bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining stop band locations in periodic waveguides by conventional finite element modal analysis
Authors: Hansen Kristian , Johansen Alexander K , Kragh Oliver
Published: June 2024

The use of metamaterials for the mitigation of structural wave propagation shows relevance in a wide range of engineering solutions. At the present time, the design of such metamaterials is often based on iterative design and numerical optimization around the Wave Finite Element Method. This approach is computationally heavy. In this paper, it is demonstrated how post-processing of mode shape results from conventional finite element modal analysis can identify partial stop bands in periodic waveguides. This provides a foundation for iterative design and efficient numerical optimization of periodic waveguides. When the modal analysis is performed on a symmetric unit periodicity cell, using ‘class-consistent’ boundary conditions, the eigenfrequency-locations coincide with the beginning and end of partial stop bands. Identifying which eigenfrequencies pair up, to indicate a partial stop band, is a matter of determining which modeshapes belong to the same branch in the dispersion diagrams. A novel algorithm is developed and tested, able to pair-wise match modal solutions belonging to the same branch of the dispersion diagrams, only based on mode shape information, available from any commercial finite element code.
Development of a new vibroacoustic superelement for heavy-fluid cavities
Authors: Buron G , Thouverez F , Jézéquel L , Beley A , Thévenon F
Published: June 2024

We propose a Reduced Order Model (ROM) of heavy-fluid cavities with the objective to build a superelement in a finite element substructuring context. We consider the non-symmetric displacement-pressure finite element formulation. While there are numerous fluid-structure ROM in the literature, few are generalized to superelements. Typical vibroacoustic substructuring methods involve modal synthesis using uncoupled rigid-wall fluid modes and in vacuo structure modes. Vibroacoustic domains are composed of a structural domain and a fluid domain coupled on a fluid-structure boundary. Each domain can be modeled by symmetric monophysics formulations. Only the fluid-structure boundary requires a non-symmetric multiphysics formulation. Being defined on a submanifold, this subproblem is typically significantly smaller than the other subproblems. We propose to condense the uncoupled subdomains onto the fluid-structure boundary and use a Petrov-Galerkin procedure to obtain a reduced order representation of this loaded boundary. The captured boundary dynamics is then propagated to each uncoupled subdomain. Galerkin procedures are also applied to the uncoupled subproblems to increase the reduction bases. At the end, a Petrov-Galerkin procedure is applied to the full order model to build the superelement. The proposed superelement generation strategy is used to study an industrial water tank in a seismic analysis context. Results show a significant improvement over typical uncoupled superelements at the same reduction basis size. While the uncoupled superelements cannot describe the dynamics of the model beyond the weakly-coupled sloshing regime, the proposed superelement accurately captures the strongly-coupled dynamics in the studied frequency bandwidth.
Rrecommendations for Full Long-Term Analysis of Long-Span Bridges
Authors: Castellon Dario , Fenerci Aksel , Øiseth Ole A.
Published: June 2024

Investigations of extreme buffeting responses on long-span bridges suggest revisiting the current design guidelines as these might be non-conservative. For such purposes, the full long-term analysis is the most accurate methodology. Despite its well-known advantages, the method is not the standard practice in bridge design, mainly due its high computational demand. Recent studies have contributed to make the analysis feasible by employing enhancing strate-gies such as machine learning and efficient simulation techniques. The results are promising, and the computational effort can be reduced to a fraction of the original formulation. It’s necessary that the more accurate long-term methods are included in the design guidelines for long-span bridges. In the Norwegian Handbook for bridge design, only a simplified methodology is recommended, which exposes a gap between research and engineering practice that must be fulfilled. Therefore, this paper presents a set of recommendations for implementing the full long-term analysis based on our experience with the calculations from the Sulafjord bridge, a 2800m single span suspension bridge currently in design and feasibility stage. The objective is to provide recommendations to back-up the abovementioned regulating effort and contribute to close the gap between academia and engineering practice.
Example of bispectral analysis of a transmission line pylon
Authors: Esposito Marzino M. , Bastin T. , Duchene Y. , Denoël V.
Published: June 2024

It is common practice to tackle buffeting analysis by means of spectral analysis, assuming a Gaussian context. However, natural actions, as wind, or wave loading, might sometimes show important non-Gaussian behaviour. This is known to have an important impact on the extreme values of such random processes. In this context, a non-Gaussian bispectral turbulent wind analysis has been conducted on a transmission line pylon model. The non-Gaussian nature of the wind load is the result of the adoption of a nonlinear polynomial wind model applied to the Gaussian wind turbulent velocity components. Results of a stochastic dynamic analysis are compared with respect to their Gaussian counterpart, as well as to the Eurocode approach based on the equivalent static loads, which was also object of comparison of engineers in the original computation with respect to turbulent wind dynamic analysis. Importance of non-Gaussian nature of wind loading is highlighted, and considerations on why and when it should not be underestimated are discussed.
A frequency-time domain approach for soil-structure interaction involving embedded structures
Authors: Barbosa J , Aukselis A , Goulas E , Meijers SJH
Published: June 2024

The design of structures to seismic excitation in which soil-structure interaction (SSI) is not considered with enough detail can lead to overdesigned solutions and, in the case of large structures, lead to significant increases in the overall budget of the project. For such large structures, spending more effort in modelling SSI to derive less conservative solutions (yet, solutions that satisfy the seismic demand) can be advantageous. In this work, we report on the method recently developed at Royal HaskoningDHV (RHDHV) to assess the seismic response of a large building, which is partly deeply embedded in soil and partly founded on piles. Due to the critical nature of the project, SSI is not just of financial interest, but also a requirement from the relevant authorities.

