• Title/Summary/Keyword: Damage Function

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Numerical simulation of structural damage localization through decentralized wireless sensors

  • Jeong, Min-Joong;Koh, Bong-Hwan
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.938-942
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    • 2007
  • The proposed algorithm tries to localize damage in a structure by monitoring abnormal increases in strain measurements from a group of wireless sensors. Initially, this clustering technique provides an effective sensor placement within a structure. Sensor clustering also assigns a certain number of master sensors in each cluster so that they can constantly monitor the structural health of a structure. By adopting a voting system, a group of wireless sensors iteratively forages for a damage location as they can be activated as needed. Numerical simulation demonstrates that the newly developed searching algorithm implemented on wireless sensors successfully localizes stiffness damage in a plate through the local level reconfigurable function of smart sensors.

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Fracture Analysis of Concrete using Plastic-Damage Model (소성-손상 모델을 이용한 콘크리트의 파괴해석)

  • 남진원;송하원;김광수
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2004.10a
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    • pp.534-541
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    • 2004
  • The modeling of crack initiation and propagation is very important for the failure analysis of concrete. The cracking process in concrete is quite different from that of other materials, such as metal and glass, in that it is not a sudden onset of new free surface but a continuous forming and connecting of microcracks. The failure process of concrete by cracking causes irreversible deformations and stiffness degradation. Those phenomenon can be modeled using plasticity and damage theory in macroscopic aspect. In this study, a plastic-damage model based on homogenized crack model considering velocity discontinuity and damage variable which is a function of plastic strain is proposed for fracture analysis of concrete. Finally, the plastic-damage model is verified with experimental data.

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Dynamic Characteristics of the Plate with Structural Damages (구조손상을 갖는 평판의 동적특성)

  • Kim, Nam-In;Lee, U-Sik
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.357-362
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    • 2000
  • Though there have been many researches to investigate the relationship between the damage location, damage size and the changes in eigenparameters, there have been few studies on the small-sized damages. Thus, this paper considers the plate with small local damages. The equation of motion for damaged plate is derived in terms of the damage distribution function and then the effects of small damages on the dynamic characteristics of plate are investigated. It is observed that the damage-induced modal coupling and a sufficient number of vibration modes should be considered especially for small damage detections.

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Structural damage identification using cloud model based fruit fly optimization algorithm

  • Zheng, Tongyi;Liu, Jike;Luo, Weili;Lu, Zhongrong
    • Structural Engineering and Mechanics
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    • v.67 no.3
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    • pp.245-254
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    • 2018
  • In this paper, a Cloud Model based Fruit Fly Optimization Algorithm (CMFOA) is presented for structural damage identification, which is a global optimization algorithm inspired by the foraging behavior of fruit fly swarm. It is assumed that damage only leads to the decrease in elementary stiffness. The differences on time-domain structural acceleration data are used to construct the objective function, which transforms the damaged identification problem of a structure into an optimization problem. The effectiveness, efficiency and accuracy of the CMFOA are demonstrated by two different numerical simulation structures, including a simply supported beam and a cantilevered plate. Numerical results show that the CMFOA has a better capacity for structural damage identification than the basic Fruit Fly Optimization Algorithm (FOA) and the CMFOA is not sensitive to measurement noise.

Damage detection based on MCSS and PSO using modal data

  • Kaveh, Ali;Maniat, Mohsen
    • Smart Structures and Systems
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    • v.15 no.5
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    • pp.1253-1270
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    • 2015
  • In this paper Magnetic Charged System Search (MCSS) and Particle Swarm Optimization (PSO) are applied to the problem of damage detection using frequencies and mode shapes of the structures. The objective is to identify the location and extent of multi-damage in structures. Both natural frequencies and mode shapes are used to form the required objective function. To moderate the effect of noise on measured data, a penalty approach is applied. A variety of numerical examples including two beams and two trusses are considered. A comparison between the PSO and MCSS is conducted to show the efficiency of the MCSS in finding the global optimum. The results show that the present methodology can reliably identify damage scenarios using noisy measurements and incomplete data.

