The Experts below are selected from a list of 381 Experts worldwide ranked by ideXlab platform

Erik A Johnson - One of the best experts on this subject based on the ideXlab platform.

  • experimental verification of substructure identification for damage detection in shear buildings
    Journal of Engineering Mechanics-asce, 2016
    Co-Authors: Charles Devore, Zhaoshou Jiang, Richard Christenson, Gannon Stromquistlevoir, Erik A Johnson
    Abstract:

    AbstractDamage detection for civil structures is limited by several factors including poor signal-to-noise ratios, a large number of unknown parameters, and a limited set of measured responses. Global vibration techniques that track modal parameters often remain insensitive to common forms of structural damage. Moreover, large sets of identified parameters make inverse problems ill-conditioned. To overcome some of these limitations, researchers have advanced substructure identification as a methodology to directly detect local Stiffness changes using measured responses to improve damage detection and scalability in civil structures. This paper develops a substructure identification estimator that identifies the Story Stiffness of a shear building. Concurrent with the estimator derivation, identified parameter confidence intervals are developed and identification performance is predicted. Using the developed estimator, experimental testing is performed on a 3.66-m (12-ft) four-Story steel structure subject...

  • Substructure identification for plane frame building structures
    Engineering Structures, 2014
    Co-Authors: Dongyu Zhang, Erik A Johnson
    Abstract:

    Abstract In previous studies (Zhang and Johnson, 2012, 2013) [1,2], the authors proposed a substructure identification method for shear structures. This method is extended herein to accommodate more complicated plane frame building structures. Via a model reduction technique, a multi-Story multi-bay plane frame is converted into a beam-like model, having one translational and two rotational degrees-of-freedom (DOFs) for each floor. Based on this model, an inductive substructure identification method is formulated, using the cross power spectral densities between the frame floor horizontal accelerations and a reference response, to identify the equivalent Story Stiffness and damping parameters of the frame from top to bottom inductively. An identification error analysis reveals how structural responses affect the identification accuracy. Exploiting this result, a reference selection rule is proposed to select the best reference response and further improve the identification accuracy. Finally, a five-Story two-bay frame structure is used to demonstrate the efficacy of the proposed substructure identification, very accurately identifying the structural parameters even under the influence of large measurement noise; based on the estimated parameters, a hypothesis testing method is used to detect and locate structural damage, simulated by Stiffness reduction of some columns.

  • Substructure Identification for Shear Structures with Nonstationary Structural Responses
    Journal of Engineering Mechanics-asce, 2013
    Co-Authors: Dongyu Zhang, Erik A Johnson
    Abstract:

    AbstractIn previous studies by the authors, a substructure identification method for shear structures was proposed to identify all structural Story Stiffness and damping parameters from top to bottom inductively. In the method derivation, the structural responses were required to be wide sense stationary to convert structural dynamic equations to differential equations in the correlation functions of structural responses, which are used to formulate substructure identifications. In this paper, this method is extended to accommodate nonstationary structural responses. A different derivation procedure is adopted to formulate substructure identifications directly from the Fourier transform of the structural dynamic equations, resulting in a formulation nearly the same as its stationary response predecessor. An identification error analysis for the substructure identification method reveals how structural responses affect the identification accuracy. On the basis of this result, a smart reference selection ru...

  • Substructure identification for shear structures I: Substructure identification method
    Structural Control & Health Monitoring, 2012
    Co-Authors: Dongyu Zhang, Erik A Johnson
    Abstract:

