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1
Shang, Xin, Yue Xu und Geng Feng Ren. „Research on Curvature Mode Characteristics of Damaged Simply Supported Beam“. Applied Mechanics and Materials 455 (November 2013): 261–66. http://dx.doi.org/10.4028/www.scientific.net/amm.455.261.
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This paper approaches the rules of curvature mode and curvature mode difference about a simply supported beam. On the basis of the theory of curvature mode, through numerical simulation analysis of simply supported beam on four conditions, the result of simply supported beam with curvature mode and curvature mode difference were obtained. The results show that for the damaged beam information with numerical simulation, the curvature mode and curvature mode difference index calculated by difference method at the unit length unevenly is with strong noise, which can even submerge the beam damage information, and for different damage index of the beam, damage information from curvature mode difference curve is stronger and effected by unit length weaker than those from curvature mode curve, and damage information from curvature mode curve and curvature mode difference curve decrease with the increasing mode order.
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Xu, Y. F., und J. S. Kim. „Baseline-Free Structural Damage Identification for Beam-Like Structures Using Curvature Waveforms of Propagating Flexural Waves“. Sensors 21, Nr. 7 (02.04.2021): 2453. http://dx.doi.org/10.3390/s21072453.
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Curvatures in mode shapes and operating deflection shapes have been extensively studied for vibration-based structural damage identification in recent decades. Curvatures of mode shapes and operating deflection shapes have proved capable of localizing and manifesting local effects of damage on mode shapes and operating deflection shapes in forms of local anomalies. The damage can be inversely identified in the neighborhoods of the anomalies that exist in the curvatures. Meanwhile, propagating flexural waves have also been extensively studied for structural damage identification and proved to be effective, thanks to their high damage-sensitivity and long range of propagation. In this work, a baseline-free structural damage identification method is developed for beam-like structures using curvature waveforms of propagating flexural waves. A multi-resolution local-regression temporal-spatial curvature damage index (TSCDI) is defined in a pointwise manner. A two-dimensional auxiliary TSCDI and a one-dimensional auxiliary damage index are developed to further assist the identification. Two major advantages of the proposed method are: (1) curvature waveforms of propagating flexural waves have relatively high signal-to-noise ratios due to the use of a multi-resolution central finite difference scheme, so that the local effects of the damage can be manifested, and (2) the proposed method does not require quantitative knowledge of a pristine structure associated with a structure to be examined, such as its material properties, waveforms of propagating flexural waves and boundary conditions. Numerical and experimental investigations of the proposed method are conducted on damaged beam-like structures, and the effectiveness of the proposed method is verified by the results of the investigations.
3
Jing, Hang, Ling Ling Jia und Yi Zhao. „Structural Damage Detection Using Curvature Mode Difference Curve“. Advanced Materials Research 250-253 (Mai 2011): 1248–51. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.1248.
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Damage detection in civil engineering structures using the dynamic system parameters has become an important area of research. The sensitivity of damage indicator is of great value to structural damage identification. The curvature mode is an excellent parameter in damage detection of structures, while in case that certain curvature mode curve can’t show existence of damage. In this paper, numerical studies are conducted to demonstrate the deficiency of curvature mode to damage detection. Then a new damage indicator called “curvature mode changing rate” (CMCR) is introduced which is processed by numerical differentiation of curvature mode curve. The simulation results show that the new index is superior to curvature mode for structural damage identification, and it is still sensitive to the damaged location in the mode node.
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Xiang, Chang-Sheng, Ling-Yun Li, Yu Zhou und Zi Yuan. „Damage Identification Method of Beam Structure Based on Modal Curvature Utility Information Entropy“. Advances in Civil Engineering 2020 (19.09.2020): 1–20. http://dx.doi.org/10.1155/2020/8892686.
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Generally, the damage of the structure will lead to the discontinuity of the local mode shape, which can be well reflected by the modal curvature of the structure, and the local information entropy of the beam structure will also change with the discontinuity of the mode. In this paper, based on the information entropy theory and combining the advantages of modal curvature index in damage identification of beam structure, the modal curvature utility information entropy index is proposed. The modal curvature curves of nondestructive structures were obtained by fitting the modal curvature curves of damage structures with the gapped smoothing technique to avoid dependence on the baseline data of nondestructive structures. The index comprehensively reflects the damage state of the structure by calculating mutual weight change matrix and the weight-probability coefficient. The performance of the new index was verified by the finite element simulation and model test of simply supported beam, respectively. The results show that the modal curvature utility information entropy index takes advantage of the modal curvature index which is sensitive to damage and can overcome its shortcomings effectively. The index proposed can identify the damage location and damage degree accurately and has certain noise immunity, which provides an effective damage identification indicator for beam structures.
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Ge, Ji Ping. „Damage Quantitative Investigation of Beam Structure Based on Changing Ratio of Modal Curvature“. Advanced Materials Research 255-260 (Mai 2011): 654–58. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.654.
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The changing ratio of modal curvature is proposed for damage recognition, and its ability of damage localization and damage quantitative has been studied in this paper. For testing the effect of damage recognition, two research parameters, the different section rigidity and the scope of damages, are included. And changing rules of the index with structure rigidity, constraints, and structure supporting system have been studied at the same time. The numerical analysis results indicated: The relation of linear increase exists between the changing ratio of modal curvature and the extent of damage, the changing slope of the index is bigger with the increase of damage extent; The boundary condition and the structure supporting system will affect the value of index; In the view of one special structure, case study should be carried to establish the relationship between value of index and the extent of damage.
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Kim, Byeong Hwa. „Online Monitoring of Flexural Damage Index of a Cable-Stayed Bridge“. Shock and Vibration 2019 (23.11.2019): 1–13. http://dx.doi.org/10.1155/2019/7607214.
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This work introduces a recent application of the online nondestructive damage assessment system into a cable-stayed bridge. A set of ambient modal parameters are automatically extracted every 20 minutes using real-time signal data collected from a total of 26 accelerometers attached on the deck plate of the bridge. Then, a set of modal flexibilities are reconstructed by the combination of the extracted modal parameters with the approximated modal mass of the girder. Next, the curvature of the modal flexibility is approximated by a central difference formula. Finally, the set of flexural damage index equations is constructed by comparing the modal curvature of the damaged state to that of the undamaged state. Solving the overdetermined flexural damage index equations, the desired damage index is finally quantified. The resulting index clearly indicates the location and severity of the potential structural damage on the girder. Based on the overall performance of the implemented health monitoring system, the bridge operator’s damage index control criteria are set to ±20% of the undamaged state.
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Xiang, Yi Qiang, Li Si Liu und Yu Liang He. „Damage Identification of Multi-Box Steel-Concrete Composite Bridges Based on Modal Curvature Difference Method“. Applied Mechanics and Materials 226-228 (November 2012): 1689–92. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.1689.
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Based on the data from dynamic analysis of a 40m-span multi-box steel-concrete composite bridge and the difference value of its modal curvature before and after the structural damage, this paper detects the damage locations in steel-concrete composite bridge by modal curvature difference method (MCDM). Here we adopt the updated finite element model in last work as analytical model, taking concrete density and elastic modulus as updating parameters and modal frequency+MAC as reference data. The results indicate that the modal curvature difference method can well locate the damages in steel-concrete composite bridge, especially the damage in concrete. But the change rate of frequency as damage index is insensitive to the bridge damage and the method can’t be applied solely for practical.
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Zhu, Hua Wei, Hong Mou Wang und Wei Peng. „Study on Box Girder Damage Identification of Cable-Stayed Bridges“. Applied Mechanics and Materials 101-102 (September 2011): 1156–60. http://dx.doi.org/10.4028/www.scientific.net/amm.101-102.1156.
