Resistance Bridge Research Articles

Anomalous influence of electrode width on the critical current of Nb/Au Josephson junctions

Abstract We study the effect of electrodes width on superconducting current transport in Nb-Au-Nb Josephson bridges. The critical current as well as the normal bridge resistance drop with decreasing electrode width on scales of a few μm, which are orders of magnitude larger than the estimated coherence length of Au strip. We consider several physical reasons of such an anomalous influence of the width W of the superconducting electrode on the critical current Ic (AIWIc) and provide model fits for the resistive and superconducting properties of the bridges. {The smooth dependence of the Nb-Au-Nb bridge parameters on the electrode width can be used to optimize the design of superconducting devices for specific applications.

Seismic performance and calculation method for plastic hinge length of RC pier reinforced with UHPC

Piers are highly vulnerable load-bearing components, and their seismic performance determines the integral seismic resistance of bridges to a certain degree. They play crucial roles in evacuation during earthquakes and post-earthquake rescue. The manner in which piers meet the seismic performance requirements after reinforcement has become a popular research topic. In this study, ultra-high-performance concrete (UHPC) and HTRB600E high-tensile reinforcements were used to expand the cross section of a cast-in-place square pier with severe bending damage. The earthquake-resistant behaviour indicators of the pier were compared and analysed by conducting pseudo-static tests on a reinforced concrete pier before and after reinforcement. These indicators included the hysteretic curve, skeleton curve, energy dissipation curve, rigidity degradation, residual displacement, and pier body curvature. Based on the results of the seismic reinforcement quasi-static tests, a finite element model (FEM) of the bridge pier was constructed using the ABAQUS software, and the accuracy of the FEM was averaged. The impact of the reinforcement layer height, thickness, longitudinal strength and axial compression ratio on the equivalent plastic-hinge length of the reinforced pier was analysed, and the formula for the equivalent plastic-hinge length of the reinforced pier was obtained based on multiple linear regression fitting. The analysis results demonstrated that the broadened section method, utilising UHPC and high-tensile reinforcement, significantly enhanced the flexural capacity, energy dissipation, and first rigidity of the bridge pier. The earthquake-resistant behaviour of pier was effectively restored and improved, and the seismic reinforcement effect was significant. The equivalent plastic hinge length of the pier after reinforcement is proportional to the height of the reinforcement layer, the thickness of the reinforcement layer, the strength of the longitudinal reinforcement, and inversely proportional to the axial compression ratio.

Impact force-damage depth model for ship-bridge collision

The impact force-damage depth model, i.e., P-a model, provides a feasible approach to design and evaluate bridge resistance under ship collisions, which is inadequately addressed in the existing specifications and literature. In the present study, based on an 18500 DWT (deadweight tonnage) bulbous bow bulk carrier and the main tower of cable-stayed bridges, the P-a model for ship-bridge collision is established with consideration of pile cap, bridge pylon and striking ship. Firstly, the refined finite element (FE) model of prototype ship was established with detailed modeling of both the main and stiffening components. The material model parameters and FE analysis approach were validated through the existing tensile tests on marine steel coupons and crush tests on ship bow specimens. It is found that the modeling of stiffening components has rationality in predicting the impact force and asymmetrical folding collapse of ship bow. Then, concerning two collision scenarios with the main tower of cable-stayed bridges, i.e., only bulbous bow-pile cap collision and sequential bulbous bow-pile cap and bow overhang-bridge pylon collisions, the influences of nine critical parameters from pile cap (height, curvature and water level), bridge pylon (width, curvature, angle and bow overhang-bridge pylon distance) and striking ship (mass and velocity) on the impact forces and failure patterns of ship bow were comprehensively discussed. It indicates that: (i) the larger impact forces of bulbous bow and bow overhang appear with increased pile cap height, decreased bridge pylon curvature and inward inclined pylon angle; (ii) the loading paths of P-a relationships are approximately identical with different striking ship masses and velocities. Finally, the P-a model for ship-bridge collision was established by response surface methodology, and the corresponding calculation procedure was further given and validated.

Evaluation of the Dislodgement Resistance of Traditional Adhesive Posterior Bridges Compared With Adhesive Posterior Bridges Prepared With Standard and Modified Slot-Back Dummies: An In Vitro Study.

