Single Bridge Research Articles

Establishing the True Dynamic Bending Moment of Propeller Shaft Using a Single Bridge of Strain Gauge

The measurement of shaft bending (whirling) moment can be performed via a telemetry system including strain gauges which can obtain the bending stress. By using a single bridge of strain gauge, it was possible to obtain only the nominal bending moment. However, in case of the propeller shaft vibration measurement, the true dynamic bending moment is needed to evaluate the effect of propeller forces on the stability of the bearings. To deal with this, typically two bridges of strain gauge at 90 degrees are needed. This research presents a novel reliability assessment method in establishing the true dynamic bending moment using only one bridge of strain gauge. This is achieved by using the actual bending stress measured by strain gauge combined with its own phase lag stress at an angle of 90 degrees. To validate this technique, the experiments were performed under the rapid turning transient states during a sea trial of a 50,000 DWT oil/chemical tanker. As a result, great fluctuations in propeller force were detected, resulting in a non-uniform oil film in the bearings. The displacement sensor was also installed and confirmed the established true dynamic bending moment.

Control strategy of series–parallel DC wind farm with fault isolation

The series–parallel DC wind farm composed of a large number of DC wind turbine (DCWT) is a potential scheme for offshore wind power collection with lower construction costs and power losses. However, enhanced coupling issues, such as energy curtailment and fault isolation, exist in the DC wind farm. To overcome the difficulties, a series–parallel DC collection system is proposed, where DCWTs based on the single active bridge (SAB) are connected in series and then are connected in parallel via DC/DC converters. The coupling mechanism among series–parallel strings is analyzed first, and a coordinate control strategy for the whole system is proposed based on the characteristics of SAB. DC fault located at different strings is analyzed and strategies are proposed to protect the whole system. Simulation results in PSCAD/EMTDC verifies the proposed control strategy with the less coupling among series–parallel DC wind farms under unequal wind speeds and fault.

An ab initio study on resistance switching in hexagonal boron nitride

Two-dimensional materials have been widely investigated to implement memristive devices for data storage or neuromorphic computing applications because of their ultra-scaled thicknesses and clean interfaces. For example, resistance switching in hexagonal boron nitride (h-BN) has been demonstrated. This mechanism is most of the time attributed to the movement of metallic ions. It has however also been reported when h-BN is contacted with two inert electrodes such as graphene or Pt. We suggest here that the switching mechanism of the latter devices, which has not yet been clearly established, relies on locals change of the electronic structure of h-BN as caused by atomic defects, e.g., multi-vacancies. This class of intrinsic h-BN defects can create electrically controllable interlayer bridges. We use a combination of hybrid density functional theory and the Non-equilibrium Green’s function formalism to show that a single interlayer bridge resulting from the presence of a trivacancy in a graphene/h-BN/graphene stack leads to a switching voltage of ~5 V and a high-to-low resistance ratio >100. Both values lie within the reported experimental range and thus confirm the likelihood that intrinsic defects play a key role in the resistance switching of h-BN in contact with inert electrodes.

Vibrations of a Bridge with Random Structural Irregularities Under Random Traffic Load and a Probabilistic Structural Degradation Assessment Approach

PurposeDynamic loads like traffic make bridges vibrate. Especially for bridges with a large span, vibrations have a significant impact on their structural stability and durability. Due to material defects, fatigue and other influences, a bridge typically has random structural irregularities, which affect its dynamic response. In this work, an effective mathematical approach is presented to study the dynamic response of a model single span slender beam bridge, in the presence of random structural irregularities. In addition, an approach to assess the structural degradation of a bridge is presented.MethodsThe slender beam bridge is modelled as an Euler-Bernoulli beam and the random structural irregularities are considered by random fields in the bending stiffness and the mass per unit length. As an illustrative example, the vibrations of a model road bridge are investigated for randomly crossing vehicles. After Monte Carlo experiments with and without random structural irregularities the vibrations and mechanical stresses of the bridge are determined and analysed.ResultsThe study shows statistically significant variations in the most dominant frequencies with and without random structural irregularities.ConclusionThe influence of the random irregularities on the structural stability status of a bridge may not be negligible. The probability of a serious structural degradation in the bridge can be assessed by means of a binomial logistic model. The developed approach enables a better understanding of the vibrations and structural status of bridges, taking into account random structural irregularities and random traffic.

