Bridge Method Research Articles

Installation for measuring the dielectric anisotropy of liquid crystals at low frequencies by the bridge method with constant displacement

Installation designed to measure the dielectric anisotropy in laboratory studies of liquid crystal polymer films is described. The installation operates on the principle of a balanced alternating current (AC) bridge, allowing the application of a direct external current (bias) to the liquid crystal cell. The internal resistance of the direct current (DC) source, which affects the equilibrium condition of the bridge, is compensated. The frequency of the AC current feeding the bridge and the offset voltage of the cell is regulated within a wide range, which makes it possible to study various functional dependences of the dielectric parameters of liquid crystals and their modifiers.Introduction

Non-Destructive Testing Applications for Steel Bridges

The growing population and increasing demand for surface transportation have highlighted the importance of maintaining safe and reliable civil infrastructures for daily use. Among all civil infrastructures, bridges are one of the most important elements in the transportation system. As such, to prevent any failures caused by aging and environmental impacts, bridges require periodic inspections. This becomes even more critical due to climate change and its effect on bridges, especially in the coastal regions. Most of the inspections conducted incorporate the visual type of evaluation due to its simplicity. However, with the current developments in new technologies, there is a need for more advanced techniques of structural health monitoring (SHM) methods to be incorporated in the maintenance programs for more accurate and efficient surveys. In this paper, non-destructive testing (NDT) methods applicable to steel bridges are reviewed, with a focus on methods applicable to local damage detection. Moreover, the methodology, advantages and disadvantages, and up-to-date research on NDT methods are presented. Furthermore, the application of novel NDT techniques using innovative sensors, drones, and robots for the rapid and efficient assessment of damages on small and large scales is emphasized. This study is deemed necessary as it compiles in one place the available information regarding NDT methods for in-service steel bridges. Access to such information is critical for researchers who intend to work on new or improved NDT techniques.

Securing Transplanted Meniscal Allografts Using Bone Plugs Results in Lower Risks of Graft Failure and Reoperations: A Meta-analysis

Background: Meniscal allograft transplant (MAT) is an important treatment option for young patients with deficient menisci; however, there is a lack of consensus on the optimal method of allograft fixation. Hypothesis: The various methods of MAT fixation have measurable and significant differences in outcomes. Study Design: Meta-analysis; Level of evidence, 4. Methods: A single-arm meta-analysis of studies reporting graft failure, reoperations, and other clinical outcomes after MAT was performed. Studies were stratified by suture-only, bone plug, and bone bridge fixation methods. Proportionate rates of failure and reoperation for each fixation technique were pooled with a mixed-effects model, after which reconstruction of relative risks with confidence intervals was performed using the Katz logarithmic method. Results: A total of 2604 patients underwent MAT. Weighted mean follow-up was 4.3 years (95% CI, 3.2-5.6 years). During this follow-up period, graft failure rates were 6.2% (95% CI, 3.2%-11.6%) for bone plug fixation, 6.9% (95% CI, 4.5%-10.3%) for suture-only fixation, and 9.3% (95% CI, 6.2%-13.9%) for bone bridge fixation. Transplanted menisci secured using bone plugs displayed a lower risk of failure compared with menisci secured via bone bridges (RR = 0.97; 95% CI, 0.94-0.99; P = .02). Risks of failure were not significantly different when comparing suture fixation to bone bridge (RR = 1.02; 95% CI, 0.99-1.06; P = .12) and bone plugs (RR = 0.99; 95% CI, 0.96-1.02; P = .64). Allografts secured using bone plugs were at a lower risk of requiring reoperations compared with those secured using sutures (RR = 0.91; 95% CI, 0.87-0.95; P < .001), whereas allografts secured using bone bridges had a higher risk of reoperation when compared with those secured using either sutures (RR = 1.28; 95% CI, 1.19-1.38; P < .001) or bone plugs (RR = 1.41; 95% CI, 1.32-1.51; P < .001). Improvements in Lysholm and International Knee Documentation Committee scores were comparable among the different groups. Conclusion: This meta-analysis demonstrates that bone plug fixation of transplanted meniscal allografts carries a lower risk of failure than the bone bridge method and has a lower risk of requiring subsequent operations than both suture-only and bone bridge methods of fixation. This suggests that the technique used in the fixation of a transplanted meniscal allograft is an important factor in the clinical outcomes of patients receiving MATs.

