Loading Configurations Research Articles

Finite Element Model Updating of RC Bridge Structure with Static Load Testing: A Case Study of Vietnamese ThiThac Bridge in Coastal and Marine Environment.

Diagnostic load testing refers to the use of the measured historical responses of the structure in the field data to better understand its dynamic and static structural behaviours. It is important and necessary to predict the health state, load capacity, and aging of the structure by updating the finite element (FE) model, which can give useful information to aid the design of retrofits and the maintenance of the existing bridge in the future. The paper presents an update of the full-scale FE model for the reinforced concrete (RC) bridge structure over the seawater river based on the experimental strains under the static load testing in which the representative FE model of the actual structure is determined from the optimisation procedures. The optimisation variables are applied, including the cross-sectional properties and concrete material calibrated through the genetic algorithm (GA) optimisation in the MATLAB software, which interfaces with the FE modelling in the scripting of the SOFISTIK TEDDY software automatically. The bending moments at the mid-span of the RC girders are determined in the FE modelling to compute stresses, which are compared with the measured stresses through optimisation scenarios with a percentage error of the objective function less than 10%. The measured data of concrete strains are recorded from reusable strain transducers installed on the mid-span girders for every bridge span, which are used to calibrate the bridge model in static load testing. The novelty of the solution is to implement innovative techniques using field data as an improved approach for calibrating automatically the analytical FE model parameters of all RC spans of the bridge until its static behaviours are very similar to those of the actual bridge. The final updated FE modelling is used to apply truck load configurations according to bridge design standards such as the AASHTO specifications, which can predict the load limits of the existing bridge structure more accurately and reliably. These proposed approaches can be applied to large bridges as well as complex structures with supporting FE analysis software and data processing software.

Experimental investigation on screw reinforcement of timber members under compression perpendicular to the grain

This paper investigates the effect of screw reinforcement on the capacity of timber members under compression perpendicular to the grain. The predictions of existing capacity models are compared to the experimental results of 39 timber specimens, distinguished by different load, screw and geometric configurations. Current capacity models assume two failure mechanisms, mainly characterized by their location, i.e. the contact area of the applied load (first mode) or the screw tips (second mode). However, the experimental tests reveal that the second mode never occurs despite the model predicting the occurrence of the second mode in more than half of the tested specimens. Additionally, the experimental tests show the fallacy of existing models in accurately estimating the capacity associated with the second failure mode. Parallely, the model appears to be relatively conservative for the first failure mode.

Numerical modeling of iron-based SMA confined concrete columns under axial compressive loading

This paper presents the results of a Finite Element (FE) model developed to simulate the behavior of confined concrete columns with iron-based shape memory alloys (Fe-SMA) under compressive loading. The performed simulations aimed to accurately demonstrate the combined effect of external shape memory alloy (SMA) reinforcement and internal transverse steel reinforcement under different loading conditions and presented a simplified approach to model external confinement as discrete elements near the surface of the concrete element.The primary objective of this study was to develop a FE model that can be used to predict and replicate the response of actively confined columns using Fe-SMA. The FE model was developed using the results of an experimental study conducted on circular Fe-SMA confined columns under concentric loading. The experimental study evaluated the influence of: 1) the presence of internal reinforcement, and 2) the ratio of external SMA confinement used. The simplifications and approximations considered in the numerical approach to predict the capacity and deformation responses showed to be adequate, and the results obtained were in good agreement with the compressive behavior of the actively SMA confined columns obtained from the experimental work.In addition to the concentric case, eccentric loading simulations are presented in this study to evaluate the combined confinement mechanism in terms of the structural element response to a different loading configuration. The predictions obtained in terms of load-carrying capacity and deformations can be used to expand the research work done using the SMA as a form of active confinement.

Qualification de stérilisateurs à basse température au peroxyde d’hydrogène : vers une meilleure harmonisation des pratiques ?

