Suparno Mukhopadhyay | Columbia University (original) (raw)

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Papers by Suparno Mukhopadhyay

Research paper thumbnail of Modal Parameter Based Damage Detection in Operational Modal Analysis: A Statistical Pattern Recognition Approach

Research paper thumbnail of A new denoising procedure based on Empirical Mode Decomposition for SHM purpose

Research paper thumbnail of Directivity pulses in near-fault ground motions—I: Identification, extraction and modeling

Soil Dynamics and Earthquake Engineering, 2013

ABSTRACT The simulation of directivity pulse-type ground motions through superimposition of model... more ABSTRACT The simulation of directivity pulse-type ground motions through superimposition of modelled directivity pulse(s) on a non-pulse type motion is a possible approach to meet the scarcity of such motions in studying the structural response under those. It is shown in the companion paper that the amplitude and dominant Fourier period of the expected velocity pulse for a given seismic scenario may be sufficient to model the shapes of the expected acceleration and velocity pulses. Scaling models are proposed in this paper for the estimation of these parameters and time of occurrence of the expected pulse in the case of primary pulse, together with relationships between the parameters of the primary and secondary pulses. The pulses extracted in the companion paper are considered for this purpose. A sensitivity analysis shows that uncertainties in the estimation of the primary pulse parameters significantly affect the pseudo-spectral acceleration (PSA), non-linear maximum displacement (SD) and hysteresis energy dissipation (EH) responses to the simulated motions, whereas uncertainties in the primary-secondary pulse relationships affect only the SD response significantly. It has been shown that for a pulse-type motion, an increase in earthquake magnitude may sometimes lead to a significantly lower response. Further, the presence of a directivity pulse leads to a significantly greater response at lower magnitudes, and at higher magnitudes for the periods near the pulse period and in the case of a nonlinear response.

Research paper thumbnail of Damage Detection Using Flexibility Proportional Coordinate Modal Assurance Criterion

Conference Proceedings of the Society for Experimental Mechanics Series, 2013

Research paper thumbnail of Structural identification with incomplete instrumentation and global identifiability requirements under base excitation

Structural Control and Health Monitoring, 2015

ABSTRACT Estimating the mass and stiffness parameters of a structural system via its vibration re... more ABSTRACT Estimating the mass and stiffness parameters of a structural system via its vibration response measurements is the primary objective in the field of modal testing and structural health monitoring. The attainment of this objective, however, is hindered by various practical and theoretical issues. One such issue is incomplete instrumentation, leading to spatially incomplete mode shapes and often nonunique identification results. When the excitation is induced by ground motion, the problem is further complicated because of arbitrary normalization of mode shapes. This study attempts to address these issues for shear-building type structures. Mode shape normalization and expansion approaches are developed that utilize the topology of the structural matrices. Theoretical constraints regarding minimal instrumentation and the necessity for any a priori information are addressed vis-à-vis the requirements for global identifiability. Some practical implementation issues are discussed. The performance of the method is evaluated using numerical simulations and shake table experiments. Copyright © 2015 John Wiley & Sons, Ltd.

Research paper thumbnail of Propagation of mode shape errors in structural identification

Journal of Sound and Vibration, 2012

ABSTRACT It is of interest to the modal testing and health monitoring community to quantify how a... more ABSTRACT It is of interest to the modal testing and health monitoring community to quantify how an error in any identified mode shape propagates to the identified flexibility matrix. Here this problem is investigated in a probabilistic framework. The approach followed involves deriving analytical expressions to track how errors, due to random deviations between identified and “true” mode shapes, propagate to the Modal Assurance Criterion (MAC) and the Coordinate Modal Assurance Criterion (COMAC) values as well as the estimated flexibility matrix. The comparison of the expected values and variances of these errors identifies the inconsistency between the magnitude of errors in the MAC and COMAC values and the identified flexibility matrix. The analytical results are further validated via Monte Carlo simulations. Finally, two mode shape comparison criteria, termed as the Flexibility Proportional Modal Assurance Criterion (FPMAC) and the Flexibility Proportional Coordinate Modal Assurance Criterion (FPCOMAC), are proposed. These new criteria aim to mimic the expected error in the predicted flexibility matrix in a direct comparison of the identified and “true” mode shapes, and hence they can be used to complement MAC and COMAC in interpreting the analysis results.