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A comparative study of the girder damage identification of Jintang Cable-stayed Bridge in Zhoushan Island-Land Project using the deflection index, the cable tension index, the beam bottom bending stress index, the modal curvature index and the modal flexibility matrix is introduced. By means of finite element method, a series of damage cases associated with the box girder are analyzed. The result shows that, for different damage types, the best effect of the girder damage identification is the modal curvature index, followed by the cable tension index, the beam bottom bending stress index is nearly of the same effect as the modal flexibility matrix index, and the worst is the deflection index.
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Wang, Pengbo, und Qinghe Shi. „Damage Identification in Structures Based on Energy Curvature Difference of Wavelet Packet Transform“. Shock and Vibration 2018 (28.05.2018): 1–13. http://dx.doi.org/10.1155/2018/4830391.
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Damage identification is of tremendous significance in engineering structures. One key issue in damage identification is to determine an index that is sensitive to the structural damage. Current damage identification indices are generally focused on dynamic characteristics such as the natural frequencies, modal shapes, frequency responses, or their mathematical combinations. In this study, based on the wavelet packet transform, we propose a novel index, the energy curvature difference (ECD) index, to identify the damage in structures. The ECD index is the summation of component energy curvature differences after a signal is decomposed using WPT. Moreover, two numerical examples are used to demonstrate the feasibility and validity of the proposed ECD index for damage identification. Stiffness reduction is employed to simulate the structural damage. The damage can be identified by the ECD index curve plot. The results of the examples indicate that the proposed ECD index is sensitive to low damage levels because even 5% stiffness reduction can be apparently identified. The proposed ECD index can be employed to effectively identify structural damage.
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Nayyar, Ayisha, Ummul Baneen, Syed Abbas Zilqurnain Naqvi und Muhammad Ahsan. „Detection and localization of multiple small damages in beam“. Advances in Mechanical Engineering 13, Nr. 1 (Januar 2021): 168781402098732. http://dx.doi.org/10.1177/1687814020987329.
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Localizing small damages often requires sensors be mounted in the proximity of damage to obtain high Signal-to-Noise Ratio in system frequency response to input excitation. The proximity requirement limits the applicability of existing schemes for low-severity damage detection as an estimate of damage location may not be known a priori. In this work it is shown that spatial locality is not a fundamental impediment; multiple small damages can still be detected with high accuracy provided that the frequency range beyond the first five natural frequencies is utilized in the Frequency response functions (FRF) curvature method. The proposed method presented in this paper applies sensitivity analysis to systematically unearth frequency ranges capable of elevating damage index peak at correct damage locations. It is a baseline-free method that employs a smoothing polynomial to emulate reference curvatures for the undamaged structure. Numerical simulation of steel-beam shows that small multiple damages of severity as low as 5% can be reliably detected by including frequency range covering 5–10th natural frequencies. The efficacy of the scheme is also experimentally validated for the same beam. It is also found that a simple noise filtration scheme such as a Gaussian moving average filter can adequately remove false peaks from the damage index profile.
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Qin, Yong. „Study on Damage Identification of Simple Beam Bridge Based on the First-Order Curvature Mode Ratio“. Applied Mechanics and Materials 578-579 (Juli 2014): 1032–36. http://dx.doi.org/10.4028/www.scientific.net/amm.578-579.1032.
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Starting with damage identification index method on the basis of the curvature mode, the first-order curvature mode ratio is proposed, and then it is made a numerical simulation analysis for a single span simple beam bridge with ANSYS. The identification of structure damage degree under the damage on the single position is studied. The fitted polynomial based on the derivation of the first-order curvature mode ratio can estimate the damage degree; it has a good reference value for the damage detection of structures in practical engineering.
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Rucevskis, Sandris, Pavel Akishin und Andris Chate. „Numerical and Experimental Study on the Application of Mode Shape Curvature for Damage Detection in Plate-Like Structures“. Solid State Phenomena 220-221 (Januar 2015): 264–70. http://dx.doi.org/10.4028/www.scientific.net/ssp.220-221.264.
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The paper describes on-going research effort at detecting and localizing damage in plate-like structures using mode shape curvature based damage detection algorithm. The proposed damage index uses data on exclusively mode shape curvature from the damaged structure. This method was originally developed for beam-like structures. The article generalizes the method of plate-like structures characterized by two-dimensional mode shape curvature. To examine limitations of the method, several sets of simulated data are applied and the obtained results of the numerical detection of damage are validated by comparing them with the findings of the case of the experimental test. The simulated test cases include the damage of various levels of severity. In order to ascertain the sensitivity of the proposed method for noisy experimental data, numerical mode shapes are corrupted with different levels of random noise. Modal frequencies and corresponding mode shapes of an aluminium plate containing mill-cut damage are obtained via finite element models for numerical simulations and by using a scanning laser vibrometer (SLV) for the experimental study.
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He, Wen-Yu, Wei-Xin Ren, Lei Cao und Quan Wang. „FEM Free Damage Detection of Beam Structures Using the Deflections Estimated by Modal Flexibility Matrix“. International Journal of Structural Stability and Dynamics 21, Nr. 09 (19.05.2021): 2150128. http://dx.doi.org/10.1142/s0219455421501285.
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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.
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Hu, Zhixiang, und Peiguan Zhang. „Damage Identification of Structures Based on Smooth Orthogonal Decomposition and Improved Beetle Antennae Search Algorithm“. Advances in Civil Engineering 2021 (27.02.2021): 1–14. http://dx.doi.org/10.1155/2021/8857356.
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A novel damage identification method that utilizes the smooth orthogonal decomposition (SOD) combined with the improved beetle antennae search algorithm (BAS) presented by previous scholars is proposed. Firstly, the damage index which can track the curvature changing of mode shape identified by the SOD method is generated by an adaptive polynomial fit method. The locations of structure damages are determined according to the damage index. Thus, the number of possible damaged elements needed to be taken into account can be reduced when calculating the degree of damage. Then, the reduction in the stiffness at the damage location of the structure is calculated by the improved BAS in which the fitness function is constructed by calculated frequencies of the damaged structure in each iteration and the modal frequencies obtained by SOD. The BAS algorithm is improved through a fusion strategy of simulated annealing theory. Thus, the improved BAS algorithm is efficient and adaptive. The effect of this combined application in damage identification has been verified by numerical examples of a simply supported beam with single damage and a cantilever beam with double damage. The numerical results show that this combined algorithm exhibits high reliability in damage identification of beam-like structures.
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Han, Dongying, Shimin Wei, Peiming Shi, Ying Zhang, Kai Gao und Nengyuan Tian. „Damage Identification of a Derrick Steel Structure Based on the HHT Marginal Spectrum Amplitude Curvature Difference“. Shock and Vibration 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/1062949.
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For the damage identification of derrick steel structures, traditional methods often require high-order vibration information of structures to identify damage accurately. However, the high-order vibration information of structures is difficult to acquire. Based on the technology of signal feature extraction, only using the low-order vibration information, taking the right front leg as an example, we analyzed the selection of HHT marginal spectrum amplitude and the calculation process of its curvature in practical application, designed the damage conditions of a derrick steel structure, used the index and intrinsic mode function (IMF) instantaneous energy curvature method to perform the damage simulation calculation and comparison, and verified the effect of identifying the damage location in a noisy environment. The results show that the index can accurately determine the location of the damage element and weak damage element and can be used to qualitatively analyze the damage degree of the element; under the impact load, the noise hardly affects the identification of the damage location. Finally, this method was applied to the ZJ70 derrick steel structure laboratory model and compared with the IMF instantaneous energy curvature method. We verified the feasibility of this method in the damage location simulation experiment.
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Jiang, Zeng Guo, und Bo Chen. „Performance Degradation Assessment of a Beam Structure by Using Wavelet Packet Energy“. Applied Mechanics and Materials 166-169 (Mai 2012): 1102–7. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.1102.
