Load Movement Research Articles

Physical Modeling of Ice Cover Deformation Under the Action of a Moving Load at Low Speed

The current paper considers the possibility of physical modeling of ice cover deformation under the action of a moving load at low speed. Using an equation for elastic plate oscillations on the foundation of a hydraulic type, it is shown that similarity of a stress and strain state (SSS) of model ice can be achieved but within the scope of the approaches based on a classical theory of Nogid-Shimansky modeling of ice cover. Taking into account certain complications connected with practical implementation of the above method, the applicability of a reduced-thickness ice model developed at NNSTU is investigated. This model uses the ice thickness that intentionally does not comply with the similarity requirements, all other requirements being satisfied, thus providing incomplete similarity of the model. Some disagreements with a Nogid-Shimansky model connected with that are revealed and their influence on the end result is evaluated. The applicability of a thin ice model is investigated in natural cooled model tanks of classical shape used for modeling of load movement at low speed. The results of the experimental investigation of ice cover deformation under the action of a moving load using a model for the natural thin ice are given. The modification of a wave shape and maximum ice deflection depending on change of a movement speed and loading are investigated. The connection of decrease of a ratio of the deflection basin profile area to the outward ice bending profile in front of a moving load with increase of speed at the start of the movement is demonstrated, which can be an evidence of a sharp growth of energy expenses for ice cover deformation when the interaction between the technical facility and ice cannot be considered as quasistatic. An exact evaluation of such expenditures is crucial when designing the ice-breaking facilities clearing a path through floe ice.

Investigation of Dynamic Behaviour of Four-Leg Hydraulic Support under Double-Impact Load

Hydraulic support is the key support equipment for underground coal mining. The frequent impact load during the mining process easily causes damage to the hinge joints and reduces the stability of the hydraulic support. To improve the stability of the hydraulic support, a rigid-flexible coupling numerical model of the support has been developed. The validity of the model is verified through the static loading test. Next, the impact loading test of the hydraulic support is carried out. The force response characteristics of the hinge joints and the vibration response characteristics of the leg system are discussed when both the canopy and goaf shield bear impact load. The results indicate that when only the canopy bears the impact load, the hinge joint of the front leg is the most sensitive (up to 139.4 %). When the impact load acts both on the canopy and goaf shield, the dynamic response of each hinge joint of the hydraulic support (except the rear leg) reaches the peak value. With the backward movement of the impact load on the goaf shield, the hinge joint force presents different pressure-relief characteristics.

Crack Identification in Cantilever Beam under Moving Load Using Change in Curvature Shapes

Cracks in structural components may ultimately lead to failure of the structure if not identified sufficiently early. This paper presents a crack-identification method based on time-domain. Captured time-domain data are processed into central difference approximation of displacement of each node (point) in the structure. Abnormally high central difference approximation of displacement of a node relative to those of its neighborhood points indicates a crack at that point. A suite of simulation experiments and numerical calculations was conducted to find out whether the proposed identification method could accurately identify the location of a crack in a cantilever beam under moving load compared to the location found by an exact solution method, and the outcomes indicated that it was as able as the analytical method. The proposed method is an FEA analysis, an approach familiar to virtually every engineer. Therefore, the relative amount of time and effort spent on developing the proposed method for a specific application is much less than those spent on developing an analytical method. The saved time and effort should enable more engineering personnel to perform routine checks on structural elements of their interest more simply and frequently.

A Novel Moving Load Integration Method for Real-Time Hybrid Shaking Table Test of High-Speed Maglev Vehicle–Bridge Interaction System

Real-time hybrid shaking table test for high-speed maglev vehicle–bridge interaction (VBI) system is an important method to study dynamic response of the system. Numerical experiments are usually conducted in advance to guarantee the test performed smoothly. This paper presents a novel moving load integration method combined with a truncated bridge model for fast calculation of bridge responses, and presents a framework for performing numerical experiment of a real-time hybrid test of VBI system. A realistic numerical experiment is conducted on a real-time simulator, i.e. xPC Target, integrating three commercial software, i.e. SIMPACK, ANSYS, and MATLAB-Simulink[Formula: see text], to model a real TR08 single-carriage maglev train, a 5-spans bridge and 28 shaking tables, respectively. The driving speed is 400–600[Formula: see text]km/h and the time step size in the test is 1/256[Formula: see text]s. The accuracy of moving load integration method with truncated bridge model is verified, the effects of speed on the dynamic responses of VBI systems are studied, the time delay of shaking tables and compensation algorithm is investigated, and the effects of local nonlinearity of the bridge on system responses are studied. This paper provides a practical method and valuable reference for the real-time hybrid shaking table test of vehicle–bridge coupled systems.

