Magnitude Of Load Research Articles

The Role of Internal Phosphorus Loading in the Archipelago Sea Ecological Status

In eutrophic aquatic ecosystems like the Archipelago Sea in the northern Baltic, the role of the sediment as a sink and source of nutrients is especially important. Based on previous research on the Archipelago Sea, it can be concluded that the amount of stored phosphorus that can be released with time from sediments is large, and internal phosphorus recycling processes may thus play a key role in phosphorus fluxes in the coastal zone. The release of nutrients from the sediment has been suggested as an explanation for the fact that a substantial reduction in the external nutrient load does not always result in a corresponding reduction in nutrient concentrations and phytoplankton biomass in recipient waters. However, the magnitude of the actual internal phosphorus load in the Archipelago Sea has not been successfully estimated, or the estimates have been evidently too high. In this study, calculations were performed based on the measured water quality data to estimate how much phosphorus has been transported from the bottom water layer to the surface layers during the biological production season for use in algal production. In other words, the magnitude of the effective internal phosphorus load in the Archipelago Sea was determined. The calculations resulted in a summer internal net phosphorus load in the surface layer of approximately 270 tons over 5 months. The other total phosphorus load in the Archipelago Sea, which mainly (60%) originates from the catchment area, was 575 t/a. A permanent way to mitigate internal loading has been thought to be to reduce external loading. However, a decrease in internal loading occurs with an unknown delay, making it impossible to predict the recovery rate.

Seismic capacity of purely compressed shells based on Airy stress function

Purely compressed shells are often elegant and highly efficient structural forms, but this leanness may create risk if they are subjected to unexpected patterns and magnitudes of loading, such as may arise due to seismic events. In the same way that historic masonry structures were designed to sustain loads by activating purely compressive force paths, a modern metamaterial can be designed for specific purposes following the same logic. Conventional analysis methods for compression-only shells and vaults, often developed for masonry structures, have tended not to model combined vertical and horizontal loads directly. This has created a significant challenge for engineers assessing historic vaults or designing new shells. To address this gap, this paper presents an enhanced method based on membrane equilibrium analysis (MEA) and the static theorem of limit analysis. This approach is the first application of MEA to directly consider vertical and horizontal body forces acting on a compression-only shell through a parametric formulation of an Airy stress function. The method is applied to a case study of a sail vault subjected to vertical and horizontal loads. Moreover, it is demonstrated how this approach can be used to define iso-resistant shapes that offer more sustainable design options while preserving structural capacity.

A new workspace estimation method for heavy-load parallel kinematic machine considering mechanism deformation and motor loading performance

Abstract The estimation of workspace for parallel kinematic machines (PKMs) typically relies on geometric considerations, which is suitable for PKMs operating under light load conditions. However, when subjected to heavy load, PKMs may experience significant deformation in certain postures, potentially compromising their stiffness. Additionally, heavy load conditions can impact motor loading performance, leading to inadequate motor loading in specific postures. Consequently, in addition to geometric constraints, the workspace of PKMs under heavy load is also constrained by mechanism deformation and motor loading performance. This paper aims at developing a new heavy load 6-PSS PKM for multi-degree of freedom forming process. Additionally, it proposes a new method for estimating the workspace, which takes into account both mechanism deformation and motor loading performance. Initially, the geometric workspace of the machine is predicted based on its geometric configuration. Subsequently, the workspace is predicted while considering the effects of mechanism deformation and motor loading performance separately. Finally, the workspace is synthesized by simultaneously accounting for both mechanism deformation and motor loading performance, and a new index of workspace utilization rate is proposed. The results indicate that the synthesized workspace of the machine diminishes as the load magnitude and load arm increase. Specifically, under a heavy load magnitude of 6000 kN and a load arm of 200 mm, the utilization rate of the synthesized workspace is only 9.9% of the geometric workspace.