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The evaluation on damage event of a beam structure is carried out in this study through an integration of knowledge in damage detection and signal process. A damage detection approach based on wavelet packet transform (WPT) is developed by decomposing and reconstructing the structural dynamic responses to obtain the signal energy distribution at different levels. The WPT coefficients are reconstructed to extract the signals in various frequency ranges and determine the signal energy in different frequency bands. A WPT component energy index is proposed to establish the slope vector as well as curvature vector and then the judge on the slope vector and curvature vector can indicate the damage event. Parametric study is carried out to investigate the relationship between the index amplitude and the damage extent. The results from this study demonstrate that the detection approach proposed can accurately identify the damage event in the structure.
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Ratcliffe, Colin P. „A Frequency and Curvature Based Experimental Method for Locating Damage in Structures“. Journal of Vibration and Acoustics 122, Nr. 3 (01.01.2000): 324–29. http://dx.doi.org/10.1115/1.1303121.
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This paper presents a method for locating structural damage using experimental vibration data. The method uses measured frequency response functions to obtain displacement as a function of frequency. The displacement functions are converted to curvature functions, which are further processed to yield a damage index, displayed on a plot of position versus frequency. The method can be applied when there is no a priori knowledge about the undamaged structure, and it is suitable for automation. This paper details the theory of the broadband method, and the results of an experimental demonstration in which a steel beam was damaged with a narrow slot. It is shown that this proposed damage detection method is highly sensitive, and can locate a very small amount of damage. For example, the narrow slot was correctly located when there was only a 0.8 percent reduction in thickness in the beam. Traditionally, damage causes a change in natural frequencies, but at this small level of damage the frequency changes were within experimental error. Other published methods failed to locate the slot until it was significantly deeper. [S0739-3717(00)01403-3]
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Zhao, Jiangang, Yuxiang Zhang und Jiazhao Chen. „Damage Identification of Plate Structure Based on the Method of Modal Flexibility Curvature Difference“. MATEC Web of Conferences 256 (2019): 02015. http://dx.doi.org/10.1051/matecconf/201925602015.
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According to the higher order modes of the structure are difficult to extract and the lower order are easy to obtain in practice, it is put forward that only uses the parameters of lower or first-order modal to constitute the modal flexibility curvature difference (MFCD) as the index of damage identification, which based on the flexibility matrix of structure being sensitive to the structure modal characteristics. Numerical analysis is made on different damage conditions of a plate structure, and the result shows that the MFCD can not only accurately identify the single-damage and multi-damage position of plate structure, but also reflect the size of damage degree. It has a great significance to apply the index into the range of damage identification of actual structures.
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Li, Yong Mei, Bin Zhou, Xi Yuan Zhou, Guo Fu Sun und Bo Yan Yang. „Structural Damage Detection Depending on Curvature Matrix of Change in Flexibility“. Advanced Materials Research 255-260 (Mai 2011): 389–93. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.389.
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Flexibility is more sensitive to structural damage than frequency or mode. Curvature matrix of change in flexibility is presented as a new index of nondestructive damage detection, which is derived from change in structural flexibilities calculated from before damaging and after damaging by means of difference calculation twice, firstly to columns, and then to rows. Therefore a new indicator called as δ Flexibility Curvature Matrix Diagonal (δFCMD) is constructed from the principal diagonal elements based on curvature matrix of change in flexibility. The numerical simulation examples indicate that the damage location and severity in structures, with single damage, multiple ones, slight ones and ones at the supports, can be detected efficiently for a cantilever beam, a fixed supported beam, a simply supported beams and so on by the indicator of δFCMD depending on only a few of lower order modes.
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Shen, Sheng, Huaxin Lv und Sheng-Lan Ma. „Damage Detection and Evaluation for an In-Service Shield Tunnel Based on the Monitored Increment of Neutral Axis Depth Using Long-Gauge Fiber Bragg Grating Sensors“. Sensors 19, Nr. 8 (18.04.2019): 1840. http://dx.doi.org/10.3390/s19081840.
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It is difficult to detect and evaluate the structural damage in a shield tunnel during operation because many traditional techniques based on the observation of vibrations are limited in daily monitoring in tunnels. Thus, the curvature radius of a static longitudinal settlement curve is used to identify the residual health and safety of an in-service shield tunnel. However, there are still two problems. The curvature radius is suitable for a qualitative judgment rather than a quantitative evaluation for longitudinal damage detection. Moreover, the curvature radius, which is calculated from the measured settlements of three neighboring points, gives an average damage degree in a wide scope only and is difficult to use to identify the damage’s precise location. By means of the analysis of three kinds of longitudinal failure modes in a shield tunnel, this paper proposes: (1) a damage detection method based on the monitored increment of the neutral axis depth; and (2) an index to evaluate longitudinal damage. The index is composed of the residual ratios of the equivalent flexural stiffness (HFM1) and the equivalent shear stiffness (HFM3). The neutral axis position and the proposed damage index can be determined using long-gauge Fiber Bragg Grating sensors. Results from numerical simulations show that the deviation between the HFM1 and the true value residual ratio of the equivalent flexural stiffness is no more than 1.7%. The HFM3 is equal to its true value in the entire damage process. A loading experiment for a scaled-down model of a shield tunnel using long-gauge Fiber Bragg Grating sensors indicated that the errors in the HFM1 were no more than 5.0% in the case of early damage development (HFM1 ≥ 0.5). The maximum error did not exceed 9.0% even under severe damage conditions in the model. Meanwhile, the HFM3 also coincided with its true value in the entire testing process.
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Zenkov, Solon. „Localization of structural damage based on its dynamic analysis“. Transactions of the Krylov State Research Centre, SPECIAL ISSUE 1 (16.04.2019): 170–76. http://dx.doi.org/10.24937/2542-2324-2019-1-s-i-170-176.
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This paper gives the results of analytical and experimental data on localization of structural damage, obtained through comparison of vibration modes for intact and damaged structure. The paper studies a standard dog-bone sample used for highcycle fatigue tests, the analysis being performed for its finite-element model. Necking damage of the sample was simulated by step-by-step elimination of elements from the model. Physical tests were performed as per the same approach. This paper studies the following damage localization methods: direct method of shape variation; shape curvature method and damage index method. The analysis of vibration shapes performed as per various approaches yielded damage locations and made it possible to identify the most accurate of above-mentioned methods.
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He, Wen-Yu, Jian He und Wei-Xin Ren. „The Use of Mode Shape Estimated from a Passing Vehicle for Structural Damage Localization and Quantification“. International Journal of Structural Stability and Dynamics 19, Nr. 10 (Oktober 2019): 1950124. http://dx.doi.org/10.1142/s0219455419501244.
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Mode shapes estimated from the vehicle responses are normally used to detect bridge damage efficiently for their high spatial resolution. However, an updated baseline finite element model (FEM) is normally required to quantify damages for such an approach. A two-stage damage detection procedure is presented for bridges by utilizing the mode shape estimated from a moving vehicle. Damage locations are first determined through a damage localization index (DLI) defined by regional mode shape curvature (RMSC). Then the relationship between the damage extents and the RMSC changes is investigated by FEM simulation. Finally, an equation set to quantify the single and multiple damages is deduced by combining the RMSCs and the relationship between the damage extents and the RMSC changes established by an un-updated FEM. Numerical and experimental examples are carried out to verify the validity and efficiency of the two-stage method. The results revealed that it can localize and quantify damages with satisfactory precision by using the response measured from one sensor only.
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Peng, Wei, und Zhi Xiang Zha. „Sensitivity Study on Damage Indexes of Cable-Stayed Bridges“. Advanced Materials Research 243-249 (Mai 2011): 1573–77. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.1573.
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Damages in a structure alter its static and dynamic characteristics. These changes occur in some structural parameters such as the mass, the stiffness, the flexibility and the damping matrices of the structure and can be characterized by changes in the modal parameters, i.e., modal frequencies, modal damping values and mode shapes, and their derivatives, such as the modal curvature and modal stress energy. According to the properties of cable-stayed bridges, various damage indexes of static and dynamic are constructed to indicate damage of cable, tower and girder respectively. A comprehensive index accounting for their interaction and the whole bridge damage is presented which is robust to measurement noises and uncertainties in ambient conditions. The sensitivities of these damage indexes are illustrated by numerical studies. The effectiveness of the proposed damage detection method of cable-stayed bridges is demonstrated through an engineering project.
