Accurate deformation monitoring on bridge structures using a cost-effective sensing system combined with a camera and accelerometers

This is the author accepted manuscript. The final version is available from American Society of Civil Engineers via the DOI in this record.Information on deformation is critical for bridge condition evaluation but accurate characterisation, usually via discrete displacement measurements, remains a challenging task. Vision-based systems are promising tools, possessing advantages of easy installation, low cost and adequate resolution in time and frequency domains. However, vision-based monitoring faces several field challenges and might fail to achieve the required level of working performance in some real-world test conditions e.g.involving low-contrast patterns and mounting instability of optical sensors. To make the best use of the potential of vision-based systems, a mixed sensing system consisting of a consumer-grade camera and an accelerometer is proposed in this study for accurate displacement measurement. The system considers automatic compensation of camera shake and involves autonomous data fusion process for noise reduction. The proposed system is demonstrated through a field monitoring test on a short-span railway bridge and is validated to offer higher accuracy and wider frequency range than using a camera alone. Displacement data by the mixed system are demonstrated to be viable for estimating bridge influence line, indicating the potential for bridge condition assessment

Sturm-Liouville operators on time scales

We establish the connection between Sturm-Liouville equations on time scales and Sturm--Liouville equations with measure-valued coefficients. Based on this connection we generalize several results for Sturm-Liouville equations on time scales which have been obtained by various authors in the past.Comment: 12 page

Deformation monitoring of a simply supported railway bridge under varying dynamic loads

This is the author accepted manuscript. The final version is available from IABMAS via the link in this recordStructural health monitoring is a useful tool for evaluating the condition of bridges, with permanent systems installed on bridges which form vital links on the major transport network. The economic cost of the monitoring systems limits their installation on smaller bridges which make up the wider transport network. A short-term monitoring system can be quickly installed and adjusted to suit the requirements of individual bridges. These systems are ideal for rural regions with a high number of single span bridges on isolated road and rail networks. This report will review a single span bridge on a private heritage railway under loading from passing steam engines, including the Flying Scotsman. Acceleration data are used to determine the rotations and deflections of the bridge deck. To verify the data, deflection measurements at mid-span were recorded using a video-based measurement system. The deflection measurements from the accelerometers correlate with the video imagery measurements

Tracking bridge tilt behaviour using sensor fusion techniques

This is the final version. Available on open access from Springer via the DOI in this recordThe resilience of the built environment to extreme weather events is fundamental for the day-to-day operation of our transport network, with scour representing one of the biggest threats to bridges built over flowing water. Condition monitoring of the bridge using a structural health monitoring system enhances resilience by reducing the time needed to return the bridge to normal use by providing timely information on structural condition and safety. The work presented in this report discusses use of rotational measurements in structural health monitoring. Traditionally tiltmeters (which can be a form of DC accelerometer) are used to measure rotation but are known to be affected by dynamic movements, while gyroscopes react quickly to dynamic motion but drift over time. This review will introduce gyroscopes as a complementary sensor for accelerometer rotational measurements and use sensor fusion techniques to combine the measurements from both sensors to get an optimised rotational result. This method was trialled on a laboratory scaled model, before the system was installed on an in-service single-span skewed railway bridge. The rotational measurements were compared against rotation measurements obtained using a vision-based measurement system to confirm the validity of the results. An introduction to gyroscopes, field test measurement results with the sensors and their correlation with the vision-based measurement results are presented in this article.Engineering and Physical Sciences Research Council (EPSRC

Identifying damage on a bridge using rotation-based Bridge Weigh-In-Motion

Funder: University of CambridgeAbstractBridge Weigh-in-Motion (B-WIM) systems use the bridge response under a traversing vehicle to estimate its axle weights. The information obtained from B-WIM systems has been used for a wide range of applications such as pre-selection for weight enforcement, traffic management/planning and for bridge and pavement design. However, it is less often used for bridge condition assessment purposes which is the main focus of this study. This paper presents a bridge damage detection concept using information provided by B-WIM systems. However, conventional B-WIM systems use strain measurements which are not sensitive to local damage. In this paper the authors present a B-WIM formulation that uses rotation measurements obtained at the bridge supports. There is a linear relationship between support rotation and axle weight and, unlike strain, rotation is sensitive to damage anywhere in the bridge. Initially, the sensitivity of rotation to damage is investigated using a hypothetical simply supported bridge model. Having seen that rotation is damage-sensitive, the influence of bridge damage on weight predictions is analysed. It is shown that if damage occurs, a rotation-based B-WIM system will continuously overestimate the weight of traversing vehicles. Finally, the statistical repeatability of ambient traffic is studied using real traffic data obtained from a Weigh-in-Motion site in the U.S. under the Federal Highway Administration’s Long-Term Pavement Performance programme and a damage indicator is proposed as the change in the mean weights of ambient traffic data. To test the robustness of the proposed damage detection methodology numerical analysis are carried out on a simply supported bridge model and results are presented within the scope of this study.</jats:p

