Load Behavior Research Articles

Studying the mode shape participation factor of wave loads for offshore wind turbine structures

This paper introduces a method for analyzing resonance between Offshore Wind Turbine (OWT) structures and wave loads using Wave Participation Factor ratios (WPFs). Despite temporal fluctuations in WPFs due to wave loads, they prove effective for identifying key modes influencing wave load behavior in both fixed and floating OWT structures. For fixed OWT foundations, nonlinear soil behavior causes some natural frequency variations under wave forces, but they typically remain within a limited range. Lower natural frequency modes show minor WPFs, reducing the risk of resonance with wave loads. Modes with higher natural frequencies have substantial WPFs and are less prone to resonance. However, precautions are needed to avoid rotor-induced wind load resonance. Floating OWT structures have large WPFs in their first six near-rigid body motion modes, while mooring line stiffness leads to substantial variations in these modes. It's crucial to control the first six nonlinear frequencies outside the dominant wave load range. Beyond these six modes, natural frequencies significantly exceed wave load frequencies, reducing resonance concerns. In summary, this study presents an effective method for assessing resonance between OWT structures and loads, providing valuable insights for structural design and operational safety.

Neural digital twins: reconstructing complex medical environments for spatial planning in virtual reality

PurposeSpecialized robotic and surgical tools are increasing the complexity of operating rooms (ORs), requiring elaborate preparation especially when techniques or devices are to be used for the first time. Spatial planning can improve efficiency and identify procedural obstacles ahead of time, but real ORs offer little availability to optimize space utilization. Methods for creating reconstructions of physical setups, i.e., digital twins, are needed to enable immersive spatial planning of such complex environments in virtual reality.MethodsWe present a neural rendering-based method to create immersive digital twins of complex medical environments and devices from casual video capture that enables spatial planning of surgical scenarios. To evaluate our approach we recreate two operating rooms and ten objects through neural reconstruction, then conduct a user study with 21 graduate students carrying out planning tasks in the resulting virtual environment. We analyze task load, presence, perceived utility, plus exploration and interaction behavior compared to low visual complexity versions of the same environments.ResultsResults show significantly increased perceived utility and presence using the neural reconstruction-based environments, combined with higher perceived workload and exploratory behavior. There’s no significant difference in interactivity.ConclusionWe explore the feasibility of using modern reconstruction techniques to create digital twins of complex medical environments and objects. Without requiring expert knowledge or specialized hardware, users can create, explore and interact with objects in virtual environments. Results indicate benefits like high perceived utility while being technically approachable, which may indicate promise of this approach for spatial planning and beyond.

Multiple heating loads participate in the system power regulation control strategy

With the addition of a high proportion of new energy and power electronic equipment, the power system has shown characteristics such as low inertia and significant energy output fluctuation, which has brought great challenges to power/frequency regulation and control of the power system. Therefore, this article uses the inertia characteristics of heat energy on the load side and exerts reasonable start-stop control to play a positive and beneficial role in the power regulation of the power system. Firstly, the room temperature variation process was transformed into a lumped parameter equivalent model. A lumped parameter heat transfer model of a single typical load was built in Simulink, and its dynamic characteristics were analyzed by symbolic calculation. Based on this, a time-domain simulation was carried out to explore the influence of the law of system parameters and external input on the change of system state quantity. Based on time domain simulation, the behavior of the heating load is analyzed. Then, the effects of typical and multiple loads on system power regulation at different outdoor temperatures are studied. It is found that when the average outdoor temperature decreases, the sustainable time of system power upturn will increase, and the sustainable time of downturn will decrease. The power curve of multiple loads simultaneously is more stable, and the adjustment ability is stronger. The reasonable and flexible control method of load switch setting, namely the coherent characteristic load power regulation strategy, realizes the sustainable power optimization of the load to the system in the specified period.

