Current Bridge Research Articles

곡선 강박스 거더의 휨-뒤틀림 응력비에 따른 중간 다이아프램 간격

Although distortions of horizontally curved box girder are more susceptible than which of the straight girder due to curvature effect, current domestic design standards does not present spacing of intermediate diaphragms for the curved box girder. In this study, parametric studies for straight and curved box girder considering distortional warping normal stresses based on linear finite element analysis were carried out. Single span curved girders were chosen for analysis based on current domestic bridge data with 1-6 of solid intermediate diaphragms, 0-30 degree of subtended angle, 30m and 60m of span length and 2-3m of flange width and web height. The adequate spacing of diaphragms for the box girder were suggested considering subtended angles and bending and distortional warping normal stress ratios with 5%, 10%, 15% and 20%. The analysis results were also compared to a current design standard and suggested spacing of diaphragm were evaluated.

Towards UAV-based bridge inspection systems: a review and an application perspective

Visual condition inspections remain paramount to assessing the current deterioration status of a bridge and assigning remediation or maintenance tasks so as to ensure the ongoing serviceability of the structure. However, in recent years, there has been an increasing backlog of maintenance activities. Existing research reveals that this is attributable to the labour-intensive, subjective and disruptive nature of the current bridge inspection method. Current processes ultimately require lane closures, traffic guidance schemes and inspection equipment. This not only increases the whole-of-life costs of the bridge, but also increases the risk to the travelling public as issues affecting the structural integrity may go unaddressed. As a tool for bridge condition inspections, Unmanned Aerial Vehicles (UAVs) or, drones, offer considerable potential, allowing a bridge to be visually assessed without the need for inspectors to walk across the deck or utilise under-bridge inspection units. With current inspection processes placing additional strain on the existing bridge maintenance resources, the technology has the potential to significantly reduce the overall inspection costs and disruption caused to the travelling public. In addition to this, the use of automated aerial image capture enables engineers to better understand a situation through the 3D spatial context offered by UAV systems. However, the use of UAV for bridge inspection involves a number of critical issues to be resolved, including stability and accuracy of control, and safety to people. SLAM (Simultaneous Localisation and Mapping) is a technique that could be used by a UAV to build a map of the bridge underneath, while simultaneously determining its location on the constructed map. While there are considerable economic and risk-related benefits created through introducing entirely new ways of inspecting bridges and visualising information, there also remain hindrances to the wider deployment of UAVs. This study is to provide a context for use of UAVs for conducting visual bridge inspections, in addition to addressing the obstacles that are required to be overcome in order for the technology to be integrated into current practice.

Reference-Free Displacements for Condition Assessment of Timber Railroad Bridges

Current railroad bridge inspection and rating practices include observing bridge movement under live loads to help assess bridge conditions. Recent research has shown that transverse displacements of timber trestle bridges can capture critical changes in bridge serviceability (the ability to safely carry out railroad operations) as a function of railroad loading, speed, and direction. Measuring bridge movement under trains in the field is difficult and expensive because a fixed reference point is not normally available, thus creating the need to erect independent scaffolding to create good reference points near a timber bridge. This research demonstrates the potential of using reference-free accelerations collected with wireless smart sensors to estimate railroad bridge transverse displacements under live train loads. Focus is placed on timber trestle bridges, which comprise approximately 24% of the total inventory length of railroad bridges in the United States. The results show that wireless smart sensors can estimate transverse displacements of timber railroad trestles and could become an effective tool for campaign monitoring of railroad bridges (with applications toward helping overall bridge assessment).

Negative internal causal attributions of a specific offense and forgiveness

AbstractCausal attributions are important social‐cognitive predictors of forgiveness. This article presents the Transgression Attribution Questionnaire (TAQ), a measure of one's negative internal causal attributions of a specific offense. In 4 studies, scores on the TAQ showed initial evidence of estimated internal consistency, temporal stability, and construct validity. Negative internal attributions for the cause of a transgression predicted lower levels of empathy and forgiveness. Furthermore, scores on the TAQ predicted forgiveness over and above the hurtfulness of the offense, relationship commitment, and a general measure of internal causal attributions in relationships. The current research bridges research on internal causal attributions and forgiveness. Implications for the social‐cognitive study of forgiveness and the measurement of causal attributions are discussed.