    A substructure identification method for shear structures is proposed herein. A shear structure is partitioned into many simple substructures; an inductive identification procedure is derived to estimate the structural parameters from top to bottom. In each identification step, the dynamic equilibrium of a one-floor substructure is utilized to construct a substructure identification problem, estimating the Story Stiffness and damping coefficient. An identification error analysis for least-square error identification problems, based on the linearization of the least-square error problem, is proposed and applied to the substructure identification method. The results show that the identification errors are closely related to two important structural responses: the frequency response of the interStory acceleration of the identified Story and the frequency response ratio between adjacent interStory accelerations. Further, these responses are critical to the substructure identification only near a certain frequency, the substructure natural frequency of the identified Story substructure. The larger the first response is and/or the smaller the second response is, the more accurate the estimation results will be. A numerical example of a five-Story shear structure is given to demonstrate the effectiveness of the proposed substructure identification method and to verify the identification error analysis results. From the results of the identification error analysis, a companion paper proposes a controlled substructure identification method, utilizing specially designed algorithms for structural control devices to change the two key structural responses that affect the identification accuracy, to improve the accuracy of the substructure identification. Copyright © 2012 John Wiley & Sons, Ltd.

  • Design of a VSDD brace control system for parameter estimation of shear structures
    2009 American Control Conference, 2009
    Co-Authors: Dongyu Zhang, Erik A Johnson
    Abstract:

    In this paper, a new function of variable Stiffness & damping device (VSDD) brace control systems is explored: facilitating structural parameter estimation and damage detection. In previous studies by the authors, a substructure identification method has been proposed to identify the structural parameters (Story Stiffness and damping coefficients) of a shear building. An error analysis shows that the accuracy of the estimated parameters can be greatly improved by amplifying the interStory acceleration near the substructure natural frequency. To achieve this structural response change, two kinds of control strategies are studied herein to design a VSDD system: an on-off passive strategy and a semiactive strategy. Since the accuracy of substructure identification is only dependent on the controlled substructure responses, it is shown that the proposed control-facilitated identification is robust to one common control system error: feedback measurement noise. Finally, a numerical example of a 5-Story shear building structure is used to illustrate the efficacy of the proposed control method for improving the accuracy of the substructure identification.

Koichi Morita - One of the best experts on this subject based on the ideXlab platform.

  • structure observation identification considering soil structure interaction of Story Stiffness and damping ratio of 8 Story steel encased reinforce concrete structure by microtremor
    Applied Mechanics and Materials, 2012
    Co-Authors: Koichi Morita
    Abstract:

    In this article, the authors identify the one built in 1998, eight-Story structure of steel reinforced concrete body dynamic parameters, and discussed the soil - structure interaction on the identification results.In this study, an 8 degrees of freedom analytical model and the impact analysis model of soil-structure interaction to be established; through the analysis of microseismic observations, using non-parametric (transfer function and Random Decrement method) and parameter techniques (off-line system identification method, ARX :Auto-Regression with eXtra input) to identify the structure of the natural frequency, damping ratio and the Story Stiffness. Finally, in considering the soil-structure interaction cases, structural parameters were identification and compared the results to confirm the impact of soil-structure interaction.

  • Structure Observation & Identification Considering Soil-Structure Interaction of Story Stiffness and Damping Ratio of 8-Story Steel Encased Reinforce Concrete Structure by Microtremor
    Applied Mechanics and Materials, 2012
    Co-Authors: Koichi Morita
    Abstract:

    In this article, the authors identify the one built in 1998, eight-Story structure of steel reinforced concrete body dynamic parameters, and discussed the soil - structure interaction on the identification results.In this study, an 8 degrees of freedom analytical model and the impact analysis model of soil-structure interaction to be established; through the analysis of microseismic observations, using non-parametric (transfer function and Random Decrement method) and parameter techniques (off-line system identification method, ARX :Auto-Regression with eXtra input) to identify the structure of the natural frequency, damping ratio and the Story Stiffness. Finally, in considering the soil-structure interaction cases, structural parameters were identification and compared the results to confirm the impact of soil-structure interaction.