Modeling a Solenoid Driver with Nonlinear Inductive Load Using Circuit Simulation and Magnetic Flux Measurement

This paper describes the procedure for creating a electronic simulation model of a solenoid power electronic driver with a nonlinear inductive load. Furthermore, it discusses the electromagnetic interaction between the driver and the load example electromagnetic valve. The consideration of nonlinear effects in the power electronic components MOSFET and diode is particularly important to distinguish their effects from the nonlinear behaviour of the inductive load.

Centrifuge Modeling of the Monotonic Capacity of Offshore Ring Anchors in Sand

The development of offshore wind technology has become a feasible solution to meet the increasing demands for clean and renewable energy. The United States has a total of 4250GW offshore wind energy potential; however, 65% of it is in deep water zones (Lopez et al., 2022) where wind turbines with fixed foundations typically are economically and technically unfeasible. In those situations, floating turbines supported by subsea anchors are a more competitive solution. Based on previous studies, ring anchors can be more material-efficient than piles and caissons because they require less material. Ring anchors also perform better than drag anchors due to their greater embedment depth. To further understand the behavior of ring anchors in saturated sand, a series of centrifuge load tests were performed at the University of California Davis Center for Geotechnical Modeling (CGM) at an acceleration of 70g. This test series investigated the effect of the anchor embedment depth and loading angle on the monotonic loading behavior. The ring anchor models were embedded in dense saturated sand, and then connected to an actuator using taut steel wire ropes. Sensors were used to measure the line tension, displacement, and inclination. The results indicate that the ring anchors mobilize greater capacities as their embedment depth is increased and when they are loaded at angles close to the horizontal direction, while vertical loading leads to the smallest capacity. The anchor displacement during the tests deviated slightly from the loading direction, showing a horizontal deviation at the earlier stages of the tests and a vertical one after the peak load. Furthermore, soil disturbance induced by the anchor installation was found to have a strong effect on the vertical capacity of the ring anchors. Overall, this study provides valuable information regarding the monotonic loading behavior of ring anchors which can aid in their future field deployment.

Building a model of the abrasion grinding mechanism in a tumbling mill based on data visualization

The object of this study is the grinding process in a tumbling mill when the mechanism of destruction by abrasion is implemented, which is caused by the mechanism of shear loading. The abrasive effect due to the impulse interaction during the mutual chaotic movement of granular particles in the shear layer of loading, characterized by the granular temperature, is taken into account. The task solved was determining the parameters of the shear interaction, which is caused by the difficulties of modeling and complexity of the hardware analysis of behavior of the internal loading in the mill. A mathematical model was built based on data visualization for the abrasion grinding mechanism. The power of the shear interaction forces was taken as an analog of the grinding performance. The initial shear characteristic was considered to be the average value of the shear velocity gradient in the central averaged normal section of the shear layer. The impact on productivity of the granular temperature and mass fraction of the shear layer and loading turnover was taken into account. The effect of rotation speed on performance was evaluated by experimental modeling at a chamber filling degree of 0.45 and a relative particle size of 0.0104. The maximum value of the energy and productivity of grinding by abrasion was established at the relative speed of rotation ψω=0.55–0.6. The results have made it possible to establish a rational speed when grinding by abrasion, ψω=0.5–0.6. This value is smaller in comparison with grinding by crushing ψω=0.55–0.65 and breaking ψω=0.75–0.9. The established effect is explained by the detected activation of the chaotic quasi-thermodynamic movement of particles of the shear layer at slow rotation. The model built makes it possible to predict rational technological parameters of the energy-saving process of fine grinding in a tumbling mill by abrasion

Cyclic loading behavior of novel internally stiffened double steel plate shear wall