Comparing performance qualification procedures for low temperature vaporized hydrogen peroxide sterilization. Assessing conformity with draft standard ISO/DIS 22441. Qualification reports from several providers have been compared according to specific criteria: choices of cycles, loads, sterile barrier systems, probes, biological and chemical indicators; checking of packaging integrity and exposure to sterilizing agent. Six out of 8reports based on 4distinct sterilizers have been performed by third-party providers. Routine and process challenge devices are respectively used in 6and 3of these reports. Sizes and masses are never mentioned whereas load configuration is always specified. All reports use at least one biological indicator and 50% of them use one chemical indicator at a minimum. Most frequent wrapping materials are Ultra® and Tyvek® bags (respectively 50% and 37.5% of reports). Each qualification monitors per process pression and temperature, and 37.5% of them also quantify hydrogen peroxide concentration. Packaging integrity and environmental exposure are checked in respectively 50% and 12.5% of all reports. All reports have received providers approval. Qualification procedure is based on steam sterilization NF EN 14937standard, which seems unsuitable for low temperature process. The lack of autonomy, the heterogeneity of loads and measurement choices reveal a low harmonization of practices. New standard should dispel the doubts about this heterogeneity.

Nonlinear dynamic stability analysis of axial impact loaded structures via the nonlocal strain gradient theory

In engineering applications, there has been an overwhelming tendency towards portability, miniaturization, and integration in recent years. To link the intrinsic size dependency feature of the small-scale structure with its structural stability, the nonlocal strain gradient theory, which captures the size effect in a more general size-dependent continuum-based model, is introduced to explore the nonlinear dynamic stability behaviour of nanoplates. Four types of axial impact loading configurations, namely, sinusoidal, exponential, rectangular, and damping, are considered. Some practical factors, such as Winkler-Pasternak elastic foundation and damping, are taken into account in the analysis. The equations of motion for the size-dependent initially imperfect plate are derived in the framework of the first-order shear deformation plate theory in conjunction with the Von Kármán nonlinear terms. Then the Airy stress function corresponding to simply supported nanoplate is introduced; then, by applying the Galerkin method, the obtained differential equations are addressed by the fourth-order Runge-Kutta algorithm. Subsequently, the specific value of the critical dynamic buckling load is determined by the Volmir criterion. Organic solar cells (OSCs), a type of emerging solar-to-electrical energy conversion nanodevice, are used as an illustrative example within the existing framework. The effects of size dependency in conjunction with the pulse load configuration, the initial imperfection, the elastic foundation, as well as the damping ratio on the nonlinear dynamic buckling behaviour of the OSC are thoroughly investigated.

Drayage routing with heterogeneous fleet, compatibility constraints, and truck load configurations

This paper addresses drayage routing problems with heterogeneous fleets, compatibility constraints, and truck load configurations. In these problems, containers can be of any size and cargo category. In addition, compatibility and load configuration constraints define which and how many containers can be transported by each truck. We propose a state transition logic to model these constraints. Based on this logic, we develop two mixed-integer programming models for this family of problems. The first model is a compact formulation that can be input into a black-box solver. The second model combines partial routes in a space–time network and is solved with a tailored branch-and-cut approach. To analyze the efficiency of the proposed models, we conduct extensive computational tests on instances with different numbers of requests, geographical distributions of locations, time-window lengths, and fleet compositions. Moreover, we discuss how our modeling approach can assist decision-making in three different drayage routing applications.

Determination of optimal dimensions of polymer-based rectangular hollow sections based on both adequate-strength and local buckling criteria: Analytical and numerical studies

Most studies have focused on determining optimal dimensions of metal- or composite-based rectangular hollow sections (RHSs) by considering only the design requirement of strength. Different from those, an analytical procedure for the determination of optimal sectional dimensions of polymer-based RHS beams by accounting for both adequate-strength and local buckling for the first time has been presented in the context of this study. Analytical expressions which give the optimal sectional dimensions simultaneously satisfying the adequate-strength and local buckling conditions have been derived for two different loading configurations such as a pure major axis bending and a combined axial compression and major axis bending. The analytical procedure proposed in this study depends on the idea of preventing the polymer-based RHS from buckling prior to its compressive strength. This has been achieved by increasing the critical buckling stress of the RHS up to its compressive strength via optimizing its sectional dimensions. During the optimum design, different elastic and plastic material behaviors of polymers in tension and in compression have been taken into calculations. The results attained analytically have been validated against numerical predictions obtained from linear elastic eigenvalue buckling and postbuckling analyses implemented in Abaqus engineering finite element code. Thus, the analytical procedure reported in this study can be used as a benchmark in identifying the optimal dimensions of RHS members manufactured from polymers. Communicated by Davide Spinello.