Anti-overturning safety performance investigation for single column pier bridge

Anti-overturning safety performance investigation for single column pier bridge

Power Compensation-Oriented SVM-DPC Strategy for a Fault-Tolerant Back-to-Back Power Converter Based DFIM Shipboard Propulsion System

For safety critical transportation applications like all-electric ship propulsion systems (SPS), the reliable system operation is definitely the primary concern. In this paper, a fault-tolerant back-to-back power converter based on the four-switch three-phase (FSTP) topology is applied to a doubly-fed induction machine (DFIM) based all-electric SPS. A power compensation-oriented space vector modulation direct power control (PCSVM-DPC) strategy with dc-bus voltage unbalance elimination is proposed to ride through the single bridge arm open-circuit fault in the source-side converter (SSC) and improve the system dynamic performance simultaneously. Besides, the DFIM-SPS is endowed with excellent steady-state performance by applying the proposed control strategy. The dc-bus voltage deviation is suppressed based on the calculation of active and reactive power compensation terms to increase the dc-bus voltage utilization rate. Moreover, good post-fault system operation performance can be achieved with fast active power and electromagnetic torque tracking speeds. The proposed PCSVM-DPC strategy for the fault-tolerant FSTP SSC based DFIM-SPS is easy to implement without high computational burden. The SVM-DPC method is also presented for the load-side converter. The proposed control strategy is verified by experiments on a 1.5 kW DFIM-SPS experimental platform.

Studying single molecule electrochemistry with scanning tunneling microscope break-junction technique

The fundamental principle of molecular electronics is to comprehend electrical properties of single molecules connected between two probe electrodes. In recent years, substantial advances in this field have been made to underpin experimental and theoretical understanding of single molecule electrochemistry. By using scanning tunneling microscope (STM) break-junction technique, the switching events of electrical current from single molecule bridge tuning by electrochemical gating are investigated to uncover the relationship between electrochemical electron transfer and charge transport processes in chemical and biological molecule junctions. In this short review, we outline the latest works of single molecule electrochemistry studied with STM break-junction technique from Nongjian Tao's group, and share the insights on the opportunities and challenges for future research.

Assessment of Performance Indicators of a Large-Span Reinforced Concrete Arch Bridge in a Multi-Hazard Environment

Assessment of a single bridge and management system for all bridges in the network is still a major challenge, although much research has been carried out and implemented in existing networks over the last four decades. This paper presents a case study of a long-span arch bridge, the Maslenica Motorway Bridge, located in a multi-hazard maritime environment. Although special attention was paid to durability during design, the bridge required repair after 20 years of operation. The analysis includes an overview of the design project, structural health monitoring during construction and operation, numerous laboratory and in-situ testing, numerical analysis of structural capacity and remaining service life, and meteorological monitoring of the bridge site. A new approach to bridge assessment is presented that includes not only a deterioration index, but five groups of key performance indicators: (1) safety, reliability, and security; (2) availability and maintainability; (3) costs; (4) the environment; and (5) health and politics. Incorporating all available data and evaluating various aspects of bridge performance provides greater insight into the condition of the bridge, not only at the structure level but also at the network level. The method is applied to the reinforced concrete arch bridge in a harsh maritime environment and evaluation is provided based on the comprehensive data analysis. The key performance assessment procedure and lessons learned from this case study can be applied to a wide range of structures.

X-Ray Radiological Study for Skeleton of Rounded Fantail Stingray Taeniura grabata from Susah, Libya

A sample of Round Fantail Stingray Taeniura grabata was brought, from Susah harbor in east Libya, to establish radiographically, it was situated Dorsal-ventrally, to diagnose skeleton and tooth plate, using Siemens X-ray System (Multix Fusion). In the Multi-graded radiograph, the specimen skeleton was so pale white in most of the axial skeleton and parts of the cranium, and poorly calcified. 88 pectoral radials: 41 propterygials, 15 mesopterygial, and 32 metapterygial radials, with 22 pelvic radials counted. Fin radials were attached to the scapulocoracoid by three enlarged basal radials. The superficial muscles were darker in coloration. About 80 Pre-sting vertebrae, 50 Post-sting with 62 pre-caudal vertebrae, were collected into 192 vertebrae in the tail. There were 32 upper teeth rows, and 36 lower teeth rows, they were small, blunt, and arranged into flattened surfaces. The neurocranium is slightly elongated, longer than 1.5 times in width. Nasal capsules process about 30% of neuro-cranial desk length. Meckel’s cartilages were broadly triangular. The bronchial skeleton comprises five arches. Also, a single small bridge projects ventrally from the medial plate. Jaws are very robust and small.

