• 제목/요약/키워드: Structural Parameters

검색결과 4,450건 처리시간 0.024초

Probabilistic damage detection of structures with uncertainties under unknown excitations based on Parametric Kalman filter with unknown Input

  • Liu, Lijun;Su, Han;Lei, Ying
    • Structural Engineering and Mechanics
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    • 제63권6호
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    • pp.779-788
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    • 2017
  • System identification and damage detection for structural health monitoring have received considerable attention. Various time domain analysis methodologies based on measured vibration data of structures have been proposed. Among them, recursive least-squares estimation of structural parameters which is also known as parametric Kalman filter (PKF) approach has been studied. However, the conventional PKF requires that all the external excitations (inputs) be available. On the other hand, structural uncertainties are inevitable for civil infrastructures, it is necessary to develop approaches for probabilistic damage detection of structures. In this paper, a parametric Kalman filter with unknown inputs (PKF-UI) is proposed for the simultaneous identification of structural parameters and the unmeasured external inputs. Analytical recursive formulations of the proposed PKF-UI are derived based on the conventional PKF. Two scenarios of linear observation equations and nonlinear observation equations are discussed, respectively. Such a straightforward derivation of PKF-UI is not available in the literature. Then, the proposed PKF-UI is utilized for probabilistic damage detection of structures by considering the uncertainties of structural parameters. Structural damage index and the damage probability are derived from the statistical values of the identified structural parameters of intact and damaged structure. Some numerical examples are used to validate the proposed method.

SMIT를 활용한 지진하중을 받는 전단 구조물의 응답모드 특성에 관한 연구 (Application Studies on Structural Modal Identification Toolsuite for Seismic Response of Shear Frame Structure)

  • 장민우
    • 한국지진공학회논문집
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    • 제22권3호
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    • pp.201-210
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    • 2018
  • The improvement in computing systems and sensor technologies devotes to conduct data-driven structural health monitoring algorithms for existing civil infrastructures. Despite of the development of techniques, the uncertainty oriented from the measurement results in the discrepancy to the actual structural parameters and let engineers or decision makers hesitate to adopt such techniques. Many studies have shown that the modal identification results can be affected by the uncertainties due to the applied methods and the types of loading. This paper aims to compare the performance of modal identification methods using Structural Modal Identification Toolsuite (SMIT) which has been developed to facilitate multiple identification methods with a user-friendly designed platform. The data fed into SMIT processes three stages for the comprehensive identification including preprocessing, eigenvalue estimation, and post-processing. The seismic and white noise response for shear frame model was obtained from numerical simulation. The identified modal parameters is compared to the actual modal parameters. In order to improve the quality of coherence in identified modal parameters, several hurdles including modal phase collinearity and extended modal amplitude coherence were introduced. Numerical simulation conducted on the 5 dof shear frame model were used to validate the effectiveness of using these parameters.

상시진동 계측자료를 이용한 Nanjing TV탑의 강성계수 추정 (Identification of Stiffness Parameters of Nanjing TV Tower Using Ambient Vibration Records)

  • Kim Jae Min;Feng. M. Q.
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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    • pp.291-300
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    • 1998
  • This paper demonstrates how ambient vibration measurements at a limited number of locations can be effectively utilized to estimate parameters of a finite element model of a large-scale structural system involving a large number of elements. System identification using ambient vibration measurements presents a challenge requiring the use of special identification techniques, which ran deal with very small magnitudes of ambient vibration contaminated by noise without the knowledge of input farces. In the present study, the modal parameters such as natural frequencies, damping ratios, and mode shapes of the structural system were estimated by means of appropriate system identification techniques including the random decrement method. Moreover, estimation of parameters such as the stiffness matrix of the finite element model from the system response measured by a limited number of sensors is another challenge. In this study, the system stiffness matrix was estimated by using the quadratic optimization involving the computed and measured modal strain energy of the system, with the aid of a sensitivity relationship between each element stiffness and the modal parameters established by the second order inverse modal perturbation theory. The finite element models thus identified represent the actual structural system very well, as their calculated dynamic characteristics satisfactorily matched the observed ones from the ambient vibration test performed on a large-scale structural system subjected primarily to ambient wind excitations. The dynamic models identified by this study will be used for design of an active mass damper system to be installed on this structure fer suppressing its wind vibration.