  • investigation and estimation of Story Stiffness and damping ratio of a 4 Story wooden structure by microtremor and mass sliding shaker
    Bulletin of the International Institute of Seismology and Earthquake Engineering, 2009
    Co-Authors: Sithipat Palanandana, Koichi Morita
    Abstract:

    In this study, the structural dynamic properties of a 4-Story wooden structure were investigated. Microtremor observation was carried out to determine the first and second natural frequencies of the structure. Based on these preliminary results, mass sliding shaker was mounted on the structure to apply harmonic force vibration in order to excite the resonant behavior of the structure. Target frequencies were applied to the mass sliding shaker to obtain the responses for all four modal shapes. Signal obtained from the measurement was then mathematically converted from time domain to frequency domain using Fast Fourier Transform for better interpretation to determine all four natural frequencies. Based on these results, resonance curves for all four modal shapes were constructed. Curve fitting based on mathematical formula was also drawn by changing the values of damping ratio and peak amplitude to fit the resonance curve. From microtremor observation data and time hiStory responses of free vibration, damping ratio of the structure was determined for comparison. Based on curve fitting of resonance curves, natural frequencies and participation functions were also identified. Using Story mass in addition to these identified properties, Stiffness matrix could be determined. Finally, each Story's Stiffness was obtained by multiplying Stiffness matrix by unit displacement vector.

  • Structural health monitoring of an existing 8-Story building using strong motion observation data and structural design data
    Smart Structures and Materials 2006: Sensors and Smart Structures Technologies for Civil Mechanical and Aerospace Systems, 2006
    Co-Authors: Koichi Morita, Masaomi Teshigawara
    Abstract:

    Target building is an 8-Story steel encased reinforced concrete building which was constructed in 1998. In this structural health monitoring system, strong motion observation data is used and accelerometers were installed just after the completion of construction at 1st Story, 2nd Story, 5th Story and 8th Story. By use of system identification using ARX model, natural frequency, damping ratio and participation function are calculated, and concentrated equivalent Story Stiffness can be also determined by using Moore and Penrose generalized inverse matrix. From the identification results, natural frequency and concentrated equivalent Story Stiffness tend to decrease by the aging. Especially, just after the completion of construction and after a large earthquake, changes of natural frequency and concentrated equivalent Story Stiffness are very remarkable. From the point of amplitude dependence, natural frequency and concentrated equivalent Story Stiffness tend to change more by equivalent velocity of input energy than by peak ground acceleration. Analytical frame model is constructed from the structural design documents and concentrated equivalent Story load-displacement relationships are obtained by carrying out push-over analysis. By the comparison between analytical and identified concentrated equivalent Story Stiffness, the structural conditions is estimated. From the identification results, a model using stick-slip elements is proposed. Natural frequency and Story Stiffness described by this model are consistent with identified results.

  • Damage detection and estimation of a steel frame through shaking table test and measurements
    Smart Structures and Materials 2004: Sensors and Smart Structures Technologies for Civil Mechanical and Aerospace Systems, 2004
    Co-Authors: Koichi Morita, Masaomi Teshigawara
    Abstract:

    We carry out shaking table test using a three-Story large-scale steel structure with cementitious devices to detect and estimate damages. The test frame floor height is 1.8m, total height is 5.4m, floor plan is 4mx3m. Shaking table test is carried out at large-scale earthquake simulator facility of the National Research Institute for Earth Science and Disaster Prevention. Cementitious devices are installed in the center frame of tested structure and devices are actually damaged during the shaking. Two types of identification are tried. One is identification using the data under excitation and the other is identification using the data of before and after of the excitation. In both cases, we use identification method by ARX model. From identified results, natural frequency decreases, damping ratio increases and Story Stiffness decreases as experienced amplitude increases or input amplitude increases. A model using stick-slip elements is proposed. Natural frequency, damping ratio and Story Stiffness described by this model are consistent with experimental results. The fitting of the experimental result based on this model is carried out, and skeleton curve got from structural design and fitting result are corresponded well. Damage evaluation method using this fitting results and skeleton curve is proposed.