Security Management Policies and Work Accidents

Abstract Research purpose. The aim of the research is to demonstrate the impacts of an absence of organizational policies and strategies in the field of work security on enterprise competitiveness. The movement of loads in the warehouses of industrial and distribution companies is critical in optimizing the times of availability of products to market. This is an activity that, in the field of management, appears to be simple and not very complex, duly framed by national and international laws. However, when poorly managed, it can express significant costs that affect competitiveness and even significantly affect the operational functioning of companies. Knowing that the safety of cargo handling by different equipment presupposes rules and safety policies at different levels, the present study aims to demonstrate the economic impacts based on a real situation in one of the largest handling equipment companies in Portugal. Design / Methodology / Approach. Given the nature and objectives of the study, which seeks to demonstrate that the work security rules and policies compliance or non-compliance has benefits or costs and affects the competitiveness of economic organizations, the work was developed based on three phases. The first phase focused on direct observation of safety practices in operational activities. After this observation, in a second phase, we proceeded to collect and analyze existing data in the company under study, referring to the number of work accidents recorded in the past. In the last phase, we sought to understand and justify the results with the company’s top management. This last phase provided the understanding of the administrators’ view on the subject and the confrontation with the associated impacts, not only at the financial level but at the level of the company’s operation. Findings. This study made it possible to show the impact (associated costs) on organizational performance and that this reality, unfortunately, is not often part of top management’s concern. As a management issue that is often relegated to middle management, this study demonstrates the frequent failure to comply with safety rules due to the pressure of daily activities, the increased number of accidents with the personnel growing in the company, and that this situation can be enhanced through the low degree of control by the enterprise top management over the existing reality. With this concrete study, it was possible to verify the weak relevance of the topic for the company’s administration and the assumption of the difficulty in regularizing the existing situation. The need to review management practices and models in this field became evident. Originality / Value / Practical implications. The relevance of this study made it possible to point out to the top management administration that, in terms of competitiveness. However, the direct costs of the operation are relevant; there are indirect and opportunity costs, such as accidents or unavailability of equipment, which represent costs that can compromise the competitiveness of the company. This study also had the advantage of providing management with evidence of the existing reality in the company, which tends to be undervalued or go unnoticed in the day-to-day company’s current activities. In addition, it should also be noted that a proposal for an improvement plan for the company’s safety was made available.

Dynamic Responses of the Pile-Saturated-Soil System to a Moving Load

According to the basic solution of viscoelastic and saturated soil subjected to moving load on the surface and circular uniform harmonic load on the inside, the integral equation of soil-pile interaction under moving load in frequency domain is established by using Muki virtual pile method, and then the time-space dynamic response characteristics of a single pile in viscoelastic saturated soil to moving load vibration source are analyzed by using inverse Fourier transform. The factors that affect the dynamic response of single pile, such as load speed, length of single pile, saturated soil parameters, vibration source properties, etc., are analyzed and compared with the known results in related literature.

Damage Detection in Truss Bridges under Moving Load Using Time History Response and Members Influence Line Curves

Damage Detection in Truss Bridges under Moving Load Using Time History Response and Members Influence Line Curves

Dynamic Response Analysis of Ballasted Railway Track–Ground System under Train Moving Loads using 3D Finite Element Numerical Modelling

The faster and heavier trains in modern railway traffic are getting popularity in the public transportation authorities of many countries. Such trains cause higher stresses and excessive deformations in the ballasted railway track substructure under train dynamic loadings, which raises the risk of track damage and derailment. It is thus essential to investigate the impact of different influencing factors on the dynamic response of ballasted railway track–ground systems. In this study, a sophisticated three-dimensional finite element model simulating realistic train moving loads is presented and used to investigate the dynamic response of ballasted railway tracks in terms of stress transmission and track deflections under various train–track–ground conditions. The influencing factors considered in this study include the modulus and thicknesses of track substructure layers, the amplitude of train moving loads and the train speed. The outcomes of this study encompass important guidance to railway engineers to assist in finding the best possible scheme for the design of ballasted railway tracks and lifetime maintenance.