Research paper thumbnail of Modal parameter based structural identification using input–output data: Minimal instrumentation and global identifiability issues

Mechanical Systems and Signal Processing, 2014

It is of interest to the modal testing and structural health monitoring community to be able to i... more It is of interest to the modal testing and structural health monitoring community to be able to identify the mass and stiffness parameters of a system from its vibration response measurements. On the other hand, incomplete instrumentation of the monitored system results in measured mode shapes which are incomplete and may lead to non-unique identification results. In this study, the problem of mass normalized mode shape expansion, and subsequent physical parameter identification, for shear-type structural systems with input-output measurements is investigated. While developing a mode shape expansion algorithm, the issue of global identifiability of the system is also addressed vis-à-vis instrumentation set-ups. Several possible minimal and near-minimal instrumentation set-ups which guarantee a unique estimation of the unmeasured mode shape components from the measured components are identified for various experimental designs. An input-output balance approach, applicable to any general structural model, is proposed to mass normalize the mode shape components observed at the instrumented degrees of freedom. Using the proposed mode shape expansion and the input-output balance procedures, along with the modal orthogonality relations, the mass and stiffness matrices of the system can be estimated. The advantage of the algorithm lies in its ability to obtain a reliably accurate identification using the minimal necessary instrumentation with no a priori mass or stiffness information. The performance of the proposed algorithm is finally discussed through numerical simulations of forced vibration experiments on a 7 degree of freedom shear-type system. (R. Betti).

Research paper thumbnail of A statistical framework with stiffness proportional damage sensitive features for structural health monitoring

SMART STRUCTURES AND SYSTEMS

Research paper thumbnail of Modal Parameter Based Damage Detection in Operational Modal Analysis: A Statistical Pattern Recognition Approach

Research paper thumbnail of A new denoising procedure based on Empirical Mode Decomposition for SHM purpose

Research paper thumbnail of Directivity pulses in near-fault ground motions—I: Identification, extraction and modeling

Soil Dynamics and Earthquake Engineering, 2013

ABSTRACT The simulation of directivity pulse-type ground motions through superimposition of model... more ABSTRACT The simulation of directivity pulse-type ground motions through superimposition of modelled directivity pulse(s) on a non-pulse type motion is a possible approach to meet the scarcity of such motions in studying the structural response under those. It is shown in the companion paper that the amplitude and dominant Fourier period of the expected velocity pulse for a given seismic scenario may be sufficient to model the shapes of the expected acceleration and velocity pulses. Scaling models are proposed in this paper for the estimation of these parameters and time of occurrence of the expected pulse in the case of primary pulse, together with relationships between the parameters of the primary and secondary pulses. The pulses extracted in the companion paper are considered for this purpose. A sensitivity analysis shows that uncertainties in the estimation of the primary pulse parameters significantly affect the pseudo-spectral acceleration (PSA), non-linear maximum displacement (SD) and hysteresis energy dissipation (EH) responses to the simulated motions, whereas uncertainties in the primary-secondary pulse relationships affect only the SD response significantly. It has been shown that for a pulse-type motion, an increase in earthquake magnitude may sometimes lead to a significantly lower response. Further, the presence of a directivity pulse leads to a significantly greater response at lower magnitudes, and at higher magnitudes for the periods near the pulse period and in the case of a nonlinear response.