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The effects of uncertainties in structural analysis

  • Pellissetti, M.F.;SchueIler, G.I.
    • Structural Engineering and Mechanics
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    • 제25권3호
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    • pp.311-330
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    • 2007
  • Model-based predictions of structural behavior are negatively affected by uncertainties of various type and in various stages of the structural analysis. The present paper focusses on dynamic analysis and addresses the effects of uncertainties concerning material and geometric parameters, mainly in the context of modal analysis of large-scale structures. Given the large number of uncertain parameters arising in this case, highly scalable simulation-based methods are adopted, which can deal with possibly thousands of uncertain parameters. In order to solve the reliability problem, i.e., the estimation of very small exceedance probabilities, an advanced simulation method called Line Sampling is used. In combination with an efficient algorithm for the estimation of the most important uncertain parameters, the method provides good estimates of the failure probability and enables one to quantify the error in the estimate. Another aspect here considered is the uncertainty quantification for closely-spaced eigenfrequencies. The solution here adopted represents each eigenfrequency as a weighted superposition of the full set of eigenfrequencies. In a case study performed with the FE model of a satellite it is shown that the effects of uncertain parameters can be very different in magnitude, depending on the considered response quantity. In particular, the uncertainty in the quantities of interest (eigenfrequencies) turns out to be mainly caused by very few of the uncertain parameters, which results in sharp estimates of the failure probabilities at low computational cost.

직물 구조인자와 표면 가공특성이 스포츠 의류용 투습직물의 발수/방수/투습특성에 미치는 영향 (Effect of Fabric Structural Parameters and Surface Finishing Characteristics to Water Repellency/Proofing/Vapor Permeability of Breathable Fabrics for Sportswear Clothing)

  • 김현아
    • 한국의류산업학회지
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    • 제22권1호
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    • pp.112-118
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    • 2020
  • This paper examined the water repellency, water proofing and water vapor permeability of twelve types of woven fabrics for sports wear clothing. Their physical properties were compared and discussed with the fabric structural parameters and surface finishing effect. A water repellent property of 100% was obtained in the coated or laminated water repellent finished fabrics; in addition, cotton/nylon breathable composite fabrics treated with a laminated finishing and with low fabric density showed a 90% water repellency. Water proofing fabric above 6,000 mm H2O hydraulic pressure was achieved by coated or laminated finishing; however, high density fabric or medium-level coated fabrics exhibited 100% water repellent and low water proofing characteristics. Superior water vapor permeability characteristics with good water repellency and proofing properties were achieved at the 2.5 layered low density and with 0.7 - 0.9 cover factor nylon fabrics treated with hydrophilic laminated finishing. The regression analysis for examining the effects of fabric structural parameters and surface finishing such as coating and laminating to the water vapor permeability exhibited a high determination coefficient of fabric structural parameters of 63.5%; in addition,, main factors among fabric structural parameters appeared to be cover factor and fabric thickness per weight. Coating and Laminating factors exhibited determination coefficient of water vapor permeability parameters of 36.5%.

주파수 응답함수를 이용한 구조 파라메터 예측 (Identification of Structural Parameters from Frequency Response Functions)

  • 김규식;강연준
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2007년도 추계학술대회논문집
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    • pp.863-869
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    • 2007
  • An improved method based on a normal frequency response function (FRF) is proposed to identify structural parameters such as mass, stiffness and damping matrices directly from the FRFs of a linear mechanical system. The method for estimating structural parameters directly from the measured FRFs of a structure is presented. This paper demonstrates that the characteristic matrices are extracted more accurately by using a weighted equation and eliminating the matrix inverse operation. The method is verified for a four degree-of-freedom lumped parameter system and an eight degree-of-freedom finite element beam. Experimental verification is also performed for a free-free steel beam whose size and physical properties are the same as those of the finite element beam. The results show that the structural parameters, especially the damping matrix, can be estimated more accurately by the proposed method.