Dongyu Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Substructure identification for plane frame building structures
    Engineering Structures, 2014
    Co-Authors: Dongyu Zhang, Erik A Johnson
    Abstract:

    Abstract In previous studies (Zhang and Johnson, 2012, 2013) [1,2], the authors proposed a substructure identification method for shear structures. This method is extended herein to accommodate more complicated plane frame building structures. Via a model reduction technique, a multi-Story multi-bay plane frame is converted into a beam-like model, having one translational and two rotational degrees-of-freedom (DOFs) for each floor. Based on this model, an inductive substructure identification method is formulated, using the cross power spectral densities between the frame floor horizontal accelerations and a reference response, to identify the equivalent Story Stiffness and damping parameters of the frame from top to bottom inductively. An identification error analysis reveals how structural responses affect the identification accuracy. Exploiting this result, a reference selection rule is proposed to select the best reference response and further improve the identification accuracy. Finally, a five-Story two-bay frame structure is used to demonstrate the efficacy of the proposed substructure identification, very accurately identifying the structural parameters even under the influence of large measurement noise; based on the estimated parameters, a hypothesis testing method is used to detect and locate structural damage, simulated by Stiffness reduction of some columns.

  • Substructure Identification for Shear Structures with Nonstationary Structural Responses
    Journal of Engineering Mechanics-asce, 2013
    Co-Authors: Dongyu Zhang, Erik A Johnson
    Abstract:

    AbstractIn previous studies by the authors, a substructure identification method for shear structures was proposed to identify all structural Story Stiffness and damping parameters from top to bottom inductively. In the method derivation, the structural responses were required to be wide sense stationary to convert structural dynamic equations to differential equations in the correlation functions of structural responses, which are used to formulate substructure identifications. In this paper, this method is extended to accommodate nonstationary structural responses. A different derivation procedure is adopted to formulate substructure identifications directly from the Fourier transform of the structural dynamic equations, resulting in a formulation nearly the same as its stationary response predecessor. An identification error analysis for the substructure identification method reveals how structural responses affect the identification accuracy. On the basis of this result, a smart reference selection ru...

  • Substructure identification for shear structures I: Substructure identification method
    Structural Control & Health Monitoring, 2012
    Co-Authors: Dongyu Zhang, Erik A Johnson
    Abstract:

    A substructure identification method for shear structures is proposed herein. A shear structure is partitioned into many simple substructures; an inductive identification procedure is derived to estimate the structural parameters from top to bottom. In each identification step, the dynamic equilibrium of a one-floor substructure is utilized to construct a substructure identification problem, estimating the Story Stiffness and damping coefficient. An identification error analysis for least-square error identification problems, based on the linearization of the least-square error problem, is proposed and applied to the substructure identification method. The results show that the identification errors are closely related to two important structural responses: the frequency response of the interStory acceleration of the identified Story and the frequency response ratio between adjacent interStory accelerations. Further, these responses are critical to the substructure identification only near a certain frequency, the substructure natural frequency of the identified Story substructure. The larger the first response is and/or the smaller the second response is, the more accurate the estimation results will be. A numerical example of a five-Story shear structure is given to demonstrate the effectiveness of the proposed substructure identification method and to verify the identification error analysis results. From the results of the identification error analysis, a companion paper proposes a controlled substructure identification method, utilizing specially designed algorithms for structural control devices to change the two key structural responses that affect the identification accuracy, to improve the accuracy of the substructure identification. Copyright © 2012 John Wiley & Sons, Ltd.

  • Design of a VSDD brace control system for parameter estimation of shear structures
    2009 American Control Conference, 2009
    Co-Authors: Dongyu Zhang, Erik A Johnson
    Abstract:

    In this paper, a new function of variable Stiffness & damping device (VSDD) brace control systems is explored: facilitating structural parameter estimation and damage detection. In previous studies by the authors, a substructure identification method has been proposed to identify the structural parameters (Story Stiffness and damping coefficients) of a shear building. An error analysis shows that the accuracy of the estimated parameters can be greatly improved by amplifying the interStory acceleration near the substructure natural frequency. To achieve this structural response change, two kinds of control strategies are studied herein to design a VSDD system: an on-off passive strategy and a semiactive strategy. Since the accuracy of substructure identification is only dependent on the controlled substructure responses, it is shown that the proposed control-facilitated identification is robust to one common control system error: feedback measurement noise. Finally, a numerical example of a 5-Story shear building structure is used to illustrate the efficacy of the proposed control method for improving the accuracy of the substructure identification.