Наружный чрескостный остеосинтез при лечении внесуставных переломов костей голени: показания, осложнения, результаты применения

Введение. Выбор оптимальной методики остеосинтеза внесуставных переломов большеберцовой кости продолжает обсуждаться в научной литературе. При открытых переломах, высокоэнергетической травме, повреждениях мягких тканей, особенно в нижней трети голени, нередко используется метод наружной фиксации. Отказ от более широкого его применения объясняется опасениями воспалительных осложнений и неудобствами для больного. Цель исследования: анализ опыта применения наружного чрес­костного остеосинтеза при внесуставных переломах костей голени и обоснование показаний к его использованию. Материалы и методы. Проведен ретроспективный анализ лечения 67 пострадавших с внесуставными переломами большеберцовой кости методом наружного остеосинтеза. Изучены осложнения и результаты лечения. Проанализированы показания к применению, при которых преимущества метода превосходят неудобства, связанные с наличием внешнего модуля. Результаты. Несросшиеся переломы отмечены у 4 (5,9 %) пострадавших, воспалительные осложнения — у 2 (2,9 %), контрактуры голеностопного сустава — у 4 (5,9 %). Хороший результат отмечен у 55 (80,9 %) пострадавших, удовлетворительный — у 8 (11,1 %), неудовлетворительный — у 5 (7,3 %). Пациенты в период лечения сохраняли мобильность, возможность самообслуживания, осуществляли осевую нагрузку и движения в суставах. Анализ показаний к применению наружного остеосинтеза показал, что при некоторых ситуациях (переломы, сопровождающиеся травматическими или трофическими нарушениями со стороны мягких тканей; переломы большеберцовой кости типа С, двойные (тройные) переломы; перелом костей голени как компонент политравмы; внесуставные переломы костей обеих голеней; лечение несросшихся переломов и дефектов костей) преимущества, которые обеспечивает применение внешней фиксации, превышают неудобства, связанные с наличием наружной конструкции. Выводы. Таким образом, наружный чрескостный остеосинтез является эффективным методом лечения внесуставных переломов костей голени. Опасения, связанные с высокой частотой воспалительных осложнений и неудобствами пребывания в аппарате, при использовании современных конструкций являются преувеличенными. Условием эффективного применения метода является использование конструкций, предусматривающих возможность осевой нагрузки и движений в суставах, этапного воздействия на костные фрагменты, строгое соблюдение технологии вмешательства.

Synchronized Assessment of Bridge Structural Damage and Moving Force via Truncated Load Shape Function

Moving load and structural damage assessment has always been a crucial topic in bridge health monitoring, as it helps analyze the daily operating status of bridges and provides fundamental information for bridge safety evaluation. However, most studies and research consider these issues as two separate problems. In practice, unknown moving loads and damage usually coexist and influence the bridge vibration synergically. This paper proposes an innovative synchronized assessment method that determines structural damages and moving forces simultaneously. The method firstly improves the virtual distortion method, which shifts the structural damage into external virtual forces and hence transforms the damage assessment as well as the moving force identification to a multi-force reconstruction problem. Secondly, a truncated load shape function (TLSF) technique is developed to solve the forces in the time domain. As the technique smoothens the pulse function via a limited number of TLSF, the singularity and dimension of the system matrix in the force reconstruction is largely reduced. A continuous beam and a three-dimensional truss bridge are simulated as examples. Case studies show that the method can effectively identify various speeds and numbers of moving loads, as well as different levels of structural damages. The calculation efficiency and robustness to white noise are also impressive.

A survey of physical and occupational therapists' views on lumbar loading movements.

[Purpose] To identify the lumbar loading movements necessary in clinical practice. [Participants and Methods] A questionnaire survey was conducted among physical and occupational therapists in Japan. There were no exclusion criteria regarding the number of years of experience, age, or field of employment. The participants were randomly selected and administered the questionnaire. They were asked to list and rank the lumbar loadings they considered necessary. [Results] A total of 739 respondents participated in the survey. The results of this nationwide survey indicated that the lifting movement of heavy objects in the trunk flexion position was the most common movement (for 354 participants). [Conclusion] The main loading movements of the lumbar spine were reported to be heavy lifting movements (in the trunk flexion position) and trunk rotation movements. As perspectives, we aim to conduct an analytical study of some of lumbar spine loading movements outlined in this study, using a musculoskeletal simulator and electromyography.