Dynamic Behaviours of Non-Uniform Rayleigh Beam under Variable-Magnitude Accelerating Masses and Resting on Non-Uniform Bi-parametric Foundation with General Boundary Conditions

This paper investigates the dynamic behaviours of non-uniform Rayleigh beam under variable-magnitude accelerating masses and resting on non-uniform bi-parametric foundation with general boundary conditions. The problem is governed by a fourth-order partia l differential equation, generalised Galerkin’s method use to reduces the fourth-order partial differential equation to sequence second-order ordinary differential equations. Two cases are examined: moving force (neglecting inertia term) and moving mass (considering inertia). In order to solve the moving force problem, the transverse displacement response is obtained by variation of parameters. In order to solve the moving mass problem, the Runge-Kutta of fourth order is used to obtain the approximate solution because the commonly used Struble asymptotic method was unable to simplify the coupled second order ordinary differential equation due to the variability of the load magnitude. Analytical and numerical solutions (Runge-Kutta) are compared for validation of accuracy of the Runge-kutta scheme and found compared favourably. The results are presented in plotted curves, illustrating the effects of shear modulus, rotatory inertia correction factor results show increased shear moduli and rotatory inertia decrease response amplitudes, and critical speed for moving mass is lower than for moving force, leading to earlier resonance. Resonance conditions for the dynamical system are also established.

MODIFIED FUZZY SPEED CONTROLLER OF INDUCTION MOTOR DRIVE USING EXTENDED KALMAN FILTERING

This paper focuses on application of fuzzy logic to enhance induction motor drive performance in case where the measured stator currents are distorted by Gaussian noise. For different load torques, the fixed proportional-integral (PI) speed controller provides an undesired drive performance for both transient and steady-state responses. At first, load torque is computed thanks to extended-Kalman-filtered stator currents. Next, load magnitude is employed to adjust the proportional gain and integral constant time of the fuzzy logic (FL) proportional-integral (PI) speed controller. Simulations of drive using two controllers: FL-PI and fixed PI ones, are carried out in different cases of stator current noise and load variation. Performance evaluations indicate that the FL-PI speed controller reduces the assessed indices and increases robustness to noise and load variation.

Research on the Mechanism of Spinal Stability Under Body Load

In modern society, the prevalence of musculoskeletal disorders and spinal problems has become increasingly concerning, particularly among students and working professionals who regularly carry heavy loads. The growing awareness of health issues related to load carrying has sparked significant research interest in this field. This study investigated the mechanisms of spinal stability under various loading conditions among college students. While backpacks are essential in daily life, their impact on spinal biomechanics and potential injury risks remains a concern. Twenty university students (10 males, 10 females) participated in this research examining the effects of different load magnitudes (0%, 5%, 10%, 20%, and 30% body weight) and carrying durations on spinal stability. Using three-dimensional motion capture, force platform measurements, and surface electromyography, we analyzed participants' postural control and muscle activity during both static stance and dynamic walking conditions at various gradients (0°, 5°, 10°, 20°). Results showed that loads exceeding 20% body weight caused significant alterations in spinal alignment, with forward lean angles increasing by 7-8 degrees at 30% body weight loading. During inclined walking, the combination of slope and load had multiplicative effects, with 30% body weight load at 20° slope resulting in approximately 10-12 degrees more spine forward flexion compared to level ground. Prolonged loading (60 minutes) led to a 30-35% increase in center of pressure sway range, indicating deteriorated postural control. EMG analysis revealed significant muscle fatigue, with erector spinae and multifidus muscles showing primary roles in maintaining spinal stability. Recovery of spinal stability parameters required approximately 30 minutes following heavy load carrying. These findings provide important guidance for establishing evidence-based recommendations for load carrying among college students and emphasize the need for appropriate rest periods and carrying techniques to maintain spinal health.

Deterioration Analysis of Pavement Structures Incorporating Polymer-Modified Asphalt

It is well-established that structural pavement deterioration is largely influenced by the frequency and magnitude of wheel loads. Furthermore, Polymer-Modified Asphalt (PMA) has gained a widespread application in pavement engineering, as the incorporation of polymers enhances the mechanical properties and improves the overall performance of the pavement, particularly with regard to fatigue resistance. In this study, an experimental program was conducted, comprising the Beam Wheel Tracker Fatigue Test (BWTFT), the Indirect Tensile Stiffness Modulus (ITSM) test, and the Indirect Tensile Fatigue Test (ITFT), on three types of asphalt mixtures: one conventional and two polymer-modified asphalt mixtures, under various conditions. Three distinct pavement structure scenarios were assumed/created/built to perform a deterioration analysis. Subsequently, an iterative approach was developed utilizing the average stiffness reduction and stiffness modulus data obtained from the laboratory results. The findings indicated that this method allows for a more accurate simulation of pavement behavior, confirming that strain levels fluctuate throughout the lifespan of the pavement. Furthermore, the study concluded that the use of PMA provides significantly greater benefits when a deterioration analysis is conducted, compared to traditional approaches.

