Now showing 1 - 10 of 26
- PublicationMaximum dynamic stress on bridges traversed by moving loadsMost current research on dynamic effects due to traffic load on simply supported bridges focuses on the mid-span section of the bridge, since this location corresponds to the worst static bending moment. However, the maximum total moment allowing for dynamics, may differ considerably from the maximum moment at mid-span. This paper shows how the maximum can occur in a section relatively far from mid-span with a significant difference in magnitude.
Scopus© Citations 25 2204
- PublicationModelling the vehicle in vehicle-infrastructure dynamic interaction studiesThis paper presents the equations of motion for a general articulated road vehicle, with variable numbers of wheels for the tractor and trailer. The equations are applicable to vehicle-bridge dynamic interaction problems for two and three dimensional systems.
Scopus© Citations 32 1759
- PublicationDrive-by detection of railway track stiffness variation using in-service vehiclesRailway track stiffness is an important track property which can help with the identification of maintenance related problems. Railway track stiffness can currently be measured using stationary equipment or specialised low-speed vehicles. The concept of using trains in regular service to measure track stiffness, has the potential to provide inexpensive daily 'drive-by' track monitoring to complement data collected by less-frequent monitoring techniques. A method is proposed in this paper for the detection of track stiffness variation through an analysis of vehicle accelerations resulting from the vehicle-track dynamic interaction (VTI). The Cross Entropy optimisation technique is applied to determine the track stiffness profile that generates a vehicle response that best fits the measured vertical accelerations of a railway carriage bogie. Numerical validation of the concept is achieved by using a 2-dimensional half-bogie dynamic model, representing a railway vehicle, to infer a global track stiffness profile along a track. The Track Stiffness Measurement Algorithm (TSMA) is implemented in Matlab. This paper reports the results of the numerical simulations. The proposed method gives good estimates of the track stiffness. To the authors' knowledge this is the first time an optimisation technique has been applied to the determination of railway track stiffness.
Scopus© Citations 44 707
- PublicationDynamic increment for shear force due to heavy vehicles crossing a highway bridgeMost of the current research on dynamic amplification factors caused by traffic flow on a bridge has focused on bending moment effects. Although bending stresses often govern the requirements of the bridge section, sufficient shear capacity must be provided too. Shear stresses near the support are strongly influenced by damaged expansion joints and/or differential settlements between the bridge deck and the approach road. The latter is taken into account in this theoretical investigation to evaluate the dynamics associated with the shear load effect caused by heavy trucks and how it relates to the length of the bridge span.
Scopus© Citations 57 1941
- PublicationThe non-stationarity of apparent bridge natural frequencies during vehicle crossing eventsIn this paper, it is shown numerically how the natural frequencies of a bridge change during the crossing of a vehicle. An Euler-Bernoulli beam is modelled traversed by a single DOF vehicle. The use of such a simple Vehicle-Bridge interaction model is justified by the objective of providing insight into the structural dynamics of a moving load interacting with a bridge. The numerical results indicate that the variations in natural frequencies depend greatly on vehicle-to-structure frequency ratio and mass ratio. In some conditions, significant variations in modal properties are observed. Additionally, it can be analysed from the passing vehicle response. Time-frequency signal analysis of the vehicle's vertical acceleration clearly shows how the frequencies evolve during the event. The frequency localization properties of the Wavelet transform (Modified Littlewood-Paley) are exploited in analysing the signal and highlighting the relevant results.
- PublicationRailway Bridge Condition Monitoring Using Numerically Calculated Responses from Batches of TrainsThis study introduces a novel method to determine apparent profile of the track and detect railway bridge condition using sensors on in-service trains. The concept uses a type of Inverse Newmark-β integration scheme on data from a batch of trains. In a self-calibration process, an optimization algorithm is used to find vehicle dynamic properties and speed. For bridge health monitoring, the apparent profile of the bridge is first determined, i.e., the true profile plus components of ballast and bridge deflection under the moving train. The apparent profile is used, in turn, to calculate the moving reference deflection influence line, i.e., the deflection due to a moving (static) unit load. The moving reference influence line is shown to be a good indicator of bridge stiffness. This numerical approach is assessed using an elaborate finite element model operated by an independent research group. The results show that the moving reference influence line can be found accurately and that it constitutes an effective indicator of the condition of a bridge.