  • ACC - Design of a VSDD brace control system for parameter estimation of shear structures
    2009 American Control Conference, 2009
    Co-Authors: Dongyu Zhang, Erik A Johnson
    Abstract:

    In this paper, a new function of Variable Stiffness & Damping Device (VSDD) brace control systems is explored: facilitating structural parameter estimation and damage detection. In previous studies by the authors, a substructure identification method has been proposed to identify the structural parameters (Story Stiffness and damping coefficients) of a shear building. An error analysis shows that the accuracy of the estimated parameters can be greatly improved by amplifying the interStory acceleration near the substructure natural frequency. To achieve this structural response change, two kinds of control strategies are studied herein to design a VSDD system: an on-off passive strategy and a semiactive strategy. Since the accuracy of substructure identification is only dependent on the controlled substructure responses, it is shown that the proposed control-facilitated identification is robust to one common control system error: feedback measurement noise. Finally, a numerical example of a 5-Story shear building structure is used to illustrate the efficacy of the proposed control method for improving the accuracy of the substructure identification.

Yavuz Kaya - One of the best experts on this subject based on the ideXlab platform.

  • System identification of civil structures : Earthquake Engineering Course
    Individual studies by participants to the International Institute of Seismology and Earthquake Engineering, 2020
    Co-Authors: Yavuz Kaya
    Abstract:

    This study contains the identification of modal dynamic properties of a 3-Story large-scale steel test frame structure through shaking table measurements. Shaking table test is carried out to estimate the modal properties of the test frame such as natural frequencies, damping ratios and mode shapes. Among many different model structures, ARX (Auto Recursive eXogenous) model structure is used for modal identification of the frame structure system. The unknown parameters in the obtained ARX model structure are estimated by Least-Square method by minimizing the AIC criteria with the help of a program coded in advanced computing software MATLAB®. The adopted model structure is then tested out in time domain to verify the validity of the model with the selected model parameters. Then the modal characteristics of test frame and the Story Stiffness are estimated using the white noise shakings. An attempt is done to determine the change of modal characteristics and the Story Stiffness of test frame according to the velocity, which the test frame structure experienced during the shaking schedule and also during the input shaking of El Centro 1940 NS. Results shows that there is an increase in damping ratio and a decrease in both Story Stiffness and natural frequency for all modes when the damage forms at cementitious device and the test frame structure itself during the shaking schedule.

  • System identification and model calibration of multi-Story buildings through estimation of vibration time histories at non-instrumented floors
    Bulletin of Earthquake Engineering, 2015
    Co-Authors: Yavuz Kaya, Sedef Kocakaplan, Erdal Şafak
    Abstract:

    A simple approach is introduced to identify and calibrate analytical models of multi-Story buildings from their vibration records. The method is based on the Transfer Matrix formulation of the response, and requires that vibration time histories are known at every floor of the building. Since this is typically not the case, first a methodology is developed to estimate vibration time histories at non-instrumented floors of the building from those recorded at the instrumented floors, based on the assumption that the mode shapes of a multi-Story building can be approximated as a linear combination of the mode shapes of a shear beam and a bending beam. Once the vibration time histories are known at every floor, it is shown by using the Transfer Matrix formulation that the top-to-bottom spectral ratio of the records at a particular Story is dependent only on the properties of this Story and the stories above. In other words, any change in the characteristics of the stories below does not affect the spectral ratio for this Story. Therefore, starting from the top Story, we can identify frequency of each Story (i.e., Story Stiffness/Story mass), or directly Story Stiffness if the Story mass is known. In addition to system identification, the approach also provides a simple tool to calibrate analytical models of multi-Story buildings from their vibration records.