Twisted Tall Building Structural Response Under Lateral Wind-Induced Loads

The design and construction of tall structures have consistently presented unique difficulties as architectural pushes limits continuously. Such building challenges demands from engineers' innovative structural solutions. Among these problems, a particularly notable one is the definition of twisted tall buildings structural system, which demand breakthrough designs to guarantee stability, safety, and functionality. The first twisted building, Turning Torso in Sweden, is a 190m tower designed by Santiago Calatrava with a total rotation of 90 degrees and its construction was completed in 2005.Twisted tall buildings, in contrast to prismatic ones, have non-uniform floor layouts and facades that spiral upwards, resulting in a visually appealing architecture. Nevertheless, this aesthetic innovation brings benefits and drawbacks to all building subsystems. Some authors have studied that the facade spiral decrease the natural illumination, other postulated that this shape reduces the magnitude of wind loads but decreases the lateral stiffness of the building. There are few studies on the structural form and on the response of twisted tall buildings under lateral loads. In this study, the behavior of tall buildings with 120m height under wind-induced loads will be investigated and contrasted between a prismatic model and various twisted ones, increasing the angle of rotation between different stories for each model from 0.5 to 6 degree. The analysis will be performed with procedural generated models in SAP2000 using Python programming language.The wind load will be estimated for the prismatic model according to the Brazilian Code NBR 6123:2023 and will be applied to the columns nodes each floor. The same numerical value of the load will then be applied to the columns of all twisted models and the only variable will be the twist angle between stories. The objective of this study is to evaluate and compare the maximum story drift, horizontal displacement, and the ratio between cross-sectional pre-dimensioning at the bottom level of the columns according to Brazilian Code NBR 6118:2023 and the total floor area.

Effect of platform design of dental implant abutment on loosening and fatigue performance

Under the influence of daily occlusal forces, mechanical complications such as loose connections and fatigue damage are significant factors contributing to dental implant failure. The structural design of implant components is crucial in enhancing the long-term durability of implant systems. This research explores the impact of the platform structure of the abutment on connection loosening and fatigue properties. Four abutments with varying platform structures were designed and produced. The study involved testing and comparing screw loosening behavior before and after loading, as well as evaluating static load strength and fatigue characteristics. Observations were made on abutment surface wear and fatigue sections. A three-dimensional model was utilized to confirm damage location using the finite element method. Results indicate that the abutment’s platform structure enhances anti-loosening performance and static failure load, while reducing fatigue life. Additionally, the position of fatigue fracture in the abutment is influenced by the load magnitude. The finite element analysis (FEA) findings align with the results of the static load tests.

Evaluation of Structural Equation Model Forests' Performance to Identify Omitted Influential Covariates

Model misspecification is typical in applied structural equation modeling (SEM). Traditional specification search methods, such as modification indices, search for misspecifications within the model’s variables but overlook influential variables not initially included and fail to detect interactions. This study evaluates SEM forests as a complementary method to conduct SEM specification search related to omitted influential covariates. The omitted influential paths include unique, mixed, and interaction paths. SEM forests’ performance is evaluated under different factor loading magnitudes, covariate path magnitudes, and sample sizes. Results show SEM forests accurately identify omitted influential covariates without falsely identifying non-influential covariates in large samples (1,000) with strong covariate-latent variable paths ( β = .5).

Limb Underloading in Walking Transmits Less Dynamic Knee Joint Contact Forces after Anterior Cruciate Ligament Reconstruction.