Адаптивное управление мостовым краном по скорости перемещения тележки

A method is proposed for automatic control of the speed of an overhead-type crane trolley with direct tracking of the horizontal movement of load in conditions of current uncertainty of load parameters and external disturbances. The purpose of the control is to find the precise positioning of the transported cargo with the damping of its pendulum oscillations and the parrying of external disturbances. The dynamics of an overhead crane when moving a trolley along one axis is described. The proposed control method is based on an adaptive control scheme with an identifier and an implicit reference model using «simplified» adaptability conditions. The stability of a closed control system is proved and the conditions for this are determined. For the current identification of load parameters, the recursive least squares method with a forgetting factor is used. This control method was developed specifically for research and debugging on an experimental layout, so all the parameters of the crane and load were approximated to the layout during calculations. The results of computer simulation the proposed control method with different mass-inertial properties of the load, the length of its suspension and perturbations in the Matlab Simulink software environment are presented. The results showed the high efficiency of the proposed adaptive control system. It ensures accurate movement of the load in a short period of time, prevents the load from swinging during acceleration and braking of the cart, and is also able to fend off external disturbances, for example, the impact of wind. The developed approach can be recommended for any crane installations using a suspended load.

He Relationship between External and Internal Load during Elite Pre-season Friendly Basketball Games.

The aim of this study was to analyse the relationship between External Load (EL) and internal load (IL). Thirteen male basketball players competing at professional level in First Spanish Division (ACB) during six friendly games throughout the 2020/2021 preseason were monitored. The EL variables collected were movement load (ML), movement intensity (MI), box score time (BST), and total duration (TD)] while IL variables monitored were heart rate (HR), respiratory rate (RR), training impulse (TRIMP) and time invested in five HR zones. Very large to almost perfect correlation (r= 0.77-0.91) exists between EL variables except TD. In addition, HR, TRIMP and RR present large to very large correlation (r= 0.55-0.79) with all EL variables except TD. Monitoring HR-based variables would present general information and an estimated prediction of players EL which could allow basketball practitioners to prioritize time invested players internal/external load.

МЕТОД РАСЧЕТА ВЗАИМОДЕЙСТВИЯ МОСТОВОГО ПЕРЕХОДА И СКОРОСТНОГО ЖЕЛЕЗНОДОРОЖНОГО СОСТАВА ПРИ ПЕРЕМЕННОЙ СКОРОСТИ ДВИЖЕНИЯ (к формированию норм для ВСМ)

Boundary elements for rods on an elastic base are proposed for the calculation of bridges on the HSR when moving at a variable speed of an inertial load (railway train). A set of linear and trigonometric functions is used to approximate the displacements at the construction of boundary elements. These elements are used to calculate the vibrations of the rail track outside the bridge and the track on the bridge, together with double-track girder superstructures connected through the interlayers at high-speed movement of arbitrary power and inertial loads. To construct the methodology, the step method proposed earlier by the author of the article for solving problems of unsteady dynamics of structures and the method of calculating structures for the action of mobile force and inertial loads (the method of nodal accelerations) are used.

Predictor-Based Current Limitation Method for a DC Motor-Actuated Upper-Limb Rehabilitation Exoskeleton

Current limitation is crucial to protect DC motors from overheating in overload situations. This consideration is more critical in applications that involve the movement of variable loads, such as exoskeleton applications, where there exists dynamic human-robot interaction. This work presents a software current limitation method based on a continuous DC motor model predictor. By predicting, according to the motor model, the voltages that would make the current match a threshold, the proposed method dynamically saturates the maximum voltages applicable to the motor to maintain the current under the predefined threshold. Using this method, a full-time current limitation can be obtained, but if desired, it also allows current peaks of configurable duration. Only motor parameters need to be known for the application of this algorithm, and it is easily adjustable to different DC motor models. Stand-alone motor tests show an effective limitation of current, achieving up to a 98.04% of maximum current when limited. The method has also been successfully validated in a rehabilitation exoskeleton application with four participants, obtaining an average current of 92.34% of current threshold when limited.

Analytical investigations of vibratory transportation of pool materials on a horizontally stepped surface

The work is devoted to the study of the process of vibratory transportation of bulk cargo on a special surface oscillating in a horizontal plane. The stepped surface allows the authors of the work to use vibrations in the horizontal plane, which is already an energy-saving type of transportation, since it is known that much less power is required to create horizontal vibrations than for inclined or vertical vibrations. This work explores the transportation process comprehensively: the geometric parameters of the steps and the desired parameters of the particles of the transported bulk cargo are determined and justified, all stages of the movement of the simulated cargo are established, all phase angles are mathematically determined. The possible directions of movement of the simulated load are established, depending on the kinematic parameters of vibration displacement, set by the working body. The dependence for the average speed of the movement of the cargo is obtained, the dependence of the speed of the movement of the cargo on its coefficient of friction on the working surface is also determined.