In this paper, a novel Internally Stiffened Double Steel Plate Shear Wall (ISD-SPSW) is proposed based on the concept of improving the buckling mode of steel plates and enhancing the lateral resistance of steel plate shear wall (SPSW). The ISD-SPSW consists of double outer steel plates on both sides, inner stiffened rib plates, and boundary members. The seismic behavior of ISD-SPSW was investigated through tests and numerical simulations. Five ISD-SPSW specimens with different heights of the wall, thickness of the outer steel plate and boundary member, and different numbers of internally stiffened steel plates were investigated in cyclic loading tests. The performance indexes such as hysteresis curves, strain curves, and skeleton curves of ISD-SPSW were obtained. The finite element model of ISD-SPSW was established and verified by the test results. The test results reveal two distinct failure modes for the ISD-SPSW. The first mode involves the failure of diagonal tension bands, which is a result of local buckling in the outer steel plates. The second mode is characterized by the overall instability of the shear wall, resulting from the out-of-plane deformation of the boundary members. Lowering the height of the wall can markedly improve the load-bearing capacity and out-of-plane stability of ISD-SPSW. Increasing the thickness of the outer steel plate can improve the ultimate load-bearing capacity, but has adverse effect on the boundary members. Reducing the thickness of the boundary member can significantly reduce the load-bearing capacity and seismic performance. Reducing the number of inner stiffened rib plates decreases the shear load-bearing capacity and energy dissipation capacity. The ductility coefficient of most specimens is greater than 3.0, indicating that the ISD-SPSW has good ductility. In addition, the results of the established finite element model are in good agreement with the test results, which verifies the accuracy of the model.

Deploying WordPress in Docker: A Scalable and Secure Solution

Deploying WordPress in Docker offers a flexible and efficient solution for managing web applications. This approach encapsulates WordPress and its dependencies within containers, facilitating easy deployment across various environments. Embracing Docker for WordPress deployment introduces a dynamic and efficient approach to elevate web application management and fortify security. WordPress in docker provides dedicated focus on load balancing. In our study, we implemented various load balancing algorithms and evaluated the performance and behavior in loading balancing the request.

Mechanical responses and deformation mechanisms in the AZ31 magnesium alloy during cyclic bending

Cyclic loading behavior, such as cyclic bending, is unavoidably involved in various forming processes and the service of end products. Understanding the mechanical behavior of magnesium (Mg) alloys under cyclic bending is essential for promoting their application. Despite existing research, the microscopic mechanisms at play during cyclic bending, specifically the slip and twinning-de-twinning (TDT), warrant further exploration, which is the innovative focus of our study. To address this need, cyclic bending tests were performed on an extruded AZ31 Mg plate with the in-situ digital-image-correlation (DIC) technology. And the texture evolution was determined through electro backscattered diffraction (EBSD) measurements. Concurrently, the crystal-plasticity-based bending-specific approach, EVPSC-BEND, incorporating the TDT scheme, is utilized to interpret the mechanisms involved in cyclic bending. The impact at the macroscopic level is manifested in asymmetric cyclic moment-curvature curves, stress-strain distribution, and shifting of the neutral layer. The developed textures at different regions of the beam and the twin volume fraction distribution further directly illustrate twinning-de-twinning behaviors. Particularly, the upper and lower halves of the beam experience very distinct cyclic behaviors simultaneously. The upper half experiences a twinning, detwinning, and twinning cycle, while the lower half experiences a twin-free, twinning, and detwinning cycle. Additionally, through modeling the cyclic bending with different initial textures, the strong texture dependence has been revealed. The behaviors of magnesium alloy beam under cyclic bending discovered in this work can shed light on the application of Mg alloys, such as forming processes and service of end product.