Seismic conceptual design and analysis method of Bridges crossing active fault

For bridges crossing active fault, combined with relevant standards and recent research results, the seismic conceptual design such as bridge axis trend planning, bridge type selection, fault trace avoidance distance of substructure, fault span and lap length are systematically summarized; some suggestions on seismic analysis methods such as the value of horizontal and vertical acceleration response spectrum, the generation of ground motion acceleration and displacement time history, and the input mode of time history are put forward.

Stochastic Transverse Earthquake-Induced Damage Track Irregularity Spectrum Considering the Uncertainty of Track-Bridge System

The track irregularity spectrum of longitudinally connected ballastless track (LCBT)-bridge systems of high-speed railway was proposed in this paper. First, a simulation model of an LCBT-continuous girder bridge was established by considering the influences of approach bridges and subgrade with track structure. Further, a large number of sample analyses were carried out by taking into account the uncertainty of LCBT-bridge systems and stochastic behaviors of ground motions based on the simulation model. The damage laws of residual deformation of track-bridge system after earthquake actions were studied. Then, an interlayer deformation coordination relationship (IDCR) considering the track irregularity caused by earthquake-induced damage of bearings was developed, and the superposed track irregularity samples were obtained. Finally, by using the improved Blackman–Turkey method and Levenberg–Marquardt algorithm, the LCBT irregularity spectrum, track irregularity spectrogram, track irregularity limit spectrum, and a fitting formula for the track irregularity spectrum on a bridge after the action of earthquakes were obtained. Results obtained from the fitting formula and IDCR were compared, and they indicated that tracks undergone significant high-frequency irregularity diseases after the earthquake action. It was found that the track irregularity spectrum could be roughly divided into three ranges: high-, medium- and low-frequency wavebands. Consequently, this led to an application of a three-segment power function for the fitting of the track irregularity spectrum after the earthquake action. The track irregularity spectrum after the action of earthquakes provides an important theoretical basis for the establishment of seismic design methods for high-speed railway bridges based on the traffic safety performance.

Intracolic ultrasound molecular imaging: a novel method for assessing colonic tumor necrosis factor-\u03b1 expression in inflammatory bowel disease

BackgroundWhile anti-tumor necrosis factor alpha (TNF-α) therapy has been proven effective in inflammatory bowel disease (IBD), approximately 40% of patients lose the response. Transmembrane TNF-α (mTNF-α) expression in the intestinal mucosa is correlated with therapeutic efficacy, and quantification of mTNF-α expression is significant for predicting response. However, conventional intravenous application of microbubbles is unable to assess mTNF-α expression in intestinal mucosa. Herein, we proposed intracolic ultrasound molecular imaging with TNF-α-targeted microbubbles (MBTNF-α) to quantitatively detect mTNF-α expression in the intestinal mucosa.MethodsMBTNF-α was synthesized via a biotin–streptavidin bridging method. TNF-α-targeted ultrasound imaging was performed by intracolic application of MBTNF-α to detect mTNF-α expression in surgical specimens from a murine model and patients with IBD. Linear regression analyses were performed to confirm the accuracy of quantitative targeted ultrasound imaging.ResultsOn quantitative TNF-α-targeted ultrasound images, a greater signal intensity was observed in the mouse colons with colitis ([1.96 ± 0.45] × 106 a.u.) compared to that of the controls ([0.56 ± 0.21] × 106 a.u., P < 0.001). Targeted US signal intensities and inflammatory lesions were topographically coupled in mouse colons. Linear regression analyses in specimens of mice and patients demonstrated significant correlations between the targeted ultrasound signal intensity and mTNF-α expression (both P < 0.001). Furthermore, TNF-α-targeted ultrasound imaging qualitatively distinguished the varying inflammatory severity in intestinal specimens from IBD patients.ConclusionIntracolic ultrasound molecular imaging with MBTNF-α enables quantitative assessment of mTNF-α expression. It may be a potential tool for facilitating the implementation of personalized medicine in IBD.