Analysis of composite girders with hybrid GFRP hat-shape sections and concrete slab

Most of current bridge decks are made of reinforced concrete and often deteriorate at a relatively rapid rate in operational environments. The quick deterioration of the deck often impacts other critical components of the bridge. Another disadvantage of the concrete deck is its high weight in long-span bridges. Therefore, it is essential to examine new materials and innovative designs using hybrid system consisting conventional materials such as concrete and steel with FRP plates which is also known as composite deck. Since these decks are relatively new, so it would be useful to evaluate their performances in more details. The present study is dedicated to Hat-Shape composite girder with concrete slab. The structural performance of girder was evaluated with nonlinear finite element method by using ABAQUS and numerical results have been compared with experimental results of other researches. After ensuring the validity of numerical modeling of composite deck, parametric studies have been conducted; such as investigating the effects of constituent properties by changing the compressive strength of concrete slab and Elasticity modulus of GFRP materials. The efficacy of the GFRP box girders has been studied by changing GFRP material to steel and aluminum. In addition, the effect of Cross-Sectional Configuration has been evaluated. It was found that the behavior of this type of composite girders can be studied with numerical methods without carrying out costly experiments. The material properties can be modified to improve ultimate load capacity of the composite girder. strength-to-weight ratio of the girder increased by changing the GFRP material to aluminum and ultimate load capacity enhanced by deformation of composite girder cross-section.

Behavior of 1 Ω resistors at frequencies below 1 Hz and the problem of assigning a dc value

This paper presents a systematic study of the effects of reversals of current polarity on 1 Ω standard resistors. A selection of 1 Ω standards were measured on a dc cryogenic current comparator bridge and also on an ac current comparator bridge operating at 1 Hz. We find that the apparent 4 terminal resistance depends strongly on the dc reversal rate, in one case showing a variation of more than 0.1 μΩ/Ω for cycle times between 10 s and 1000 s. Even in the best cases, effects of at least 0.01 μΩ/Ω are present. Furthermore, the assumption that the apparent resistance value converges to a limiting value for long waiting times after reversal is not always upheld, making it difficult to quote a simple dc value. Existing models of Peltier heating at wire junctions do not completely explain our observations. The problems presented have been the limiting factor for 1 Ω measurements as part of a recent on-site comparison of quantum Hall effect resistance standards.

A Three-Arm Current Comparator Bridge for Impedance Comparisons Over the Complex Plane

We present here the concept of three-arm current comparator impedance bridge, which allows one to perform comparisons among three unlike impedances. Its purpose is the calibration of impedances having arbitrary phase angles against calibrated nearly pure impedances. An analysis of the bridge optimal setting and proper operation is presented. To test the concept, a two-terminal-pair digitally assisted bridge has been realized; preliminary measurements of an air-core inductor and of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$RC$ </tex-math></inline-formula> network versus decadic resistance and capacitance standards, at kilohertz frequency, have been performed. The bridge measurements are compatible with previous knowledge of the standard values with relative deviations of parts in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-5}$ </tex-math></inline-formula> .

Review of the Rapid Damage Diagnosis of Medium and Short-Span Bridges

Damage accumulation and resistance decrease inevitably happen to bridge structures due to the effects of earthquakes, impact loads, wind load and corrosion during their service time. Once the damages of the key components accumulate to a certain level, they would spread promptly, causing the sudden destruction of the whole structure if not found and dealt with in time. So the structural damages would not only shorten the operation life of structure but also threaten the human lives and financial safety. Therefore, the technology of damage diagnosis of bridge structure holds supreme significance. This paper summarized the current research situation of the existing bridge diagnosis methods and analyzed the characteristics of each method through the reading and studying of the related material both domestically and internationally. Among those methods, only the diagnosis method based on load tests is the most direct and effective one for current bridge diagnosis, the diagnosis results of which shows higher reliability. And the structural dynamic characteristic method based on dynamic load tests could beautifully avoid the disadvantages of the static load tests, becoming the main development direction of rapid diagnosis of bridge. Furthermore, lastly it elaborated the analysis of the key problems of breaking through the development bottleneck of current rapid diagnosis methods of bridge, creating a solid foundation for the future research.