The method described in this work consists of a substructuring technique, where the structure is decoupled from soil. This enables each part to be analyzed with the most suitable domain: frequency for soil and time for the structure. The two parts are thereafter re-coupled in a time-implicit FEM solver. The division between substructures is made at the edges of the floors and walls in contact with soil (for the embedded parts of the structure) and at the foundation beams for the more superficial parts of the buildings. Piles are included in the part containing soil.

For the soil part (and piles), a frequency-domain FEM strategy is adopted. This limits the analysis to linear elasticity. Nevertheless, the soil properties can be made linearly equivalent based on the non-linear ‘freefield’ response (i.e., without the presence of the building), as specified in some standards, e.g., ASCE-4-16. In order to consider appropriate reflection-free boundaries and radiation of waves, perfectly matched layers (PML’s) are used at the edges of the FEM model. A Python program has been developed for this purpose, and parallel computing was used to take advantage of the multiple cores available at calculation servers.

For the upper structure, an implicit time stepping scheme is used, in which structural non-linearities (e.g., sliding between components) can be modelled. The structural model is created and solved using ABAQUS software. The coupling between the upper structure and soil is done after transforming the soil response to the time-domain. This results in time convolutions at the interaction surfaces, which in turn can lead to an unstable stepping algorithm. Therefore, one must be critical and careful when deciding the time-step to use in the simulation.

In this work, we further present our approach to analyze the stability of the system (without having to solve it in its entirety, which is a time-consuming task), and present a strategy/simplification which showed to improve the convergence of the coupled algorithm.
Dynamical behaviour and Control of a Magnetic structure, composed by a Shape Memory spring driven by a DC motor with limited power supply to harvesting energy
Authors: Ribeiro M A , Balthazar J M , Daum H H , Tusset A M
Published: June 2024

In this work, we explore a non-linear dynamic mathematical model containing Shape Memory Alloy (SMA) and a non-ideal engine for energy production. However, numerical analyzes of the device showed chaotic behavior for a given set of parameters. Thus, we used the classical tools of non-linear dynamics (Lyapunov Maximum Exponent, bifurcation diagrams, phase maps, and Poincaré maps) that corroborated to determine the regions of chaos. However, to produce energy, the chaotic behavior makes the production of unpredictable electric current that compromises the operation of the device. Therefore, we apply two control techniques to suppress the chaotic behavior for a desired periodic orbit. The first is the State-Dependent Riccati Equation (SDRE) which considers the non-linearities of the system and Optimal Linear Feedback Control (OLFC) which employs a linear methodology to control the device. The results were promising due to the trajectory errors between the controllers that show that chaos was suppressed, and the current produced by the system became periodic.
Effects of wind-induced vibrations in tall buildings on human balance and risk of falls
Authors: Rouzegari Keynaz , Shahabpoor Erfan , Heshmati Kaveh
Published: June 2024

The rise in demand for housing in large cities has resulted in the construction of increasingly tall and slender buildings which are susceptible to wind-induced vibrations. Such vibrations may affect human balance and even put vulnerable occupants at risk of falls. Issues such as these are not currently considered in design guidelines, which could result in drastic social and economic consequences. To address this concern, a pilot study was conducted at the University of Bath’s VSimulator facility to experimentally investigate the impact of wind-induced vibrations in tall buildings on human balance. Four young and healthy adults were exposed to synthesised bi-directional ‘wind-induced’ vibrations with a building natural frequency of 0.2-0.5Hz, peak factor of 3.5 and peak acceleration magnitudes of 0, 5 and 10 milli-g, while performing various tasks. Their performance was assessed by a test administrator, and they were also asked to carry out a self-reflection questionnaire to assess their level of motion sickness and general discomfort after each round of testing. Results from the study showed a consistent positive correlation between increasing acceleration magnitude and loss of balance in participants. An increase in effort required to maintain balance was observed, as well as a slight increase in motion sickness and general discomfort at 10 milli-g. It was also found that factors such as fatigue and practice/learning significantly affect the performance of occupants. By extending this study, a ‘risk’ threshold of vibration could be established, contributing to the development of guidelines that enable the design of safer and more suitable tall buildings for individuals susceptible to falls.
Statistics of wind-induced vibrations for a flexible roof
Authors: Rizzo F , Pistol A , Kłaput R , Mansour S , Sabbà M F , La Scala A , Flaga Ł
Published: June 2024