Iterative reference-driven S-transform time-varying parameter identification for bridges under moving vehicle

Traditional bridge health monitoring is both expensive and time-consuming because of the need for installing a large quantity of sensors on the bridge. The indirect monitoring method as a feasible alternative has become popular over the last decade, as useful information can be gathered from moving vehicles installed with sensors by considering vehicle-bridge interaction. This paper describes an indirect time-varying modal parameter identification method for bridges under a moving test vehicle. A novel reference-driven S-transform is proposed for the parametric modal identification of time-varying structural systems with non-stationary characteristics based on a multisensory arrangement, comprising a fixed reference sensor installed on the bridge and another movable sensor installed on a moving test vehicle. By the phase-preservation property of S-transform and the multisensory time-frequency analysis, the proposed iterative reference-driven S-transform can be used to extract the time-varying modal parameters of the vehicle-bridge system when the vehicle moves on the bridge. Based on the coherence between measurements from the sensors mounted on the bridge and vehicle, one can track the time-varying characteristics by combining the spatial and time-frequency information obtained by the multisensory array. The efficiency of the proposed reference-driven S-transform method is validated by numerical simulations and laboratory experiments using a simply supported beam with a moving vehicle. The effects of the vehicle property, driving speed, road roughness and measurement noise are discussed. The numerical and experimental results have demonstrated that the proposed method is useful for time-varying parameter extraction with a multisensory system. This will be useful to structural condition monitoring of bridges.

Suspender Replacement Method for Long-Span Concrete-Filled Steel Tubular Arch Bridges and Cable Force Measurement Based on Frequency Method

The suspenders on the sides of an arch bridge are highly vulnerable to damage caused by traffic load and environmental corrosion. To accurately estimate the cable force of suspenders, herein, we analyse the influencing factors through a suspender tension test based on the principle of suspender vibration. The frequency of each suspender of the bridge is evaluated using the frequency method. By combining the cable force data measured directly and the measured suspender frequency, the formulas for calculating the cable forces of long and short suspenders are fitted, and a reasonable estimation method for the calculated length of short suspenders is provided. The formulas are verified through application to a CFST arch bridge. Results indicate that the proposed formula effectively considers the influence of the sleeve on the overall calculated length of the suspender. The formula calculates the suspender cable force with higher accuracy, proving its suitability for engineering use.

Thermal Conductivity of VO2 Nanowires at Metal-Insulator Transition Temperature.

Vanadium dioxide (VO2) nanowires endowed with a dramatic metal−insulator transition have attracted enormous attention. Here, the thermal conductance of VO2 nanowires with different sizes, measured using the thermal bridge method, is reported. A size-dependent thermal conductivity was observed where the thicker nanowire showed a higher thermal conductivity. Meanwhile, the thermal conductivity jump at metal−insulator transition temperature was measured to be much higher in the thicker samples. The dominant heat carriers were phonons both at the metallic and the insulating regimes in the measured samples, which may result from the coexistence of metal and insulator phases at high temperature. Our results provide a window into exploring the mechanism of the metal−insulator transition of VO2 nanowires.

Mechanical state inversion method for structural performance evaluation of existing suspension bridges using 3D laser scanning

AbstractThe abnormal mechanicalstate will cause the structural performance degradation of a suspension bridge. This paper presents a mechanical state inversion method for suspension bridges based on the measured intersection points of main cables using 3D laser scanning. First, based on the catenary, the mathematical model between the suspender force and the measured intersection points coordinates is established, and an accurate calculation method of suspender force is proposed. Then, an accurate calculation method for the internal force of suspension bridge components with abnormal suspender force is proposed to evaluate the structural performance. Numerical experiments show that the proposed method is accurate in theory. Finally, 3D laser scanning is used to capture the shape of the main cable, and an automated algorithm is developed to calculate the intersection point of the main cables precisely. The accuracy and reliability of the proposed method have been verified on a completed suspension bridge with a span of 808 m.

