Full-scale Monitoring Research Articles

Autonomous end-to-end wireless monitoring system for railroad bridges

One of the most critical components of the US transportation system is railroads, accommodating transportation for 48% of the nation’s total modal tonnage. Despite such vital importance, more than half of the railroad bridges, an essential component of railroad infrastructure in maintaining the flow of the network, were built before 1920; as a result, bridges comprise one of the most fragile components of the railroad system. Current structural inspection practice does not ensure sufficient information for both short- and long-term condition assessment while keeping the operation cost low enough for mandatory annual inspection. In this paper, we document the development process of an autonomous, affordable system for monitoring railroad bridges using the wireless smart sensor (WSS) so that a complete end-to-end monitoring solution can provide relevant information directly from the bridges to the end-users. The system’s main contribution is to capture the train-crossing event efficiently and eliminate the need for a human-in-the-loop for remote data retrieval and post-processing. In the proposed system, an adaptive strategy combining an event-based and schedule-based framework is implemented. The wireless system addresses the challenges of remote data retrieval by integrating 4G-LTE functionality into the sensor network and completes the data pipeline with a cloud-based data management and visualization solution. This system is realized on hardware, software, and framework levels. To demonstrate the efficacy of this system, a full-scale monitoring campaign is reported. By overcoming the challenges of monitoring railroad bridges wirelessly and autonomously, this system is expected to be an essential tool for bridge engineers and decision-makers.

Groundwater environmental forensic investigation combining multivariate statistical techniques and screening analyses

Heavy metal contamination was identified in groundwater monitoring wells surrounding a waste deposit facility at the Rönnskär Cu–Pb–Zn smelter in Skellefteå, northern Sweden. The main objective of this study is to identify the sources of contamination, utilizing element screening analyses and multivariate statistical techniques. A second objective is to determine the usefulness of these techniques in Environmental Forensics investigations of contaminated groundwater at a complex industrial site. Water samples were collected from four groundwater monitoring wells and six waste deposit cells surrounding the contaminated area. Seventy-two elements are statistically examined and the dataset is reduced to the variables representative of the contaminated source material from the smelting process. A three-component model is identified and explains 88% of the total variation in the dataset. Component 1 includes concentrations of Cd, Co, Ni, Rb, Re, and Zn. This component displays a high correlation with two of the deposit cells and their associated groundwater monitoring wells. Component 2 is comprised of Sb, Cu, and Mo. This component displays a correlation between all monitoring wells and deposits likely due to the high mobility of these elements as oxyanions. Component 3 is dominated by As and displays high correlation to three older deposit cells representing a completely different source than for Components 1 and 2. The application of screening analyses and multivariate statistics in this study has achieved a meaningful identification of sources of contamination in the investigated area. It was also shown to be useful as an initial survey aiming to optimize a full-scale monitoring program at the site.

Multilabel Image Classification Based Fresh Concrete Mix Proportion Monitoring Using Improved Convolutional Neural Network.

Proper and accurate mix proportion is deemed to be crucial for the concrete in service to implement its structural functions in a specific environment and structure. Neither existing testing methods nor previous studies have, to date, addressed the problem of real-time and full-scale monitoring of fresh concrete mix proportion during manufacturing. Green manufacturing and safety construction are hindered by such defects. In this study, a state-of-the-art method based on improved convolutional neural network multilabel image classification is presented for mix proportion monitoring. Elaborately planned, uniformly distributed, widely covered and high-quality images of concrete mixtures were collected as dataset during experiments. Four convolutional neural networks were improved or fine-tuned based on two solutions for multilabel image classification problems, since original networks are tailored for single-label multiclassification tasks, but mix proportions are determined by multiple parameters. Various metrices for effectiveness evaluation of training and testing all indicated that four improved network models showed outstanding learning and generalization ability during training and testing. The best-performing one was embedded into executable application and equipped with hardware facilities to establish fresh concrete mix proportion monitoring system. Such system was deployed to terminals and united with mechanical and weighing sensors to establish integrated intelligent sensing system. Fresh concrete mix proportion real-time and full-scale monitoring and inaccurate mix proportion sensing and warning could be achieved simply by taking pictures and feeding pictures into such sensing system instead of conducting experiments in laboratory after specimen retention.