The wind-induced vibration of flexible structures is an important topic in the field of wind engineering in terms of human comfort and safety and of global instability of cable structures. In particular, cable structures used for roofs, for example, cable net and membrane tensile structures, are very sensitive to wind-induced vibrations because the axial force in a cable depends on its geometry. When the cable changes its geometry during the vibrations, it may either lose its tension or the cable tension may exceed the cable’s material strength. The wind-structure interaction on flexible roofs is most frequently investigated through numerical analyses using forces time-histories calculated by aerodynamic tests on rigid models. However, this approach fails to predict the effective dynamic deformation of the roof. This paper discusses results obtained from aeroelastic tests in a wind tunnel on flexible roofs. Signals were divided into slots and the statistics of peaks were estimated and discussed through the cumulative distribution function plot. Quantiles of 79%, 93% and 95% of the wind-induced acceleration were compared with the values provided in literature, codes and standards. The comparison showed that the values of accelerations provided in the literature are underestimated.
Dynamic Wind Loading of the Arnulf-Bridge in Munich
Authors: Katz Casimir
Published: June 2024

A very slender footbridge across the 32 rails of the central main station with a total length of 240 m had been evaluated for aeroeleastic effects. The drag and lift coefficients and the Strouhal number have been evaluated numerically with RANS. To avoid galloping effects, a certain small damping must be reached. It has been decided to measure the real damping before installing a tuned mass damper. The measurements during construction showed a sufficient damping value, but after completing the bridge better measurements showed a significant smaller value, which would trigger galloping effects. As the installation of tuned mass dampers was not only expensive, but also an issue for the interruption of railway services, a nonlinear wind history analysis has been performed, showing that the accelerations of the oscillations remain within the critical limits for a footbridge.
Assessing Seismic Vulnerability of Precast Post-Tensioned Segmental Piers
Authors: Kocakaplan Sedef , Ahmadi Ehsan , Kashani Mohammed M.
Published: June 2024

Precast post-tensioned segmental (PPS) bridge piers mitigate global and local damages of bridge structures through natural hinges. The application of PPS piers has increased recently in Accelerated Bridge Construction (ABC). Therefore, to increase their use in high-seismicity regions, this paper examines seismic vulnerability assessment of post-tensioned segmental bridge piers with Shape Memory Alloy (SMA) bars through a Finite Element (FE) framework. First, to investigate the energy dissipation capacity of the PPS piers with SMA, an extensive parametric study performed on the key design parameters including, (i) number of segments or aspect ratio, (ii) length, area, and post-tensioning of the SMA bars, and (ii) area and post-tensioning of the tendon. The results are also compared with the piers without SMA bars. Furthermore, an equivalent reinforced concrete (RC) pier to one of the PPS piers is also analysed. Incremental dynamic analysis (IDA) is performed, and fragility curves are generated to evaluate seismic performance of the PPS piers with and without SMA bars using a suite of 44 far-fault ground motions. The IDA results show that, slenderizing the PPS piers tends to change failure criterion from the yielding of the post-tensioning tendon to strength loss of the pier. For squat piers, the yielding of the tendon governs the failure of the pier while for very slender PPS piers, the strength of PPS piers drops due to second-order effects at small drift values prior to the yielding of the post-tensioning tendon. Furthermore, the equivalent RC pier reaches slight and medium damage states in lower intensity measures compared to the PPS piers. Finally, IDA results of PPS piers with SMA bars show that their median IDA curves for drift responses are lower than the ones without SMA bars.
Flexural Wave Control Using a Far Field Adaptive Vibration Neutraliser
Authors: Menguzzo A , Casado P M , Mace B R , Brennan M J , Rustighi E
Published: June 2024

The subject of this paper is the control of flexural waves on an infinite beam using a vibration neutraliser located in the far field of a forcing input. The neutraliser analytical model consists of a beam carrying three concentrated masses that can be further simplified to a mass-spring-mass system given the system symmetry. Depending on the input frequency, position and value of the masses, the neutraliser can be tuned either to maximise the power reflection or the power absorption. The bandwidth of attenuation is limited so the neutraliser may become ineffective when the forcing frequency changes. To overcome this limitation, shape memory alloy wires are used to design an adaptive beam neutraliser. The wires, made of a Nitinol alloy, exhibit a change with temperature in the elastic modulus of the material caused by a lattice structure reorganisation. This property allows adaptive tuning for different input frequencies via flexural rigidity variation. A preliminary design of the neutraliser is proposed. Analytical and experimental data are compared to assess the validity of the model.
Design and optimization of seismic metamaterials to mitigate ground vibration
Authors: Kabirian Zohre , Carneiro David , Reumers Pieter , Lombaert Geert , Degrande Geert
Published: June 2024