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Feng, Dongming, und Maria Q. Feng. „Output-only damage detection using vehicle-induced displacement response and mode shape curvature index“. Structural Control and Health Monitoring 23, Nr. 8 (06.01.2016): 1088–107. http://dx.doi.org/10.1002/stc.1829.
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Nie, Zhen Hua, Jun Zhao und Hong Wei Ma. „Damage Detection and Quantification of Circular Arch Structures Based on Strain Mode Data“. Applied Mechanics and Materials 94-96 (September 2011): 1120–28. http://dx.doi.org/10.4028/www.scientific.net/amm.94-96.1120.
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Intensive research efforts have been spent on vibration-based structural condition monitoring since structural vibration parameters are closely related to structural stiffness which can be used to identify, locate and quantify structural damage. This makes the vibration-based methods quite attractive for structural condition monitoring. This paper proposes to use strain mode for structural damage identification. A new index named Breach Threshold Value of Damage Levels (BTVDL) is proposed to quantify damage. To demonstrate the proposed method, responses of a circular arch with single and multiple damages are simulated using commercial software ANSYS. The simulated dynamic responses are used to identify the location and degree of the damage of the arch. The results demonstrate that strain mode is more sensitive to damages than others indexes such as frequencies and curvature modes. To further verify the method, a scaled arch model was fabricated and tested in the laboratory. Experimental results also confirm the high sensitivity and accuracy of using strain mode in structural damage identification. It is found that the simulated damages can be reliably identified by using the first two strain modes. The proposed method is more sensitive to damages and can be applied to monitoring structural conditions.
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Ditommaso, Rocco, Chiara Iacovino, Gianluca Auletta, Stefano Parolai und Felice Carlo Ponzo. „Damage Detection and Localization on Real Structures Subjected to Strong Motion Earthquakes Using the Curvature Evolution Method: The Navelli (Italy) Case Study“. Applied Sciences 11, Nr. 14 (14.07.2021): 6496. http://dx.doi.org/10.3390/app11146496.
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In recent years, structural health monitoring (SHM) has received increasing interest from both research and professional engineering communities. This is due to the limitations related to the use of traditional methods based on visual inspection for a rapid and effective assessment of structures and infrastructures when compared with the great potential offered by newly developed automatic systems. Most of these kinds of systems allow the continuous estimation of structural modal properties that are strictly correlated to the mechanical characteristics of the monitored structure. These can change as a result of material deterioration and structural damage related to earthquake shaking. Furthermore, a suitable configuration of a dense sensor network in a real-time monitoring system can allow to detect and localize structural and non-structural damage by comparing the initial and a final state of the structure after a critical event, such as a relevant earthquake. In this paper, the modal curvature evaluation method, used for damage detection and localization on framed structures, considering the mode curvature variation due to strong earthquake shaking, is further developed. The modified approach is validated by numerical and experimental case studies. The extended procedure, named “Curvature Evolution Method” (CEM), reduces the required computing time and the uncertainties in the results. Furthermore, in this work, an empirical relationship between curvature variation and damage index has been defined for both bare and infilled frames.
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Liu, Chun Cheng, Shang Yu Hou, Wen Qiang Li und Zhao Wen He. „Fine Damage Identification Method of Transmission Tower Based on Concurrent Multi-Scale Modeling“. Applied Mechanics and Materials 680 (Oktober 2014): 374–78. http://dx.doi.org/10.4028/www.scientific.net/amm.680.374.
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In order to study the damage problem caused by the transmission tower fatigue cracks and bolt pretightening force loss ,this paper proposes a transmission tower damage identification method based on concurrent multi-scale model, namely establish solid model on nodes of fatigue crack and bolt looseness based on large scale model., subdividing elements size. Take a practical engineering 500kV transmission towers as an example to establish a concurrent multi-scale models. This paper simulates 8 kinds of conditions including bolt pretightening force loss and angle steel crack, research shows that the sum of wavelet packet energy curvature difference can effectively identify minute damage, and then get the function relation between damage level and damage index with no noise interference, also this provides a theoretical basis for it as actual damage monitoring indicators index.
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Govindasamy, Mahendran, Gopalakrishnan Kamalakannan, Chandrasekaran Kesavan und Ganesh Kumar Meenashisundaram. „Damage Detection in Glass/Epoxy Laminated Composite Plates Using Modal Curvature for Structural Health Monitoring Applications“. Journal of Composites Science 4, Nr. 4 (14.12.2020): 185. http://dx.doi.org/10.3390/jcs4040185.
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This paper deals with detection of macro-level crack type damage in rectangular E-Glass fiber/Epoxy resin (LY556) laminated composite plates using modal analysis. Composite plate-like structures are widely found in aerospace and automotive structural applications which are susceptible to damages. The formation of cracks in a structure that undergoes vibration may lead to catastrophic events such as structural failure, thus detection of such occurrences is considered necessary. In this research, a novel technique called as node-releasing technique in Finite Element Analysis (FEA), which was not attempted by the earlier researchers, is used to model the perpendicular cracks (the type of damage mostly considered in all the pioneering research works) and also slant cracks (a new type of damage considered in the present work) of various depths and lengths for Unidirectional Laminate (UDL) ([0]S and [45]S) composite layered configurations using commercial FE code Ansys, thus simulating the actual damage scenario. Another novelty of the present work is that the crack is modeled with partial depth along the thickness of the plate, instead of the through the thickness crack which has been of major focus in the literature so far, in order to include the possibility of existence of the crack up to certain layers in the laminated composite structures. The experimental modal analysis is carried out to validate the numerical model. Using central difference approximation method, the modal curvature is determined from the displacement mode shapes which are obtained via finite element analysis. The damage indicators investigated in this paper are Normalized Curvature Damage Factor (NCDF) and modal strain energy-based methods such as Strain Energy Difference (SED) and Damage Index (DI). It is concluded that, all the three damage detection algorithms detect the transverse crack clearly. In addition, the damage indicator NCDF seems to be more effective than the other two, particularly when the detection is for damage inclined to the longitudinal axis of the plate. The proposed method will provide the base data for implementing online structural health monitoring of structures using technologies such as Machine Learning, Artificial Intelligence, etc.
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Dowling, M. E., A. C. Schlink und J. C. Greeff. „Wool weathering damage as measured by Methylene Blue absorption is linked to suint content“. Australian Journal of Experimental Agriculture 46, Nr. 7 (2006): 927. http://dx.doi.org/10.1071/ea05364.
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Weather damage of wool in grazing sheep has long been recognised by the wool industry as a problem, resulting in fibre damage, fibre loss and poor dyeing performance. Merino wool from 3538 ewe and ram hoggets was used to estimate the heritability of Methylene Blue absorption. Methylene Blue absorption has a high heritability of 0.44 ± 0.04 and was strongly genetically correlated with suint index (0.88 ± 0.02) and wool moisture index (0.92 ± 0.03). Methylene Blue absorption was moderately genetically, negatively correlated with measures of clean wool colour and yield and positively with dust penetration. There was no significant correlation between Methylene Blue absorption and dust content or economically important measures of fleece value such as fibre diameter, curvature and staple strength. The strong genetic relationship between Methylene Blue absorption and suint index indicates that Methylene Blue absorption is a very good indirect measure of greasy wool suint content but may not be a satisfactory indicator trait to select for low weather damage.
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Sun, Hong Chun, Yue Cheng Deng und Yuan Cheng You. „Study on the Method of Crack Detection of Steel Rods Based on Modal Analysis“. Applied Mechanics and Materials 249-250 (Dezember 2012): 3–8. http://dx.doi.org/10.4028/www.scientific.net/amm.249-250.3.