Damage in Rubble Mound Breakwaters. Part I: Historical Review of Damage Models

The term “damage” in rubble mound breakwaters is usually related to the foremost failure mode of this kind of coastal structures: their hydraulic instability. The characterization of the breakwater response against wave action was and will be the goal of hundreds of studies. Because of the large amount of information, the present review on damage in rubble mound breakwaters is divided in two papers, which are closely linked but conceptually different; whereas Part II is focused on the various approaches for defining and measuring damage, Part I summarizes the diverse strategies for modelling damage development and progression. The present paper compiles 146 references on this topic, chronologically discussed over almost a century of history: from 1933 to 2020. It includes 23 formulations of hydraulic stability models and 11 formulations of damage progression models, together with main advances and shortcomings up to date. The future of rubble mound design is linked to risk-based tools and advanced management strategies, for which deeper comprehension about the spatial and temporal evolution of damage during the useful life of each particular structure is required. For this aim, damage progression probabilistic models, full-scale monitoring and standardization will presumably be some of the key challenges in the upcoming years.

Performance Enhancement of the Location and Recognition of a Φ-OTDR System Using CEEMDAN-KL and AMNBP

It is commonly known that for characteristics, such as long-distance, high-sensitivity, and full-scale monitoring, phase-sensitive optical time-domain reflectometry (Φ-OTDR) has developed rapidly in many fields, especially with the arrival of 5G. Nevertheless, there are still some problems obstructing the application for practical environments. First, the fading effect leads to some results falling into the dead zone, which cannot be demodulated effectively. Second, because of the high sensitivity, the Φ-OTDR system is easy to be interfered with by strong noise in practical environments. Third, the large volume of data caused by the fast responses require a lot of calculations. All the above problems hinder the performance of Φ-OTDR in practical applications. This paper proposes an integration method based on a complete ensemble empirical mode decomposition with adaptive noise and Kullback–Leibler divergence (CEEMDAN-KL) and an adaptive moving neighbor binary pattern (AMNBP) to enhance the performance of Φ-OTDR. CEEMDAN-KL improved the signal characteristics in low signal-to-noise ratio (SNR) conditions. AMNBP optimized the location and recognition via a high calculation efficiency. Experimental results show that the average recognition rate of four kinds of events reached 94.03% and the calculation efficiency increased by 20.0%, which show the excellent performance of Φ-OTDR regarding location and recognition in practical environments.

Assessing the performance of a versatile and affordable geotechnical monitoring system for river embankments

River embankments stability is a key aspect in geohazard assessment and underestimating its failure risk may result in unexpected and severe damages. Changes in hydraulic and climatic boundary conditions are responsible for transient water flow within the embankments, consequently the related soil water content and pore-water pressure distributions vary with time. Therefore, it is crucial to investigate their hydraulic and retention behaviour in order to assess in a reliable way the safety margins towards instability mechanisms. To obtain a realistic estimate of key variables in time and space, as a function of external conditions, a combination of field measurements, laboratory testing and suitably calibrated numerical analyses should be used. To achieve this purpose, a full-scale monitoring system was implemented on a cross section of an embankment along the river Secchia (Modena, Italy), mainly measuring the pore-water pressure (including suction) and the water content at different depths. A relatively large variety of different sensors have been installed, to compare their performance in terms of robustness and reliability, and collected data have been interpreted with the help of laboratory and field geotechnical characterisation. The article describes such system and the sensors used, their capabilities and the installation techniques, resulting in quite innovative solutions for the specific application. The spatial variability of the monitored variables is also finally presented and discussed. The proposed integrated monitoring system, which aims at making use of affordable and commercially available sensors that can be therefore installed along extensive river stretches, appears a fundamental starting point to assess potential risks of such geotechnical infrastructures in real-time and to devise well-balanced related mitigation measures.

Buffeting response of long-span bridges considering uncertain turbulence parameters using the environmental contour method

Full-scale monitoring of the Hardanger Bridge has revealed significant turbulence-induced variability in the measured acceleration response. In this paper, a probabilistic model is used to describe the uncertain turbulence parameters, and the environmental contour method is used to investigate the long-term root-mean-square (RMS) response of the Hardanger Bridge. The results show that turbulence-induced variability has a significant impact on the bridge girder section moments. It is also interesting that the critical combination of environmental parameters does not necessarily involve the maximum mean wind velocity. By using the environmental contour method to account for turbulence uncertainty, the scattered acceleration RMS response measurements from the Hardanger Bridge are successfully eclipsed by 100-year return period response estimates, showing vast improvements compared with the traditional design methodology. The investigations presented in this paper show that the environmental contour method can be used to improve the accuracy and reduce the uncertainty in buffeting response calculations for long-span bridge design.