Design of tie-columns in confined masonry structures for lateral loads

Confined masonry (CM) buildings are generally designed with an expectation that masonry walls withstand all possible loads imparted on the buildings. The reinforced concrete (RC) confining members, also known as tie-members, have the sole purpose of constraining the masonry and avoiding its outward spread during lateral earthquake loading. Reliable design rules for tie-columns are scarce in design codes of CM structures, often resulting in the nominal design of tie-elements without considering the influence of all the important parameters related to the material and geometric properties of CM wall. This often results in the construction of weaker tie-members, especially the tie-columns, that can lead to their direct failure and the failure of the entire wall during earthquakes. To address this issue, a methodology was developed for assessing the design shear forces for the tie-columns as well as masonry subjected to lateral loading by utilizing the past observations from systematic experimental and numerical studies. The efficacy of this methodology was evaluated in the present experimental study conducted on CM walls with varying aspect ratios. The test results demonstrated that the proposed methodology can result in a significant improvement in the lateral load behavior of CM walls, by delaying the shear failure of tie-columns without jeopardizing other functional requirements.

Compressive loading and response time behavior of concrete containing refractory brick coarse aggregates

This research aimed to determine compressive stress and response time of using refractory brick waste as alternative natural coarse aggregates combined with blended cement in manufacturing sustainable concrete. The experiment was conducted by adding 15–50% aggregates volume of refractory bricks coarse aggregate (RBCA) to concrete mix in order to determine the suitability as coarse aggregates. The results showed that the slump values for the combination of standard concrete (SC) with all RBCA satisfied the design value of ± 20 cm and this showed easy handling and workability of the fresh concrete produced. Moreover, the peak stress and toughness were reduced as RBCA increased from 15 to 50% at both w/c of 0.52 and 0.49. The relationship between compressive stress and response time also showed that the travel time at the elastic, peak, and ultimate stages decreased as RBCA increased from 15 to 50% at both w/c. It was concluded that concrete mix with 50% RBCA did not meet the required criteria at w/c of 0.49 but those with 15–50% RBCA satisfied the minimum requirements at w/c of 0.52.

Effect of varying core density and material on the quasi‐static behaviors of sandwich structure with 3D‐printed hexagonal honeycomb core

AbstractAdditive manufacturing (AM) involves the development of complex, lightweight sandwich structures for the automotive and aerospace industries. These structures are essential for load bearing and impact resistance. Nevertheless, there is a significant obstacle of failure under compressive loading, e.g. through brittle fractures and crushing. To address this issue, this study evaluates the compressive properties, energy absorption and failure damage in quasi‐static tests (flatwise, in‐plane, and flexural) of sandwich composites with 3D‐printed hexagonal honeycomb cores of different unit cells (6, 8 and 10 mm) and materials (polylactic acid (PLA), PLA‐Carbon and PLA‐Wood). The results show that increasing the core density enhances compressive strength, modulus, and energy absorption. An 8 mm unit cell absorbs energy optimally for lightweight structures. In PLA flatwise testing, the 8 mm unit cell absorbed 419.49 J more energy than the 10 mm unit cell. Additionally, PLA‐Wood has better mechanical performance than PLA‐Carbon due to the better filler with the PLA‐ matrix. In flatwise testing with an 8 mm unit, PLA‐Wood absorbs 214.01 J, while PLA‐Carbon absorbs 122.49 J. The failure modes vary depending on tests performed. The study highlights the potential of 3D‐printed honeycomb core structures for load‐bearing applications in various industries, including aerospace and automotive.Highlights Quasi‐static loading behavior of 3D‐printed hexagonal honeycomb cores. Increased core density improves compressive stress, modulus, and absorbed energy. An optimal unit cell size for lightweight 3D printed core structures is 8 mm. PLA‐Wood performs better in energy absorption due to filler compatibility. The failure modes are related to the type of quasi‐static loads applied.

