• Title/Summary/Keyword: substructural method

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An accurate substructural synthesis approach to random responses

  • Ying, Z.G.;Zhu, W.Q.;Ye, S.Q.;Ni, Y.Q.
    • Structural Engineering and Mechanics
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    • v.39 no.1
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    • pp.47-75
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    • 2011
  • An accurate substructural synthesis method including random responses synthesis, frequency-response functions synthesis and mid-order modes synthesis is developed based on rigorous substructure description, dynamic condensation and coupling. An entire structure can firstly be divided into several substructures according to different functions, geometric and dynamic characteristics. Substructural displacements are expressed exactly by retained mid-order fixed-interfacial normal modes and residual constraint modes. Substructural interfacial degree-of-freedoms are eliminated by interfacial displacements compatibility and forces equilibrium between adjacent substructures. Then substructural mode vibration equations are coupled to form an exact-condensed synthesized structure equation, from which structural mid-order modes are calculated accurately. Furthermore, substructural frequency-response function equations are coupled to yield an exact-condensed synthesized structure vibration equation in frequency domain, from which the generalized structural frequency-response functions are obtained. Substructural frequency-response functions are calculated separately by using the generalized frequency-response functions, which can be assembled into an entire-structural frequency-response function matrix. Substructural power spectral density functions are expressed by the exact-synthesized substructural frequency-response functions, and substructural random responses such as correlation functions and mean-square responses can be calculated separately. The accuracy and capacity of the proposed substructure synthesis method is verified by numerical examples.

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

  • 윤정방;이형진
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1996.04a
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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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Identification of Connection Stiffnesses of Bolted Structures Using a Substructural Sensitvitity Analysis (부분구조 기반 민감도 해석을 이용한 볼트겹합 구조물의 결합강성 추정)

  • 서세영;방극호;김찬묵;이두호
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.7
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    • pp.287-294
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    • 2001
  • The identification of connection stiffnesses of bolted structures is presented using FRT-based substructural sensitivity analysis. The substructural design sensitivity formula is derived and plugged into the optimization module of MATLAB to identify connection stiffnesses of an air-conditioner compressor or passenger Car. The air-conditioner composed of a compressor and a bracket, is analysed by using the FRT-based substructural(FBS) method to obtain FTRs an FE model is generated for the bracket, and the impact hammer test is performed for the compressor, Obtained FRTs are combined to calculate the reaction force at the connection point and the system response. By minimizing the difference between a target FRT and calculated one the connection element properties of the air-conditioner syste are identified It is shown that the proposed identification method is effective for a real problem.

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Identification of Connections of Vibration Systems Using Substructural Sensitivity Analysis (부분구조 기반 민감도 해석을 이용한 진동시스템의 연결부 특성 추정)

  • 서세영;김도연;김찬묵;이두호
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.786-792
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    • 2001
  • In this paper, the identification of connections for a vibration system has been presented using FRF-based substructural sensitivity analysis. The substructural design sensitivity formula is derived and plugged into a commercial optimization program, MATLAB, to identify connection stiffness of an air-conditioner system of passenger car. The air-conditioner system, composed of a compressor and a bracket is analyzed by using FRF-based substructural(FBS) method. To obtain the FRFs, FE model is built for the bracket, and the impact hammer test is performed for the compressor. Obtained FRFs are combined to calculate the reaction force at the connection point and the system response. Connection element properties are determined by minimizing the difference between a target FRF and calculated one. It is shown that the proposed identification method is effective even for a real problem.

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A Study on the Substructural Synthesis Method using the Spatial Properties (특성행렬을 이용한 부분구조합성법에 관한 연구)

  • 정우진;이헌곤
    • Journal of KSNVE
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    • v.3 no.2
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    • pp.145-153
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    • 1993
  • The Substructural Synthesis Method is effectively used for the calculation of complex structures. An alternative substructural synthesis, using spatial properities which can be directly inedtified from the frequency reponse function, was proposed. It has been shown that the rotational degree of freedom in the coupled region should be required to synthesize the substructures and the residual effect in the rotational degree of freedom should be considered. Through the simulations and experiments, this alternative was proven to be useful for the dynamic analysis of complex structures.