This paper presents a first step towards developing an optimization method to improve the vibration mitigation performance of seismic metasurfaces. Two alternative objective functions are considered in the optimization problem. First, the vibration at a single receiver due to a harmonic source is minimized. Second, the energy dissipated by the metasurface during harmonic excitation is maximized. The dynamic properties of the resonators are the design variables. Forward modelling relies on a 3D coupled finite element-boundary element method, where the resonators are modeled as single-degree-of-freedom systems on top of square concrete foundations that are positioned on a homogeneous halfspace. A local optimization method with a gradient-based algorithm is used. In both cases, significant vibration reduction is obtained at the target frequency. When the vibration amplitude is minimized, resonators with a mass equal to the maximum allowed mass are obtained, whereas resonators with a lower mass are found when the energy dissipation is maximized. Dynamic soil-structure interaction requires the natural frequency of the resonators to be slightly higher than the excitation frequency. The optimization formulation needs to be further adapted to target vibration reduction over a larger area and in a wider frequency range.
Risk mitigation/performances incrementation of an offshore wind turbine with a flexible monopile foundation by means of a pendulum-tuned mass damper
Authors: Colherinhas G B , Petrini F , de Morais M V G
Published: June 2024

This paper proposes a multi-level system modeling for studying the structural behavior of an Offshore Wind Turbine (OWT) with a flexible monopile foundation considering the Pile-Soil Interaction (PSI). This analysis shows that the structural response is affected by a significant uncertainty due to the randomness of the geometric and mechanical properties of the tower and foundation and by the environmental loads and rotating blades. With a Monte Carlo simulation, the sources of uncertainty of the so-called “environmental” and “exchange” zones are generated for a Performance-Based Wind Engineering (PBWE) design of OWTs. Hence, the structural response, the stresses along the foundation, and the power production are evaluated in probabilistic terms assisting the optimal design process of a Pendulum Tuned Mass Damper (PTMD) used to mitigate the structural vibration of an OWT.
Decentralized H2-Based Semi-Active Control To Suppress Transient Vibration Of Structures
Authors: Panda Jagajyoti , Adarsh S. , Chakraborty Sanjukta
Published: June 2024

This study presents a novel decentralized active control algorithm for vibration mitigation of structures subjected to random seismic excitations. In recent years, the applicability of decentralization technique has gained momentum in the field of control theory to overcome the complexity and computational burden of centralized system. Advancement in instrumentation scheme, i.e., sensors, actuators and computing units in the feedback loop is the reason behind the growing interest of decentralized control concept. In this case, the controller framework is designed through suboptimal H2-based proportional control algorithm. The objective of this optimal strategy is to reduce structural energy and control force simultaneously. Further, the concept of decentralized switched state-feedback control law is incorporated, and the detailed formulations are presented in digital domain for easy implementation. A set of communication channels are considered to exchange the state information between the neighbouring subcontrollers. The performance of the designed control strategy is numerically illustrated for an 8-storey building model with multiple magneto-rheological dampers. Comparative assessment with passive case and standard centralized scheme confirms better adaptiveness of the proposed control scheme.
Analysis of the dynamic properties of urban bridges with different slopes
Authors: Gómez Soberón M C , Cruz Vargas J G , Gómez J M
Published: June 2024

Irregular bridges present more complex behavior than regular systems. A bridge is considered irregular when there are changes in stiffness or resistance in elements of the substructure, the superstructure or both, or when the higher modes have greater participation. Most of the previous studies consider irregular bridges with different height of piers and horizontal and straight superstructure. In this work, bridges with piers of different heights are analysed due to the presence of a longitudinal slope of the deck, which is more common for urban systems. The slopes considered range from 1% to an extreme 6%. With this information, elastic and inelastic models are generated with piers whose length gradually increases to achieve the slope. The bridges have equal-length four spans, simply supported, and three axes of single piers. The superstructure consists of a concrete slab and six AASTHO type beams. Responses of these bridges are compared with a regular model, with columns of equal height and without slope. For each structure, Ruaumoko code was used to create models. Typical vehicle load for Mexico is considered and bridges are located in three characteristic soil zones of Mexico City (firm, transition and soft). Results show that bridges with regular increment of the piers length have minor higher modes participation and a more predictable response.
One-year dynamic monitoring of a steel-concrete composite overpass
Authors: Gentile Carmelo , Pirrò Marco
Published: June 2024

Selected results collected in the continuous dynamic monitoring of a 3-span overpass using MEMS accelerometers are reported in the paper. The investigated structure is a steel-concrete composite bridge with a trapezoidal box girder of variable height and curved cross-beams, so that the overall geometry is rather complex. The overpass has a total length of 108 m and spans of 30 m + 48 m + 30 m. The paper firstly presents the dynamic characteristics of the structure obtained from preliminary ambient vibration tests. Subsequently, the effects of environmental and operational variability during the continuous monitoring are highlighted, with the temperature significantly affecting all natural frequencies. A clear effect of changing environment is detected for torsion modes as well, whereas no remarkable changes of bending mode shapes are observed.
Effects of orientation angle of spectrum-compatible bidirectional ground motions on nonlinear seismic response of bridge piers considering progressive damage process
Authors: Zhou Jian , Igarashi Akira
Published: June 2024