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부분구조 추정법을 이용한 국부구조계수추정 (Estimation of Localized Structural Parameters Using Substructural Identification)

  • 윤정방;이형진
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1996년도 봄 학술발표회 논문집
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    • pp.119-126
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    • 1996
  • In this paper, a method of substructural identification is presented for the estimation of localized structural parameters. for this purpose, an auto-regressive and moving average with stochastic input (ARMAX) model is derived for the substructure to process the measurement data impaired by noises. The sequential prediction error method is used fer the estimation of unknown localized parameters. Using the substructural method, the number of unknown parameters can be reduced and the convergence and accuracy of estimation can be improved. For some substructures, the effect of the input excitation is expressed in terms of the responses at the inferences with the main structure, and substructural identification may be carried out without measuring the actual input excitation to the whole structure. Example analysis is carried out for idealized structural models of a multistory building and a truss bridge. The results indicate that the present method is effective and efficient for local damage estimation of complex structures.

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유한요소 - 경계요소 조합에 의한 지반매개변수 추정에 관한 연구 (A Study on the Estimation of Underground Parameters by Coupling of Finite and Boundary Elements)

  • 김문겸;장정범;오금호
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1995년도 봄 학술발표회 논문집
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    • pp.28-34
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    • 1995
  • Behavior of underground structural systems is usually complicated because of various unknown parameters. In order to construct those structural systems safely and economically, exact identification of the system parameters and accurate analysis of the system behaviors are essentially required. In this study, a forward analysis program, which is able to eliminate numerical errors due to far field boundary effect, is developed by coupling finite and boundary elements. In this coupled analysis, boundary elements are used in the semi-infinite domain where stress variation is small, and finite elements in the stress concentration region where material nonlinearity should be considered. Then, a back analysis program which can identify the system parameters is developed using the direct method to be combined with the forward analysis program. The elastic modulus and initial stress, which are most important in the description of the behavior of underground structures, are taken as the system parameters. A simple example is examined 0 show that the method can be used effectively.

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A two-stage Kalman filter for the identification of structural parameters with unknown loads

  • He, Jia;Zhang, Xiaoxiong;Feng, Zhouquan;Chen, Zhengqing;Cao, Zhang
    • Smart Structures and Systems
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    • 제26권6호
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    • pp.693-701
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    • 2020
  • The conventional Kalman Filter (KF) provides a promising way for structural state estimation. However, the physical parameters of structural systems or models should be available for the estimation. Moreover, it is not applicable when the loadings applied to the structures are unknown. To circumvent the aforementioned limitations, a two-stage KF with unknown input approach is proposed for the simultaneous identification of structural parameters and unknown loadings. In stage 1, a modified observation equation is employed. The structural state vector is estimated by KF on the basis of structural parameters identified at the previous time-step. Then, the unknown input is identified by Least Squares Estimation (LSE). In stage 2, based on the concept of sensitivity matrix, the structural parameters are updated at the current time-step by using the estimated structural states obtained from stage 1. The effectiveness of the proposed approach is numerically validated via a five-story shearing model under random and earthquake excitations. Shaking table tests on a five-story structure are also employed to demonstrate the performance of the proposed approach. It is demonstrated from numerical and experimental results that the proposed approach can be used for the identification of parameters of structure and the external force applied to it with acceptable accuracy.

Stationary random response analysis of linear fuzzy truss

  • Ma, J.;Chen, J.J.;Gao, W.;Zhao, Y.Y.
    • Structural Engineering and Mechanics
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    • 제22권4호
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    • pp.469-481
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    • 2006
  • A new method called fuzzy factor method for the stationary stochastic response analysis of fuzzy truss with global fuzzy structural parameters is presented in this paper. Considering the fuzziness of the structural physical parameters and geometric dimensions simultaneously, the fuzzy correlation function matrix of structural displacement response in time domain is derived by using the fuzzy factor method and the optimization method, the fuzzy mean square values of the structural displacement and stress response in the frequency domain are then developed with the fuzzy factor method. The influences of the fuzziness of structural parameters on the fuzziness of mean square values of the displacement and stress response are inspected via an example and some important conclusions are obtained. Finally, the example is simulated by Monte-Carlo method and the results of the two methods are close, which verified the feasibility of the method given in this paper.