Hybrid Feature Extraction of Pipeline Microstates Based on Φ-OTDR Sensing System

This paper proposes a general integration method which can effectively describe the characteristics of pipeline leakage and help distinguish multiple pipeline microstates. Since the rapid development of Φ-OTDR in recent years, this technology has been applied to more and more fields, such as fiber optic safety monitoring, seismic monitoring, and structural health monitoring. Among them, Φ-OTDR has the characteristic of continuous full-scale monitoring in pipeline monitoring, but there are few researches on pipeline state characteristics at present. In this paper, based on the analysis of the pipeline state with Φ-OTDR technology, a method of extracting multiple microstates of pipelines is proposed. This method combined with the peak-to-average power ratio, short-term interval zero crossing, and fractal characteristics in the frequency domain can effectively characterize the microstate of pipes and provide support for identification of more microstates of pipelines. These features reflect the common characteristics of leaks in gas pipelines and liquid pipelines. Meanwhile, their combination features can represent the small differences in pipeline states. The experimental results show that the method can effectively characterize the microstate information of the pipeline, and the recognition rate of the hybrid feature under two kinds of pipeline leakage and multipressure conditions reaches 91% and 83%.

Experimental behaviour of concrete box culverts — comparison with current codes of practice

It is now accepted that current expeditious models for determining earth pressures on flexible underground structures under compacted layers do not include several technical nuances of the soil–structure interaction. Thus, these models are not capable of delivering an optimized design. The present paper compares the results from the well-known American Association of State Highway and Transportation Officials (AASHTO) model with two different numerical models — a user-friendly elastic model and a more robust finite element model — and with results retrieved from a full-scale monitoring of a concrete box culvert, 5.5 m high and 3.77 m width, over which a 15 m high embankment was built. This structure was instrumented selectively, over a period of almost 1 year, during which several parameters were recorded, including earth pressures and structural deformation. Results have shown that the two most significant drawbacks associated with the use of the AASHTO model are the inadequate evaluation of vertical pressure on the top slab and the coefficient of earth pressure, which results in a significant overestimation of the lateral pressures and, consequently, in an overall inefficient design of the structure.

Impact of seismic-type shock parameters on the soil-structure interaction effect in the USC mining region

The paper deals with seismic-type surface and building vibrations randomly occurring as a result of rockbursts in mining regions (random events as with earthquakes). The focus is on the problem of ground vibrations transmission to building foundation – it is one of very important phenomenon associated with soil-structure interaction effect. One of the ways of estimation of possible differences between simultaneously developing free-field vibrations next to a building and building foundation vibrations, i.e. using a ratio of response spectra (RRS), is applied to this study. Analysis concerns the ratio of dimensionless and dimensional acceleration response spectra (β and Sa) – denoted as RRS(β) and RRS(Sa), respectively. Horizontal vibrations parallel to the transverse (x) and longitudinal (y) axis of the representative (typical) two-storey, masonry office building are discussed. Calculations are based on the results of in situ surface vibration measurements performed in the seismically active Upper Silesian Coalfield (USC) mining area in Poland (long-term, full-scale monitoring). Evaluation of the dependence of the curves of ratio of response spectra on some parameters corresponding to mine-induced vibrations (i.e. epicentral distance, mining shock energy, peak value of free-field vibrations) is executed. From the obtained results, it can be definitely concluded that the influence of the most important mining tremor parameters (i.e. epicentral distance, mining shock energy, peak value of free-field vibrations) on the ratio of response spectra calculated in the successive ranges of these parameters, is clearly observed.

Optimised Triangular Weir Design for Assessing the Full-Scale Performance of Green Infrastructure

Conventional triangular weirs have been originally developed to measure, divert, and control surface water. However, a special application of these weirs, such as for low flow measurements in full-scale monitoring of Green Infrastructure (GI), is not well investigated. Available head-discharge relationships for triangular sharp-crested weirs are only valid under a free-flow regime. Literature focusing on the V-notch weir usage for GI assessment suggests that it is necessary to calibrate the head-discharge relationship before its use. This study focuses on understanding the effects of site constraints on the measurement performance of a V-notch weir at low flow rates, and the validity of equations derived for similar applications that can be found in the literature. The variation of discharge coefficient in various flow regimes was investigated experimentally based on calibration runs covering flow rates between 0.054 l/s and 7 l/s. The results show that for 30° and 45° V-notch weirs, three flow regimes can be identified. It was observed that literature equations to calculate the discharge coefficient are valid for partially-contracted triangular weirs only at heads greater than vertex distance from the channel. However, for low flows that are expected to occur when estimating the full-scale performance of GI, the equations available from the literature for similar site conditions underestimated the flow rate between 85% and 17%. This emphasises the need for accurate calibration of a V-notch device under the site conditions to achieve the necessary level of accuracy in GI performance estimation. The procedure outlined in this work can be easily replicated to determine the optimal monitoring system configuration. Alternatively, if the site conditions would match those described in this study, the computed discharge using the proposed relations, in combination with the general V-notch weir equation, provides a significant improvement in the accuracy of measurements, expands the head applicability range of V-notch weirs, and enables better understanding of GI performance at the full scale.