The Orientation Angle (OA) of bi-directional ground motions affects the nonlinear response of structures. In this study, a suite of RotD100 spectrum-compatible bi-directional ground motions is generated, such that OA remains constant regardless of the natural period and is compared with another suite with non-constant OA. Idealized single-column steel bridge piers involving a progressive damage process are utilized to investigate the effect of OA on nonlinear seismic response. Incremental Dynamic Analysis (IDA) is conducted with the two suites of bi-directional ground motions applied to the piers through 360° at an angle increment of 9°. It is shown that the difference in seismic demanding between the two suites of bidirectional ground motions becomes significant as Peak Ground Acceleration (PGA) increases. The seismic demand of bi-directional ground motions with constant OA is severer when the piers are subjected to strong earthquakes (i.e., PGA is high). This sheds light on the importance of a reasonable suite of bi-directional ground motions in designing new bridges or retrofitting old bridges.
Immersed-Boundary Fluid-Structure Interaction of Membranes and Shells
Authors: Lauber Marin , Weymouth Gabriel D. , Limbert Georges
Published: June 2024

This paper presents a general and robust method for the fluid-structure interaction of membranes and shells undergoing large displacement and large added-mass effects by coupling an immersed-boundary method with a shell finite-element model. The immersed boundary method can accurately simulate the fluid velocity and pressure induced by dynamic bodies undergoing large displacements using a computationally efficient pressure projection finite volume solver. The structural solver can be applied to bending and membrane-related problems, making our partitioned solver very general. We use a strongly-coupled algorithm that avoids the expensive computation of the inverse Jacobian within the root-finding iterations by constructing it from input-output pairs of the coupling variables from the previous time steps. Using two examples with large deformations and added mass contributions, we demonstrate that the resulting quasi-Newton scheme is stable, accurate, and computationally efficient.
A Novel Stochastic Methodology for the Generation of Artificial Seismic Accelerograms
Authors: Yanni H. , Fragiadakis M. , Mitseas I. P.
Published: June 2024

Time-history analysis requires the use of suites of accelerograms that represent the input ground motion. A simple and computationally efficient stochastic methodology for the generation of suites of fully non-stationary artificial accelerograms is presented. The proposed methodology ensures that the record suites have a given target spectral mean and variability for the whole period range of interest. The model first produces an ensemble of target spectra with a given mean and variability and then a methodology based on spectral representation techniques is used to obtain the corresponding acceleration time-histories. The proposed approach also ensures that the produced ground motions are fully non-stationary and have different duration. The outcome is a suite of ground motion time-histories whose spectral mean and variability match those obtained from a ground motion model (GMM).
The effect of dynamic soil-structure interaction on the response of periodic box girder bridges
Authors: Reumers Pieter , Lombaert Geert , Degrande Geert
Published: June 2024

This paper investigates the effect of dynamic soil-structure interaction (SSI) on the response of long, multi-span box girder bridges during the passage of high-speed trains. A periodic finite element-boundary element (FE-BE) model is used to compute the bridge receptance. The influence of foundation-soil-foundation interaction on the bridge response is studied.
Resonant Metamaterials for high-frequency vibration mitigation in Nuclear Power Plants
Authors: Kanellopoulos C , Jeremic B , Anastasopoulos I , Stojadinovic B
Published: June 2024

The paper explores the potential effectiveness of horizontally vibrating resonant metamaterials to mitigate high-frequency vibrations of critical equipment/components caused by vertically propagating horizontal shear waves. These components are housed in stiff and strong structures of high importance, such as the reactor vessel inside the reactor building of Nuclear Power Plants (NPPs). High-fidelity 3D Finite Element (FE) models of the reactor building with the resonant metamaterials embedded into the soil on the sides of the NPP reactor building in a strip-like configuration (1 x 6 x 22) are developed in the Real-ESSI Simulator. After describing the FE model, its individual components are verified. The preliminary analysis shows that properly tuned resonant metamaterials (i.e., resonant frequency at 19-20 Hz) with a total vibrating mass of only 4.3% of the NPP reactor building mass, can lead to 20% reduction of the in-structure response spectrum at the centre of the foundation, where the reactor vessel is located, at the critical vibration frequency of the reactor vessel of 20 Hz. The amplification effect of the metamaterials at lower frequencies, stemming from their in-phase vibration with the soil, could be avoided if they are designed as semi-active or active systems that vibrate exclusively at the desired frequency. Finally, it is shown that the effect of metamaterials in this high frequency range is very localized, vanishing rapidly within a distance of one unit cell, indicating that their geometric configuration could be optimized to increase their efficiency.
Seismic soil-structure interaction study of inclusion reinforced foundations with a macro-element
Authors: Shen Yuxiang , Pérez-Herreros Jesús , Cuira Fahd , Semblat Jean-François , Burlon Sébastien
Published: June 2024