Sustainable transport project evaluation and decision support: indicators and planning criteria for sustainable development

This article will expose the necessity for a sustainable planning and decision support framework for transport infrastructure assessment. This will be operationalized through a set of planning criteria and scenario alternatives, which is assessed in the SUSTAIN decision support system (SUSTAIN-DSS) model. A part of the decision support framework will be tested in a case study in Denmark, concerning the problem of congestion on the current bridge crossing Roskilde Fjord in the city of Frederikssund. This article suggests including in a combination both reference class forecasting and quantitative risk analysis as well as sustainable planning criteria in the assessment of the project uncovering new solutions. Thereof the decision support model reveals large potential for the inclusion of planning criteria if the overall objective of development toward a sustainable transportation system is adopted. The SUSTAIN-DSS model rests upon multi-criteria decision analysis and planning workshops in order to combine the use of qualitative and quantitative assessments. This article stresses the necessity of revising current planning paradigms such as cost-benefit analysis (CBA) but also to make clear definitions of the criteria planned for, in order to achieve a sustainable transport system. This alternative approach proves that with relatively small changes in objectives, sustainable development within transport planning can be reached.

A Research of the Bridge Structure Form Selection Based on the Mountains City Bridge Aaesthetics

Along with the rapid development of science and technology since the 19th century, the traditional design concept gradually replace the application of new materials, new structure and new skills by bridge engineers study. In people's living standards continue to improve conditions need to be the engineer devised a more perfect, more harmonious bridge to meet the spiritual needs of people. Modern bridge design should not only is a simple mechanical design, structure, construction, but also should be with the perfect combination of philosophy and aesthetics. How to make the bridge satisfy engineering specification, appearance and perfect coordination with the surrounding landscape, is an important topic of the current bridge construction. This paper probes into the basic principles of the mountains bridge aesthetics, with Two- river bridge as the example shows that the bridge aesthetics take the important role in bridge design,and reference for the related projects.

Uncertainty in Common NDE Techniques for Use in Risk-Based Bridge Inspection Planning: Existing Data

AbstractIn 2009, a joint American Society of Civil Engineers Structural Engineering Institute and American Association of State Highway and Transportation Officials ad hoc group was created to study how current bridge practices could be improved for the future. Among their recommendations was the wider use of nondestructive evaluation (NDE) techniques. Risk-based planning to determine the appropriate inspection frequency, scope, intensity, and methodology would help make the increased time and costs associated with NDE inspections feasible for management budgets. However, a rigorous risk-based approach requires that the accuracy and reliability be quantified for each test. This paper serves as a starting point for quantifying these important variables and identifies the type of information that is still needed. Common NDE techniques were identified, and existing studies were reviewed to identify what data relevant to accuracy and reliability are currently available for these techniques. This review indica...

Mechanical circulatory support saves lives -- three years' experience of the newly established assist device program at Semmelweis University, Budapest, Hungary

Since the celebration of the 20th anniversary of the first heart transplantation in Hungary in 2012 the emerging need for modern heart failure management via mechanical circulatory support has evolved. In May 2012 the opening of a new heart failure and transplant unit with 9 beds together with the procurement of necessary devices at Semmelweis University accomplished this need. The aim of the authors was to report their initial experience obtained in this new cardiac assist device program. Since May, 2012, mechanical circulatory support system was applied in 89 cases in 72 patients. Indication for support were end stage heart failure refractory to medical treatment and acute left or right heart failure. Treatment was initiated for acute graft failure after heart transplantation in 27 cases, for end stage heart failure in 24 cases, for acute myocardial infarction in 21 cases, for acute postcardiotomy heart failure in 14 cases, for severe respiratory insufficiency in 2 cases and for drug intoxication in one case. Among the 30 survivor of the whole program 13 patients were successfully transplanted. The available devices can cover all modalities of current bridge therapy from short term support through medium support to heart transplantation or long term support and destination therapy. These conditions made possible the successful start of a new cardiac assist device program.