Data-Enabled Prediction Framework of Dynamic Characteristics of Rural Footbridges Using Novel Citizen Sensing Approach

Rural footbridges have proved to be an impetus for growth in vulnerable areas of the developing world, increasingly being built in many isolated communities around continents. Yet, little prior assessment of their dynamic characteristics had been made due to the non-traditional constraints that arise from instrumenting footbridges in rural, off-grid settings across multiple continents. Their characteristics remain largely unknown even if the low mass and flexible nature of rural footbridges make them vulnerable to wind-induced motions. To this end, this study proposes a data-enabled prediction framework based on a novel citizen sensing protocol, which aims at predicting the dynamic properties of rural footbridges during the conceptual design phase to enhance their safety under winds. The protocol is established which enables non-experts including local citizens in isolated communities to collect vibration data of rural footbridges by way of rapidly deployable and low-cost sensing systems in a novel application to full-scale monitoring with the concept of the community engagement. This citizen sensing data helps not only establish database with dynamic properties, but also develop empirical models to predict their dynamic properties of a footbridge in the conceptual design phase without detailed and bridge-specific dynamic modeling. In addition. a simple yet effective batch processing procedure to be done by non-experts is also devised to readily process upcoming citizen sensing data from new footbridges in the future, which offers instant and continuous updates of existing database with minimal efforts for enhancing the knowledge and the prediction of dynamic characteristics of rural footbridges.

Bio materials with reclaimed asphalt: from lab mixes properties to non-damaged full scale monitoring and mechanical simulation

Three innovative environmentally friendly pavement materials, designed with 50% of Reclaimed Asphalt and three different biomaterials (2 bio-additivated bitumens and 1 bio-binder), were produced in an industrial plant. These mixes were tested in lab and also at full scale using an Accelerated Pavement Test facility. The asphalt mix viscoelastic properties were measured in lab and their intrinsic viscoelastic response were simulated. These rheological models are used to simulate the pavement mechanical response using both elastic and viscoelastic multilayer codes. Hence, full scale measurement performed during the full scale test at an early stage (without damages) can be compared with these simulations. The overall prediction accuracy, when all the signals are considered, is between 4% and 8% for all materials. It can be concluded that material characterisation in lab as well as the selected models are well adapted to simulate actual loading state under a moving load, even for these non-conventional mixes. For temperatures lower than 25°C, elastic modelling appears to be sufficient for pavement structural design with the innovative materials tested here.

Experimental Investigation of the Effect of Pre-Bond Contamination with Fingerprints and Ageing on the Fracture Toughness of Composite Bonded Joints

The effect of the pre-bond contamination with fingerprint (FP), both during the production and the application of adhesively bonded patch repairs on composite aircraft parts, and the cumulative effect of fingerprint and hygrothermal ageing on the fracture toughness of carbon fiber reinforced plastic (CFRP) bonded joints are experimentally investigated. To this end, mode I and mode II fracture toughness tests were conducted on FP contaminated coupons and mode II fracture toughness tests on FP contaminated and aged coupons. The artificial FP was supposed to mimic the accidentally applied fingerprints on the CFRP adherent and was applied on the adherent in the size of a human thumb. The two investigated FP formulations consisted of an artificial hand perspiration solution for the production scenario, and of Skydrol hydraulic-oil for the repair scenario. Three levels of contamination with FP were considered for each scenario. The hygrothermal ageing conditions applied until moisture saturation achieved were 70 °C/85% RH. Prior to bonding, the CFRP adherent surfaces were inspected using full-scale monitoring with optically stimulated electron emission (OSEE), an extended nondestructive testing method, in order to analyze the physicochemical variations at the contaminated surface of the adherents before bonding. The ANOVA statistical method was used to assist the evaluation of the results and the deduction or reliable conclusions. The results revealed that the pre-bond FP contamination of the adherents leads to the reduction of the fracture toughness of the CFRP bonded joints. After-bond hygrothermal ageing under the prescribed conditions had no significant influence on the moisture absorption and load carrying capacity of the joint. However, it influenced the bondline integrity as it led to a significant reduction of the fracture toughness of the joint. The effect of the combination of pre-bond contamination and after-bond hygrothermal ageing is more severe than the two separate effects.