Development of Badminton-specific Footwork Training from Traditional Physical Exercise to Novel Intervention Approaches

<strong>Background:</strong> Badminton has been one of the most popularised sports and physical activities around the globe with documented healthy benefits. Training of badminton footwork could enable rapid movement velocity thus improving the athletic performance. This study was aimed to review the development of badminton footwork training and summarise the different exercise training approaches and resistance training. <strong>Methods:</strong> A systematic search of “badminton footwork” and “exercise training” was conducted in the research articles of both English and Chinese languages in order to review the development of badminton sport, footwork classification and definition, traditionally employed exercise training, and resistance training. <strong>Findings and Implication:</strong> A recent popular exercise training intervention, wearable resistance (WR) training, was mainly introduced and discussed as this approach has been successfully employed in the training of other sports. Being a typical acyclic motion on badminton court, the training of badminton footwork shall consider integrating the WR approach with wearable and adjustable loads. The training intervention may attach incremental loads to either the whole body or regional limbs to practice real-competition movements with high-velocity, thus forming motor adaptation. The adaptation from task-specific training may increase footwork efficiency and transfer to match situation. Future WR research should compare different WR loading configurations from acute and longitudinal analysis, thus forming scientific evidence to support selection and design of training scheme for badminton footwork. Findings may provide implications for the selection of approaches and schemes design for badminton-specific footwork training to improve on-court performance and prevent potential injuries.

Flexible Loading Pattern Approach in Overkill Steam Sterilization Based on the Physical Properties of Steam and Thermodynamics of Sterilization.

Because overkill steam sterilization processes in autoclaves are considered critical, they are highly scrutinized, and the use of autoclaves in fixed loading patterns is a common approach to the interpretation of regulatory requirements. Many such regulations are attributed to tradition and a buildup of restrictions that aim to improve the levels of assurance of the process and minimize risk. However, these measures complicate the operation and qualification of autoclaves, becoming cumbersome, time-consuming, and costly. In actuality, overkill sterilization is one of several processes in the pharmaceutical industry that provides the highest levels of sterility assurance. This method provides a minimum reduction of highly durable spore populations of 12 logs, achieving a probability of a nonsterile unit (PNSU) of 10-6 Because these spores are far sturdier than the common microorganisms that can be found in pharmaceutical facilities, overkill sterilization effects significantly lower PNSU values for the latter. The physical properties of steam and the thermodynamics of steam sterilization constitute a predictable and repeatable process that can be monitored and verified. The high assurance level of overkill sterilization, combined with the properties of steam, actualizes a high safety margin that encompasses nearly every load type and load configuration when the cycle is performed under certain basic rules. The aim of this article is to present data that advocate and favor an approach that allows greater freedom and variability in arranging items in an autoclave when running overkill cycles, without the need to qualify each configuration.

Analysis of the effects of simplifications on the state of loads in a centrifugal compressor

This study aims to quantify and assess qualitatively the impact of modeling simplifications used to represent inertial and aerodynamic loads on the stresses and structural deformations of a centrifugal compressor in operation. The research object is the compressor of the high-pressure line of the DGEN 380 bypass turbine engine. Based on the virtual dynamometer WESTT CS/BV, the gas-dynamic parameters at the entrance to the centrifugal compressor and after the stage are determined. These values were used as initial parameters for numerical flow analysis. As part of the numerical strength analyses, a series of several load configurations were carried out: spin only, spin and inlet pressure normally applied on the working surface of the rotor blade, spin and outlet pressure normally applied on the working surface of the rotor blade, and one-way fluid–structure interaction analysis taking into account the aerodynamic loads with and without spinning. Based on the simulations, the level of similarity of a given load configuration with the last analysis, adopted as the reference, was determined. It was observed that in terms of the stress state, the rotational analysis taking into account the pressure on both sides of the blade gives satisfactory results, but the strain values are overestimated. The results obtained and the method of evaluation of compressor results can be used in research in the area of aviation, automotive, and refrigeration industries.