Optimal Seismic Reliability of Bridges Based on Minimum Expected Life Cycle Costs (최소기대비용에 기초한 교량의 최적내진신뢰성)

  • 조효남;임종권;심성택
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1999.10a
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    • pp.249-256
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    • 1999
  • This study is intended to propose a systematic procedure for the development of the reliability-based seismic safety and cost-effective Performance criteria for design and upgrading of long span PC bridges. In the paper, a set of cost function models for life cycle cost analysis of bridges is proposed. The total life cycle cost functions consist of initial cost and direct/indirect damage costs considering repair/replacement costs, human losses and property damage costs, road user costs, and indirect regional economic losses. The damage costs are successfully expressed in terms of Park-Ang median global damage indices and damage probabilities. The proposed approach is successfully applied to model bridges in both regions of a moderate seismicity area like Seoul, Korea and a high one like Tokyo, Japan. It may be expected that the proposed approach can be effectively utilized for the development of cost-effective performance criteria for design and upgrading of various types of bridges as well as long span PC bridges.

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Damage detection in beams and plates using wavelet transforms

  • Rajasekaran, S.;Varghese, S.P.
    • Computers and Concrete
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    • v.2 no.6
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    • pp.481-498
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    • 2005
  • A wavelet based approach is proposed for structural damage detection in beams, plate and delamination of composite plates. Wavelet theory is applied here for crack identification of a beam element with a transverse on edge non-propagating open crack. Finite difference method was used for generating a general displacement equation for the cracked beam in the first example. In the second and third example, damage is detected from the deformed shape of a loaded simply supported plate applying the wavelet theory. Delamination in composite plate is identified using wavelet theory in the fourth example. The main concept used is the breaking down of the dynamic signal of a structural response into a series of local basis function called wavelets, so as to detect the special characteristics of the structure by scaling and transformation property of wavelets. In the light of the results obtained, limitations of the proposed method as well as suggestions for future work are presented. Results show great promise of wavelet approach for damage detection and structural health monitoring.

Damage observability, localization and assessment based on eigenfrequencies and eigenvectors curvatures

  • Ciambella, Jacopo;Vestroni, Fabrizio;Vidoli, Stefano
    • Smart Structures and Systems
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    • v.8 no.2
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    • pp.191-204
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    • 2011
  • A technique for damage localization and assessment based on measurements of both eigenvectors curvatures and eigenfrequencies is proposed. The procedure is based on two successive steps: a model independent localization, based on changes of modal curvatures, and the solution of a one-dimensional minimization problem to evaluate damage intensity. The observability properties of damage parameters is discussed and, accordingly, a suitable change of coordinates is introduced. The proposed technique is illustrated with reference to a cantilever Euler beam endowed with a set of piezoelectric transducers. To assess the robustness of the algorithm, a parametric study of the identification errors with respect to the number of transducers and to the number of considered modal quantities is carried out with both clean and noise-corrupted data.

Seismic Risk Assessment of Piers Using Fragility Analysis (취약도 분석을 통한 교각의 지진위험도 평가)

  • Lee, Dae-Hyoung;Kim, Hyun-Jun;Park, Chang-Kyu;Chung, Young-Soo
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2006.03a
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    • pp.261-268
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    • 2006
  • This study represents results of fragility curve development for 3-span continuous bridge. To research the response of bridge under earthquake excitation, Monte Carlo simulation is performed to study nonlinear dynamic analysis. Because of limited number of real time histories from the Korean peninsula, a set of 150 synthetic time histories were generated. Fragility corves in this study are represented by lognormal distribution functions with two parameters and developed as a function of PGA. Five damage states were defined to express the condition of damage based on the actual experimental damage data of bridge column. As a result of this research, the value of damage probability corresponding to each damage state were determined. This approach may be used in constructing the fragility curves for all of bridge structure and, by extension, in constructing the seismic hazard map.

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A study on the damage process of fatigue crack growth using the stochastic model (확률적모델을 이용한 피로균열성장의 손상과정에 관한 연구)

  • Lee, Won Suk;Cho, Kyu Seoung;Lee, Hyun Woo
    • Journal of the Korean Society for Precision Engineering
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    • v.13 no.10
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    • pp.130-138
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    • 1996
  • In general, the scattler is observed in fatigue test data due to the nonhomogeneity of a material. Consequently. It is necessary to use the statistical method to describe the fatigue crack growth process precisely. Bogdanoff and Kozin suggested and developed the B-model which is the probabilistic models of cumulative damage using the Markov process in order to describe the damage process. But the B-model uses only constant probability ratior(r), so it is not consistent with the actual damage process. In this study, the r-decreasing model using a monotonic decreasing function is introduced to improve the B-model. To verify the model, thest data of fatigue crack growth of A12024-T351 and A17075-T651 are used. Compared with the empirical distribution of test data, the distribution from the r-decreasing model is satisfactory and damage process is well described from the probabilistic and physical viewpoint.

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