First results of the introduction of bedaguiline for patients with multidrug resistens tuberculosis in Ukraine: recommendations for practical doctor resume

Objective — to implement approaches for the proper use of new and reprogrammed drugs for the treatment of drug-resistant tuberculosis.Materials and methods. Such an implementation took place within the pilot project Challenge TB implemented in Ukraine by PATH in association with the KNCV (Royal Dutch Society for TB Control) and supported by USAID at the clinical base of the department of drug-resistant tuberculosis SO «National Institute of Phthisiology and Pulmonology named after F.G. Yanovsky of NAMS of Ukraine».The introduction of bedaguiline was carried out under the condition of the rapid detection of the XDR and modern principles of treatment of drug-resistant tuberculosis. The article describes: the characteristic of 144 patients with drug-resistant tuberculosis, which were included in the treatment with bedaguiline from 07.2017 to 09.2018, according to anamnestic, clinical and laboratory indicators; the process of treatment of these patients, which provided for the use of a modern algorithm for the step-by-step prescribing of antimycobacterial drugs, which was supposed to include at least 4 effective ones, and at least 2 — with bactericidal action.Results and discussion. Among the total number of patients, 134 (93.1 %) patients were treated or continued treatment with a positive effect and a forecast for treatment. Were received «death» in 4 (2.8 %) patients: non-curable TB process from the beginning of treatment– in 1 patient, severe concomitant pathology — in 1 patient; ІRIS — in 1 patient and 1 patient died at the ambulatory phase, not TB. Interrupted treatment were received in 5 (3.5 %) patients: low adherence to treatment– in 3 patients, critically ill of the concomitant diseases which not used antituberculosis drugs — in 2 patients; TB diagnosis was performed in 1 (0.7 %) patient.Conclusions. Before starting treatment for patients with new drugs, it is necessary to estimate the prognosis for treatment according to the criteria: preservation of reserves of antimycobacterial therapy; the developed adherence to treatment. In addition to this, treatment with new drugs can only be initiated provided: a sufficient supply of all antimycobacterial drugs, in the first place-re-profiled (linzolid, clophasimin, carbapenems), for the possibility of their course appointment to the patient; the availability of reliable laboratory data from laboratories that successfully undergo regular quality control studies; access to full-scale monitoring of the safety of treatment at any stage of the provision of medical care; at traction of different models of medical care provision, depending on needs and wishes of patients (priority — video-DOT); psychological support for all patients.

Application of geoinclusions for sustainable rail infrastructure under increased axle loads and higher speeds

Given the ongoing demand for faster trains for carrying heavier loads, conventional ballasted railroads require considerable upgrading in order to cope with the increasing traffic-induced stresses. During train operations, ballast deteriorates due to progressive breakage and fouling caused by the infiltration of fine particles from the surface or mud-pumping from the underneath layers (e.g. sub-ballast, sub-grade), which decreases the load bearing capacity, impedes drainage and increases the deformation of ballasted tracks. Suitable ground improvement techniques involving geosynthetics and resilient rubber sheets are commonly employed to enhance the stability and longevity of rail tracks. This keynote paper focuses mainly on research projects undertaken at the University of Wollongong to improve track performance by emphasising the main research outcomes and their practical implications. Results from laboratory tests, computational modelling and field trials have shown that track behaviour can be significantly improved by the use of geosynthetics, energy-absorbing rubber mats, rubber crumbs and infilled-recycled tyres. Full-scale monitoring of instrumented track sections supported by rail industry (ARTC) has been performed, and the obtained field data for in situ stresses and deformations could verify the track performance, apart from validating the numerical simulations. The research outcomes provide promising approaches that can be incorporated into current track design practices to cater for high-speed freight trains carrying heavier loads.