A Review of the Hydraulic Fracturing in Ductile Reservoirs: Theory, Simulation, and Experiment

The bottom-hole pressure of hydraulic fracturing in ductile reservoirs is much higher than that of the hydraulic fracturing simulation, and the fracture toughness inferred from the field data is 1–3 orders of magnitude higher than that measured in the laboratory. The rock apparent fracture toughness increases with the increase in the confining pressure. Excluding the influence of the fluid viscosity and the fluid lag on the apparent fracture toughness, the fracture process zone (FPZ) at the fracture tip can explain the orders of magnitude of difference in the apparent fracture toughness between the laboratory and the field. The fracture tip is passivated by plastic deformation, forming a wide and short hydraulic fracture. However, the size of the FPZ obtained in the laboratory is in the order of centimeters to decimeters, while an FPZ of 10 m magnitude is speculated in the field. The FPZ size is affected by the rock property, grain size, pore fluid, temperature, loading rate, and loading configuration. It is found that the FPZ has a size effect that tends to disappear when the rock specimen size reaches the scale of meters. However, this cannot fully explain the experience of hydraulic fracturing practice. The hydraulic fracturing behavior is also affected by the relation between the fracture toughness and the fracture length. The fracture behavior of type II and mixed type for the ductile rock is poorly understood. At present, the apparent fracture toughness model and the cohesive zone model (CZM) are the most suitable criteria for the fracture propagation in ductile reservoirs, but they cannot fully characterize the influence of the rock plastic deformation on the hydraulic fracturing. The elastic-plastic constitutive model needs to be used to characterize the stress–strain behavior in the hydraulic fracturing simulation, and the fracture propagation criteria suitable for ductile reservoirs also need to be developed.

Nonlinear Finite Element Analysis of Flexural Laminated Veneer Lumber (LVL) Sengon Slender Beam

Laminated Veneer Lumber (LVL) is one of the engineered wood products consisting of wood veneers that are glued and pressed together. In this study, the behavior of LVL Sengon slender beam is numerically investigated by means of nonlinear finite element analysis (FEA), where only half of the experimental beam was modeled due to symmetry of the load configuration. The LVL Sengon wood material used Hill failure criterion with isotropic hardening rules, and its mechanical properties in both tension and compression are modelled according to its mechanical properties in tension obtained from the clear specimen test. The contact analysis is defined for each contacting and contacted elements. The FEA results well agreed with the experimental results in term of the load-deflection curve and failure mode of the beam. It is found that the lateral support has no effect on the stiffness of the beam. The beam stiffness and ultimate load increase by the increase of beam height-to-width ratio (𝑑/𝑏).

Head responses subjected to frontal translational acceleration loads

It is important to understand the relationship between impact accelerations and head responses to improve the protection of head against impact loads. This study aims to parametrically investigate the effects of different frontal translational acceleration loading configurations on head responses using a finite element head model. A series of translational accelerations defined by loading curve shape, impact duration and peak magnitude is applied to a head model to simulate different head impact accidents. The effects of loading configurations on the brain tissue-level responses, including intracranial pressure (ICP), von Mises stress (σv) and maximum principal strain (εp), were studied, and the correlations between head injury criterion (HIC) and tissue-level predictors were analysed. It is found that the head responses increase with the increase of peak magnitudes and the acceleration loading curve shape has significant influences on head responses. The largest head responses were observed for the equivalent square shape (ESS) acceleration case. Both the σv and εp responses increase with the increase of impact durations; however, the impact durations do not affect the ICP responses. Based on the thresholds for tissue-level injury predictors, it is found that both ICP-induced and εp-induced head injuries may occur whereas the σv-induced head injury is less likely to occur under translational acceleration loading conditions. For translational acceleration loading, good correlation can be found between HIC and the εp responses; however, the HIC show a significant difference with the ICP responses for the head injury prediction. To improve the accuracy of head injury prediction with considering different injury mechanisms, ICP responses should be considered when HIC and εp responses are applied in head injury analyses.

