Department of Civil Engineering Faculty Publications
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Item Dynamic measurements using digital image correlation(Emerald ICE Publishing, 2017-02-24) Murray, C. A.; Hoult, Neil A.; Take, W. AndyDigital image correlation (DIC), which enables non-contact measurement of displacements and strains, has seen widespread adoption within the geotechnical physical modelling community for the measurement of static displacements. Advances in high temporal resolution cameras now permit the use of DIC to calculate accelerations. However, it is currently unclear how the image acquisition rate and the choice of DIC algorithm influence the quality of this data. This paper describes the sources of error that affect the dynamic measurement accuracy. Numerical and physical experiments are used to demonstrate the relevance of (a) bias error in the sub-pixel interpolation scheme, (b) the ratio of sample rate to the frequency of the signal being monitored and (c) the signal-to-noise ratio on the accuracy and precision of DIC acceleration measurements. The results demonstrate that by using appropriate image texture, sampling frequencies and signal-to-noise ratios, measurements with an accuracy similar to accelerometers can be achieved. The displacement measurement error due to bias errors was found to be 0·0015 pixels. The error in the calculated velocity and acceleration was a function of the amplitude of displacement measurements with an optimum ratio between the sampling frequency to the signal frequency found to be between 25 and 50.Item Distributed fibre optic sensors for the purposes of structural performance monitoring(Emerald ICE Publishing, 2016-03-23) Brault, A.; Hoult, Neil A.; Trudeau, I.; Greenough, T.; Charnish, B.The structural design and construction industries have the potential to have a significant positive impact on the environment while at the same time reducing the cost of projects through optimized design. However, these benefits must not come at the expense of public safety or the serviceability of the structure. More comprehensive data is required to better understand the performance of structures designed using current procedures so that these procedures can be optimized. Until recently, the use of sensors during construction and operation of a building to acquire this data was difficult, expensive, and ultimately provided limited useful information. Distributed fibre optic sensors have the potential to overcome these difficulties including providing an extensive data set that can be used to more comprehensively evaluate the serviceability and ultimate limit states performance of a structure. This paper introduces the installation of a distributed fibre optic strain sensing system in a reinforced concrete commercial building. The system, based on measuring Rayleigh backscatter, enables strain to be measured with high accuracy over a gauge length that can be adjusted by the user along up to 70 m of fibre optic cable. The results of a live load test performed on a beam are introduced. The results were used to explore the beam's performance in terms of strain, deflection, flexural crack spacing, and support conditions. Distributed fibre optic sensors were found to show promise in this study, though future work is required.Item Bridge model updating using distributed sensor data(Emerald ICE Publishing, 2016-03-23) Bentz, Evan C.; Hoult, Neil A.One of the challenges of managing bridge infrastructure is developing numerical models that can be usedto accurately assess highly redundant bridge systems. One way to refine the model is to use sensor data to performmodel updating. However, conventional sensors provide limited data with which to update the model, given themany degrees of freedom associated with indeterminate structures, resulting in a large potential error. Distributedsensing technologies such as digital image correlation and fibre optic strain sensors have the potential to providemore extensive data sets for model updating. This paper presents a case study of a reinforced concrete bridge thatwas modelled numerically to predict the bridge performance. The bridge was then load tested, and distributedsensor data were acquired. Using the sensor data, the numerical model was updated and refined estimates of thebridge behaviour were obtained. The initial and final models produced estimates of bridge behaviour that differedby an order of magnitude, illustrating the importance of sensor data for some bridge assessments. Additionally, themodel indicated that the stiffness of the bridge had increased with time owing to an increase in the elastic modulusof the concrete and the development of compressive stresses.Item Assessment of a bascule lift bridge using digital image correlation(Emerald ICE Publishing, 2017-05-03) Hoag, Adam; Hoult, Neil A.; Take, AndyThe LaSalle Causeway lift bridge is a 100 year old highway bridge that is integral to the transportation network of Kingston, Ontario, Canada. Rehabilitation of the bridge was planned to address corrosion of the bottom chord and a gap identified at the support of the lifting end. To determine the effectiveness of this rehabilitation, the displacements of the bridge were monitored before and after the rehabilitation, during a static load test, and under regular traffic loading. Since the bridge crosses the Cataraqui River, there are no stationary reference points near midspan from which to measure displacement using conventional sensors. For this reason, digital image correlation was selected as an appropriate monitoring technology. Displacements at the midspan and supports of the bridge were recorded and used to assess the performance of the bridge. The results of this research indicate that the bridge complies with displacement limits and that the rehabilitation of the bridge was successful in rehabilitating the support conditions of the bridge. Keywords: bridges; field testing & monitoring; steel structuresItem Evaluation and comparison of different detection technologies on simulated voids near buried pipes(Elsevier, 2022-02-25) Wang, Dong; Moore, Ian D.; Hoult, Neil A.; Lan, HaitaoErosion voids near buried pipes may reduce the service lives of buried infrastructure assets and present a concern to municipalities as they are difficult to detect accurately and effectively. Various technologies exist to detect erosion voids but limited testing has been performed to evaluate their effectiveness. In order to evaluate and compare different existing erosion void detection technologies, a blind experiment (i.e., without operators having prior information about void locations and geometries) was conducted. Two kinds of pipes were used for the evaluation: a corrugated steel pipe and a reinforced concrete pipe. A total of five artificial voids were made near the pipes. Four commercially available void detection technologies were evaluated: (i) conventional Backscatter Computed Tomography (BCT), (ii) handheld BCT, (iii) Ground Penetrating Radar (GPR) and (iv) Pipe Penetrating Radar (PPR). Additionally, Infrared Thermography (IRT) was also employed by the authors although this was not a blind study. Each technology and the data provided by that technology are presented. Based on the results, Handheld BCT and IRT were recommended for initial detection of the voids near corrugated steel pipes. To obtain higher accuracy and geometry detail, conventional BCT and PPR were suggested for the corrugated steel pipe and concrete pipe, respectively. GPR was able to detect a large void simulated between the two test pipes.