Supplementing Current Visual Highway Bridge Inspections with Gigapixel Technology

Developing an efficient bridge condition evaluation procedure is economically critical to a state highway department; however, any adopted bridge condition approach needs to be accurate. A state highway department typically conducts a bridge condition evaluation by visual inspection on a 24-month cycle. During the evaluation, a bridge inspector visually inspects bridge components to derive a bridge condition rating on a 0–9 scale; a 0 value represents failure. The intrinsic weakness in a visual inspection system is the nonuniformity in the process due to the subjective nature of the approach. This paper proposes an approach to supplement visual bridge inspections by implementing gigapixel technology to promote quality assurance and control in a state bridge management system. The discussed approach supplements the visual inspection of a bridge with panoramic images to be later reviewed by a trained group of bridge engineers. This trained group of bridge engineers is enlisted in the inspection review process to promote uniformity in the bridge rating process. Additionally, the presented approach creates a bridge panorama that can be cataloged as a permanent bridge condition record in a state DOT’s structural health monitoring system. The presented approach uses gigapixel technology to create high-resolution panoramas that can be reviewed by an engineer using Google Earth tools. The hardware needed for gigapixel technology is inexpensive, but can greatly improve conditional bridge rating consistency between bridge sites.

Based on Energy-Variational Principle Derived Moment Amplified Coefficient of Tied Arch Rib

AbstractThe arch rib, tie beam, and rod of the tied arch are considered common forces. According to the characteristics of these forces, the calculation equation of the moment augment factor of the tied arch is derived. The equation is based on the energy variational principle. The calculated results of the derived equation and the current bridge code are compared with the project example. For examples 1 and 2, the difference in calculation results between the derived practical equations and naked-arch simplified equivalent straight bar under the existing bridge specification is 12.9% to 24.3% before simplification. After simplification, the calculation results of the derived equation deviates by about 1%. The derived equation is comparatively economic and practical because the current bridge code is calculated according to the nude arch. The moment-amplified factor increases with increasing axial force and is related to the constraint and load form. The moment augment factor of the eccentric compress bar...

Geotechnical considerations in hydraulic modeling of bridge abutment scour

Scour-related failure of earthen abutments in bridge waterways involves interacting geotechnical and hydraulic processes. Current bridge design guides, however, inadequately account for geotechnical factors influencing scour depth. Our paper presents results of laboratory experiments investigating how soil strength affects scour depth at spill-through abutments. We focus on several difficulties faced when conducting flume experiments on scour at abutments formed of erodible soil. The difficulties include attaining scale-reduced shear strengths, controlling soil compaction, and quantifying the shear strength of model soil. We indicate the similitude considerations involved, and describe a process of soil tests relating model soil strength to soil compaction that uses hand-held devices to determine soil strengths. The correlations developed between soil compaction and shear strength helped to work around some of the difficulties in flume experiments. We suggest practical solutions to issues pertaining to simulating the shear strength of compacted soils used in flume studies of abutment scour.

A new look at the restrictions on the speed and magnitude of train loads for bridge management

In current bridge management systems (BMSs), load and speed restrictions are applied on unhealthy bridges to keep the structure safe and serviceable for as long as possible. But the question is, whether applying these restrictions will always decrease the internal forces in critical components of the bridge and enhance the safety of the unhealthy bridges. To find the answer, this paper for the first time in literature, looks into the design aspects through studying the changes in demand by capacity ratios of the critical components of a bridge under the train loads. For this purpose, a structural model of a simply supported bridge, whose dynamic behaviour is similar to a group of real railway bridges, is developed. Demand by capacity ratios of the critical components of the bridge are calculated, to identify their sensitivity to increase of speed and magnitude of live load. The outcomes of this study are very significant as they show that, on the contrary to what is expected, by applying restriction on speed, the demand by capacity ratio of components may increase and make the bridge unsafe for carrying live load. Suggestions are made to solve the problem.

