Now showing 1 - 8 of 8
  • Publication
    A New Damage Indicator for Drive-by Monitoring using Instantaneous Curvature
    Drive-by monitoring has enhanced the possibilities for bridge damage detection, with the potential to deliver a bridge rating in the time it takes an instrumented vehicle to pass overhead. This paper outlines the importance of Instantaneous Curvature (IC) as an indicator of local damage. For the IC calculation, bridge deflections are measured from the vehicle before and after the occurrence of damage, so that a comparison between the two situations can be made. Differences in curvature are clearly visible in numerical simulations, especially at the damage location. A Finite Element model of a simply supported bridge subject to a crossing vehicle is modelled dynamically. In this paper, the Curvature Ratio (CR) is proposed as the damage indicator, defined as the ratio of IC in the current bridge to IC in the corresponding healthy bridge. Road profile and random noise in the simulated measurements are considered to represent realistic conditions. Simulations in MATLAB demonstrate that CR is an effective indicator in most of the analysis cases.
      288
  • Publication
    The feasibility of using Laser Doppler Vibrometer measurements from a passing vehicle for bridge damage detection
    Bridges play an important role in transport infrastructure and it is necessary to frequently monitor them. Current vibration-based bridge monitoring methods in which bridges are instrumented using several sensors are sometimes not sensitive enough. For this reason, an assessment of sensitivity of sensors to damage is necessary. In this paper a sensitivity analysis to bridge flexural stiffness (EI) is performed. A discussion between the use of strain or deflections is provided. A relation between deflection and stiffness can be set by theorem of virtual work, expressing the problem as a matrix product. Sensitivity is obtained by deriving the deflection respect to the reciprocal of the stiffness at every analysed location of the bridge. It is found that a good match between the deflection and the bridge stiffness profile can be obtained using noise-free measurements. The accuracy of sensors is evaluated numerically in presence of damage and measurement noise. Field measurements in the United States are also described to identify the potential issues in real conditions.
    Scopus© Citations 26  311
  • Publication
    Damage detection using curvatures obtained from vehicle measurements
    This paper describes a new procedure for bridge damage identification through drive-by monitoring. Instantaneous curvature (IC) is presented as a means to determine a local loss of stiffness in a bridge through measurements collected from a passing instrumented vehicle. Moving reference curvature (MRC) is compared with IC as a damage detection tool. It is assumed that absolute displacements on the bridge can be measured by the vehicle. The bridge is represented by a finite element (FE) model. A Half-car model is used to represent the passing vehicle. Damage is represented as a local loss of stiffness in different parts of the bridge. 1% random noise and no noise environments are considered to evaluate the effectiveness of the method. A generic road surface profile is also assumed. Numerical simulations show that the local damage can be detected using IC if the deflection responses can be measured with sufficient accuracy. Damage quantification can be obtained from MRC.
    Scopus© Citations 21  640
  • Publication
    Examining Changes in Bridge Frequency due to Damage using the Contact-Point Response of a Passing Vehicle
    (Taylor & Francis, 2021-06-07) ;
    Ongoing inspection and maintenance of bridges poses a challenging task for infrastructure owners who must manage large bridge stocks with limited budgets. Drive-by monitoring approaches, using sensors in a vehicle, provide a promising solution to this challenge. This paper investigates the use of the response at the point-of-contact between the tyre and the bridge as a means of monitoring bridge frequency. An expression is derived to allow the contact-point (CP) response to be inferred directly from in-vehicle measurements, expanding on previous studies by allowing the vehicle suspension characteristics to be considered. The sensitivity of the CP-response to the pavement characteristics is investigated in detail and a rigid-disk model is used to overcome issues with how existing vehicle-bridge interaction models consider the interaction between the wheel and the pavement. The feasibility of the CP-response as a measure of bridge condition is investigated and results show that the CP-response significantly outperforms the response measured directly on the vehicle. The CP-response is successful in identifying the bridge frequency and changes caused by damage, without being influenced by the vehicle frequencies. Incorporating the CP-response into drive-by bridge monitoring will improve accuracy over existing methods which use the vehicle response alone.
    Scopus© Citations 42  224
  • Publication
    Investigating the Contact-Point Response for Drive-By Damage Detection in Bridges
    Bridges are critical elements in any road or rail transport network and ensuring their safety is paramount. Recent years have seen significant research efforts to develop cost-effective techniques for bridge monitoring on a large scale. Drive-by bridge inspection techniques, whereby sensors inside a vehicle are used to monitor bridge condition, are at the focus of much of this work. This paper develops a relationship between the measured response in a vehicle and the contact-point response between the wheel and the surface of a bridge using a quarter-car representation of the vehicle. Numerical simulations are carried out to examine the feasibility of using the contact-point response as an indicator of damage. A number of passages of the quarter-car vehicle model traversing a Finite Element representation of a bridge are simulated and the contact-point response is evaluated for each passage. Varying levels of damage are simulated in the bridge to assess whether the presence of damage can be detected by the contact-point response. Results show that the method is very effective at identifying the bridge frequencies and can also detect changes in bridge frequency with increasing damage levels. A major advantage of using the contact-point response as a damage indicator lies in its ability to detect bridge frequencies without being influenced by the vibrational frequencies of the vehicle itself. The contact-point response shows promise for implementation into drive-by bridge inspection regimes, however further work is required to investigate the feasibility of the approach at higher vehicle speeds.
      86
  • Publication
    Railway track monitoring using drive-by measurements
    This paper presents the possibility of detecting considerable changes in track stiffness using the measurements from a laser vibrometer installed on a passing train. A numerical model of a two-dimensional train-track system is implemented in Matlab using the finite element method. The loss of stiffness in the track is modeled by reducing the stiffness of the sub-ballast layer of the track at specified points. The instantaneous velocity of the rail under the train is measured using four laser vibrometers mounted on the train. The simulations show that a change in the sub ballast stiffness of the track can be detected and located from the drive-by measurements.
      241
  • Publication
    On the estimation of bridge mode shapes from drive-by measurements
    This paper summarizes the latest approaches proposed on indirect bridge monitoring and provides recommendations for future development. The possibility of the estimation of bridge mode shapes from indirect measurements, is investigated. The Hilbert transform is applied to the responses measured from two following axles to extract the amplitudes of the signals. The global bridge mode shapes are constructed by applying a rescaling process to the local mode shapes obtained from the amplitudes. The performance of the proposed method is demonstrated using a numerical case study.
      339
  • Publication
    Application of Laser Measurement to the Drive-by Inspection of Bridges
    (National Technical University of Athens (NTUA), 2015-05-27) ;
    This paper introduces the application of laser vibrometer measurements to the drive-by inspection of bridges. Drive-by methods usually process the acceleration response measured from an accelerometer installed on a vehicle passing over a bridge. In this paper, two laser vibrometers and two accelerometers are installed on the vehicle to measure a rela-tive velocity between the bridge and vehicle and the vehicle acceleration. The vehicle velocity is removed from the relative velocity by subtracting the time integration of the vehicle accel-eration. It is shown by subtracting two following bridge spatial velocities at moving coordi-nates, that the spatial velocity of the road roughness can be removed. As a result, the bridge velocity at the moving coordinate is obtained. By applying the FFT to the bridge velocity, the fundamental frequency of the bridge is visible in the spectrum.
      493