Seismic Analysis of Elevated Metro Bridge

Abstract: A metro rail system is more preferred type of metro system due to ease of construction and also it makes urban areas more accessible with very less construction difficulty. metro concept is very easy to transport large numbers of people and transportation. In metro city like Delhi, Kolkata, Chennai and Mumbai is very populated city An elevated metro system has two major elements pier and box girder. The codes are now moving towards a performance-based (displacement-based) design approach, which consider. All the information are given by MMRC and considered the data value in this design as per the target performances at the design stage. Which is located to ShyamNager metro station in Mumbai, The present study focuses on pier of an elevated metro structural system conventionally the Double Decker pier of a metro bridge is designed using a force based approach. During a seismic loading, the behaviour of a single pier elevated bridge relies mostly on the ductility and the displacement capacity. It is important to check the ductility of such single piers. Force based methods do not explicitly check the displacement capacity during the design. The codes are now moving towards a performance-based (displacement-based) design approach, which consider the design as per the target performances at the design stage. Performance of a pier designed by a Direct Displacement Based Design is compared with that of a force-based designed one. The design of the pier is done by both force based seismic design method and direct displacement based seismic design method the study.

Analysis of light and no‐load operation of a 300 kW resonant single active bridge based on 3.3 kV SiC‐devices

The resonant single active bridge topology (R-SAB) operated in the half-cycle discontinuous current mode (HC-DCM) is a very attractive solution due to its high efficiency, low complexity and fixed voltage transfer ratio (DCX). However, as expected for a series-resonant converter (SRC), its DCX operation depends on the resonant tank circuit-parameters, parasitic capacitive elements and output load. Specially, at light and no-load operation, when the system is extremely underdamped, it may present a large output overvoltage due to resonance interactions. This is of prime importance for converters using medium voltage (MV) SiC-MOSFETs, which feature significant output capacitances that can lead to voltage breakdown of the rectifier semiconductors. Therefore, the supposed fixed-voltage transfer ratio is not entirely valid and deserves a proper understanding due its criticality. This paper reviews the subject, clarifying its root cause and its multifactorial dependencies. Moreover, it provides a simple solution based on a variable dead-time with fixed magnetizing current experimentally verified with a 300kW/1.8kV R-SAB prototype implemented with MV SiC-devices.

Data‐driven rapid damage evaluation for life‐cycle seismic assessment of regional reinforced concrete bridges

AbstractRapid and accurate post‐earthquake damage evaluation of regional reinforced concrete (RC) bridges is a key issue for assessing the seismic resilience of cities and communities. Especially, RC bridges are susceptible to the aggressive environment, which can induce time‐dependent aging effects such as corrosion, and thus, it should be considered in the assessment. This paper presents an approach for regional seismic performance assessment of RC bridges in a life‐cycle context based on machine‐learning techniques. The life‐cycle seismic demand and capacity of the bridges are, firstly, obtained by the elaborated numerical model, which includes the deterioration induced by the aging corrosion effect. Then, the tagging‐based damage state (green, yellow, or red) is easily obtained by comparing the pairs of demand and capacity through machine learning. Four hundred and eighty bridge models are generated to develop the machine‐learning models and the performance of the machine learning models is evaluated. Results show that the extreme gradient boosting (XGBoost) model has the best performance, which has an accuracy of 81% in predicting the damage states. The proposed approach is demonstrated with a single bridge example and bridges in a sample region. It is shown that the machine learning model can accurately predict the post‐earthquake damage states of the single bridge, and it can also rapidly assess the damage states of the bridges in the sample region. Approximately 30% bridges in the sample region will experience damage states shift after 100 years, which highlights the importance of considering the aging effects on the post‐earthquake damage assessment of bridges.