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Steel rods are widely used in the areas of petroleum, chemical, architecture and transportation, steel rods with cracks will cause terrible accident and great losses when working in production practice. In view of traditional Non-destructive Testing (NDT) method can only realize static detection, this paper provide the method based on modal calculate analysis, including the choice of damage index and the judgment of damage degree and damage location for cracks of steel rods. The damage location is judged by the strain mode shape difference curve and the function expression of damage degrees and mutation degrees of curvature mode shapes is acquired by the method of least square fitting, which can achieve quantitative analysis of single crack of steel rods, this provide theoretical support and technical reference for experimental modal analysis and dynamic NDT.
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Lee, Eun-Taik, und Hee-Chang Eun. „Detection of Local Damage of Flexural Member Using Measured Frequency Response Functions“. International Journal of Acoustics and Vibration 23, No 3, September 2018 (September 2018): 314–20. http://dx.doi.org/10.20855/ijav.2018.23.31075.
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Measurements by sensors provide inaccurate information, including external noises. This study considers a method to reduce the influence of the external noise, and it presents a method to detect local damage transforming the measured frequency response functions (FRFs) to reduce the influence of the external noise. This study is conducted by collecting the FRFs in the first resonance frequency range from the responses in the frequency domain, taking the mean values at two adjacent nodes, and transforming the results to the proper orthogonal decomposition (POD). A damage detection method is provided. The curvature of the proper orthogonal mode (POM) corresponding to the first proper orthogonal value (POV) is utilized as the damage index to indicate the damage region. A numerical experiment and a floor test of truss bridge illustrate the validity of the proposed method for damage detection.
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Nielsen, Christoffer P. „Deriving Pavement Deflection Indices from Layered Elastic Theory“. Transportation Research Record: Journal of the Transportation Research Board 2674, Nr. 12 (05.10.2020): 278–90. http://dx.doi.org/10.1177/0361198120953433.
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Pavement deflection indices such as the surface curvature index or base damage index are widely used to characterize the condition of pavements. Often, the indices are constructed to provide an estimate of a particular strain component somewhere in the pavement structure. Since the pavement damage is a function of the strain, structural indices provide a simple way of estimating the damage rate in a pavement. Despite their widespread use, it has so far proven difficult to derive deflection indices from first principles; instead, new indices are found by evaluating a range of candidates using a trial-and-error approach. In this paper, a systematic method of deriving deflection indices is presented. The method is based on applying the convolution theorem for Hankel transforms to the solution of a layered elastic problem. Besides allowing for easy derivation of new deflection indices, the method can be used to account for the impact of varying layer thicknesses in the pavement.
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Zhou, Ling, Hua Cheng, Zhong Gang Wang und Yun Bo Lei. „Model Experimental Study on Damage Identification for Transmission Tower“. Advanced Materials Research 243-249 (Mai 2011): 699–703. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.699.
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The analytical signal for time-frequency analysis is obtained by Hilbert transform from free vibration response under suddenly unloading. Mathematical deduction of Wigner-Ville Distribution (WVD) auto-terms reveals the function relation between WVD auto-terms and modal parameters. A new method based on the amplitude curvature of WVD auto-terms (WAC) is then forwarded for damage identification of transmission tower. An elastic model of transmission tower with 1/35 scale and 5.2 m height has been designed and manufactured to verify the proposed method, the model has been tested in the laboratory for acceleration response under suddenly unloading, and essential dynamic characteristics of the scale model is also compared with that of its prototype tower. The damage identification test of the model is then carried out. Totally three cases, related with chord rod weakening, flank rods failures, different damage degree and position, are tested to testify the proposed damage identification index.
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Guo, Qi, Lei Feng, Ruyi Zhang und Haijun Yin. „Study of damage identification for bridges based on deep belief network“. Advances in Structural Engineering 23, Nr. 8 (09.01.2020): 1562–72. http://dx.doi.org/10.1177/1369433219898058.
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To solve the problem of poor anti-noise ability faced by traditional pattern recognition methods in damage identification field, a bridge damage identification method based on deep belief network was proposed. Taken the modal curvature difference as the damage index, three restricted Boltzmann machines were constructed for pre-training. Then, the Softmax classifier and neural network were used to identify the damage location and degree under the environmental cases of no noise, weak noise, and strong noise, respectively. Subsequently, the influence of incomplete measurement modal data on the method was studied. Finally, damage identification based on deep belief network was implemented to a continuous beam bridge and compared with that of the back propagation neural network. The results showed that the proposed method could be highly effective not only on damage location but also on degree identification. Compared with back propagation neural network, deep belief network method may possess better identification ability and stronger anti-noise ability. It also demonstrates good identification effect under the condition of incomplete measurement modal data.
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Li, Xuan, Ya Hui Wang, Lei Jiang und Fan Fang Tang. „Research on the Damage Identification of Weld Metal Cracking of Metal Structure Based on PVDF“. Applied Mechanics and Materials 751 (April 2015): 143–49. http://dx.doi.org/10.4028/www.scientific.net/amm.751.143.
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A new detection method for measuring weld crack of crane’s metal structure is developed.It works by combining polyvinylidene fluoride (PVDF) with curvature operational shapes (COS) algorithm. First, the theory of damage identification using the imaginary part of frequency response function was analyzed, and the extraction approach of COS was illuminated in detail. Then, the fitting method which is called gapped-smoothing method (GSM) was chosen to obtain the COS of healthy structure.Next, experiments were carried out on a steel plate with weld cracks based on PVDF. The experiment result expresses that the positions of cracks could be located precisely and the index is very sensitive to the different length of cracks. Therefore it can provide reliable information for positioning and quantitative analysis of the weld cracks.
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Zhang, Xiu Fang, und Shi Lang Xu. „Ductility Evaluation of Reinforced UHTCC Structural Members“. Advanced Materials Research 150-151 (Oktober 2010): 229–34. http://dx.doi.org/10.4028/www.scientific.net/amr.150-151.229.
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Ultra-high toughness cementitious composite (UHTCC) is a PVA fiber reinforced cementitious composite. Tensile strain hardening behavior with ultimate tensile strain of more 3% under direct tensile loading is one of its important characteristics. In the current article, nine simply-supported reinforced UHTCC beams were subjected to four-point bending loading to experimentally investigate the influence of ductile deformation behavior of UHTCC on ductility capacity of reinforced structural members. Ductility index is determined by adopting three different parameters, i.e., deformation capacity, energy dissipation capacity as well as curvature capacity. The effect of longitudinal tensile reinforcement ratios on the variation of ductility in UHTCC reinforced beams was examined. It was found from the experimental results that the combination of ductile matrix (UHTCC) and steel bar prevents from occurrence of localized cracks in pure bending zone, showing high damage tolerance and ductile failure behavior. The results also show that as longitudinal tensile reinforcement ratio increases, deformation ductility and curvature ductility both exponentially decrease while a small reduction is demonstrated for energy ductility at ultimate failure.
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Zhang, Jian, Yongqiang Zhang, Jilin Wang und Xiaobin Wen. „Prediction of gas pressure in thin coal seams in the Qinglong Coal Mine in Guizhou Province, China“. Journal of Petroleum Exploration and Production Technology 11, Nr. 11 (02.09.2021): 4075–86. http://dx.doi.org/10.1007/s13202-021-01267-2.