Background Bridges with minimal preparation have received great acceptance in recent years. Since their first appearance, they have undergone many types of modifications and improvements. Aim This study aimed to compare three types of minimal preparation bridgesin terms of force required for dislodgement and the type of deformation incurred for each of the abutments and prostheses. Materials and methods The research sample consisted of 36 adhesive bridges divided into three equal groups. The first group contained traditional adhesive bridges prepared from the proximal and lingual surfaces with a thickness of 1 mm, the second group contained adhesive bridges with standard slot-back dummies, and the third group contained adhesive bridges with modified slot-back dummies. Each bridge underwent a pressure test, which was directed from the buccal toward the lingual sideand was inclined to the horizontal plane at an angle of 45°. A one-way analysis of variance (ANOVA) test was conducted with a significance level of 0.05. Results The average dislodgement resistance value in the traditional adhesive bridges group was 480,858 N, with no statistically significant difference from the standard slot-back dummy group (p = 1), for which the average dislodgement resistance value was 486,050 N. The average dislodgement resistance valuein the modified slot-back dummy group was 746,733 N, with a statistically significant difference compared with other study groups (p < 0.05). Conclusion The adhesive bridge with the modified slot-back dummy showed higher dislodgement resistance compared to the traditional adhesive bridge and the adhesive bridge with the slot-back dummy.

Investigation on flooding dynamic response and mitigation measure of river bridge

Flood-induced failure of river bridges is intense due to frequently extreme and undesigned precipitation for global climate change. To reveal the dynamic characteristics and failure mechanism of bridges, flooding dynamic analysis is fully investigated via fluid–structure interaction simulation and Arbitrary Lagrangian-Eulerian method. Parametric analysis of different fluids and bridge configurations and pre-ballast mitigation measure are further conducted based on a simply-supported box-girder bridge. This study reveals several significant findings: the narrow channel can accelerate downstream flood velocity of the bridge piers to over double that of the upstream flow; moreover, unsubmerged piers experience vertical downward wave force surpassing buoyancy; the box girders exhibit three flood-response states, i.e., intact, slip and collapse, dependent on the hydraulic loading and bridge resistance capacity. Maximum horizontal wave force and displacement increase exponentially with the depth of water storage. Post-slip damage, bearing stress on the wave-facing side tends towards zero, while the wave-backing side presents a twofold increase. Maximum horizontal displacement (Xmax) distinguishes the failure states, such as 0 m ≤ Xmax ≤ 0.03 m (intact), 0.03 m < Xmax ≤ 1.39 m (slip), Xmax > 1.39 m (collapse), whose relation to the maximum horizontal wave force has been proposed for design reference and the inversion analysis of the bridge force. Applying a pre-ballast equivalent to 75 % of girder weight reduces Xmax by up to 91.5 %, shifting failure from collapse to slip. These insights offer crucial guidance for enhancing bridge safety amidst escalating flood risks.

Study of the State Primary Measurement Standard of the Unit of Phase Shift Angle Between Two Voltages

Phase measurements are necessary for determining main parameters of the oscillatory process in complex electrical networks. Most often, it is precisely the phase shift angle (PSA) between two oscillatory processes of the same frequency that is measured. An essential indicator of the quality of electrical energy is the coefficient of asymmetry in a three-phase electrical network, which depends on the load of consumers in this network. This indicator is affected by a short circuit between two phase voltages. Phase measurement standards, phase meters, and phase converters are included in the measuring equipment for phase measurements. They are widely used in such fields as radiolocation, radio navigation, non-destructive testing, radio engineering, telecommunications, acoustics, metallurgy, machine and aircraft industry, space industry, as well as in scientific research and defence. The State Measurement Standard of Ukraine of the PSA unit between two voltages in the frequency range from 0.01 Hz to 10 MHz is maintained at the State Enterprise “UKRMETRTESTSTANDARD”, Kyiv. It provides metrological traceability of phases measured in the country. The main components of the standard were calibrated at the PTB, the National Metrology Institute of Germany. In Ukraine, numerous measurement standards and measurement instruments for phase measurements (more than 500.000 units) are used, in particular, phase calibrators, phase meters, phase shifters, synchronoscopes etc. Regular study of metrological characteristics of the DETU 09-07-11 measurement standard is conducted both in the main (from 5 Hz to 200 kHz) and in the extended (from 0.01 Hz to 10 MHz) frequency range. The PSA values obtained as a result of the research in the main frequency range do not exceed 0.001° (which is maximum according to measurements at all calibration points 0.00015°), and in the extended frequency range – 0.01° (which is maximum according to measurements at all calibration points 0.0053°). To eliminate the systematic measurement uncertainty component of the phase measurement standard, a special calibration is regularly performed using a set of resistive and capacitive phase bridges.

Steady Heat Transfer Analysis of the Refrigerator Seal Considering Rigid and Flexible Contact

The rigid and flexible contact of the refrigerator seal has a significant impact on its heat transfer characteristics, but existing research has ignored this important factor. In this paper, the assembly physical model at the seal region is established by static structural analysis. Then a three-dimensional heat transfer numerical simulation is carried out. The assembly distance affects the contact state of the seal by changing the contact position between the seal and the door or the cabinet. The calculation results show that the calculated temperature at the seal region considering the actual assembly deformation is closer to the measured temperatures. In the case study, the heat leakage load decreases by 18.57% and 19.99% at the compressed state, while it increases by 4.45% under the stretching state. The proportion of heat transfer load in the path of rubber strip-cold air and rubber strip-outer shell of the cabinet is the largest, reaching over 30.0%. The heat transfer load of the cold bridge also accounts for over 20.0%. When optimizing the seal structure, reducing the contact interface length of rubber strip-cold air, reducing thermal conductivity, and increasing the contact thermal resistance of cold bridge should be focused on.

Experimental research on PPF anti-cracking effect in scale model of hollow rigid frame bridge

The hollow rigid frame bridge has many advantages, such as being lightweight, having strong spanning ability, and having slight deflection in span. This type of bridge has a broad potential for application in regions of many canyons and hills. While there has been less research into the application of this type of bridge, some of the bridges in early service have cracking problems. To satisfy the demand for cracking resistance of the Yunnanzhuang large-span hollow rigid frame bridge, our group proposed using Polypropylene Fibers (PPF) to enhance the strength of concrete against cracking. After analyzing the structure of the whole bridge, we gave the critical sections of the bridge and carried out a series of tests to give the PPF dosage that applies to the project. This paper focuses on the use of reduced-size bridge model tests to investigate the effect of PPF on the cracking resistance of hollow rigid frame bridges under bending.In this paper, the similarity criterion between the actual bridge and the model was calculated by the method of magnitude analysis, according to which scale-down model beams of the upper chord S4 segment and mid-span jointing segment of Yunnanzhuang Bridge were designed under the geometry of 1:5. We respectively made these models using the same C55 concrete as the actual bridge and Polypropylene Fibre Reinforced Concrete (PPFRC) with 0.3 % volumetric admixture of PPF in the same mix ratio, and three-point bending static load tests were performed on these models. To make up for the insufficiency of test groups, we performed a finite element analysis using ABAQUS and the CDP constitution, which led us to some reliable conclusions.Considering that concrete materials have size effect, directly using the results of model tests to predict the cracking stresses of the actual bridge is not accurate. In this paper, some theories on size effects were examined. Finally, the Size Effect Model (SEM), Boundary Effects Model (BEM), and Weibull's brittle strength theory were selected to correct the test results.The results show that PPF can increase the cracking load of the test beams, ranging from 11.22 % to 13.49 %. After using selected size effect theories to predict the cracking stresses in actual bridges, the results show that PPF can enhance the cracking strength of C55 concrete, with an increase ranging from 9.15 % to 18.75 %. Combined with the results of the structural analysis of the whole bridge, the critical section has a cracking stress between 2.6 MPa and 3.5 MPa when using C55 concrete, which has a certain risk of cracking. However, when using PPFRC, the cracking stress ranges from 3.1 MPa to 4.2 MPa, with no risk of cracking in most unfavorable cases, which can satisfy the demand for concrete cracking resistance of Yunnanzhuang Bridge.

Implementation of binarized neural networks immune to device variation and voltage drop employing resistive random access memory bridges and capacitive neurons

Resistive Random Access Memories (ReRAM) arrays provides a promising basement to deploy neural network accelerators based on near or in memory computing. However most popular accelerators rely on Ohm’s and Kirchhoff’s laws to achieve multiply and accumulate, and thus are prone to ReRAM variability and voltage drop in the memory array, and thus need sophisticated readout circuits. Here we propose a robust binary neural network, based on fully differential capacitive neurons and ReRAM synapses, used in a resistive bridge fashion. We fabricated a network layer with up to 23 inputs that we extrapolated to large numbers of inputs through simulation. Defining proper programming and reading conditions, we demonstrate the high resilience of this solution with a minimal accuracy drop, compared to a software baseline, on image classification tasks. Moreover, our solution can achieve a peak energy efficiency, comparable with the state of the art, when projected to a 22 nanometer technology.

Effect of elastic deformation on the heat transfer characteristic of refrigerator gasket based on static analysis of structural assemblies

ABSTRACT Soft and hard contact deformation is most common issue of the refrigerator gasket and it has almost been ignored in previous studies. In this paper, the novelty is to propose a thermal-solid coupling simulation to study the effect of assembly states on the heat transfer of gaskets, improving the accuracy of heat transfer simulation analysis. The numerical results indicate that the calculated temperature based on physical model of assembly state is closer to measured temperature. The assembly distance affects the assembly state of the gasket by changing the contact positions and lengths of contact interfaces. As a result, the heat transfer path and condition at the gasket region also changes. As the deformation increases form −1.0 mm to 5.0 mm, the heat leakage load of gasket rises firstly and then falls, in the range of 1.61 ~ 3.33 W•m−1. The heat leakage at the transfer paths of internal cold air, outer shell and cold bridge accounts for over 20%. Thus, it is recommended to reduce the contact interface length of internal cold air, increase the thermal resistance of auxiliary air-bag, reduce the thermal conductivity and thickness of magnetic strip and increase the contact thermal resistance of cold bridge.

A Comparative Study of Fragility Model for RC Girder Bridges and Buildings

Field surveys and data on the earthquake reveal that RC (reinforced concrete) bridges and buildings have been widely found in engineering structures, with abundant samples at disposal. By taking actual seismically damaged samples in the Wenchuan Earthquake happened in 2008 as examples, the paper established probability models for fragility matrix within Intensity VH-X/XI for the said two engineering structures based on EMS-98, MSK-81 and CSIS-08, and analyzed the comparative models for failure ratio and exceedance probability curves defined by these three scales. The paper, according to these analytical findings, proposed relevant measures and methods for improving the earthquake resistance of RC bridges.

Mechanical performance of concrete-encased prismatic girders with corrugated steel webs

To enhance the shear buckling resistance of girder bridges with corrugated steel webs (CSWs), especially near the intermediate support where maximum shear force and negative bending moment are experienced, it is common practice to encase the CSWs with concrete. This paper analyses the mechanical performance of concrete-encased prismatic girders with CSWs based on finite element (FE) simulations, theoretical analysis and existing experiments. The concrete encasement restricts the axial free deformation of the concrete-encased CSWs (CCSWs), thereby diminishing the accordion effect of the CSWs. As a result, the normal strains in both the CCSWs and the concrete encasement become nearly identical, demonstrating a linear distribution that aligns with the plane section assumption. The study reveals that the concrete encasement assists the CCSWs in shouldering a portion of the shear force, and shear stress in the CCSWs is no longer uniformly distributed. In addition, a stiffness-based shear carrying calculation method for CCSWs and concrete encasement is theoretically derived. It is observed that due to the constraint of concrete encasement, the actual shear modulus of CCSWs surpasses that of CSWs without encased concrete, rendering it more similar to that of a flat steel plate. Lastly, this study firstly proposes a shear stress calculation formula for CCSWs, which theoretically explains the parabolic shear stress distribution in CCSWs. Error analysis reveals that traditional basic shear method, which assumes uniform shear stress distribution in CSWs, significantly underestimates the actual shear stress in CCSWs. Remarkably, the modified shear method proposed in this study accurately predicts shear stresses in CCSWs.

Shape memory alloy-reinforced UHPC tube confined bridge piers for enhancing the seismic resistance of highway bridges

Multi-span continuous highway bridges supported with reinforced concrete (RC) bridge piers may experience large permanent deformation after strong earthquakes. To overcome the limitations, an innovative UHPC tube-confined SMA reinforced bridge pier, i.e., shape memory alloy (SMA) replacing the steel rebars at the plastic hinge region and a prefabricated UHPC tube substituting the cover concrete, is proposed. To fully utilize the tensile strength of UHPC, the UHPC tube is embedded into the foundation. A performance-based seismic design procedure considering target residual drift as engineering demand parameter (EDP) is proposed to design this novel UHPC-SMA pier. The seismic responses of novel bridge systems supported by UHPC piers (Bridge II) and UHPC-SMA piers (Bridge III) are investigated and compared with reference bridge (Bridge I) having RC piers. The results indicate that both UHPC piers and UHPC-SMA piers are efficient in improving the seismic resistance of highway bridges. Compared with Bridge I, the prefabricated UHPC tube significantly decreases the residual deformation of Bridge II piers by 22.9 % as a result of the bridging effect of steel fibers. Due to the excellent self-centering property of SMA, the residual deformation of Bridge III piers decreases further by 57.8 % in comparison to reference bridge. The UHPC tube increases the low stiffness of bridge piers caused by SMA rebars at the plastic hinge region. The combination of UHPC tube and SMA can effectively prevent core concrete from severe damage with less dissipated energy of bridge piers.

Stayed Buckle Cable Recycling for Seismic Upgrading of Super-long-span Concrete Filled Steel Tube Arch Bridges

A seismic upgrading approach for super-large-span upper-deck concrete-filled steel tube arch bridges using the stayed buckle cables (SBCs, which are temporary facilities for construction of long-span arch bridges) was proposed. The arrangement of SBCs most beneficial to the seismic resistance of arch bridges was determined. The results show that the reasonable arrangement of SBCs can achieve significant seismic performance improvement, reduce the stress demand on the diagonal of the arch rib, and improve the capacity-demand ratios of the weak sections of the arch rib. In upgrading model, the max displacement response of the structure is decreased by 41.3%, the max tensile stress on the diagonal is decreased by 30.1%, the max compression stress demand on the diagonal decreased by 18.0%, the CDRs of sections of the arch ribs are greatly improved.

Biopotential multi-path current feedback instrumentation amplifier with automatic offset cancellation loop for resistive bridge microsensors

&lt;span lang="EN-US"&gt;This study introduces a refined current feedback instrumentation amplifier (CFIA) specifically designed for amplifying biopotential signals that originate from resistive-bridge sensors. The proposed architecture uniquely incorporates a multipath chopper-stabilized CFIA which has been developed to minimize the effects of bridge offsets, while maintaining low power usage, high input impedance, and reduced noise characteristics. The engineering blueprint employs a ripple reduction loop (RRL) to mitigate output ripple caused by chopper up-modulation. To speed up offset cancellation and to limit the offset caused by bridge mismatch, an automatic offset cancellation loop (AOCL) circuit is integrated within the analog front end (AFE). Crafted using a conventional 0.18 µm CMOS process, the CFIA in this design provides adjustable gain between 20.35 dB to 55.14 dB, with a power supply rejection ratio (PSRR) and a common mode rejection ratio (CMRR) of 103 dB and 114 dB, respectively. The system demonstrates an input-referred noise (IRN) value of 16 ηV/√Hz at 200 Hz frequency, equivalent to a noise efficiency factor (NEF) of 5.18. Operating from a supply voltage of 1.8V, the AFE shows a power consumption of 291 μW.&lt;/span&gt;

Improving Fracture Resistance of 5Y-PSZ-based Three-unit Bridge Prosthesis.