The multi-center validation of an intelligent blood gas analyzer quality management system

Objective To compare and study the two kinds of quality control methodologies related to intelligent quality management system (iQM) and traditional quality control, and the quality control performance of iQM equivalent to traditional quality control were evaluated, ensuring the accuracy of the results of blood gas testing. Methods Beijing Chaoyang Hospital of Capital Medical University, Beijing Tiantan Hospital of Capital Medical University, Shanghai Longhua Hospital of Shanghai University of Chinese Medicine, and Sichuan Provincial People′s Hospital, these 4 medical institutions were selected to implement this study. During the period from June 2016 to December 2016, in the routine detection of total 3 712 specimen, the iQM and traditional quality control modes were used simultaneously to calculate the mean values of all blood gas parameters quality controls, SD, CV (%) and Sigma values, to evaluate the quality control performance and difference of the two quality control modes. Results During the process of testing blood gas samples from 3 712 specimen in 4 hospitals, iQM process control solution (PCS) A, B, C ran 1 089, 7 678 and 154 quality control samples respectively, and 732 external quality control samples were run by traditional quality control mode. Considering the most sensitive parameters of blood gas testing pO2, iQM PCS A, B, C′s Sigma value are higher than 8, however, the traditional quality control′s Sigma value are less than 6; For parameters pCO2, pO2 and Na+ , there exists significant difference between two quality control methods (P=0.004 8, P=0.000 1, P=0.004 4, P 0.01). Totally 22 errors detected by iQM, includes 14 micro-clots and 8 interferences samples, which were not detected by traditional quality control . Conclusions The error in blood gas analysis mainly comes from the pre-analytical phase. iQM enhanced specimen inspection capabilities and make up for the inability of traditional quality control to monitor the quality of specimens, enabling full-scale, real-time, and dynamic monitoring of each specimen, powerful error detection capabilities, and automatic error correction capabilities. Besides, automatic documentation saves staff much time. The system can effectively ensure the accuracy of blood gas test results, meet the quality requirements of related laws and regulations and related industry standards, and also can meet the clinical intended use, providing new ideas for POCT quality management and improvement.(Chin J Lab Med, 2018, 41: 475-480) Key words: Blood Gas; Point of Care Testing; Quality Control; Intelligent Quality Management

TEMPERATURE CHANGE AND THE TOTAL STRESS ANOMALY IN PASTE BACKFILL

This paper presents preliminary results from a laboratory backfill model test in order to explain the effect of temperature change during the cement hydration on the total stress within cemented paste backfill. It is conducted via temperature control test in the absence of the cement. This investigation is an attempt to resolve an anomalous behavior reported in recent full scale monitoring reports, where the total vertical stress at the stope base shows a progressive increase after backfilling is terminated. The result in this paper shows that the total vertical stress is not affected by the level of the temperature but rather by the temperature gradient. The empirical relationship between the temperature gradient and the change in the total vertical stress is proposed. The total stress anomaly found in the full scale monitoring of paste backfill could be explained by the finding. © 2018, Int. J. of GEOMATE.

Full-scale monitoring of wind and suspension bridge response

Monitoring of real structures is important for many reasons. For structures susceptible to environmental actions, full-scale observations can provide valuable information about the environmental conditions at the site, as well as the characteristics of the excitation acting on the structure. The recorded data, if properly analyzed, can be used to validate and/or update experiments and models used in the design of new structures, such as the load description and modelling of the structural response. Various aspects of full-scale monitoring are discussed in the paper and the full-scale wind engineering laboratory at the Lysefjord suspension bridge introduced. The natural excitation of the bridge comes from wind and traffic. The surrounding terrain is complex and its effect on the wind flow can only be fully studied on site, in full-scale. The monitoring program and associated data analysis are described. These include various studies of the relevant turbulence characteristics, identification of dynamic properties and estimation of wind- and traffic-induced response parameters. The overall monitoring activity also included a novel application of the remote optical sensing in bridge engineering, which is found to have an important potential to complement traditional “single-point” wind observations by sonic anemometers.

Time-varying relative displacement field on the surface of concrete cover caused by reinforcement corrosion based on DIC measurement

To investigate the cracking process of concrete cover due to corrosion of reinforcement for concrete specimens subjected to semi-immersed accelerated corrosion, digital image correlation (DIC) was applied to quantitatively and visually characterize the development of relative displacement on the viewed surface. The impacts of stirrups and concrete cover thickness on the evolution of relative displacement were interpreted. And a detailed analysis covered the initial cracking time, position and relative displacement distribution on the surface during the cracking procedure. The study indicates that the corrosion of stirrups is prior to longitudinal reinforcement as the longitudinal reinforcement is cathodic protected by stirrups. The full-scale monitoring on the relative displacement reveals that a thicker concrete cover can retard the initial cracking but will promote the propagation speed of corrosion cracks. The investigation on the initial cracking zone implies that the initial cracking has high probability to appear within a region and its width is approximately close to the concrete cover thickness.