Scopus© Citations 6 131
- PublicationThe Virtual Axle concept for detection of localised damage using Bridge Weigh-in-Motion dataThis paper proposes a new level I damage identification method for short span statically indeterminate bridges using the information provided by a Bridge Weigh-in-Motion system. Bridge Weigh-In-Motion systems measure the bridge deformation due to the crossing of traffic to estimate traffic attributes, namely axle weights and distances between axles for each vehicle. It is theoretically shown that it is convenient to introduce a fictitious weightless axle, which has been termed 'Virtual Axle', in the Bridge Weigh-in-Motion calculations to derive a damage indicator. The latter can be used both as a new robust output-only model-free level I structural health monitoring technique and as a new self-calibration method for Bridge Weigh-In-Motion systems. The response of a fixed-fixed beam traversed by a 2-axle vehicle travelling over an irregular profile is used to validate the proposed method. By means of Monte Carlo simulation the influence of the key parameters such as the degree and location of damage, noise levels, span lengths and profile irregularities on the accuracy of the method are investigated. The results show that the 'Virtual Axle' method is able to detect small local damages in statically indeterminate structures.
Scopus© Citations 21 431
- PublicationDynamic impact of heavy long vehicles with equally spaced axles on short-span highway bridgesExtremely large trucks with a weight exceeding the standard require a permit before they are allowed to cross the bridges of a specific route. For the purpose of safety, an escort is often employed to maintain a distance between vehicles and to ensure that the bridge load remain below the allowed maximum. Given that the speed of these large vehicles is quite slow and that the amplitude of vibrations normally declines when the vehicle mass is large, a minor dynamic amplification of the bridge response is expected. However, some of these large trucks have a unique feature characterized by “multiple equally-spaced axles”, something that is uncommon in normal vehicle. The application of axle forces at equal intervals can dynamically excite bridges to a considerable extent, even at low speeds. These “critical” low speeds are estimated a priori from the axle spacing of the truck and the main frequency of vibration of the bridge. This paper demonstrates that when the “critical” speed is unavoidable, a relatively high dynamic allowance must be added to static calculations before granting a permit to a long heavy vehicle.
366Scopus© Citations 10
- PublicationIdentification of sudden stiffness changes in the acceleration response of a bridge to moving loads using ensemble empirical mode decompositionThe growth of heavy traffic together with aggressive environmental loads poses a threat to the safety of an aging bridge stock. Often, damage is only detected via visual inspection at a point when repairing costs can be quite significant. Ideally, bridge managers would want to identify a stiffness change as soon as possible, i.e., as it is occurring, to plan for prompt measures before reaching a prohibitive cost. Recent developments in signal processing techniques such as wavelet analysis and empirical mode decomposition (EMD) have aimed to address this need by identifying a stiffness change from a localised feature in the structural response to traffic. However, the effectiveness of these techniques is limited by the roughness of the road profile, the vehicle speed and the noise level. In this paper, ensemble empirical mode decomposition (EEMD) is applied by the first time to the acceleration response of a bridge model to a moving load with the purpose of capturing sudden stiffness changes. EEMD is more adaptive and appears to be better suited to non-linear signals than wavelets, and it reduces the mode mixing problem present in EMD. EEMD is tested in a variety of theoretical 3D vehicle–bridge interaction scenarios. Stiffness changes are successfully identified, even for small affected regions, relatively poor profiles, high vehicle speeds and significant noise. The latter is due to the ability of EEMD to separate high frequency components associated to sudden stiffness changes from other frequency components associated to the vehicle–bridge interaction system.
562Scopus© Citations 59
- PublicationCharacteristic Dynamic Increment for Extreme Traffic Loading Events on Short and Medium Span Highway BridgesMore accurate assessment of safety can prevent unnecessary repair or replacement of existing bridges which in turn can result in great cost savings at network level. The allowance for dynamics is a significant component of traffic loading in many bridges and is often unnecessarily conservative. Critical traffic loading scenarios are considered in this paper with a model that allows for vehicle–bridge interaction and takes into account the road surface condition. Characteristic dynamic allowance values are presented for the assessment of mid-span bending moment in a wide range of short to medium span bridges for bidirectional traffic.
Scopus© Citations 89 908