Lateral load behavior of shear connections between steel storage racks and the spine bracing with posts

High-rise steel storage racks are cold-formed thin-walled steel frames, which achieve their lateral strength and stiffness by the use of a spine bracing system in the down-aisle direction commonly located at a short horizontal distance away from the main rack frames. The shear connections between the main rack frame and the spine bracing system play a dominant role in the effectiveness of the spine bracing system. This paper experimentally investigates the behavior of the shear connections used in industrial practice between a steel storage rack and the spine bracing system with posts using four groups of three nominally identical connection specimens. By employing a digital image correlation (DIC) system, the tests generate comprehensive data and establish the real-time deformation fields of individual components of such shear connections. Based on the component-based approach, a linear-elastic analytical model is developed for the type of shear connections under consideration. The proposed analytical model explicitly captures the behavior of the individual connection components, including the three-dimensional flexural bending of endplates, as well as the distortions of the open sections of the upright and the bracing post. Based on the proposed model, this paper quantifies the contribution of each component towards the total deformation of the shear connections. The investigation establishes that the cross-sectional distortion of the bracing post and the out-of-plane bending of the upright web are the most flexible components of such shear connections. Recommendations associated with the shear connections under consideration are proposed for the rack designers and manufacturers.

Research and analysis of tower crane load behavior when the rope breaks

The object of research is the behavior of the load of the tower crane during the break of the sling. One of the most problematic areas is the safety of work and the prevention of emergency situations. Despite the presence of mandatory safety measures, during cargo transportation, one of the sling branches may be destroyed due to the presence of a dynamic component during the operation of the crane, or errors of the slinger when securing the cargo. Also, the presence of hidden internal or unnoticed defects in the sling construction itself cannot be ruled out. Also, one of the most problematic places is the chaotic fluctuations of the load, which negatively affect the stability of the crane and safety. The paper describes the case of the destruction of one of the branches of a two-rope sling during the transportation of a long product by a tower crane. The proposed method of cargo behavior analysis is based on the use of a dynamic description of cable system failure modes within the framework of setting and solving differential-algebraic equations. This makes it possible to more accurately describe the behavior of the cargo when the sling breaks. The obtained results show that the application of the proposed method makes it possible to bring the mathematical model of the two-link mathematical pendulum significantly closer to the actual mutual oscillations of the load during the sling break. This is due to the fact that the proposed method has a number of features, in particular, high sensitivity to changes in the behavior of the cargo and a quick reaction to a rope break. These results can be used in practice in the design and operation of tower cranes. Thanks to the application of the proposed method, it is possible to obtain accurate values of cargo behavior indicators and timely detection of a rope break. Compared to similar known methods, this method has such advantages as high efficiency, reliability and safety of operation.

Self-assembled poloxamer-legumin/vicilin nanoparticles for the nanoencapsulation and controlled release of folic acid

Plant-based food proteins are a promising choice for the preparation of nanoparticles (NPs) due to their high digestibility, low cost, and ability to interact with various compounds and nutrients. Moreover, nanoencapsulation offers a potential solution for protecting nutrients during processing and enhancing their bioavailability. This study aimed to develop and evaluate nanoparticles (NPs) based on legumin/vicilin (LV) proteins extracted from fava beans, with the goal of encapsulating and delivering a model nutraceutical compound, folic acid (FA). Specifically, NPs were self-assembled from LV proteins extracted from commercially available frozen fava beans using a pH-coacervation method with poloxamer 188 (P188) and chemically cross-linked with glutaraldehyde. Microscopy and spectroscopy studies were carried out on the empty and FA-loaded NPs in order to evaluate the particle morphology, size, size distribution, composition, mechanism of formation, impact of FA loading and release behavior. In vitro studies with Caco-2 cells also confirmed that the empty and FA-loaded nanoparticles were non-toxic. Thus, the LV-NPs are good candidates as food additives for the delivery and stabilization of nutrients as well as in drug delivery for the controlled release of therapeutics.