Comparative Study and Analysis of Composite Bridge and Concrete Bridge for Moving Loads

Comparative Study and Analysis of Composite Bridge and Concrete Bridge for Moving Loads

The High-Speed Railway Bridges Under Vehicle Moving Load And Near Fault Seismic Ground Motions – Review.

All-time needs of maintenance of high-speed train system and its infrastructure safety are must all over the world. Nowadays, for the smooth running of HSR trains, most of the country depends on the HSR bridge structures, but there is still a lack of understanding of the behavior of structures under various factors like seismic and high speed moving load effects. To study the dynamic behavior of HSR bridges, it is important to consider the interaction of moving vehicle – Bridge structure – Ground surface showing that the different parameters involved in understanding the response of the structure. The main motivation of this study is to initiate a better understanding of the various parameters effects by those seismic and moving vehicles over the dynamic behavior of the HSR bridges. The effects of forwarding directivity pulses were considered to understand the behavior of HSR bridges against near-fault earthquakes, which can make a substantial impact on the seismic demand capacity of the moving vehicles and structures. The effects of high-speed moving vehicles over the HSR bridges to understanding the parameters involved in the dynamic behavior of the coupled system. This literature review can help the beginners and who initiate the study based on the dynamic behavior of high-speed railway bridges and their components under seismic and moving load effects.

Precast Pre-stressed Deck Slab Units

The prestress concrete technology was developed to make concrete section of smaller size which can effectively resist the bending stresses developed due to heavy loads on it, but in earlier practice, it is now being an application to make long span bridges without any risk of failure. The prestressing technique is now used widely in construction industry for making long span bridges, large span slabs, Railway sleepers, precast pavements etc. As we commonly seen that this prestressing has been done in Girders (Which resists the Transverse Moving loads) of a bridge, act as a beam for deck slab of a bridge, but in recent practice, we have seen that the small block of slabs with ducts, which are further prestress, can also be made which we can be used to resist the loads (or we can say the bending stresses) effectively which will further help us to reduce the number of girders and also it will  lead to reduce the erection problems as they are precast units so it can anchored easily and it will not affect the traffic flow along the construction work.

The effect of the filling degree of the tumbling mill chamber on the bifurcation value of the froude number

The influence of the filling degree of the drum chamber on the bifurcation value of the Froude number in the case of self-excitation of self-oscillations of a two-fraction granular charge with a minimum swing is considered. Such a pulsating mode of the charge movement is used in the self-oscillating grinding process in a tumbling mill. The coarse fraction that simulated the milling bodies consisted of spherical particles of an incoherent granular material with a relative size in the chamber ψb=0.00733. The fine fraction, simulating the material to be ground, was cement with a relative particle size ψm≈0.092∙10-3. The value of the adopted analogue of the kinematic viscosity of the two-fraction granular loading approached the value of 10-3 m2/s. The main variable factor in experimental studies was the filling degree of the drum chamber with loading at rest κb=0.25, 0.35, and 0.45. An additional factor was the degree of filling the gaps between the spherical particles of the coarse fraction with particles of the fine fraction κb=0, 0.25, 0.5, and 1. The method of visual analysis through the transparent end wall of the chamber of transient processes of the loading behavior with a smooth change and fixation of the velocity was applied. The bifurcation minimum value of the rotation speed was recorded, at which the steady-state circulation mode of the load movement turns into a transient pulsation one with a minimum swing. A decrease in the bifurcation values of the Froude number Frb on the cylindrical surface of the chamber with an increase in κb has been established. An increase in the intensity of the decrease in Frb with an increase in κm was revealed. The recorded effect is due to an increase in the connected properties of a two-fraction loading during self-excitation of self-excited oscillations with an increase in κb and κm. The numerical values of the boundaries of the range of bifurcation values of the Froude number for a tumbling mill Frb=0.0484–1.17 have been determined. The obtained Frb range corresponds to the Reynolds value in the range Re=40–197. The maximum Frb value is obtained with coarse grinding. An increase in the likelihood of self-excitation of self-oscillations of the intra-chamber loading with a decrease in the fineness of grinding was revealed