Scheduling Out-of-Coverage Vehicular Communications Using Reinforcement Learning

Performance of vehicle-to-vehicle (V2V) communications depends highly on the employed scheduling approach. While centralized network schedulers offer high V2V communication reliability, their operation is conventionally restricted to areas with full cellular network coverage. In contrast, in out-of-cellular-coverage areas, comparatively inefficient distributed radio resource management is used. To exploit the benefits of the centralized approach for enhancing the reliability of V2V communications on roads lacking cellular coverage, we propose VRLS (Vehicular Reinforcement Learning Scheduler), a centralized scheduler that proactively assigns resources for out-of-coverage V2V communications \textit{before} vehicles leave the cellular network coverage. By training in simulated vehicular environments, VRLS can learn a scheduling policy that is robust and adaptable to environmental changes, thus eliminating the need for targeted (re-)training in complex real-life environments. We evaluate the performance of VRLS under varying mobility, network load, wireless channel, and resource configurations. VRLS outperforms the state-of-the-art distributed scheduling algorithm in zones without cellular network coverage by reducing the packet error rate by half in highly loaded conditions and achieving near-maximum reliability in low-load scenarios.

In vivo quantification of 3D displacement in sacral soft tissues under compression: Relevance of 2D US-based measurements for pressure ulcer risk assessment

Objective2D Ultrasound (US) imaging has been recently investigated as a more accessible alternative to 3D Magnetic Resonance Imaging (MRI) for the estimation of soft issue motion under external mechanical loading. In the context of pressure ulcer prevention, the aim of this pilot MRI study was to design an experiment to characterize the sacral soft tissue motion under a controlled mechanical loading. Such an experiment targeted the estimation of the discrepancy between tissue motion assessed using a 2D imaging modality (echography) versus tissue motion assessed using a (reference) 3D imaging modality (MRI). MethodsOne healthy male volunteer participated in the study. An MRI-compatible custom-made setup was designed and used to load the top region of the sacrum with a 3D-printed copy of the US transducer. Five MR images were collected, one in the unloaded and four in the different loaded configurations (400–1200 [g]). Then, a 3D displacement field for each loading configuration was extracted based on the results of digital volume correlation. Tissue motion was separated into the X, Y, Z directions of the MRI coordinate system and the ratios between the out-of-plane and in-plane components were assessed for each voxel of the selected region of interest. ResultsRatios between the out-of-plane and in-plane displacement components were higher than 0.6 for more than half of the voxels in the region of interest for all load cases and higher than 1 for at least quarter of the voxels when loads of 400–800 [g] were used. ConclusionThe out-of-ultrasound-plane tissue displacement was not negligible, therefore 2D US imaging should be used with caution for the evaluation of the tissue motion in the sacrum region. The 3D US modality should be further investigated for this application.

High efficient low cost gamma-ray radiation sensor based on IoT platform

In the radiation sensing community, it's very important to detect gamma-ray radiation using remote sensing like IoT platforms. In this paper, high efficient low cost gamma-ray radiation sensor is designed to monitor and early detect radioactive materials that are present in the environment, and this is to be achieved based on IoT platform. Such platform provides a safer monitoring technique that helps avoiding the direct exposure to radiation and allows the exploration of inaccessible places. This paper conducts a deep informed study of N-channel (NMOS) and P-channel (PMOS) MOSFETs to be used as a dosimeter and sensor for gamma-ray radiation. The proposed technique herein uses the active load configuration of MOSFETs to detect the output current or the channel on resistance.MOSFET drain current and channel resistance values are changed based on variations of threshold voltage (VT) that are affected directly by the dose of absorbed gamma-ray radiation. For the purpose of sensing the ionizing radiation, the change ratios of output current or channel resistance values; due to threshold voltage shifting, are measured. A complete prototype of the proposed gamma-ray radiation IoT monitoring solution has been built and tested in a real gamma radiation environment over a dose range from 10 Gy up to 40 Gy. The highest current sensitivity of the proposed dosimeter was 0.579 mA/Gy and 0.529 mA/Gy for NMOS and PMOS respectively. The practical results show that the IoT monitoring radiation system is able to efficiently detect the gamma radiation remotely using low cost MOSFET transistors.