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AbstractThin coal seams in mines usually lack gas data. Thus, preventing and controlling gas outbursts of thin coal seams are difficult. In this study, a coal structure index, which is used to express the damage degree of coal, was estimated by logging curve. In accordance with the contour line of the floor of the coal seam, structural curvature was calculated to express the complexity of the coal seam structure quantitatively. Subsequently, relationships among the burial depth, thickness, coal structure index, structural curvature were analyzed on the basis of the gas pressure of coal seam. The gas pressure values of the coal seams of Nos. 22, 24, and 27 in the study area were predicted by multiple linear regression (MLR) and were then verified and analyzed. The deviation rate of the MLR method was 6.5%–19.7%, with an average of 13.0%. The average deviation rate between the predicted value and the measured value was 11.6%, except for the measuring point of No. 2, which had a large deviation. Results show that the prediction accuracy of the aforementioned method is acceptable and has practical value in the prediction of gas pressure in thin coal seams without measured data. The results in the gas pressure prediction provide a basis for evaluating the risk of gas outbursts in thin coal seams.
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Ciobotaru, Ana-Maria, Ion Andronache, Helmut Ahammer, Marko Radulovic, Daniel Peptenatu, Radu-Daniel Pintilii, Cristian-Constantin Drăghici et al. „Application of Fractal and Gray-Level Co-Occurrence Matrix Indices to Assess the Forest Dynamics in the Curvature Carpathians—Romania“. Sustainability 11, Nr. 24 (05.12.2019): 6927. http://dx.doi.org/10.3390/su11246927.
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The mountain ecosystems face significant damage from deforestation and environmental forest changes. We investigated the evolution of tree types of cover areas, deforested areas and total deforested areas from Curvature Carpathians using Gray-Level Co-occurrence Matrix and fractal analysis. The forest dynamics mapping was one of the main objectives of this study and it was carried out using multiple fractal and GLCM indices. We approached the analysis of satellite forest images by calculation of four fractal indices such as Pyramid dimension, Cube Counting Dimension, Fractal Fragmentation-Compaction Index and Tug-of-War lacunarity. We also calculated fractal dimension because it is an index of complexity comparing how the detail in a pattern changes with the scale at which it is measured. Fractal dimension is useful for estimation of irregularity or roughness of fractal and natural objects that do not conform to Euclidian geometry. While the fractal dimension quantifies how much space is occupied, the Tug-of-War lacunarity complements fractal dimension with its ability to quantify how space is occupied. Analysis was further supplemented by the Gray-Level Co-occurrence Matrix analysis because it quantifies spatial probability distributions of gray level values between pixel pairs within an image. The calculated Gray-Level Co-occurrence Matrix features included Angular Second Moment, Contrast, Correlation, Inverse Difference Moment and Entropy. Such comprehensive analysis has the advantage of combining fractal analysis that extracts quantitative information about the morphological complexity of the image with the spatial distribution of the gray pixel intensities as calculated by the co-occurrence features provided by Gray-Level Co-occurrence Matrix. Evolution of deforested areas, expansion of agricultural land and the increased demand for quality timber have affected the forests ecosystems and, the regional sustainable development of local communities.
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Othman, A. A., R. Gloaguen, L. Andreani und M. Rahnama. „Landslide susceptibility mapping in Mawat area, Kurdistan Region, NE Iraq: a comparison of different statistical models“. Natural Hazards and Earth System Sciences Discussions 3, Nr. 3 (06.03.2015): 1789–833. http://dx.doi.org/10.5194/nhessd-3-1789-2015.
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Abstract. During the last decades, expansion of settlements into areas prone to landslides in Iraq has increased the importance of accurate hazard assessment. Susceptibility mapping provides information about hazardous locations and thus helps to potentially prevent infrastructure damage due to mass wasting. The aim of this study is to evaluate and compare frequency ratio (FR), weight of evidence (WOE), logistic regression (LR) and probit regression (PR) approaches in combination with new geomorphological indices to determine the landslide susceptibility index (LSI). We tested these four methods in Mawat area, Kurdistan Region, NE Iraq, where landslides occur frequently. For this purpose, we evaluated 16 geomorphological, geological and environmental predicting factors mainly derived from the advanced spaceborne thermal emission and reflection radiometer (ASTER) satellite. The available reference inventory includes 351 landslides representing a cumulative surface of 3.127 km2. This reference inventory was mapped from QuickBird data by manual delineation and partly verified by field survey. The areas under curve (AUC) of the receiver operating characteristic (ROC), and relative landslide density (R index) show that all models perform similarly and that focus should be put on the careful selection of proxies. The results indicate that the lithology and the slope aspects play major roles for landslide occurrences. Furthermore, this paper demonstrates that using hypsometric integral as a prediction factor instead of slope curvature gives better results and increases the accuracy of the LSI.
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Efendi, Didik, Entin Hidayah und Akhmad Hasanuddin. „Mapping of Landslide Susceptible Zones by Using Frequency Ratios at Bluncong Subwatershed, Bondowoso Regency“. UKaRsT 5, Nr. 1 (03.04.2021): 126. http://dx.doi.org/10.30737/ukarst.v5i1.1455.
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Landslides are the disasters that frequently happen in Bluncong sub-watershed. These incidents have caused damage and malfunction of road infrastructure, bridges, and irrigation buildings. Therefore, it is important to anticipate landslides through mapping of landslide-susceptibility areas The objective of this study is to map landslide susceptibility at Bluncong sub watershed, Bondowoso, by using Geographical Information System and remote sensing. The landslide susceptibility analysis and mapping are conducted based on landslide occurrences with the Frequency Ratio approach. The landslide sites are identified from field survey data interpretation. Digital Elevation Model maps, geological data, land uses and rivers data, and Landsat 8 images are collected, processed, and then built into the GIS platform's spatial database. The selected factors that cause landslide occurrences are land use, distance to river, aspect, slope, elevation, curvature, and the vegetation index (NDVI). The results show that the accuracy of the map is acceptable. The frequency ratio model gained the area under curve (AUC) value of 0.79. It is found that 9.08% of the area has very high landslide susceptibility. Local governments can use this study's mapping results to minimize the risk at landslidesusceptible zones
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Ai-Qadi, Imad L., und Alexander Kwasi Appea. „Eight-Year Field Performance of Secondary Road Incorporating Geosynthetics at Subgrade-Base Interface“. Transportation Research Record: Journal of the Transportation Research Board 1849, Nr. 1 (Januar 2003): 212–20. http://dx.doi.org/10.3141/1849-23.
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In June 1994 an instrumented 150-m-long secondary road pavement section was built in Bedford County, Virginia. This pavement section was composed of nine individual segments each 15 m long. The nine sections include three groups with aggregate base layer thicknesses of 100, 150, and 200 mm. Three sections from each group were stabilized with geotextiles and three were stabilized with geogrids at the base-subgrade interface. The remaining three sections were kept as control sections. As part of the structural analysis, deflection data parameters such as the base damage index and surface curvature index calculated from falling weight deflectometer (FWD) data were analyzed after being corrected for temperature variations from the time of construction until October 2001. Performance criteria such as rutting measurements were also collected over the whole period. A nonlinear exponential model was used to describe the development of rutting versus cumulative equivalent single-axle loads for the 100-mm base course. A linear elastic program incorporating constitutive material properties was used to calculate vertical compressive stresses, which were used with FWD deflections to predict rutting rates with a mechanistic equation. The rutting rate results confirmed the separation function of geosynthetics that prevented the migration of fines from the subgrade to the base course layer and the penetration of the aggregate base layer into the subgrade. Rutting results, deflection data, and service life analysis showed that geosynthetically stabilized sections significantly improved the performance of the 100-mm base course sections.
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Mohammadi, Ayub, Khalil Valizadeh Kamran, Sadra Karimzadeh, Himan Shahabi und Nadhir Al-Ansari. „Flood Detection and Susceptibility Mapping Using Sentinel-1 Time Series, Alternating Decision Trees, and Bag-ADTree Models“. Complexity 2020 (16.11.2020): 1–21. http://dx.doi.org/10.1155/2020/4271376.