The reinforcement technique using rigid inclusions is a practical, cost-effective, and time-saving foundation solution. This technique has already proven successful in supporting structures that are subject to high seismic demands, such as the Rio-Antirrio bridge in Greece. In a performance-based design approach, it is important to consider the dynamic soil-structure interaction phenomenon, which is specially relevant when dealing with soft soils. Direct approaches simulating the whole soil-structure system within the same numerical model are still computationally expensive and the classic modal response spectrum analyses, based on the superposition principle, are not capable of taking into account most of nonlinear mechanisms. The macro-element approach is therefore a promising method, as it allows modelling of non-linear soil-structure interaction mechanisms at the base of the structure without increasing the numerical cost. This approach has shown particularly good performance in the dynamic analysis of shallow and piled foundations. The present paper aims to extend the application of the macro-element approach to foundations on rigid inclusions. To this end, the upper-bound kinematic exterior approach is employed to derive a yield surface corresponding to this type of foundation. Its potential application in the context of non-linear soil-structure interaction studies is also discussed.
Nonlinear dynamics of elastically connected multistable structures
Authors: de Castro C H L , Orlando D , Gonçalves P B
Published: June 2024

Recent decades have witnessed a new interest in the field of structural stability due to the use of multistable systems in several applications including vibration control, energy harvesting, deployable and collapsible structures, micro- and nanocomponents and the development of metamaterials. In many cases, multistable behavior is attained by coupling bistable elements. A basic example of bistable structure is the von Mises truss, which presents two stable equilibrium configurations. In this work, the multistable behavior of a sequence of von Mises trusses connected through flexible elements is studied. This system has several stable and unstable equilibrium configurations resulting from the geometric nonlinearity, which significantly influences its nonlinear oscillations and dynamic stability. To obtain the equilibrium paths, the nondimensional non-linear equilibrium equations are derived and solved by continuation techniques. Hamilton’s principle is then employed to obtain the nonlinear equations of motion around an equilibrium configuration. They are numerically integrated to obtain bifurcation diagrams and basins of attraction, which clarify the effect of load and system parameters on the nonlinear oscillations and instabilities of the coupled trusses, in particular the geometric nonlinearity and connection stiffness. This may help in the development of new engineering applications where multistability is desired.
Application of TRIZ for gantry crane improvement
Authors: Shu Luing Nikalus Swee , Toh Guat Guan , Chau Guan Hin
Published: June 2024

TRIZ methodologies, including tools like engineering system analysis, function analysis, cause and effect chain analysis, physical contradiction identification, separation strategies, and contradiction matrix, are utilized to discover effective and sophisticated solutions for addressing various challenges. By employing a sequence of TRIZ tools, issues related to a gantry crane are resolved, showcasing the effectiveness of TRIZ as an innovative problem-solving approach.
Analysis of influence of blade number on aerodynamic performance and noise of forward centrifugal fan
Authors: Yin Mingning , Ge Rongyu , Li Jiaqi
Published: June 2024

In this paper, the influence of the number of blades on the flow characteristics and aeroacoustics performance of a forward impeller centrifugal fan used in a milling recovery vehicle is studied by numerical simulation. The results show that the total pressure of the forward centrifugal fan increases with the increase of the number of blades. When the number of blades is 18, the vortex loss caused by boundary layer separation in the impeller is relatively low. Under the design flow and small flow conditions, the total pressure efficiency of the fan first increases and then decreases with the increase of the number of blades. The noise analysis shows that the cochlear tongue and the surface of impeller runner near the volute outlet are the main sources of fan noise. The far field noise characteristics of the fan with 16 blades are better than those of the prototype fan. The discrete noise at the fundamental frequency of monitoring point B and monitoring point D is 6.25dB and 1.2dB lower than that of the original fan, respectively. The research results have a good guiding significance for the design and optimization of forward centrifugal fan.
Throughflow inverse design of a transonic fan stage based on CFD method
Authors: Li Jinguang , Wu Hu
Published: June 2024

In this paper, a throughflow method based on Computational Fluid Dynamics (CFD), which has emerged as a focal point in the field of turbomachinery design, is developed to be universally applied across the entire speed range. For the inverse problem, the distribution of circulation is specified along streamlines. To simulate the viscous dissipation effects, isentropic efficiency is manually input into the program. The results of a subsonic ideal rotor demonstrate the correctness of the inviscid module. To showcase the design capability to design transonic axial-flow turbomachinery, a fan stage featuring a total pressure ratio of 1.59 and a tip relative Mach number of 1.35 is designed. The results indicate that the performance parameters exhibit an error of less than 0.1%, effectively providing information regarding the airflow angle along the spanwise direction of blade rows.
Structural, Morphological, and Optical Properties of as Deposited and Annealed SnO2 thin film using Thermal Evaporation Technique
Authors: Kakade S. B. , Thorat S. M. , Holkar R. R. , Supekar S. H. , Kale R. D. , Kalange A. E.
Published: June 2024