Bridge damage detection using rotation measurements – experimental validation

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record This paper presents a novel bridge condition assessment methodology using direct rotation measurements. Initially, numerical analyses are carried out to develop the theoretical basis of the proposed bridge damage detection methodology. As a result of this study the difference in rotation influence lines obtained for healthy and damaged bridge states is proposed as a damage indicator. The sensitivity of rotation to damage and the effect of sensor locations on sensor sensitivities are investigated. Subsequently, extensive laboratory experiments are conducted on a 5.4 m long simply supported bridge structure in an effort to validate the results from the numerical analyses. The test structure is instrumented with rotation sensors and axle detectors and loaded with a four-axle moving vehicle. In this study, rotations are measured using high grade uniaxial accelerometers. The procedure of measuring rotations using accelerometers is explained within the scope of this study. To test the robustness of the proposed bridge condition assessment methodology, a wide range of single and multiple damage scenarios is investigated and the results from this study show that the proposed methodology can successfully identify damage on a bridge. For the model considered, damage as low as 7% change in stiffness over an extent of 2.5% bridge span is shown to be detectable.European Union Horizon 202

Identifying damage in a bridge by analysing rotation response to a moving load

This is the author accepted manuscript. The final version is available from Routledge via the DOI in this recordThis article proposes a bridge damage detection method using direct rotation measurements. Initially, numerical analyses are carried out on a one-dimensional (1D) simply supported beam model loaded with a single moving point load to investigate the sensitivity of rotation as a main parameter for damage identification. As a result of this study, the difference in rotation measurements due to a single moving point load obtained for healthy and damaged states is proposed as a damage indicator. A relatively simple laboratory experiment is conducted on a 3-m long simply supported beam structure to validate the results obtained from the numerical analysis. The case of multi-axle vehicles is investigated through numerical analyses of a 1D bridge model and a theoretical basis for damage detection is presented. Finally, a sophisticated 3D dynamic finite element model of a 20-m long simply supported bridge structure is developed by an independent team of researchers and used to test the robustness of the proposed damage detection methodology in a series of blind tests. Rotations from an extensive range of damage scenarios were provided to the main team who applied their methods without prior knowledge of the extent or location of the damage. Results from the blind test simulations demonstrate that the proposed methodology provides a reasonable indication of the bridge condition for all test scenarios.European Union Horizon 202

Extensive sampling sheds light on species-level diversity in Palearctic Placobdella (Annelida: Clitellata: Glossiphoniiformes)

The bloodfeeding leech genus Placobdella is dominated by North American diversity, with only a single nominal species known from Central America and one from the Palearctic region. This is likely due to considerable underestimation of Palearctic biodiversity, but investigations into potential hidden diversity are lacking. To shed light on this, the present study introduces new data for specimens initially identified as Placobdella costata from Ukraine (close to the type locality), Italy, Germany, Latvia, Montenegro, Bulgaria, Slovenia, Turkey, Azerbaijan, Tunisia, and Algeria, and uses both nuclear (Internal Transcribed Spacer [ITS] region) and mitochondrial (cytochrome c oxidase subunit I [COI]) sequence data in phylogenetic and DNA barcoding frameworks, in order to better understand species-level diversity. Seven independent lineages are present in the trees, five of which show adequate separation at the COI locus to suggest their unique species-level status (COI distances between these clades range from 4.86 to 8.10%). However, the ITS data suggest that speciation is recent or incipient in these clades, and that not enough time has passed for clear separation at this locus. We discuss the evolutionary and taxonomic implications of our findings and speculate on dispersal events that may have contributed to shaping this pattern of geographic distribution

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV