Bridge Configuration Research Articles

The Stability and Electronic Structure of Cu(200)/AuCu(200) Interface: An Insight from First-Principle Calculation.

AuCu phase had a significant effect on the bonding strength of Au80Sn20 alloy and Cu substrate. The formation of the AuCu(200)/Cu(200) interface significantly improves the shear strength of solder joints. Therefore, it is particularly important to analyze the strengthening mechanism of the AuCu phase in the Cu matrix. The atomic structure, interfacial stability, and interfacial bonding properties of the Cu(200)/AuCu(200) interface were investigated using first-principle calculation. The layer spacing convergence results show that seven layers of Cu(200) surface and seven layers of AuCu(200) surface are enough thick to be chosen for the interface model. The calculation shows that the surface energies are 1.463 J/m2 and 1.081 J/m2 for AuCu(200) surface and Cu(200) surface, respectively. Four interface combinations of Top sit, Long bridge, Short bridge, and Hollow were investigated by considering four stacking methods of AuCu(200). It is shown that the interfacial configuration of the Long bridge is the most stable and favorable structure, which has the largest adhesion work, the smallest interfacial energy, and the smallest interfacial spacing. The density of states and electron difference density were calculated for the four interfacial configurations, and the results showed that the main bonding mode of the Long bridge interface is composed of both Cu-Cu covalent bonds and Au-Cu covalent bonds.

Design of a Force Measuring Unit for Robotic Applications

The paper deals with design process of a force measuring unit, which is capable to mount onto a robot or to integrate into a measuring device. The main element is a beam type load cell equipped with strain gauges in Wheatstone bridge configuration. In order to measure the force only in one direction a linear guide rail is used to lock the degrees of freedom. The unit will have a microcontroller board to process and transfer the data to a personal computer. Furthermore, the system will be capable to intervene processes thanks to the digital inputs and outputs of the electric board. The paper introduces the 3D model of the device, and its components.

Seismic response of horizontally curved bridges in combination with skewed abutments

A bridge having in-plan curvature in combination with the skewed abutments is termed as skew-curved bridge. Present study explores upon the seismic response of a three-span continuous RC skew-curved concrete box-girder bridges under free and forced vibrations for which 3-D models of the bridge with varying configurations are generated in the CSiBridge. The curvature angle for the parametric study has been varied as 0°,30°,60° and 90° in combination with skew angles of 0°,15°,30°,45° and 60°. Modal analysis and response spectrum analysis for all the bridge models has been performed. Modal response of the various bridge configurations has been presented in graphical form in order to have knowledge of the mode shapes, time periods and fundamental frequencies of the bridges. Based on guidelines of AASHTO 2007 response spectrum analysis has been performed considering 0.3 g acceleration in longitudinal and transverse direction and an acceleration of 0.2 g in vertical direction. In-plane bending moments, longitudinal torsion and out-of-plane bending moments are monitored for all skew curved bridges under longitudinal, transverse and vertical excitations and it is observed that especially in-plane moments in longitudinal and transverse direction are significantly affected by inclusion of skewness and curvature in bridges.

The Crystal Plane is not the Key Factor for CO2 -to-Methane Electrosynthesis on Reconstructed Cu2 O Microparticles.

Cu2 O microparticles with controllable crystal planes and relatively high stability have been recognized as a good platform to understand the mechanism of the electrocatalytic CO2 reduction reaction (CO2 RR). Herein, we demonstrate that the in situ generated Cu2 O/Cu interface plays a key role in determining the selectivity of methane formation, rather than the initial crystal plane of the reconstructed Cu2 O microparticles. Experimental results indicate that the methane evolution is dominated on all three different crystal planes with similar Tafel slopes and long-term stabilities. Density functional theory (DFT) calculations further reveal that *CO is protonated via a similar bridge configuration at the Cu2 O/Cu interface, regardless of the initial crystal planes of Cu2 O. The Gibbs free energy changes (ΔG) of *CHO on different reconstructed Cu2 O planes are close and more negative than that of *OCCOH, indicating the methane formation is more favorable than ethylene on all Cu2 O crystal planes.

The Crystal Plane is not the Key Factor for CO2‐to‐Methane Electrosynthesis on Reconstructed Cu2O Microparticles

AbstractCu2O microparticles with controllable crystal planes and relatively high stability have been recognized as a good platform to understand the mechanism of the electrocatalytic CO2 reduction reaction (CO2RR). Herein, we demonstrate that the in situ generated Cu2O/Cu interface plays a key role in determining the selectivity of methane formation, rather than the initial crystal plane of the reconstructed Cu2O microparticles. Experimental results indicate that the methane evolution is dominated on all three different crystal planes with similar Tafel slopes and long‐term stabilities. Density functional theory (DFT) calculations further reveal that *CO is protonated via a similar bridge configuration at the Cu2O/Cu interface, regardless of the initial crystal planes of Cu2O. The Gibbs free energy changes (ΔG) of *CHO on different reconstructed Cu2O planes are close and more negative than that of *OCCOH, indicating the methane formation is more favorable than ethylene on all Cu2O crystal planes.

Dynamic gate configurations at airports: A network optimization approach

We consider the configuration of airport gates with passenger boarding bridges. The set of aircraft types that can be serviced at a gate depends on the installed boarding bridge(s). For instance, the Airbus A380 can only be serviced at gates equipped with a passenger boarding bridge that is able to access its upper level. Given the dynamic development of both the number of aircraft movements and the fleet mix at airports, the recurring decision problem is to determine for each gate whether and when the passenger boarding bridge configuration should be changed. The objective is to minimize investment and operating costs associated with the bridges as well as penalty costs for aircraft which cannot be processed because gates that are equipped with adequate gate configurations are not available. We propose a mixed-integer model formulation and present its underlying network structure. To solve the problem, we employ a column generation based heuristic approach. We demonstrate the good performance of the heuristic in a computational study and present a detailed discussion of the decisions taken as part of a case study.

A Reconstructed Cu2P2O7 Catalyst for Selective CO2 Electroreduction to Multicarbon Products

AbstractThe electrochemical CO2 reduction reaction (CO2RR) over Cu‐based catalysts shows great potential for converting CO2 into multicarbon (C2+) fuels and chemicals. Herein, we introduce an A2M2O7 structure into a Cu‐based catalyst through a solid‐state reaction synthesis method. The Cu2P2O7 catalyst is electrochemically reduced to metallic Cu with a significant structure evolution from grain aggregates to highly porous structure under CO2RR conditions. The reconstructed Cu2P2O7 catalyst achieves a Faradaic efficiency of 73.6 % for C2+ products at an applied current density of 350 mA cm−2, remarkably higher than the CuO counterparts. The reconstructed Cu2P2O7 catalyst has a high electrochemically active surface area, abundant defects, and low‐coordinated sites. In situ Raman spectroscopy and density functional theory calculations reveal that CO adsorption with bridge and atop configurations is largely improved on Cu with defects and low‐coordinated sites, which decreased the energy barrier of the C−C coupling reaction for C2+ products.

A Reconstructed Cu2P2O7 Catalyst for Selective CO2 Electroreduction to Multicarbon Products

AbstractThe electrochemical CO2 reduction reaction (CO2RR) over Cu‐based catalysts shows great potential for converting CO2 into multicarbon (C2+) fuels and chemicals. Herein, we introduce an A2M2O7 structure into a Cu‐based catalyst through a solid‐state reaction synthesis method. The Cu2P2O7 catalyst is electrochemically reduced to metallic Cu with a significant structure evolution from grain aggregates to highly porous structure under CO2RR conditions. The reconstructed Cu2P2O7 catalyst achieves a Faradaic efficiency of 73.6 % for C2+ products at an applied current density of 350 mA cm−2, remarkably higher than the CuO counterparts. The reconstructed Cu2P2O7 catalyst has a high electrochemically active surface area, abundant defects, and low‐coordinated sites. In situ Raman spectroscopy and density functional theory calculations reveal that CO adsorption with bridge and atop configurations is largely improved on Cu with defects and low‐coordinated sites, which decreased the energy barrier of the C−C coupling reaction for C2+ products.

Comparison of eigenanalysis and Ritz vector approaches for response spectrum analysis of soil-pile-bridge systems

Frequency-based analysis techniques such as response spectrum analysis (RSA) are widely used for designing bridges in seismically active regions. Two well-known analysis procedures that underlie RSA are the solution of the eigenproblem and the approximation of the solution to the eigenproblem (i.e., approximation of eigenvectors and eigenvalues) through use of force-dependent Ritz vectors. While frequency-based methods have achieved widespread adoption in practice, certain simplifications remain common, such as neglecting soil-structure interaction (SSI) due to a fixed-base assumption. In the present study, frequency-based techniques packaged within a research version of a design-oriented computational tool are employed to analyze, assess, and compare results obtained from RSA with use of the eigenanalysis, and separately, Ritz vector approaches. Importantly, for the bridge configurations analyzed, SSI is taken into account. As outcomes, the potential benefits of the Ritz vector approach (as well as modeling strategies) are demonstrated. The study outcomes are intended to aid practicing engineers when the need to account for SSI is recognized as pertinent to a given bridge seismic design application.

Numerical Analysis on the Crosswind Influence Around a Generic Train Moving on Different Bridge Configurations

In this article, a numerical approach is applied to study the flow regimes surround a generic train model travelling on different bridge configurations under the influence of crosswind. The bridge is varies based on the different geometry of the bridge girder. The crosswind flow angle (Ψ) is varied from 0° to 90°. The incompressible flow around the train was resolved by utilizing the Reynolds-averaged Navier-Stokes (RANS) equations combined with the SST k-ω turbulence model. The Reynolds number used, based on the height of the train and the freestream velocity, is 3.7 × 105. In the results, it was found that variations of the crosswind flow angles produced different flow regimes. Two unique flow regimes appear, representing (i) slender body flow behaviour at a smaller range of Ψ (i.e. Ψ ≤ 45°) and (ii) bluff body flow behaviour at a higher range of Ψ (i.e. Ψ ≥ 60°). As the geometries of the bridge girder were varied, the bridge with the wedge girder showed the worst aerodynamic properties with both important aerodynamic loads (i.e. side force and rolling moment), followed by the triangular girder and the rectangular girder. This was due to the flow separation on the windward side and flow structure formation on the leeward side, both of which are majorly influenced by the flow that moved from the top and below of the bridge structures.

Parameterized models for prediction of lifetime bearing demands

A good replacement and maintenance policy for bridge bearings is essential for bridge integrity and functionality. This requires proper estimation of the bearing life expectancy which in turn is dependent on the working condition demands. The lifetime travel and peak displacement demands are highly sensitive to the loading, bridge geometry, and bearing properties. Hence, predicting when bearings should be replaced is difficult. To facilitate the decision making process, this study proposes prediction models for the annual demands of elastomeric bridge bearings. First, random bridge configurations (e.g. elements geometry, deck type, and number of spans) and random loading conditions (e.g. temperature profiles, earthquake records, and traffic loading scenarios) are generated using Monte Carlo simulation combined with Latin hypercube sampling, and the bearing demands are computed. Bearing demand prediction models are then developed via regression analysis and used to create a general fatigue loading protocol. This protocol can be used for testing and rating sample bearings. This would aid in predicting the bearing life expectancy, allowing for better replacement scheduling, and budget estimation. The application of the proposed demand prediction models for generating fatigue loading protocols is demonstrated through a case study.

Analisis Pengaruh Pengaturan Sudut Penyalaan Thyristor Pada Tegangan Eksitasi Terhadap Keluaran Daya Reaktif Generator di PT.PJB PLTU Gresik Unit 3

The process of changing mechanical energy into electrical energy is carried out by a synchronous generator using an excitation system that functions to supply a DC source to the generator field winding. In this study, the excitation system used is a static excitation system that uses a transformer and several thyristors connected in a bridge configuration. The excitation system is then implemented on a generator with a capacity of 200 MVA / 15 kV using the MATLAB Simulink R2017b simulation. By using the above circuit, the thyristor ignition angle setting can be adjusted so that it can adjust the excitation voltage and obtain the appropriate excitation current to maintain the stability of the generator output voltage. The simulation was carried out with variations in generator load and using 2 different types of excitation settings. The first setting is to set the thyristor ignition angle to 30° with t=10 ms, at this setting the generator can maintain a stable V out value with a voltage regulation limit of ±5% and the reactive power that can be generated by the generator is +50 MVAr and - 40 MVAr. When given a constant excitation at an angle of 35° with t=1 ms, the value of Vout exceeds the expected regulatory limit and the resulting reactive power limit is between +60 MVAr and -100 MVAR where the reactive power does not match the load requirements. This can have an impact on the interconnection system, namely when the reactive power of the generator is greater than the load requirement, the generator with a smaller reactive power will absorb reactive power in the interconnection system and can disrupt the stability of the interconnection network.

High-Sensitivity Tunnel Magnetoresistance Sensors Based on Double Indirect and Direct Exchange Coupling Effect* Supported by the Framework Project of SGCC (Grant No. 5700-202058381A-0-0-00), and the National Key Research and Development Program of China (Grant No. 2017YFA0206200).

Detection of ultralow magnetic field requires magnetic sensors with high sensitivity and low noise level, especially for low operating frequency applications. We investigated the transport properties of tunnel magnetoresistance (TMR) sensors based on the double indirect exchange coupling effect. The TMR ratio of about 150% was obtained in the magnetic tunnel junctions and linear response to an in-plane magnetic field was successfully achieved. A high sensitivity of 1.85%/Oe was achieved due to a designed soft pinned sensing layer of CoFeB/NiFe/Ru/IrMn. Furthermore, the voltage output sensitivity and the noise level of 10.7 mV/V/Oe, 10 nT/Hz1/2 at 1 Hz and 3.3 nT/Hz1/2 at 10 Hz were achieved in Full Wheatstone Bridge configuration. This kind of magnetic sensors can be used in the field of smart grid for current detection and sensing.

Experimental and numerical evaluation of the wind load on the 516 Arouca pedestrian suspension bridge

The present work analyses the wind load effects on the 516 Arouca bridge, the world's longest pedestrian suspension bridge in 2020. Computational fluid dynamics (CFD) was used to model a range of wind angles of attack between −8° and +8°. The simulations were performed by solving the steady-state Reynolds averaged Navier-Stokes (RANS) equations with the k-ω shear stress transport (SST) model. The fluid domain size was analysed by comparing the fluid flow behaviour for three different downstream sizes. It was shown that the downstream flow is not greatly affected by the bridge body due to the high opening surfaces of the bridge. Therefore, the most appropriate domain size considering the computation time was selected. The simulations were carried out for different bridge configurations to determine the influence of the upper guard of the tray deck and the suspended cables on the generated loads. The numerical results were validated by performing different wind tunnel tests using a reduced scale prototype. The predicted aerodynamic characteristics showed good agreement with the experimental results.

Reliability appraisal of a system using interval-valued probabilistic dual hesitant fuzzy element

Here, under probabilistic fuzzy environment, we introduce a new technique for reliability appraisal of a system, where the reliability of a component/unit of a system is represented by interval-valued probabilistic dual hesitant fuzzy element (IVPDHFE). In present work, we evaluate the reliability for some complex systems (series configuration, parallel configuration and bridge configuration) using score function and deviation degree which is very useful in decision making, measurement theory, optimization problems and risk analysis. In addition, a numerical example is included to better illustrate the current technique.

Novel post‐tensioned rocking piles for enhancing the seismic resilience of bridges

AbstractThe rocking pile foundation system is a relatively new design concept that can be implemented in bridges to improve their seismic performance. This type of foundation prevents plastic damage at the bridge piers and the foundation system, which are difficult to repair and can lead to collapse. However, lack of adequate energy dissipation in this type of foundation can result in large deck displacements and subsequent catastrophic failures of the bridge. The present study proposes a novel foundation system that integrates post‐tensioned piles with the rocking foundation to simultaneously prevent plastic hinging at the piers and reduce the deck displacements during severe earthquakes. The effectiveness of the proposed foundation system is investigated and compared against the rocking pile and conventional fixed‐base foundation systems using identical bridge configurations. Three‐dimensional finite element models of these bridges were developed to capture possible nonlinear behavior of the bridge as well as soil‐structure interaction effects. Six strong earthquakes with both horizontal components were selected and scaled to the appropriate seismic hazard level with a return period of 2475 years. Static pushover and nonlinear time‐history analyses were then performed to compare the dynamic response of the bridges, including deck displacements, pier and pile inertial forces, and other nonlinear behavior experienced by the structure. The results reveal that by integrating the post‐tensioned piles with the rocking foundation, the deck displacements were reduced to an acceptable limit without subjecting the bridge to any damage. In contrast, the bridge with the fixed base foundation experienced extensive damage at the piers, and the bridge with the rocking foundation experienced substantial deck displacements that ultimately led to unseating, resulting in the collapse of both bridges. It was therefore concluded that the proposed rocking foundation system with post‐tensioned piles is the superior alternative and can be implemented in practice as an attractive solution due to the seismic protection it offers.

A Metal-Via Resistance Based Physically Unclonable Function With Backend Incremental ADC

This paper presents a novel physically unclonable function (PUF) for security authentication. Instead of using the variation of transistors or PDK provided passive components as entropy source, the parasitic resistance created between metal and via layers is used as the static entropy source. A symmetric bridge configuration consisted with the parasitic resistance creates the necessary voltage difference for comparison. An accurate backend incremental analog-to-digital converter (IADC) is implemented to convert the voltage difference into a digitized value. The operation of the IADC allows to achieve a good native instability. Two different types of layout structures are implemented to create the necessary parasitic resistance and compared. Fabricated in a 65nm process, the prototype PUF achieves a native instability and bit error rate of less than 1.45% and 0.12% with 5000 repeated evaluations. The proposed design shows 0.58%/0.1V and 0.53%/10°C bit error across the voltage and temperature range of 0.9 to 1.4V and 0°C to 85°C, respectively without any stabilization techniques. The distance ratio between intra-die and inter-die Hamming Distance is above $305\times $ .

Development and comparison of seismic fragility curves for bridges based on empirical and analytical approaches

The bridge network is an essential part of the transportation infrastructure for mobility. However, bridges are susceptible to seismic activity that produces damages and affects the entire transportation system. Their fragilities have been studied based mostly on analytical models but neglecting empirical data from reports. Few studies compared fragility curves from different development methods, analyzing their similarities, advantages, and limitations for a better risk assessment. This article aims to develop and compare fragility curves for bridges based on empirical and analytical methods. The empirical approach is based on damage reports from the 8.8Mw Maule earthquake, while the analytical approach is based on numerical simulations of the seismic response using ground motion components from stations that recorded the Maule earthquake. The curves are developed for bridges with steel and concrete beams, representative of 57% of Chilean bridges. The comparative Kolmogorov–Smirnov test revealed significant compatibility in moderate and severe damage curves when comparing these approaches, unlike the slight damage curves. The lognormal mean parameter varies between the methods by 36%, 1.5%, and 7.5% for the slight, moderate, and severe damage curves respectively for a particular bridge configuration, showing considerable differences in the slight damage curve between methods.

Effects of axial loads and higher order modes on the seismic response of tall bridge piers

Tall piers are essential components of the earthquake resisting system of bridges. The dynamic behaviour of tall piers differs significantly from that of short piers due to a number of factors, such as their high flexibility and inertia. This paper aims to quantify the influence of axial loads and higher order modes on the seismic response of bridges tall piers and to provide results useful for a more informed design and assessment. For this purpose, an analytical formulation of the dynamic problem, developed and validated in a previous study, is employed to analyse a wide range of piers and bridge configurations. In the first part of the paper, a thorough parametric investigation is carried out to evaluate the influence of axial loads and higher order modes on both the modal properties and the seismic response of tall piers with different geometries and vertical loads. Subsequently, three realistic case studies representing bridges with different geometrical, mechanical and dynamic conditions are analysed and seismic time-history analyses are performed to further investigate the problem. The obtained results provide useful insights into the seismic behaviour of bridges with tall piers, identify the relevant governing parameters and shed light on the accuracy of simplified approaches suggested by the Eurocode 8 to account for the second order effects.

Model and Simulation of GaN-Based Pressure Sensors for High Temperature Applications—Part II: Sensor Design and Simulation

In this part, design and optimization guidelines are presented for an Aluminium Gallium Nitride (AlGaN)/GaN-on-Silicon (Si) High Electron Mobility Transistor (HEMT)-based pressure sensor, for high temperature applications. The work presented here is based on the compact model developed and presented in Part I. The nature of the developed model allows not only the simulation of the sensor behavior for the case of a single HEMT sensor, but also for the case of a Wheatstone bridge configuration. Both configurations are analyzed in terms of temperature compensation, pressure sensitivity, and mechanical failure limits. Based on the presented analysis, we propose an optimized design of a temperature compensated pressure sensor for a pressure operation range between −10 bar and 10 bar, and for temperatures up to 500 °C. The optimization includes the epitaxial design, HEMT placement on the sensor membrane, membrane thickness and geometry, and the optimal biasing points for a maximum sensitivity. Strong temperature compensation can be achieved with less than 0.3 % sensitivity deviation up to 500 °C. The maximum sensitivity of 2.6 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mV</sup> / <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">barV</sub> can be achieved by applying a gate voltage near the pinch-off voltage of the device or as proposed here, by recessing the barrier locally under the gate. In addition, design guidelines for other pressure ranges are given. The approach taken here can be applied to a different epitaxial design with different barrier composition and substrate using the same compact model.