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Substructural parameters and dynamic loading identification with limited observations

  • Xu, Bin;He, Jia
    • Smart Structures and Systems
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    • v.15 no.1
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    • pp.169-189
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    • 2015
  • Convergence difficulty and available complete measurement information have been considered as two primary challenges for the identification of large-scale engineering structures. In this paper, a time domain substructural identification approach by combining a weighted adaptive iteration (WAI) algorithm and an extended Kalman filter method with a weighted global iteration (EFK-WGI) algorithm was proposed for simultaneous identification of physical parameters of concerned substructures and unknown external excitations applied on it with limited response measurements. In the proposed approach, according to the location of the unknown dynamic loadings and the partially available structural response measurements, part of structural parameters of the concerned substructure and the unknown loadings were first identified with the WAI approach. The remaining physical parameters of the concerned substructure were then determined by EFK-WGI basing on the previously identified loadings and substructural parameters. The efficiency and accuracy of the proposed approach was demonstrated via a 20-story shear building structure and 23 degrees of freedom (DOFs) planar truss model with unknown external excitation and limited observations. Results show that the proposed approach is capable of satisfactorily identifying both the substructural parameters and unknown loading within limited iterations when both the excitation and dynamic response are partially unknown.

Substructural Identification of Bending Stiffness in Bridge Deck (상시 진동을 사용한 교량 상부 구조계의 휨강성 추정기법)

  • Koo Ki-Young;Yun Chung-Bang;Yi Jin-Hak
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2005.04a
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    • pp.556-563
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    • 2005
  • This paper proposed a new substructural identification method to estimate the bending stiffness of a bridge deck, a fundamental structural health index of a super-structure. The proposed method can estimate the bending stiffness without considering actual supporting conditions by using substructural identification method while most of conventional methods need reasonable assumptions on supporting conditions which are hard to be assessed in a real bridge in operation. The mathematical formulation is derived and the results of laboratory tests are summarized. It was verified that the proposed method gives consistent estimation results regardless of actual supporting conditions.

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Identification of Substructural Model using Measured Acceleration (측정가속도를 이용한 부분구조해석 모델의 설정)

  • 오성호;전상현;장정환;신수봉;최광규
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2001.04a
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    • pp.435-442
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    • 2001
  • A substructural model for a part of a long continuous bridge is identified using measured acceleration at limited locations within the part. Boundary spring constants and structural properties are idenfitied using a system identification method. The proposed method has been examined through simulation studies for static and dynamic responses and the results are discussed in the paper. The method is applied to an actual plate-girder gerber bridge with modal response obtained from a moving truck and construction blasting vibration

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Structural identification based on substructural technique and using generalized BPFs and GA

  • Ghaffarzadeh, Hosein;Yang, T.Y.;Ajorloo, Yaser Hosseini
    • Structural Engineering and Mechanics
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    • v.67 no.4
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    • pp.359-368
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    • 2018
  • In this paper, a method is presented to identify the physical and modal parameters of multistory shear building based on substructural technique using block pulse generalized operational matrix and genetic algorithm. The substructure approach divides a complete structure into several substructures in order to significantly reduce the number of unknown parameters for each substructure so that identification processes can be independently conducted on each substructure. Block pulse functions are set of orthogonal functions that have been used in recent years as useful tools in signal characterization. Assuming that the input-outputs data of the system are known, their original BP coefficients can be calculated using numerical method. By using generalized BP operational matrices, substructural dynamic vibration equations can be converted into algebraic equations and based on BP coefficient for each story can be estimated. A cost function can be defined for each story based on original and estimated BP coefficients and physical parameters such as mass, stiffness and damping can be obtained by minimizing cost functions with genetic algorithm. Then, the modal parameters can be computed based on physical parameters. This method does not require that all floors are equipped with sensor simultaneously. To prove the validity, numerical simulation of a shear building excited by two different normally distributed random signals is presented. To evaluate the noise effect, measurement random white noise is added to the noise-free structural responses. The results reveal the proposed method can be beneficial in structural identification with less computational expenses and high accuracy.

Efficient Structral Safety Monitoring of Large Structures Using Substructural Identification (부분구조추정법을 이용한 대형구조물의 효율적인 구조안전도 모니터링)

  • 윤정방;이형진
    • Journal of the Earthquake Engineering Society of Korea
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    • v.1 no.2
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    • pp.1-15
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    • 1997
  • This paper presents substructural identification methods for the assessment of local damages in complex and large structural systems. For this purpose, an auto-regressive and moving average with stochastic input (ARMAX) model is derived for a substructure to process the measurement data impaired by noises. Using the substructural methods, the number of unknown parameters for each identification can be significantly reduced, hence the convergence and accuracy of estimation can be improved. Secondly, the damage index is defined as the ratio of the current stiffness to the baseline value at each element for the damage assessment. The indirect estimation method was performed using the estimated results from the identification of the system matrices from the substructural identification. To demonstrate the proposed techniques, several simulation and experimental example analyses are carried out for structural models of a 2-span truss structure, a 3-span continuous beam model and 3-story building model. The results indicate that the present substructural identification method and damage estimation methods are effective and efficient for local damage estimation of complex structures.

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