5Y-PSZ-based zirconia dental restorations exhibit high translucency and good esthetics but have a higher fracture risk compared to 3Y-TZP. To investigate the effect of BruxZir SteelTM treatment on the fracture resistance of zirconia three-unit bridges prepared using 5Y-PSZ-based zirconia blanks. Three-unit zirconia bridges were milled using CAD/CAM from homogeneous bisque zirconia blanks (5Y-PSZ-based) supplied by various manufacturers and sintered. Their fracture resistance was analyzed by dynamic loading. For each zirconia blank, the fracture resistance of the sintered test restoration (cementation surface treated with BruxZir SteelTM) was compared with the sintered control restoration (untreated cementation surface). Finite Element Analysis (FEA) was used to analyze the stress distribution on the three-unit bridge under an axial load. The fracture resistance of the test restorations was significantly higher than that of the control restorations for all the manufacturers considered in this study (P < 0.05). Furthermore, the restoration made of BruxZirⓇ Esthetic treated with BruxZir SteelTM had the highest fracture resistance compared to the other restorations. In addition, the three-unit bridge restorations prepared from 5Y-PSZ-based zirconia blocks exhibited differences in grain size and fracture toughness depending on the presence or absence of BruxZir SteelTM treatment. The locations of high stresses under FEA correlated well with the fracture locations in the corresponding experimental test. FEA also demonstrated the improved performance of BruxZir Steel-treated sample compared to the control. The fracture resistance of 5Y-PSZ-based BruxZir SteelTM-treated three-unit bridges was significantly higher (min. 30%, max. 198%) than control.

Evaluation of the effects of leakage current in the calibration of standard resistors between two dc resistance bridges and a digital sampling impedance bridge

This article discusses calibrations results of standard resistors performed with two commercially available equipment and a digital sampling impedance bridge developed at Inmetro. One of the commercial bridges uses the current comparison method and the other the potentiometric method with a binary voltage divider. Calibration was performed with standard resistors of 10 kΩ and 100 kΩ with significant leakage current. This study showed divergent results between each methodology. A specific methodology was used to estimate the leakage resistance of these resistors. This study contributes to establish criteria for correction and/or inclusion of uncertainty components in resistors calibrated in these methodologies.

Dynamic reliability analysis of the existing bridges based on probability density evolution method

Existing bridges have experienced time-varying load effects and resistance degradation during the service periods. The complex dynamic loads and diverse failure modes make the existing bridges face high service risks, therefore, it is urgent to make time-dependent reliability assessment for the service bridges. The classical time-varying reliability analysis method is increasingly complex and challenging with the increase of the number about random variables. In this paper, probability density evolution theory is introduced as a more advantageous approach to solve the above problem, which is more advantageous for solving the reliability of complex structures with multiple random variables. The dynamic reliability of the existing bridge in serviceability limit state and ultimate limit state is analyzed by considering the bridge resistance degradation and the increase of load effects, as well as the time-varying factors such as shrinkage and creep effect of concrete bridges. The accuracy and computational efficiency for this method are compared with the Monte Carlo method, and the effectiveness of the proposed method is verified, which has the advantages of higher computational efficiency and better accuracy and can be applied to complex nonlinear structures under various loads.

Development of Improved Equations for Live Load Moment Distribution in Interior Girders of Shallow Steel Tub Girder Bridges

AbstractThe focus of this paper is the development of improved live load distribution factor (LLDF) prediction equations for interior beams of press‐brake‐formed tub girder (PBFTG) bridges. PBFTGs consist of cold‐bent standard plate widths and thicknesses to form a trapezoidal box girder. Based on a survey of literature and field testing performed on PBFTG bridges across multiple states in the United States, the empirical equations found in the American Association of State Highway and Transportation Officials Load Resistance and Factor Design Bridge Design Specifications (AASHTO LRFD BDS) have been found to be conservatively applicable to shallow steel tub girder bridges. Improvements can be made to AASHTO LRFD BDS provisions relating to shallow steel tub girders and their respective live load distribution factors (LLDFs). To overcome this gap in design and analysis, rigorous three‐dimensional finite element analysis tools were developed and benchmarked against field implementations. The tools were used to analyze the live load distribution behavior of an interior girder of a matrix of approximately 18,000 PBFTG bridges. From the result of the analysis, statistical methods were employed to produce simplified empirical equations to better predict live load moment distribution in PBFTGs. The simplified equations are to be used in conjunction with line girder analysis to further simplify the design of shallow steel tub girder bridges and expand their application in the short‐span bridge market.

High Precision Experimental Exploration of Wheatstone Bridge Resistance Measurement

As is known to everyone, Wheatstone bridge has played a very important role in resistance measurement. This work has improved the accuracy of self-organized bridge and box bridge, so that the resistance measurement accuracy of the two types of bridges can arrive at an unprecedented level, and the measured value of the same resistance by the two types of bridges tends to be quite consistent, which performs the measurement of resistance value in the most accurate way