Now showing 1 - 10 of 13
  • Publication
    Monitoring of Changes in Bridge Response Using Weigh-In-Motion Systems
    (Trans Tech Publications, 2013-07) ; ;
    Weigh-In-Motion (WIM) and Bridge Weigh-In-Motion (B-WIM) are systems that allow obtaining the axle weights of road vehicles in motion, at normal traffic speeds. While WIM employs sensors embedded in the road pavement, B-WIM use the strain recordings of a bridge to infer the traversing vehicle axle weights. Both systems have been heavily improved over the past decades, and commercial versions are currently in operation. The two main applications of these systems are: (1) to assess the traffic loading on the infrastructure, and (2) to enforce the maximum weight limits. This paper suggests a novel application of these two systems to identify changes in bridge stiffness. It requires the bridge to be instrumented with a B-WIM system and a WIM system nearby. The principle is to use both systems to evaluate the gross weight of vehicles passing over the bridge and correlate their predictions. Changes in correlation of the predicted axle weights over time will indicate either structural damage or faulty sensor. A finite element model of a coupled vehicle-bridge system with different damage scenarios is used to test the approach numerically. Vehicle mechanical properties and speeds are randomly sampled within a Monte Carlo simulation. Results show how correlation changes as damage increases and how this correlation can be employed as a damage indicator.
      357
  • Publication
    Effect of tuned mass damper on the interaction of a quarter car model with a damaged bridge
    This paper considers the effects of a tuned mass damper (TMD) on damaged bridge-accelerating quarter car vehicle interaction. The damage of the bridge is considered to be an open crack. The incorporation of a TMD to control the vibration response of the bridge and the quarter car vehicle model has been investigated from different aspects. A simplified form for the tuning ratio of the TMD is proposed. The vibration mitigation of the peak displacement, velocity and acceleration of the damaged bridge and the accelerating quarter car vehicle model using such a tuning is observed, along with the effects of possible detuning of the TMD due to the progressive deterioration of the bridge. A detailed parametric study is performed on the system with the TMD, considering the effects of quarter car vehicle model velocity, acceleration and the severity of the damage of the bridge.
    Scopus© Citations 15  406
  • Publication
    Estimation of nonlinearities from pseudodynamic and dynamic responses of bridge structures using the Delay Vector Variance method
    Analysis of the variability in the responses of large structural systems and quantification of their linearity or nonlinearity as a potential non-invasive means of structural system assessment from output-only condition remains a challenging problem. In this study, the Delay Vector Variance (DVV) method is used for full scale testing of both pseudo-dynamic and dynamic responses of two bridges, in order to study the degree of nonlinearity of their measured response signals. The DVV detects the presence of determinism and nonlinearity in a time series and is based upon the examination of local predictability of a signal. The pseudo-dynamic data is obtained from a concrete bridge during repair while the dynamic data is obtained from a steel railway bridge traversed by a train. We show that DVV is promising as a marker in establishing the degree to which a change in the signal nonlinearity reflects the change in the real behaviour of a structure. It is also useful in establishing the sensitivity of instruments or sensors deployed to monitor such changes.
    Scopus© Citations 9  414
  • Publication
    A study on the effects of damage models and wavelet bases for damage identification and calibration in beams
    (Wiley Online Library, 2008-06-28) ; ;
    Damage detection and calibration in beams by wavelet analysis involve some key factors such as the damage model, the choice of the wavelet function, the effects of windowing, and the effects of masking due to the presence of noise during measurement. A numerical study has been performed in this article addressing these issues for single and multispan beams with an open crack. The first natural modeshapes of single and multispan beams with an open crack have been simulated considering damage models of different levels of complexity and analyzed for different crack depth ratios and crack positions. Gaussian white noise has been synthetically introduced to the simulated modeshape and the effects of varying signal-to-noise ratio have been studied. A wavelet-based damage identification technique has been found to be simple, efficient, and independent of damage models and wavelet basis functions, once certain conditions regarding the modeshape and the wavelet bases are satisfied. The wavelet-based damage calibration is found to be dependent on a number of factors including damage models and the basis function used in the analysis. A curvature-based calibration is more sensitive than a modeshape-based calibration of the extent of damage.
      327Scopus© Citations 47
  • Publication
    A statistical measure for wavelet based singularity detection
    (The American Society of Mechanical Engineers, 2009-07-14) ; ;
    This paper presents a statistical measure for the identification of the presence, the location, and the calibration of the strength of singularity in a signal or in any of its derivatives in the presence of measurement noise without the requirement of a baseline using a wavelet based detection technique. For this proposed wavelet based detection of singularities present in a signal, the problem of false alarm and its significant reduction by use of multiple measurements is presented. The importance of the proposed measure on baseline and nonbaseline damage calibration has been discussed from the aspect of structural health monitoring. The findings in this paper can also be used for crosschecking of background noise level in an observed signal. The detection of the existence, location, and extent of an open crack from the first fundamental modeshape of a simply supported beam is presented as an example problem.