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Flooding is one of the most damaging natural hazards globally. During the past three years, floods have claimed hundreds of lives and millions of dollars of damage in Iran. In this study, we detected flood locations and mapped areas susceptible to floods using time series satellite data analysis as well as a new model of bagging ensemble-based alternating decision trees, namely, bag-ADTree. We used Sentinel-1 data for flood detection and time series analysis. We employed twelve conditioning parameters of elevation, normalized difference’s vegetation index, slope, topographic wetness index, aspect, curvature, stream power index, lithology, drainage density, proximities to river, soil type, and rainfall for mapping areas susceptible to floods. ADTree and bag-ADTree models were used for flood susceptibility mapping. We used software of Sentinel application platform, Waikato Environment for Knowledge Analysis, ArcGIS, and Statistical Package for the Social Sciences for preprocessing, processing, and postprocessing of the data. We extracted 199 locations as flooded areas, which were tested using a global positioning system to ensure that flooded areas were detected correctly. Root mean square error, accuracy, and the area under the ROC curve were used to validate the models. Findings showed that root mean square error was 0.31 and 0.3 for ADTree and bag-ADTree techniques, respectively. More findings illustrated that accuracy was obtained as 86.61 for bag-ADTree model, while it was 85.44 for ADTree method. Based on AUC, success and prediction rates were 0.736 and 0.786 for bag-ADTree algorithm, in order, while these proportions were 0.714 and 0.784 for ADTree. This study can be a good source of information for crisis management in the study area.
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Park, Hee Mun, Y. Richard Kim und Seong Wan Park. „Assessment of Pavement Layer Condition with Use of Multiload-Level Falling Weight Deflectometer Deflections“. Transportation Research Record: Journal of the Transportation Research Board 1905, Nr. 1 (Januar 2005): 107–16. http://dx.doi.org/10.1177/0361198105190500112.
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A condition assessment procedure for pavement layers that uses multiload-level falling weight deflectometer (FWD) deflections is presented. A dynamic finite element program that incorporates a stress-dependent soil model was used to generate the synthetic deflection database. On the basis of the data in this database, the relationships between surface deflections and critical pavement responses, such as the stresses and strains in each layer, have been established. The FWD deflection data, distress survey results, temperature, and laboratory testing results used to develop this procedure were collected from the Long-Term Pavement Performance project database. Research efforts also focused on the effect of the FWD load level on the condition assessment procedure. The results indicate that the proposed procedure can estimate the asphalt concrete (AC), base, and subgrade layer conditions. The AC layer modulus and the tensile strain at the bottom of the AC layer were found to be better indicators of the condition of the AC layer than the deflection basin parameter. It was also found that the structurally adjusted base damage index and base curvature index were good indicators for prediction of the stiffness characteristics of the aggregate base and subgrade, respectively. An FWD test with a load of 71.2 kN or less does not improve the accuracy of this procedure. The results from the study of the nonlinear behavior of a pavement structure indicate that the deflection ratio obtained from multiload-level deflections can predict the type and quality of the base and subgrade materials.
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Tien Bui, Duie, Khabat Khosravi, Himan Shahabi, Prasad Daggupati, Jan F. Adamowski, Assefa M.Melesse, Binh Thai Pham et al. „Flood Spatial Modeling in Northern Iran Using Remote Sensing and GIS: A Comparison between Evidential Belief Functions and Its Ensemble with a Multivariate Logistic Regression Model“. Remote Sensing 11, Nr. 13 (04.07.2019): 1589. http://dx.doi.org/10.3390/rs11131589.
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Floods are some of the most dangerous and most frequent natural disasters occurring in the northern region of Iran. Flooding in this area frequently leads to major urban, financial, anthropogenic, and environmental impacts. Therefore, the development of flood susceptibility maps used to identify flood zones in the catchment is necessary for improved flood management and decision making. The main objective of this study was to evaluate the performance of an Evidential Belief Function (EBF) model, both as an individual model and in combination with Logistic Regression (LR) methods, in preparing flood susceptibility maps for the Haraz Catchment in the Mazandaran Province, Iran. The spatial database created consisted of a flood inventory, altitude, slope angle, plan curvature, Topographic Wetness Index (TWI), Stream Power Index (SPI), distance from river, rainfall, geology, land use, and Normalized Difference Vegetation Index (NDVI) for the region. After obtaining the required information from various sources, 151 of 211 recorded flooding points were used for model training and preparation of the flood susceptibility maps. For validation, the results of the models were compared to the 60 remaining flooding points. The Receiver Operating Characteristic (ROC) curve was drawn, and the Area Under the Curve (AUC) was calculated to obtain the accuracy of the flood susceptibility maps prepared through success rates (using training data) and prediction rates (using validation data). The AUC results indicated that the EBF, EBF from LR, EBF-LR (enter), and EBF-LR (stepwise) success rates were 94.61%, 67.94%, 86.45%, and 56.31%, respectively, and the prediction rates were 94.55%, 66.41%, 83.19%, and 52.98%, respectively. The results showed that the EBF model had the highest accuracy in predicting flood susceptibility within the catchment, in which 15% of the total areas were located in high and very high susceptibility classes, and 62% were located in low and very low susceptibility classes. These results can be used for the planning and management of areas vulnerable to floods in order to prevent flood-induced damage; the results may also be useful for natural disaster assessment.
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Haya, Laura, und Stavros Tavoularis. „Effects of bileaflet mechanical heart valve orientation on fluid stresses and coronary flow“. Journal of Fluid Mechanics 806 (29.09.2016): 129–64. http://dx.doi.org/10.1017/jfm.2016.582.
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The effects of the orientation of a bileaflet mechanical heart valve on the viscous and turbulent stresses in the flow past it and on the flow rate in the right coronary artery were investigatedin vitroin a mock circulation loop, using a fluid that matched the kinematic viscosity of blood and the refractive index of the aorta model. Measurements were made past the valve mounted in three orientations at the base of an anatomical aorta model, within physiological aortic flow conditions. At peak flow, the turbulent stresses were on average 21 % higher and viscous stresses exceeding 10 Pa (namely of a level that has been associated with blood cell damage) were 30 % more frequent when the valve was oriented with its plane of symmetry normal to the aorta’s plane of curvature than when it was parallel to it. This was attributed to the impingement of a lateral jet on the concave wall of the aorta and to steeper velocity gradients resulting from the geometrical imbalance of the sinuses relative to the valve’s central jet when the valve was in the ‘normal’ orientation. Very high levels of turbulent stresses were found to occur distal to the corners of the valve’s lateral orifices. The bulk flow rate in the right coronary artery was highest when the valve was positioned with its central orifice aligned with the artery’s opening. The coronary flow rate was directly affected by the size, orientation and time evolution of the vortex in the sinus, all of which were sensitive to the valve’s orientation.
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Lofrano, Egidio, Francesco Romeo und Achille Paolone. „A pseudo-modal structural damage index based on orthogonal empirical mode decomposition“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, Nr. 23-24 (07.11.2019): 7545–64. http://dx.doi.org/10.1177/0954406219885972.
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A structural damage identification technique hinged on the combination of orthogonal empirical mode decomposition and modal analysis is proposed. The output-only technique is based on the comparison between pre- and post-damage free structural vibrations signals. The latter are either kinematic (displacements, velocities or accelerations) or deformation measures (strains or curvatures). The response data are decomposed by means of the orthogonal empirical mode decomposition to derive a finite set of orthogonal intrinsic mode functions; the latter are used as a multi-frequency and data-driven basis to build pseudo-modal shapes. A new damage index, the so-called pseudo-mode index, is introduced to compare the response obtained for the two states of the structural system and detect potential damages. The performance of the devised index in detecting a localised damage is shown through numerical and experimental tests on two structural models, namely a 4-degrees-of-freedom system and a two-hinged parabolic arch.
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Nguyen, Viet-Nghia, Peyman Yariyan, Mahdis Amiri, An Dang Tran, Tien Dat Pham, Minh Phuong Do, Phuong Thao Thi Ngo, Viet-Ha Nhu, Nguyen Quoc Long und Dieu Tien Bui. „A New Modeling Approach for Spatial Prediction of Flash Flood with Biogeography Optimized CHAID Tree Ensemble and Remote Sensing Data“. Remote Sensing 12, Nr. 9 (26.04.2020): 1373. http://dx.doi.org/10.3390/rs12091373.