The morphological modification of thin film structures has been a focus of metal oxide semiconductor-based sensor research in recent years. Tin oxide is well known for being one of the most essential and researched materials for manufacturing semiconductor gas sensors. In the present work, thermal evaporation technique is used to deposit pure semiconductor tin oxide (SnO2) films on a glass substrate. The as-deposited thin films of SnO2 were annealed for 60 min, 120 min, and 180 min at 450 °C. The structural, morphological, and optical properties of material were investigated by using XRD, FESEM, and UV-Visible techniques as a function of annealing temperature.
Enhancement of radiation shielding properties in BaTiO3 added with Bi2O3 at the energy range of 356keV -1333keV
Authors: Nodagala Ramakumar , Ponnada Tejeswara Rao
Published: June 2024

The investigation on the radiation shielding properties of BaTiO3-xBi2O3 with (x=0, 2, 4, 6, 8 %) ceramic samples has been discussed in this paper. This study targeted especially on the radiation shielding properties such as tenth value layer (TVL) and effective electron density (Neff) by including density of sample as one of the parameters. The prepared ceramic samples radiation shielding properties were quantified with help of radioactive sources Ba133, Na22, Cs137, and Co60 at the energies 356keV, 511keV, 1173keV, 1275keV and 1333keV. The obtained experimental values compared with theoretical values by using Phy-X/PSD software. Obtained results revealed that, attenuation abilities improved due to addition of Bi2O3 at different concentration to BaTiO3 causes the rise in density of ceramic samples from 5.483 to 5.498g/cm3. S1 sample has maximum TVL value found at 10.098cm and sample S4 noticed with lowest value 9.842cm at 1333keV. The maximum Neff value recorded as 2.72 at 1333keV for sample S4 which indicating promising radiation shielding abilities.
Investigating Ion Conduction Mechanism and Dielectric Characteristics of Sodium-Based PEO + PVDF-HFP Solid Polymer Electrolyte Membranes
Authors: Ravi Varma I S , Kumar Ganta Kiran , Ramana Jeedi Venkata , Ramesh S.
Published: June 2024

This paper focuses on the preparation, characterization and dielectric studies of the flexible and free-standing solid polymer electrolyte membranes based on PEO + PVDF-HFP complexed with NaPF6 by the solution casting technique. The X-ray diffraction, Differential scanning calorimetry techniques were employed to analyse the structural properties and melting temperatures of the prepared solid polymer electrolyte membranes. In this study, we have explored the impact of polymer blending. The weight percentages of PEO and PVDF-HFP were systematically varied, while keeping the NaPF6 weight percentage constant. The impedance spectra of the prepared solid polymer electrolyte membranes are recorded using the N4L-PSM1735 Impedance Analysis Interface across a frequency range spanning from 1 Hz to 30 MHz. The obtained impedance spectroscopy data facilitated the determination of bulk resistance (R

b
) and enabled an in-depth exploration of the dielectric and electrical modulus characteristics of the prepared solid polymer electrolyte membranes. Ionic conductivity values are derived through the analysis of bulk resistance (R

b
) measurements. The most notable ionic conductivity value of 5.418x10−7 S/cm at room temperature was achieved with the solid polymer electrolyte membrane 70wt%PEO+30wt%PVDF-HFP+3wt%NaPF6. In this study, the solid polymer electrolyte membrane comprising 70wt%PEO, 30wt%PVDF-HFP, and 3wt%NaPF6 emerged as the optimum conducting composition.
Pilot fatigue evaluation with the method of weight TOPSIS
Authors: Yang Qingxuan , Li Zhi , Tong Lizhong
Published: June 2024

Fatigue is significant to many aviation accidents, so assessing pilot fatigue is critical to aviation safety. Traditional fatigue risk assessment studies often ignore the impact of difficult flight maneuvers on pilot fatigue. The study sought to develop a fatigue risk indicator system that could be integrated with airline data systems to achieve a more accurate assessment of pilot fatigue. The questionnaire content was determined by literature collection and methods, and 128 civil aviation pilots were surveyed by questionnaire. The influence of pilot scheduling, workload, working environment and other specific indicators on pilot fatigue was evaluated by Weight TOPSIS analysis method. Then the model is used to evaluate pilot fatigue for practical scheduling problems. The study found that lack of rest time, long working hours and red-eye flights were the most common causes of pilot fatigue. In practice, the fatigue evaluation system can be combined with the database information of the airline to help the airline rationally arrange the flight, minimize the fatigue index and ensure the safety.
Study on the layout of light rapid transit station connecting bus line based on GIS network analysis -- Taking Glasgow City as an example
Authors: Fan Xinyi , Liu Chang , Li Yinghua , Ding Ran
Published: June 2024

As the main body of the city’s public passenger transportation system, light rail and conventional buses are effective supplements to improve the passenger transportation network of the rail transit system. Therefore, the coordinated development of rail transit and conventional bus systems has a great effect on expanding the scope of rail passenger flow attraction. Through the network analysis tool of GIS, the service scope of public transport in Glasgow City is calculated, and through the analysis of population density, the areas where the light rapid transit station service is not available and the bus transport needs to be connected to provide service are identified. Then the location and configuration model is used to choose out three key bus stations and two key LRT stations to create connection lines. Finally, this paper studies the shared bicycle delivery point, and the points are set in the area with high population density, so as to solve the problem of “the last kilometer” of residents’ travel. Through the above research on the layout of public transport, it can provide a reference for the development of public transport in Glasgow.
Fusionformer: Exploiting the joint motion synergy with fusion network based on transformer for 3D human pose estimation
Authors: Yu Xinwei
Published: June 2024