    Scopus© Citations 18  338
  • Publication
    Experimental Detection of Sudden Stiffness Change in a Structural System Employing Laser Doppler Vibrometry
    (Erredi Grafiche Editoriali, 2012-06-20) ; ; ;
    Sudden changes in the stiffness of a structure are often indicators of structural damage. Detection of such sudden stiffness change from the vibrations of structures is important for Structural Health Monitoring (SHM) and damage detection. Non-contact measurement of these vibrations is a quick and efficient way for successful detection of sudden stiffness change of a structure. In this paper, we demonstrate the capability of Laser Doppler Vibrometry to detect sudden stiffness change in a Single Degree Of Freedom (SDOF) oscillator within a laboratory environment. The dynamic response of the SDOF system was measured using a Polytec RSV-150 Remote Sensing Vibrometer. This instrument employs Laser Doppler Vibrometry for measuring dynamic response. Additionally, the vibration response of the SDOF system was measured through a MicroStrain G-Link Wireless Accelerometer mounted on the SDOF system. The stiffness of the SDOF system was experimentally determined through calibrated linear springs. The sudden change of stiffness was simulated by introducing the failure of a spring at a certain instant in time during a given period of forced vibration. The forced vibration on the SDOF system was in the form of a white noise input. The sudden change in stiffness was successfully detected through the measurements using Laser Doppler Vibrometry. This detection from optically obtained data was compared with a detection using data obtained from the wireless accelerometer. The potential of this technique is deemed important for a wide range of applications. The method is observed to be particularly suitable for rapid damage detection and health monitoring of structures under a model-free condition or where information related to the structure is not sufficient.
      80
  • Publication
    Monitoring of changes in bridge response using Weigh-In-Motion systems
    (Trans Tech Publications, 2013-07) ; ;
    Weigh-In-Motion (WIM) and Bridge Weigh-In-Motion (B-WIM) are systems that allow obtaining the axle weights of road vehicles in motion, at normal traffic speeds. While WIM employs sensors embedded in the road pavement, B-WIM use the strain recordings of a bridge to infer the traversing vehicle axle weights. Both systems have been heavily improved over the past decades, and commercial versions are currently in operation. The two main applications of these systems are: (1) to assess the traffic loading on the infrastructure, and (2) to enforce the maximum weight limits. This paper suggests a novel application of these two systems to identify changes in bridge stiffness. It requires the bridge to be instrumented with a B-WIM system and a WIM system nearby. The principle is to use both systems to evaluate the gross weight of vehicles passing over the bridge and correlate their predictions. Changes in correlation of the predicted axle weights over time will indicate either structural damage or faulty sensor. A finite element model of a coupled vehicle-bridge system with different damage scenarios is used to test the approach numerically. Vehicle mechanical properties and speeds are randomly sampled within a Monte Carlo simulation. Results show how correlation changes as damage increases and how this correlation can be employed as a damage indicator.
      268
  • Publication
    Structural damage detection and calibration using a wavelet-kurtosis technique
    Some key factors in the field of damage detection of structures are the efficient and consistent detection of the presence, location and the extent of damage. A detailed numerical study has been performed in this paper addressing these issues for a beam element with an open crack. The first natural modeshape of the beam with an open crack has been simulated using smeared, lumped and continuous crack models involving various degrees of complexity. The static deflected shape of the same beam has also been simulated under vertical static loading. Gaussian white noise of different intensities has been synthetically introduced to both the simulated damaged modeshape and the static deflected shape. Wavelet analysis has been performed on the simulated modeshape and the static deflected shape for locating the damage. A new wavelet-kurtosis based calibration of the extent of damage has been performed for different crack depth ratios and crack positions including the effects of varying signal to noise ratio. An experimental validation of this method has been carried out on a damaged aluminium beam with open cracks of different extent. The damaged shape has been estimated by using a novel video camera based pattern recognition technique. The study in this paper shows that wavelet analysis in conjunction with a kurtosis based damage calibration can be useful in the identification of damage to structures and is applicable under the presence of measurement noise.
      513Scopus© Citations 71
  • Publication
    Nondetection, false alarm, and calibration insensitivity in kurtosis- and pseudofractal-based singularity detection
    This work isolates cases of nondetection, false alarm, and insensitivity for a general class of problems dealing with the detection and characterization of existence, location, and extent of singularities embedded in signals or in their derivatives when employing kurtosis- and pseudofractal-based methods for the detection and characterization process. The nondetection, false alarm, and insensitivity for these methods are illustrated on an example problem of damage identification and calibration in beams where the singularity to be identified lies in the derivative of the measured signal. The findings are general, not constrained to linear systems, and are potentially applicable to a wide range of fields including engineering system identification, fault detection, health monitoring of mechanical and civil structures, sensor failure, aerospace engineering, and biomedical engineering.
    Scopus© Citations 7  289
  • Publication
    A bridge-vehicle interaction based experimental investigation of damage evolution
    This article presents an experimental monitoring of the evolution of a crack in a beam using beam-vehicle interaction response signals for identification of progressively increasing crack-depth ratios. The beam is traversed by a two-axle model vehicle providing excitation in the time domain for the various extents of damage. The response of the beam in the time domain during the period of forced vibration is measured using strain gages. A consistent evolution of damage has been demonstrated in terms of the maxima values of the measured responses. The corresponding distortions of wavelet coefficients of the measured strain data due to the presence of various levels of damage have been identified. The evolution of the phase space and the wavelet transformed phase spaces have been evaluated with damage evolution. The wavelet transformed phase spaces for the undamaged and the damaged cases are observed to be distinctly different at high scales. The importance of denoising of the acquired data and the importance of vehicle configuration has been illustrated. This study presents a basis for a general model free damage assessment and structural health monitoring framework. The study presented is particularly useful in the context of continuous online bridge health monitoring, since the data necessary for analysis can be obtained from the operating condition of the bridge and the structure does not need be closed down.
    Scopus© Citations 52  323