Comparison of Markov chain and recurrent neural network in predicting bridge deterioration considering various factors

Bridge deterioration reflects changes in bridge conditions and is caused by many factors. Predicting bridge deterioration is critical for implementing predictive interventions, but developing such credible models that consider multiple influencing factors remains difficult. This study uses Markov Chain (MC) and Recurrent Neural Network (RNN) to establish deterioration prediction models. Then, comparative studies of these two models are conducted on a censored database regarding the mean deterioration progress, deterioration progress of bridges with different deck types, deterioration progress of a single bridge, and the influence of each factor on deterioration progress. The results indicate that RNN-predicted deterioration to a worse state takes less time than MC-predicted deterioration, but the difference is less than 5 years. Deterioration progresses of bridges with different deck types show that PC deck and steel deck are more durable than RC deck and concrete-steel composite deck. Qualitative and quantitative analysis infers eight factors substantially affecting the deterioration progress. Overall, the deterioration progress provided by these two models can be utilized to determine bridge’s remaining life and analyze the effects of external factors affecting the deterioration. This information is extremely valuable for assisting in developing and implementing effective management and maintenance strategies.

Single Leg Bridge Test is Not a Valid Clinical Tool to Assess Maximum Hamstring Strength.

BackgroundThe single leg bridge test (SLBT) has been introduced in the sports context as a way of estimating hamstring muscle capacity for prevention and rehabilitation of hamstring strain injuries.PurposeThe primary aim was to examine the association between SLBT scores with concentric and eccentric knee flexor peak torques. Secondarily, this study aimed examine the association of between-limb asymmetries provided by SLBT and isokinetic tests.Study designCross-sectional study.MethodsOne hundred male soccer players (20±3 years) performed the SLBT and the knee flexion-extension isokinetic dynamometry evaluation (60°/s) billaterally during a single visit. SLBT score (i.e., number of repetitions until failure) and concentric and eccentric knee flexor peak torques (normalized per body mass) were considered for analysis. For both SLBT and isokinetic dynamometry, between-limb asymmetry was calculated as the percentage difference between the left limb and the right limb. Associations were assessed through Pearson’s correlation coefficient.ResultsThe mean SLBT score was 33.6±9.6 repetitions, concentric peak torque was 2.00±0.22 Nm/kg, and eccentric peak torque was 2.79±0.44 Nm/kg. Between-limb asymmetry was 0.4±9.6%, 1.08±8.5%, and 1.64±14.61% in SLBT, concentric, and eccentric tests, respectively. There was a poor association of SLBT score with concentric (p<0.001, r=0.275) and eccentric (p=0.002, r=0.215) peak torques. The SLBT between-limb asymmetry was poorly associated with asymmetry found in concentric peak torque asymmetry (p=0.033, r=0.213) and was not associated with eccentric peak torque asymmetry (p=0.539, r=0.062).ConclusionThe SLBT should not be used as a clinical tool to assess the maximum strength of hamstring muscles.Level of EvidenceLevel 3

Sustainability-oriented maintenance management of highway bridge networks based on Q-learning

Current bridge management systems provide maintenance strategies that balance costs and structural safety of bridge networks. However, they are cost-oriented rather than sustainability-oriented. Moreover, the existing literature lacks research on reducing the environmental impacts of a bridge network during operation and maintenance periods. This paper develops a condition-based maintenance approach for highway bridges, aiming to minimize the total carbon emissions of bridge networks subject to maintenance budget constraints. A two-dimensional Markov chain model is applied to predict the deterioration processes of bridges, and a Q-learning algorithm is proposed to determine the maintenance strategy for a single bridge. Then, integer programming optimizes the budget allocation process for a bridge network. The proposed method is demonstrated using the concrete bridges in New York state. Sensitivity analyses indicate the impacts of budget levels on maintenance plans and total carbon emissions. 10% drop in budget level results in 30 additional bridge repairs delayed as well as 39 tonne extra annual carbon emissions. The proposed optimization framework would contribute to intelligent infrastructure asset management and sustainable society.

Data and evaluation model for the description of the static–dynamic interface between trains and railway bridges

This paper presents a five-level data model based on the single beam with simple supports for the static and dynamic assessment for existing railway bridges with regard to loading from trains. Through the joint representation of action and structural responses based on wavelengths, clear diagrams of the verification variables are achieved. The combination of the relevant parameters enables numerous evaluations, which can be used for the validation of an entire existing bridge stock, but also for the assessment of a single bridge.