The Japanese conservative camp's bridging method for China–Japan relations under the separation of politics and the economic policy: investigation of the case of the Kenzo Matsumura Group, 1959–1972

AbstractFrom the signing of the Treaty of San Francisco to the resumption of diplomatic relations between China and Japan, Japan has always adopted a political and economic separation policy that maintains diplomacy with Taiwan and economic and cultural relations with China. Within the ruling Liberal Democratic Party, to break the existing deadlock, Kenzo Matsumura of the Japanese House of Representatives and others formed a foreign policy group in 1959. This group spoke highly of China's importance to Japan's development on the grounds of national interests rather than ideology and national sentiments, played a bridging role in the political communication between China and Japan, and created a precedent for the nontraditional improvement of international relations in Japan.

Unified Compact Model for Thin-Film Heterojunction Anti-Ambipolar Transistors

This letter proposes an advanced compact model for anti-ambipolar transistors based on a lateral thin-film material heterojunction. The modeling idea focuses on an analytical description of component currents and bridging methods necessary for controllable transition between operation regimes. The model is validated by experimental data, and predictive simulations are carried out to demonstrate its applicabilities.

Advanced fatigue verification method for record breaking bridges

AbstractDesigning and reviewing suspension bridges with world record breaking main spans in countries like Turkey, China and Norway requires a new and advanced method for fatigue verification. COWI's in‐house software IBDAS (Integrated Bridge Design and Analysis System) is used to perform the full fatigue verification including load modelling, finite element modelling, stress history analysis and damage evaluation based on the damage accumulation method. Discussions of boundary conditions are avoided by utilizing a global IBDAS beam model for the overall static system. A few segments of the girder in the global model are replaced by a semi‐local shell model in which a fine local shell model with all local geometry is placed at the location of interest. Fatigue data points used for verification are defined in the local model, typically based on hot‐spot extrapolation methods. In IBDAS, the extrapolation can be defined whereby the fatigue data point stress histories can be used directly for fatigue evaluation with the reservoir cycle counting method. Hereby, time‐consuming bookkeeping of FE node output is avoided. This paper presents technical aspects of the fatigue verification method used for the latest suspension bridge designs including the advantages of utilizing a fully integrated system.

European traffic on road bridges and recalibration of damage equivalence factor for fatigue verification

AbstractThe evolution of European traffic, combined with the current revision works of the Eurocodes (CEN250 project 2nd Eurocode generation), represents an opportunity to improve the simplified method for fatigue checks (also known as the lambda method) for road bridges. The works reported herein focus on the reassessment of the λ1 factor curves for the damage effect of highway traffic on road bridges, using the existing Eurocode FLM3 model. The aim of the research is to model the traffic and resulting stress ranges at details on bridges with different static systems. The simulation results shall be as similar as possible to reality by introducing different parameters that were not taken into account in the EN 1993‐2 background simulations [1, 2], including the passage of multiple vehicles at the same time in the flowing and congested traffic conditions. The development of new λ1 factor curves lead to a different classification into midspan bending moment, shear force, and support midspan and shear force. Within this study, the validity of the formulas for λ2 and λ3 were also checked. The new curves have less dispersion and may be taken into consideration to update the current curves from EN 1993‐2.

Structural Study of Steel‐Concrete Double Composite Girder Bridge

AbstractIn Japan, the steel‐concrete composite girder bridge is widely used to reduce construction and maintenance cost, and improve constructability and the construction period. As an effort to decrease box girder construction cost, the narrow box girder bridge, which has a reduced box girder width, has been developed. Compared with a conventional box girder bridge, this type of box girder bridge simplifies the structure inside the box by narrowing the space between web plates. Furthermore, it is possible to reduce the number of members, welding length and painting area. The average economical span length is approximately 90m. Similarly, in European countries, a new type of composite girder bridge was developed and constructed for the same purpose as the bridge in Japan. The steel‐concrete double composite girder bridge, which has two concrete slabs on the upper and lower surfaces of the girder only in the region of the intermediate supports, is a type of medium span bridge. An advantage of adopting this structural system is that the cross sections of both the sagging and hogging bending moment areas are classified into the compact section at the ultimate limit state; that is, the maximum flexural strength of these sections can be taken full plastic moment. There are few constructed examples of this type of bridge in Japan. Because of the handling difficulty, the shop manufacturing cost of a box girder is, generally, more expensive than that of an I‐girder. Additionally, the design method for bridges has been revised since January 2018 and has changed from the allowable stress design method to the limit state design method in Japan. Therefore, the authors propose a new type of steel‐concrete double composite I‐girder bridge. The trial design of three‐span continuous girder bridges was conducted. In this paper, the effect of double composite action, for instance, the reduction of the girder height in the region of the intermediate supports, and applicable span length are discussed.

