysztof Mendrok
Keyword(s):  
Damage Detection ◽  
Laboratory Experiment ◽  
Fault Location ◽  
Element Model ◽  
Metal Plate ◽  
Aluminum Plate ◽  
Mode Shapes ◽  
Laser Vibrometer ◽  
Spatial Filters ◽  
Damage Scenarios

This paper presents the use of laser vibrometer measurements to detect and locate damage in a metal plate. An algorithm based on local spatial filters was selected, and for the purpose of comparison, the fault location was also determined based on the wavelet analysis of mode shapes. The research was carried out first on the created finite element model of aluminum plate, where two kinds of damage of increasing size and temperature change were simulated. After obtaining positive results, a laboratory experiment was carried out, which consisted of measuring the vibration of the aluminum plate with the laser vibrometer in undamaged condition, at increased temperatures, and with various damage scenarios. The conclusions of the laboratory experiment confirm the damage detection capabilities of the methods but question their damage localization potential.

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