Individuals with anterior cruciate ligament reconstruction (ACLR) often walk with a less dynamic vertical ground reaction force (vGRF), exemplified by a reduced first peak vGRF and elevated midstance vGRF compared to uninjured controls. However, the mechanism by which altered limb loading affects actual tibial plateau contact forces during walking remains unclear. Our purpose was to use musculoskeletal simulation to evaluate the effects of first peak vertical ground reaction force (vGRF) biofeedback on bilateral tibiofemoral contact forces relevant to the development of post-traumatic osteoarthritis (OA) in 20 individuals with ACLR. We hypothesized that reduced first peak vGRF would produce less dynamic tibial plateau contact forces during walking in individuals with ACLR. As the pivotal outcome from this study, and in support of our hypothesis, we found that less dynamic vGRF profiles in individuals with ACLR - observations that have associated in prior studies with more cartilage breakdown serum biomarkers and reduced proteoglycan density - are accompanied by less dynamic tibiofemoral joint contact forces during walking. We conclude that more sustained limb-level loading, a phenotype that associates with worse knee joint health outcomes following ACLR and was prescribed herein using biofeedback, alters the loading profile and magnitude of force applied to tibiofemoral cartilage.

New in assessing the fire resistance of reconstructed reinforced concrete ribbed building panel

The article describes the innovative application of a methodology for assessing the design fire resistance of a reconstructed reinforced concrete ribbed floor panel based on the criterion of the occurrence of a limit state based on loss of load-bearing capacity. In this case, the fire resistance limit of a bending element is established without thermal force destruction based on a set of single quality indicators of structural concrete and reinforcing steel, which simplifies engineering calculations and reduces the cost of expensive experiments. The results of a study of the influence of the geometric dimensions of a reconstructed reinforced concrete ribbed panel, the heating scheme of the design section in fire conditions, the placement of the main and additional reinforcement in the design section, the depth of the cores of the main and additional reinforcement and the degree of its fire protection, the thermal diffusion coefficient of structural concrete, the magnitude of the test load on the panel are presented. and the intensity of stress in the rods of longitudinal working reinforcement to the design fire resistance indicator, which is established based on the loss of load-bearing capacity. The use of the new proposed technical solution makes it possible to determine the design fire resistance of a reconstructed reinforced concrete ribbed panel without natural thermal force effects, simplifies engineering calculations, increases the reliability of statistical quality control of reinforced concrete materials and non-destructive tests, and reduces experimental costs.

Design of heat-resilient housing in hot-arid regions

Extreme heat events in urban areas increasingly challenge the capacity of electrical distribution systems to serve building cooling equipment under peak loads and, when power is interrupted, the thermal response of buildings that can delay the onset of dangerously high indoor temperatures. The design of new buildings and their operation can mitigate the risks of intense heatwaves, but architects and planners face a myriad of choices about what measures to select, and how best to estimate their individual and collective performance. To aid the design and operation of heat-resilient buildings, this paper takes a multidisciplinary approach that is novel in two key aspects. First, it evaluates the individual and aggregated impact of factors associated with architectural and urban design, equipment technologies, and human behavior. Second, its valuation metrics include the magnitude of peak electrical load, appropriate for assessing active measures aimed at reducing peak power, and the time after a power outage for indoor temperatures to reach levels associated with heat stress, an indication of the efficacy of passive (no power) measures. The application of the method in the Middle East North Africa (MENA) region, where growing populations and demand for space cooling make it particularly relevant, relies on knowledge of building codes and local construction practice. Single-factor testing shows that pre-cooling produces the largest reduction in peak electrical load during a simulated four-day heatwave, followed by building adjacency, maximum temperature set point and equipment loads. A combination of all considered factors reduces peak power by 70% and shifts the reduced peak to a later hour. In response to a power outage, the incorporation of architectural factors (roof, wall and window thermal resistance above code minima, increased thermal mass, reduced glazing solar heat gain coefficient and window shading) reduces the time above a Heat Index of 28 °C (caution) in a week-long test period in which the power failure occurs at hour 40 from 119 to 53 h. The presented methodology applies broadly to other building types and to regions affected by very hot weather.