Conductivity and Dielectric Dissipation Factor (tan δ) Measurements of Insulating Oils of New and Aged Power Transformers—Comparison of Results Between Portable Square Wave and Conventional Bridge Methods

This article compares two different techniques to assess the oil quality of new and aged transformers. It is shown that laboratory tan δ tests and measurements with a portable IEG 61620 square wave method result in comparable diagnostic classifications.

A bridge weigh-in-motion method of motorway bridges considering random traffic flow based on long-gauge fibre Bragg grating sensors

Accurate traffic conditions and their development regularity can help in the management of future traffic demand and bridge design. This study proposes a bridge weigh-in-motion method for identifying the vehicle parameters of motorway bridges considering random traffic flow and capitalizes on the advantages of long-gauge fibre Bragg grating sensors. A bridge-vehicle coupling system is numerically simulated, a 1:10 indoor experiment is used to verify the proposed method, and the vehicle parameters (e.g., traffic lane, vehicle spacing, vehicle axle weight, and speed) are identified with high accuracy. The effects of the road surface conditions, vehicle numbers, lateral positions and accelerations on the proposed method are investigated, and only find that the lateral positions are obviously related while and others have almost no influence on the method. In addition, the accuracy in axle number and weight identification is not high when the gauge length is smaller than vehicle wheelbases.

Bridge Method for Studying the Spectra of Current Fluctuations in Tungsten Filaments in the Frequency Range 1.5·10–5–5·10–1 Hz

Bridge Method for Studying the Spectra of Current Fluctuations in Tungsten Filaments in the Frequency Range 1.5·10–5–5·10–1 Hz

Declining yet persistent use of traditional contraceptive methods in low- and middle-income countries.

Traditional contraceptive methods are used by 55 million women in developing countries. This study analysed over 80 national surveys to compare traditional with modern method users, by type, region, socio-demographic characteristics, strength of family planning programmes and discontinuation rates. The advance of modern methods has greatly reduced the share held by traditional methods, but the actual prevalence of their use has declined little. Young, sexually active unmarried women use traditional contraception much more than their married counterparts. Discontinuation rates are somewhat lower for traditional methods than for the resupply methods of the pill, injectable and condom; among users of all of these methods, more than a quarter stop use in the first year to switch to alternative methods. Traditional method use is firmly entrenched in many countries, as the initial method tried, a bridge method to modern contraception and even the primary method where other methods are not easily available.

Data-driven analytical load rating method of bridges using integrated bridge structural response and weigh-in-motion truck data

Load rating is a widely used approach for evaluating the load-carrying capacity of bridges in an effort to ensure safe bridge operation under expected traffic loads. Load rating often relies on simplified analytical models including empirically derived model parameters that do not reflect bridge-specific information resulting in conservative ratings. To reduce this conservatism, this study proposes a novel data-driven framework that utilizes long-term bridge response data to extract bridge-specific model parameters that can be used within in the Load and Resistance Factor Rating (LRFR) process. The data-driven LRFR (DD-LRFR) framework is empowered by a cyber-physical system (CPS) architecture that uses Internet connectivity to integrate measured bridge responses with truck weights measured by a weigh-in-motion (WIM) station. The CPS architecture uses computer vision of camera images to confirm trucks observed at a WIM station are identical to those observed at a bridge. Bridge response and axle weight data are then used to extract probabilistic models of dynamic load allowances and unit influence lines. The DD-LRFR method is validated using a 20-mile (32.2-km) segment of the I-275 northbound highway in Michigan that is monitored continuously by the CPS architecture. Six girders associated with two bridges along I-275 are rated using the proposed DD-LRFR methodology with rating factors compared to those obtained using conventional and refined load rating methods. The DD-LRFR method yields inventory- and operational-level rating factors that are less conservative than those from the approximate LRFR method and comparable to those using finite element modeling of the bridge.