This paper proposes a 2D-3D supervised Fusionformer method for current 3D human pose estimation. It introduces self-trajectory module and cross-trajectory module to capture the motion differences and synergy of different joints. In addition, the created Global Local Fusion Block (GLF) combines global spatio-temporal pose features and local joint trajectory features in parallel. Furthermore, to eliminate the impact of poor 2D poses on 3D projection, a pose refinement network is introduced to balance the consistency of the 3D projection. Finally, the proposed method is evaluated on two benchmark datasets: Human3.6M and MPI-INF-3DHP. Compared to Poseformer and MGCN baseline methods, the results show an improvement of 3.0% MPJPE and 2.0% MPJPE on the Human3.6M dataset. By fully exploiting the characteristics of local joint synergy and adaptively fusing them with global pose features, our method demonstrates superior performance in 3D human pose estimation.
Recent advances in smart grid architecture and grid-electric vehicle-charging station interaction
Authors: Zhang Dongning
Published: June 2024

New energy sources, including renewable energy sources such as solar, wind, hydropower, and power storage technologies, are environmentally friendly, renewable, and long-lasting, reducing dependence on finite fossil energy sources and helping to mitigate climate change and reduce environmental pollution. This paper focuses on the interaction between smart grids and electric vehicle (EV) charging. The proliferation of electric vehicles contributes to better utilisation of renewable energy, reduces dependence on fossil fuels, reduces environmental pollution, improves air quality, and promotes sustainable development. Smart grids offer more possibilities and conveniences for electric vehicle charging, enabling more efficient, reliable, and sustainable distribution and management of electricity through the application of critical technological components such as smart metering, distributed energy integration and management technologies, demand response technologies, peak and valley tariff strategies, and intelligent charging station scheduling technologies. This paper further delves into the academic and practical applications of innovative grid-related technologies. It presents a case study of electric cab charging guidance strategies, demonstrating the synergy between electric vehicle charging and the power grid and road network. By optimising charging paths and improving charging efficiency, energy waste is minimised, and the market penetration of EVs is promoted. Continuous exploration and innovation in this field will provide crucial strategic support for using clean energy, reducing environmental pollution, and improving energy efficiency, contributing to constructing a sustainable future mode of transportation.
Wearable strain sensor for motion capture
Authors: Mo Zhenhua
Published: June 2024

Strain sensor is a type of sensor that is used to measure the strain or deformation applied to an object. These sensors are widely used in engineering, scientific and industrial applications to monitor and record the deformation of an object to provide information about the forces applied. Motion Capture is a technology used to capture and record human movements, postures and actions and convert them into digital data. This technology plays a key role in industries such as gaming, movies and robotics. In recent years with the growth of these industries, there has been an increasing demand for lightweight and accurate motion capture devices, which have made wearable strain sensors for motion, capture a popular research area. This review explores wearable strain sensors for motion capture by delving into their classification and the underlying working principles. Furthermore, it will offer comprehensive insights into the primary sensing materials employed in motion capture strain sensors, coupled with a thorough analysis of the structural design aspects. Finally, a reasonable conclusion is achieved: While this type of sensors has gained significant momentum in recent years, several critical shortcomings prevent their practical application and commercialization, which are expected to be overcome soon.
Threshold bounce — occupancy-dependent modulation of the discriminating threshold in silicon detectors
Authors: Basso M.J. , Buchanan E. , Gallop B.J. , John J.J. , Kaplon J. , Keener P.T. , Phillips P.W. , Poley L. , Sawyer C.A. , Sperlich D. , Warren M.
Published: June 2024

The front-end electronics of silicon detectors are typically
designed to ensure optimal noise performance for the expected input
charge. A combination of preamplifiers and shaper circuits result in
a nontrivial response of the front-end to injected charge, and the
magnitude of the response may be sizeable in readout windows
subsequent to that in which the charge was initially injected. The
modulation of the discriminator threshold due to the superposition
of the front-end response across multiple readout windows is coined
“threshold bounce”.

In this paper, we report a measurement of threshold bounce using
silicon modules built for the Phase-II Upgrade of the ATLAS detector
at the Large Hadron Collider. These modules utilize ATLAS Binary
Chips for their hit readout. The measurement was performed using a
micro-focused 15 keV photon beam
at the Diamond Light Source synchrotron. The effect of the choice of
photon flux and discriminator threshold on the magnitude of the
threshold bounce is studied. A Monte Carlo simulation which accounts
for the front-end behaviour of the silicon modules is developed, and
its predicted hit efficiency is found to be in good agreement with
the measured hit efficiency.