Numerical study on dynamic response characteristics of proton exchange membrane water electrolyzer under transient loading

Under dynamic operating conditions, the proton exchange membrane water electrolyzers are prone to voltage overshoot, resulting in fluctuations under transient operation. In this paper, a three-dimensional, two-phase, non-isothermal model is developed to investigate the role of various factors on the dynamic response characteristics of electrolyzers. The results demonstrate that the overshoot phenomenon can be significantly mitigated by using a linear loading strategy and a multi-step loading strategy compared to a step loading strategy. Meanwhile, the effect of the flow field structure was examined, revealing that single-serpentine flow field exhibited excellent dynamic response performance. Additionally, calculated through multiple evaluation methods, it was found that the effect of loading magnitude was significantly greater than that of the other factors, including temperature, flow field structure and anode porous transport layer porosity. Finally, under combined variable load conditions, research revealed that whereas single-serpentine flow field shown benefits regarding dynamic response and energy dissipation.

Loosening Phenomenon on Thin Plates Bolted Joint due to Offset Load

In this study, the new loosening behavior was discovered and investigated when offset loads were repeatedly applied to both ends of a bolted joint initially tightened to a thin plate made of high-tensile steel. In the experiments, the impact of offset distance on reduction of clamp force was investigated through multiple applications of symmetric offset axial load to the bolted joint assembly. The experimental results showed that even a slight offset load reduced the clamp force, and the larger the offset distance, the greater the reduction of the clamp force. It was also found that the decrease in clamp force depends not on the number of times the offset load is applied but on the magnitude of the offset load. Until now even if the thin plate bolted joint was subjected to an offset load, as long the plates do not deform significantly due to plastic deformation, it has been generally recognized that the clamp force is not reduced. This loosening phenomenon is new and its mechanism has not been elucidated yet. In order to clarify the mechanism that may lower the clamp force, this study conducted FE analysis using a simplified model of a bolted joint. In the FE model, the bolt and nut are considered as a single unit and the effect of slippage between the thread surfaces and the effect of plastic deformation is ignored by using elastic analysis. The results of the FE analysis showed that the main factor causing the reduction in clamp force was slippage between the thin plates to be joined, which was caused by offset load, and that the slippage didn't return to the original position resulting in the reduction in clamp force.

Performance evaluation of innovative composite wall system under extreme loads

ABSTRACT Current reports on accidents in urban areas reveal the devastation of boundary walls and the consequent risks to human lives and property damage. The present study proposes to mitigate such risks through the development and application of a robust and shock-absorbent composite wall system to replace the normal concrete wall system. The paper adopted a comprehensive Finite Element (FE) study using ABAQUS and used the three-dimensional validated model to initially evaluate the selected four different innovative wall systems (Polypropylene fibre-reinforced composite, ECC-Concrete, ECC-Rubberised concrete, and Rubberised concrete-Concrete composite walls) to evaluate their structural performances under lateral impact and blast loads. The most suitable composition of the wall system is identified after comparing the impact resistance, blast resistance, and the energy absorption capacity of all the selected wall structures. Then, an optimisation study on the best-performed composite is conducted to propose the most appropriate geometric parameters for the composite wall. ECC-Rubberised concrete composite wall shows the least deflection at the selected magnitudes of impact loads and blast loads compared to the other walls. The energy absorption capacity of the ECC-Rubberised concrete composite wall is the highest among all the walls including the normal concrete wall.

Population-based in silico modeling of anatomical shape variation of the knee and its impact on joint loading in knee osteoarthritis.

Anatomical knee joint features and osteoarthritis (OA) severity are associated, however confirming causals link to altered knee loading is challenging. This study leverages statistical shape models (SSM) to investigate the relationship between joint shape/alignment and knee loading during gait in knee OA(KOA) patients to understand their contribution to elevated medial knee loading in OA. Musculoskeletal (MSK) models were created for the mean as well as the first eightSSM principal modes of variation (-3,-2,-1, +1, +2, +3 standard deviations for each mode) and used as input to a MSK modeling framework. Using an identical KOA gait pattern (i.e., joint kinematics and ground reaction forces), we ran simulations for each MSK model and evaluated medial compartment loading magnitude and contact distribution at the instant of first and second peak of knee joint loading. An increase in external rotation, posterior tibia translation and a decrease in medial joint space and medial femoral condylar size predisposed the medial compartment knee joint to overloading during gait. This was coupled with an anterior and medial shift in contact location with increasing external rotated tibial position and increasing posterior tibial translation with respect to the femur. Next, results also highlighted a posterior shift of the medial compartment loading location with decreasing medial joint space. This study provides important population-based insights on how knee shape and alignment predispose individuals with KOA to elevated medial compartmental knee loading. This information can be crucial in assessing the risk for medial KOA development and progression.