Nonlinear Control Design and Stability Analysis of Single Phase Half Bridge Interleaved Buck Shunt Active Power Filter

This paper deals with nonlinear control of a single-phase half-bridge interleaved buck shunt active power filter (HBIB-SAPF) with a nonlinear load. The control objective for the system is twofold: performing power factor correction by compensating for harmonics and reactive current consumed by the nonlinear load from one hand and tightly regulating the HBIB converter DC capacitor voltage. Both objectives are accomplished using a two-loop nonlinear controller. The inner loop acts on the switching devices so that the active filter current tracks its reference with the aim of ensuring a unity power factor. This loop is tackled using backstepping technique and Lyapunov approach. The outer loop is responsible for regulating the DC capacitor voltage to its desired value, using a PI controller with a pre-filter. The stability analysis of the closed-loop system is formally performed by using the averaging theory. The validity of the designed nonlinear controller is checked by simulations in Matlab/SimpowerSystem showing its robustness and accuracy under various operating conditions.

Experimental Study of the Aerodynamic Characteristics of a Suspended Monorail Vehicle-Bridge System Under Crosswinds

Using wind tunnel tests, the aerodynamic characteristics of a suspended monorail transport (SMT) are systematically investigated under crosswinds for the first time. Two practical vehicle–bridge combination forms (single-line and double-line) are considered. As a contrast, single vehicle and bridge models are also studied to further reveal their aerodynamic characteristics. The mean and root mean square (RMS) wind pressure coefficients, aerodynamic coefficients and power spectrum density (PSD) distributions are used to numerically investigate the effects. The paper confirms that: (1) the mean wind pressure coefficients of the single vehicle and bridge models are close to unity at the center point of the windward side and gradually decrease from the center point to both sides. The maximum value of the RMS wind pressure coefficients mainly occurs at the top or bottom surface of the testing models due to the effect of vortex shedding; (2) the aerodynamic coefficients and the mean and RMS wind pressure coefficients are significantly increased for both the vehicle and bridge models when considering the aerodynamic coupling effects; (3) the aerodynamic characteristics of the bridge can be significantly affected by the location of the running vehicle, but the fluid flow can maintain relative stability during the meeting of the two vehicles.

Analysis and design for constant current/constant voltage multi‐coil wireless power transfer system with high EMF reduction

The investigation on the constant current (CC)/constant voltage (CV) charging for the electric vehicle wireless power transfer (WPT) system has been widely conducted. However, the CC/CV performance under misalignment cases has been scarcely studied especially for the multi-coil WPT system. The resonant tank compensation methodology for the exciter-quadrature-repeaters (EQR) transmitter-based multi-coil WPT system is studied to achieve high power factor CC/CV charging with low leakage flux over ±150 mm lateral misalignment range. The EQR transmitter consists of one small exciter coil powered by a single full bridge inverter and two larger decoupled quadrature repeater coils which are magnetically coupled to the exciter coil. A variable switched capacitor is applied on the exciter side to maintain a high power factor in the CV mode. A 3-kW experimental setup with a 200 mm nominal vertical distance was built and a three-coil WPT system with a single large repeater coil is chosen as a comparison. Experimental results show that the EQR transmitter-based WPT system achieves 92% coil-to-coil efficiency and reduces the leakage flux density by 70% compared with the existing three-coil system in the CV mode at 150-mm lateral misalignment.

Tuning of Cr-Cr Magnetic Exchange through Chalcogenide Linkers in Cr2 Molecular Dimers.

A set of three Cr-dimer compounds, Cr2Q2(en)4X2 (Q: S, Se; X: Br, Cl; en: ethylenediamine), with monoatomic chalcogenide bridges have been synthesized via a single-step solvothermal route. Chalcogenide linkers mediate magnetic exchange between Cr3+ centers, while bidentate ethylenediamine ligands complete the distorted octahedral coordination of Cr centers. Unlike the compounds previously reported, none of the chalcogenide atoms are connected to extra ligands. Magnetic susceptibility studies indicate antiferromagnetic coupling between Cr3+ centers, which are moderate in Cr2Se2(en)4X2 and stronger in Cr2S2(en)4Cl2. Fitting the magnetic data requires a biquadratic exchange term. High-frequency EPR spectra showing characteristic signals due to coupled S = 1 spin states could be interpreted in terms of the "giant spin" Hamiltonian. A fourth compound, Cr2Se8(en)4, has a single diatomic Se bridge connecting the two Cr3+ centers and shows weak ferromagnetic exchange interactions. This work demonstrates the tunability in strength and type of exchange interactions between metal centers by manipulating the interatomic distances and number of bridging chalcogenide linkers.