A new look at the restrictions on the speed and magnitude of train loads for bridge management

In current bridge management systems (BMSs), load and speed restrictions are applied on unhealthy bridges to keep the structure safe and serviceable for as long as possible. But the question is, whether applying these restrictions will always decrease the internal forces in critical components of the bridge and enhance the safety of the unhealthy bridges. To find the answer, this paper for the first time in literature, looks into the design aspects through studying the changes in demand by capacity ratios of the critical components of a bridge under the train loads. For this purpose, a structural model of a simply supported bridge, whose dynamic behaviour is similar to a group of real railway bridges, is developed. Demand by capacity ratios of the critical components of the bridge are calculated, to identify their sensitivity to increase of speed and magnitude of live load. The outcomes of this study are very significant as they show that, on the contrary to what is expected, by applying restriction on speed, the demand by capacity ratio of components may increase and make the bridge unsafe for carrying live load. Suggestions are made to solve the problem.

Study Based on Bridge Health Monitoring System on Multihazard Load Combinations of Earthquake and Truck Loads for Bridge Design in the Southeast Coastal Areas of China

Similar to AmericanLRFD Bridge Design Specifications, the current Chinese bridge design code is fully calibrated against gravity load and live load. Earthquake load is generally considered alone and has its own methodology, however, which is not covered in the code in a consistent probability-based fashion. Earthquake load and truck load are the main loads considered in the basis of bridge design in more than 70% of seismic areas in China. They are random processes, and their combination is the main subject of this paper. Seismic characteristics of southeast coastal areas of China are discussed and an earthquake probability curve is calculated through seismic risk analysis. Using measured truck load data from a Bridge Health Monitoring System, the multimodal characteristics of truck load are analyzed and a probability model for a time intervaltis obtained by fitting results and reliability theory. Then, a methodology is presented to combine earthquake load and truck load on a probabilistic basis. To illustrate this method, truck load and earthquake load combinations are used. Results conceptually illustrate that truck load and earthquake load are not dominant in southeast coastal areas of China, but the effect of their combination is. This methodology quantitatively demonstrates that the design is controlled by truck load in most ranges; that is, truck load is more important to bridge design in the region.

Design and Construction of Welded Wire Retaining Walls in the Siuslaw and Willamette National Forests

Major winter storms occasionally remove portions of the steep mountainous roads within the Siuslaw and Willamette National Forests of western Oregon. On average, at least one flexible welded wire reinforced wall is built a year in these forests to reestablish the failed roadway. This paper summarizes the procedures used for foundation investigation, analysis and design, and construction administration of welded wire reinforced retaining walls in these forests. Since 2005, the U.S. Department of Agriculture Forest Service has designed the walls according to the current AASHTO LRFD Bridge Design Specifications. The two forests follow AASHTO procedures with some modifications. These modifications include a narrower bench width at the toe of the wall, less conservative global stability resistance factors, no performance of settlement analysis, and stricter fill requirements for reinforced walls.

Diagnosis of Water Tree Aging in XLPE Cable by the Loss Current Harmonic Component Under Variable Frequency Power

Water treeing is one of the main aging in XLPE cable insulation, which has the direct effect on the reliability of cable long-term operation. The diagnosis of water tree aging is a premise to ensure the safe operation of cables. The water treed XLPE insulation shows a nonlinear conductivity characteristic, which leads to a harmonic component in the corresponding lose current under the standard sinusoidal voltage. So the loss current harmonic component method can be an effective diagnosis of water tree aging. The loss current measurement system based on the high voltage current comparator bridge is used in this paper, which is designed by Harbin University of Science and Technology and Jiangsu Electric Power Company Research Institute. The feasibility of the application of variable frequency series resonant power source in the loss current measurement, which is aimed to diagnose the water treeing in XLPE insulation, is studied in the laboratory and field test. The results show that the output voltage waveform of the variable frequency series resonant power source is quite close to the standard sinusoidal voltage, although there are some high frequency sharp peaks. So the variable frequency series resonant power source can be used as the high voltage test power supply in the loss current harmonic component measurement system. The loss current harmonic component has power frequency interference during the field test, but this can be solved by differential frequency principle. The microscopic observation of water tree structures during the anatomy of the cable not only indicates the effectiveness of the results and diagnosis during the field test, but also proves the feasibility of the application of variable frequency series resonant power source in the loss current measurement. The existence and degree of the water tree can be estimated according to the test results, which can be a strong basis of the standardization of water tree aging diagnosis. Furthermore, the expensive standard sinusoidal wave generator and linear power generator is replaced by the variable frequency series resonant power source, which reduces the cost and weight of the testing system.