Research paper thumbnail of Damage Detection Using Flexibility Proportional Coordinate Modal Assurance Criterion

Conference Proceedings of the Society for Experimental Mechanics Series, 2013

Research paper thumbnail of Structural identification with incomplete instrumentation and global identifiability requirements under base excitation

Structural Control and Health Monitoring, 2015

ABSTRACT Estimating the mass and stiffness parameters of a structural system via its vibration re... more ABSTRACT Estimating the mass and stiffness parameters of a structural system via its vibration response measurements is the primary objective in the field of modal testing and structural health monitoring. The attainment of this objective, however, is hindered by various practical and theoretical issues. One such issue is incomplete instrumentation, leading to spatially incomplete mode shapes and often nonunique identification results. When the excitation is induced by ground motion, the problem is further complicated because of arbitrary normalization of mode shapes. This study attempts to address these issues for shear-building type structures. Mode shape normalization and expansion approaches are developed that utilize the topology of the structural matrices. Theoretical constraints regarding minimal instrumentation and the necessity for any a priori information are addressed vis-à-vis the requirements for global identifiability. Some practical implementation issues are discussed. The performance of the method is evaluated using numerical simulations and shake table experiments. Copyright © 2015 John Wiley & Sons, Ltd.

Research paper thumbnail of Propagation of mode shape errors in structural identification

Journal of Sound and Vibration, 2012

ABSTRACT It is of interest to the modal testing and health monitoring community to quantify how a... more ABSTRACT It is of interest to the modal testing and health monitoring community to quantify how an error in any identified mode shape propagates to the identified flexibility matrix. Here this problem is investigated in a probabilistic framework. The approach followed involves deriving analytical expressions to track how errors, due to random deviations between identified and “true” mode shapes, propagate to the Modal Assurance Criterion (MAC) and the Coordinate Modal Assurance Criterion (COMAC) values as well as the estimated flexibility matrix. The comparison of the expected values and variances of these errors identifies the inconsistency between the magnitude of errors in the MAC and COMAC values and the identified flexibility matrix. The analytical results are further validated via Monte Carlo simulations. Finally, two mode shape comparison criteria, termed as the Flexibility Proportional Modal Assurance Criterion (FPMAC) and the Flexibility Proportional Coordinate Modal Assurance Criterion (FPCOMAC), are proposed. These new criteria aim to mimic the expected error in the predicted flexibility matrix in a direct comparison of the identified and “true” mode shapes, and hence they can be used to complement MAC and COMAC in interpreting the analysis results.

Research paper thumbnail of Modal parameter based structural identification using input–output data: Minimal instrumentation and global identifiability issues

Mechanical Systems and Signal Processing, 2014

It is of interest to the modal testing and structural health monitoring community to be able to i... more It is of interest to the modal testing and structural health monitoring community to be able to identify the mass and stiffness parameters of a system from its vibration response measurements. On the other hand, incomplete instrumentation of the monitored system results in measured mode shapes which are incomplete and may lead to non-unique identification results. In this study, the problem of mass normalized mode shape expansion, and subsequent physical parameter identification, for shear-type structural systems with input-output measurements is investigated. While developing a mode shape expansion algorithm, the issue of global identifiability of the system is also addressed vis-à-vis instrumentation set-ups. Several possible minimal and near-minimal instrumentation set-ups which guarantee a unique estimation of the unmeasured mode shape components from the measured components are identified for various experimental designs. An input-output balance approach, applicable to any general structural model, is proposed to mass normalize the mode shape components observed at the instrumented degrees of freedom. Using the proposed mode shape expansion and the input-output balance procedures, along with the modal orthogonality relations, the mass and stiffness matrices of the system can be estimated. The advantage of the algorithm lies in its ability to obtain a reliably accurate identification using the minimal necessary instrumentation with no a priori mass or stiffness information. The performance of the proposed algorithm is finally discussed through numerical simulations of forced vibration experiments on a 7 degree of freedom shear-type system. (R. Betti).

Research paper thumbnail of A statistical framework with stiffness proportional damage sensitive features for structural health monitoring

SMART STRUCTURES AND SYSTEMS