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Flash floods induced by torrential rainfalls are considered one of the most dangerous natural hazards, due to their sudden occurrence and high magnitudes, which may cause huge damage to people and properties. This study proposed a novel modeling approach for spatial prediction of flash floods based on the tree intelligence-based CHAID (Chi-square Automatic Interaction Detector)random subspace, optimized by biogeography-based optimization (the CHAID-RS-BBO model), using remote sensing and geospatial data. In this proposed approach, a forest of tree intelligence was constructed through the random subspace ensemble, and, then, the swarm intelligence was employed to train and optimize the model. The Luc Yen district, located in the northwest mountainous area of Vietnam, was selected as a case study. For this circumstance, a flood inventory map with 1866 polygons for the district was prepared based on Sentinel-1 synthetic aperture radar (SAR) imagery and field surveys with handheld GPS. Then, a geospatial database with ten influencing variables (land use/land cover, soil type, lithology, river density, rainfall, topographic wetness index, elevation, slope, curvature, and aspect) was prepared. Using the inventory map and the ten explanatory variables, the CHAID-RS-BBO model was trained and verified. Various statistical metrics were used to assess the prediction capability of the proposed model. The results show that the proposed CHAID-RS-BBO model yielded the highest predictive performance, with an overall accuracy of 90% in predicting flash floods, and outperformed benchmarks (i.e., the CHAID, the J48-DT, the logistic regression, and the multilayer perception neural network (MLP-NN) models). We conclude that the proposed method can accurately estimate the spatial prediction of flash floods in tropical storm areas.
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Gherlone, Marco, Massimiliano Mattone, Cecilia Surace, Alessandra Tassotti und Alexander Tessler. „Novel Vibration-Based Methods for Detecting Delamination Damage in Composite Plate and Shell Laminates“. Key Engineering Materials 293-294 (September 2005): 289–96. http://dx.doi.org/10.4028/www.scientific.net/kem.293-294.289.
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The paper describes an on-going research effort aimed at detecting the presence of delamination damage in composite panels based upon their higher-frequency structural response. Two alternative damage indexes are examined that facilitate the identification of the location and extent of delaminations. The damage indexes do not require vibration measurements to be performed on the undamaged structure. Use is made of the bending and twisting curvatures corresponding to the higher-frequency mode shapes that are post-processed via two different smoothing techniques. The modal data are obtained via finite element models based on Mindlin theory and including delaminations. These are introduced using a sub-laminate strategy that permits multiple damages to be modelled through the thickness. Various delamination sizes and locations are examined with a random noise superposed on the data in order to ascertain the degree of sensitivity of the damage index to the noise in the experimental data.
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Belyaeva, A. S., A. V. Kapustin, P. N. Shastin, A. M. Gulyukin und A. I. Laishevtsev. „Selection of production and control strains of Bordetella bronchiseptica for the production of a vaccine against porcine bordetelliosis“. Veterinariya, Zootekhniya i Biotekhnologiya 1, Nr. 9 (2020): 42–55. http://dx.doi.org/10.36871/vet.zoo.bio.202009005.
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Respiratory diseases of pigs are widespread in all countries of the world with developed pig farming and cause significant economic damage to the industry. Bordetelliosis (atrophic rhinitis) is an infectious disease of pigs characterized by partial or complete atrophy of the nasal septum bones, curvature or shortening of the nose, nasal discharge and bleeding, sneezing, and stunting. Against the background of the development and spread of antibiotic resistance, one of the most effective ways to combat this disease is specific prevention. However, domestic vaccines against swine atrophic rhinitis have not been developed. In view of this, the purpose of our work is to study the properties of field isolates of Bordetella bronchiseptica and select production and control strains suitable for the manufacture and control of the effectiveness of vaccines against atrophic rhinitis. To achieve this goal, 15 strains of B. bronchiseptica were isolated using bacteriological methods from various livestock enterprises in Russia. All strains had typical cultural, morphological, tinctorial and biochemical properties. When studying the pathogenicity of field isolates, the method of intraperitoneal infection of white mice at a dose of 1,5×109 microbe cell was used.it was found that only 3 strains out of 15 studied cultures have pathogenicity: № 134-VIEV, 144-VIEV and 194-VIEV. The remaining strains did not cause the death of experimental mice even with a twofold increase in the infecting dose to 3,0×109 microbe cell when determining the virulence of these cultures, expressed in the LD50 index, it was found that the LD50 of strain № 134-VIEV is 4,6×107 microbe cell, № 144-VIEV – 2,9×108 microbe cell, № 194-VIEV – 7,1×107 microbe cell, respectively. The selected strains were used in further studies as the most promising, since the severity of virulence factors should contribute to the high immunogenic activity of the drug. In the course of determining the antigenic properties of strains (in RA), it was found that after the first vaccination of animals, the antibody titer is at the level of 1:153,6±57,24 – 1:204,8±70,10, the second vaccination increased the antibody titer by 4–4,5 times – from 1:614,4±228,93 to 1: 921,6±228,97, respectively. When determining cross-antigenic activity, it was assumed that all three strains have at least one common antigenic determinant, and at least one heterologous one. The severity of cross-antigenic activity was further confirmed during the evaluation of the immunogenic activity of monovaccins. Thus, the mortality rate of animals in the control, non-vaccinated groups was 100%, while in the groups of vaccinated animals, the survival rate reached 80% or higher. This level of immunogenic protection suggests that the protective level of antibodies in the agglutination reaction for white mice with bordetelliosis should be at least 1:358.4. Analyzing the results of this work, we can conclude that specific prevention of pig bordetelliosis can be effective due to careful selection of production strains of the pathogen.
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Rabby, Yasin Wahid, und Yingkui Li. „Landslide Susceptibility Mapping Using Integrated Methods: A Case Study in the Chittagong Hilly Areas, Bangladesh“. Geosciences 10, Nr. 12 (29.11.2020): 483. http://dx.doi.org/10.3390/geosciences10120483.
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Landslide susceptibility mapping is of critical importance to identify landslide-prone areas to reduce future landslides, causalities, and infrastructural damages. This paper presents landslide susceptibility maps at a regional scale for the Chittagong Hilly Areas (CHA), Bangladesh. The frequency ratio (FR) was integrated with the analytical hierarchy process (AHP) (FR_AHP) and logistic regression (LR) (FR_LR). A landslide inventory of 730 landslide locations and 13 landslide predisposing factors including elevation, slope, aspect, plan curvature, profile curvature, topographic wetness index (TWI), stream power index (SPI), land use/land cover, rainfall, distance from drainage network, distance from fault lines, lithology, and normalized difference vegetation index (NDVI) were used. Landslide locations were randomly split into training (80%) and validation (20%) sites to support the susceptibility analysis. A safe zone was determined based on a slope threshold for logistic regression using the exploratory data analysis. The same number of non-landslide locations were randomly selected from the safe zone to train the model (FR_LR). Success and prediction rate curves and statistical indices, including overall accuracy, were used to assess model performance. The success rate curves show that FR_LR showed the highest area under the curve (AUC) (79.46%), followed by the FR_AHP (77.15%). Statistical indices also showed that the FR_LR model gave the best performance as the overall accuracy was 0.86 for training and 0.82 for validation datasets. The prediction rate curve shows similar results. The correlation analysis shows that the landslide susceptibility maps produced by FR and FR_AHP are highly correlated (0.95). In contrast, the correlation between the maps produced by FR and FR_LR was relatively lower (0.85). It indicates that the three models are highly convergent with each other. This study’s integrated methods would be helpful for regional-scale landslide susceptibility mapping, and the landslide susceptibility maps produced would be useful for regional planning and disaster management of the CHA, Bangladesh.