Toward Excellence in Photocathode Engineering for Photoelectrochemical CO2 Reduction: Design Rationales and Current Progress

AbstractPhotoelectrochemical CO2 reduction reaction (PEC CO2RR) is a promising technology which offers the possibility of a carbon‐neutral solar fuel production via artificial photosynthesis. The challenging proton‐coupled multielectron transfers with high energy barriers in CO2RR however pose as a huge hindrance to the technology, which demands strict specifications in the design of photocathode materials so as to improve PEC performances. This review underscores effective design strategies and current material progress for the judicious assembly of photocathode materials for CO2RR. The review begins with elucidating the fundamental principles of CO2 reduction process and photocathode electrochemistry. Based on these, the design criteria and trade‐offs in the design of PEC CO2RR photocathodes are highlighted. The various promotive strategies for photocathodes and their underlying rationales such as doping, defect engineering, nanostructuring, cocatalyst loading, passivation, heterojunction formation, and innovative multijunction configurations are further outlined and design propositions in the area are provided. Following that, various photocathode semiconductor materials categorized into photovoltaic (PV) grade (silicon, III–V semiconductors, chalcogenides) and non‐PV grade (metal oxides) materials are summarized and extensively discussed, along with their recent advances. Finally, perspectives on the design of photocathodes for CO2RR and new paradigms in the field are put forward.

A generalised model for direct prediction of stresses in concrete at high temperatures

A novel theoretical model capable of quantifying the stress causing transient thermal strain (TTS) in heated concrete is presented. It is applicable to numerical models and as a design equation for assessment of stress caused by combined actions of loading, heating fluxes and end restraints during heating. Three categories of concrete members are classified: heated then loaded; loaded then heated; heated with full restraint with or without load. The TTS equation is incorporated in a novel thermo-mechanical finite element model developed in ABAQUS. Material models capable of capturing degradation of concrete properties under elevated temperatures have been selected and adapted to include TTS and temperature dependence. The finite element model and stress equation have been successfully validated against experimental results under various loading configurations and boundary conditions. A number of observations were made: (i) stress developed under restraint is lower than under applied preload, but stress relaxation, in part owing to TTS, is higher under preload; (ii) the limit of elastic behaviour is reduced under free thermal expansion compared with restrained samples; (iii) free thermal expansion is critical to the overall stress–strain response and appears to vary with applied stress while significantly increasing at high temperatures.

Operation control, energy management, and power quality enhancement for a cluster of isolated microgrids

Several isolated microgrids (MGs) may exist in remote areas because of the geographical and/or utility investment limitations. The isolated MG has its challenges depending on its configuration, energy sources, and nature of loads resulting in power quality issues. Clustering these MGs based on their relative locations to form several clusters and interconnecting them may provide additional benefits such as improved reliability, stability, and cost-effective operation. This entails the capability of energy sharing between the energy sources through distributive MGs and the power exchange within MGs through designing an effective energy management system (EMS). In this work, a proposed EMS built on the marine predator algorithm (MPA) is presented, with its design based on a hierarchical decentralized strategy for a cluster of interconnected MGs. The criterion of the proposed EMS design encompasses two key steps. First, developing an MG central controller (MGCC) in each MG to optimally handle the use of power with large-scale hybrid distributed energy resources as well as the resolution of power quality issues. Second, the MG operator (MGO) assists in the power exchange among the cluster MGs to surmount any probable unbalance between generations and demand in the cluster's entire coverage area. To enhance the complete MG’s dynamic performance, an adaptive dynamic voltage restorer (ADVR) with a proportional-integral-derivative (PID) controller based on MPA is employed as a supervisory controller. Different cases are studied using the MATLAB/Simulink environment. Finally, two comparative performance assessment of various optimization strategies and with other controller like fractional order PID (FOPID) are presented in order to achieve the effectiveness and robustness of the presented ADVR.

Instrument for in situ study of rolling under normal load and torque.

Instabilities that develop at the contact interface of solid rollers or airless tires while in motion can lead to increased energy losses and reduced service life. This manuscript describes an instrument that can give better insight into the origin of such instabilities by monitoring both local and global roller mechanics. This is done by simultaneously obtaining force and displacement data from sensors as well as optical measurements and local deformation fields across two different planes, extracted from images taken by a high-speed camera. Multiple loading configurations are possible, ranging from static normal loading of the roller to free rolling and rolling with a propulsive or a braking torque. Instrument functions, elements, and design are presented in detail and its capabilities are demonstrated by obtaining measurements such as width of the contact interface under normal loading, strain fields of the roller sidewall and contact interface under normal loading, and the roller's resistance to motion for free and forced rolling.