  • MODAL IDENTIFICATION OF A TESTED STEEL FRAME USING LINEAR ARX MODEL STRUCTURE
    International Journal of Advanced Structural Engineering, 2009
    Co-Authors: Yavuz Kaya
    Abstract:

    This study contains the identification of modal dynamic properties of a 3-Story large-scale steel test frame structure through shaking table measurements. Shaking table test is carried out to estimate the modal properties of the test frame such as natural frequencies, damping ratios and mode shapes. Among many different model structures, ARX (Auto Recursive Exogenous) model structure is used for modal identification of the frame structure system. The unknown parameters in the obtained ARX model structure are estimated by Least-Square method by minimizing the AIC criteria with the help of a program coded in advanced computing software MATLAB®. The adopted model structure is then tested out in time domain to verify the validity of the model with the selected model parameters. Then the modal characteristics of test frame and the Story Stiffness are estimated using the white noise shakings. An attempt is done to determine the change of modal characteristics and the Story Stiffness of test frame according to the velocity, which the test frame structure experienced during the shaking schedule and also during the input shaking of El Centro 1940 NS. Results shows that there is an increase in damping ratio and a decrease in both Story Stiffness and natural frequency for all modes when the damage forms at cementitious device and the test frame structure itself during the shaking schedule.

Qi Ai - One of the best experts on this subject based on the ideXlab platform.

  • Analysis on Seismic-response of Different Stiffness Reinforced Concrete Frame Structure with Staircase
    Journal of Southwest University of Science and Technology, 2020
    Co-Authors: Qi Ai
    Abstract:

    Four computer models of reinfored concrete frame structure with or without staircase were made,seismic-performance of the models were calculated by adopting spectrum analysis method based on ETABS.The results show that including staircase into models will change the Story-Stiffness distribution,vibration mode,shear-ratio of staircase-frame column of frame structure significantly,the effects are different depenning on the different Stiffness of the original frame structure.The paper proposes that the Stiffness of the original frame structure should be enhanced firstly in seismic design of reinfored concrete frame structure with staircase at present.

  • Analysis on seismic-response of reinforced concrete frame structure with staircase
    Journal of Fuzhou University, 2020
    Co-Authors: Qi Ai
    Abstract:

    Three computer models of reinfored concrete frame structure with or without staircase are made,seismic-performance of the models are calcaulated by adopting spectrum analysis and baseshear method based on ETABS. The results show that including staircase into models will change the Story-Stiffness distribution,vibration mode,shear-ratio of staircase-frame column of frame structure significantly,the effects are different depenning on mid-platform connecting to staircase-frame column or not; The paper propose that the computer model-3 and the response spectrum method should be used firstly in seismic design of reinfored concrete frame structure with staircase.

  • Analysis on Seismic-response of Reinforced Concrete Frame Structure with Different-width Staircase
    Journal of Southwest University of Science and Technology, 2020
    Co-Authors: Qi Ai
    Abstract:

    Three computer models of reinfored concrete frame structure with or without different-width staircase were made,seismic-performance of the models were calcaulated by adopting spectrum analysis and base-shear method based on ETABS.The results show that including staircase into models will change the Story-Stiffness distribution,vibration mode,shear-ratio of staircase-frame column of frame structure significantly;The role of staircase is similar to K-bracing in staircase plank direction,similar to shearwall in vertical direction;Diffferent-width staircase has more effect on seimic response of frame structure in vertical to staircase plank direction,but little effect in staircase plank direction.The paper proposed that the response spectrum method should be used firstly in seismic design of reinfored concrete frame structure with staircase.

  • Analysis on seismic-response of reinforced concrete frame structure with different-thickness staircase
    Journal of Fuzhou University, 2020
    Co-Authors: Qi Ai
    Abstract:

    Three computer models of reinfored concrete frame structure are made,one without staircase,two with different-thickness staircase mid-platform disconnecting to staircase-frame column.seismic-response of the models are calcaulated by adopting spectrum analysis and time hiStory analysis method based on ETABS.The results show that including staircase into models will change the Story-Stiffness distribution,vibration mode,shear-ratio of staircase-frame column of frame structure significantly.The role of staircase is similar to bracing in staircase plank direction,similar to shearwall in vertical direction.Diffferent-thickness staircase has slight difference on seimic response of frame structure in two directions,but the difference is small.The paper propose that the response spectrum method should be used firstly in seismic design of reinfored concrete frame structure with staircase,the data of time hiStory analysis should be analysed deeply before adopted.