An Experimental Study of Wave Impact Loads on an FPSO Bow in 2D Wave-Tank

In harsh environments, an floating production storage and offloading (FPSO) is occasionally damaged by impact loads, such as bow flare slamming and green water. This study conducted an impact load measurement experiment on a model of an FPSO bow in a 2D wave tank. Three types of frequency-focused waves (steep, spilling, and plunging) were generated, and the speed and slope of the waves were measured. Seven wave probes were placed in a row, and the wave elevation was measured to determine the speed and slope of the waves. In addition, the side of the 2D wave tank was photographed with a high-speed camera. The speed and slope of the waves obtained from the wave probe array agreed well with those obtained from the photographs taken using a high-speed camera. In the case of a steep wave, wave runup occurred at the bow before the wave reached the bow of the FPSO, so no impact load was generated, and only hydrostatic pressure was measured. Impact loads were generated in the spilling and plunging waves, and the magnitude of impact loads using the Von Karman’s estimation formula and the impact loads measured in model tests showed similar values.

A novel double-arch piezoelectric energy harvester for capturing railway track vibration energy

This study introduces a novel piezoelectric stack energy harvester with a double-arched frame structure. This design effectively cushions impacts from track vibrations, thereby protecting the fragile piezoelectric stack made of brittle materials. The energy harvesting characteristics of the device are studied in detail through experiments and theoretical simulations. The harvester's output voltage depends on the external resistance and increases with higher resistance. The optimal resistance for the single X-direction piezoelectric stack is 340 kΩ, which can output 0.519 mW of power under a 3Hz frequency and an 8 kN sinusoidal load. The Y-direction piezoelectric stack outputs 0.012 mW, resulting in a total output of 1.050 mW for the entire harvester. The output power of the harvester is positively correlated with the load vibration frequency, increasing rapidly for frequencies below 9Hz. The impact of load magnitude on the harvester's output shows a generally linear increase. In impact experiments, the single X-direction piezoelectric stack successfully lit 54 LEDs under a 5J energy impact, demonstrating the harvester's high power density and potential for practical applications.

Inferring the scrape-off layer heat flux width in a divertor with a low degree of axisymmetry

Plasma facing components (PFCs) in the next generation of tokamak devices will operate in challenging environments, with heat loads predicted to exceed 10 MW/m2. The magnitude of these heat loads is set by the width of the channel, the ‘scrape-off layer’ (SOL), into which heat is exhausted, and can be characterised by an e-folding length scale for the decay of heat flux across the channel. It is expected this channel will narrow as tokamaks move towards reactor relevant conditions. Understanding the processes involved in setting the SOL heat flux width is imperative to be able to predict the heat loads PFCs must handle in future devices. Measurements of the SOL width are performed on the high-field spherical tokamak, ST40, using a newly commissioned infrared thermography system. With its high on-axis toroidal magnetic field (≥1.5 T) ST40 is uniquely positioned to investigate the influence of toroidal field on the heat flux width in spherical tokamaks, whilst also extending measurements of the SOL width in spherical tokamaks to increased poloidal field (≥0.3 T). Due to the divertor on ST40 having a low degree of axisymmetry, it is necessary for a set of radial measurements of the heat flux to be taken across the divertor, made possible using an automated toolchain that fully incorporates its 3D geometry. These radial profiles are combined with the magnetic geometry of the plasma to infer the width of the SOL, with both Eich and double exponential profiles of heat flux observed. A reduction in the heat flux is observed toroidally across part of the divertor, along with increased heat loads observed locally around the edges of the tiles. Future work in characterising the impact of tile misalignment and uncertainties in the reconstructed divertor magnetic geometry is required in order to further understand the observed heat flux patterns, as are additional investigations into the role potentially being played by an inhomogeneous sheath electric field.