Experimental Investigation of Quasi-Static and Dynamic Impact Resistance in Thin Wood Veneer Laminates

The incorporation of sustainability into the design of transport vehicles has become increasingly important in recent years. A low carbon footprint makes wood-based structures attractive to replace other lightweight materials such as aluminum or fiber-reinforced plastics. This paper investigates and compares the static and dynamic impact behavior of thin Beech wood veneer laminates in standardized mechanical tests. The results obtained from Quasi-Static Indentation (QSI) and dynamic Low-Velocity Impact (LVI) tests reveal similarities and differences with regard to load vs. displacement behavior, damage mechanisms, permanent deformation, and energy absorption. While yield strength and damage modes are comparable in both test cases, it is found that the bending stiffness is strain-rate sensitive. Plastic deformation in compression is identified as the governing mechanism for energy absorption. These results can guide the design of sustainable wood-based structures for future transport applications where a thorough understanding of impact and crashworthiness is important.

An experimental and parametrical study on repair of cracked titanium airframe structures with single-side bonded carbon fiber-reinforced polymer prepreg patches

The present research aims to investigate efficient repair techniques of cracked Ti-alloy aircraft structures with adhesively bonded carbon fiber-reinforced polymer prepreg patches. The repaired specimens in the configuration of a Ti-alloy butt joint with one-side bonded composite patch were prepared under multiple repair factors including patch thickness, patch length, adhesive thickness, cure pressure, patch layup and surface treatment. The repair efficiency was evaluated by loading behavior, bonded interface microstructure and failure mode. The results reveals that the geometric factors affect the loading performance and alter failure modes by adjusting stress distribution in the repair system, whereas the cure pressure and surface treatment act on the bondline and change interfacial properties. A sensitivity-optimization model based on analysis of variance was established for parametrical study to quantify the contribution of repair factors and obtain optimal values. The optimum parameters were validated by repaired central-cracked specimens via static and fatigue tests, which proved that the repaired structure could restore 90.7% loading capacity of intact ones and endure more than 106 fatigue cycles of 25% ultimate failure load level of center-cracked ones. The proposed experimental and parametrical study possessed good efficacy in refurbishing strength and stiffness of cracked metallic structures.

Efficient surface modification of silica-alginate nanocarrier as smart drug release platform

A hybrid nanocarrier based on silica-alginate modified by gelatin-folic acid was designed as a pH-sensitive drug delivery system and investigated in the terms of in terms of the amount of doxorubicin loading and release behavior in two different mediums with pH 7.4 and 5.6. The loading content and entrapment efficiency were measured at about 21% and 67%, respectively. The results showed a rapid release of the doxorubicin from the unmodified carrier at initial times (first 24 h). While the use of gelatin-folate modification led to the improvement of the release behavior. Here, the amount of drug released from the silica-alginate carrier after 72 h in a neutral and acidic environment was measured as 82% and 73%, respectively. While using gelatin modification, the amount of released drug decreased to 71% and 63%. These results show that the prepared carrier is sensitive to pH. Furthermore, the cross-linking effect of the gelatin modifier layer on the release pattern was investigated and results indicated the improvement of the release pattern in both acidic and natural media. The findings of this research show the appropriate performance of carriers designed for drug delivery.

Enhanced multi-springs model for estimating suction caisson responses under cyclic lateral loading

Offshore wind turbines (OWTs) are situated in intricate marine environments and consistently subjected to cyclic loadings, leading to an accumulation of foundation displacement along with stiffness variation. Employing the multi-spring system, improvements are made to the p-y and t-z model of multi-springs, according to the bounding surface plasticity-based theory, supporting the ongoing loading and unloading behaviors at the caisson-soil interface, which is also verified by the monopod caisson's tests under both uni-directional and multi-directional cyclic lateral loadings. The comparative analysis further indicates that ignoring the combined effect of p-y and t-z springs may result in overstating the deformation of the caisson. Then, incorporating the enhanced multi-spring model into the soil-structure module, allows for the implementation of the dynamic analysis procedure designed for caisson-based OWTs under multi-directional cyclic lateral loading. An increase in the cycle count leads to a larger load deflection angle for the case studied, initiating a continuous accumulation of plastic displacement and the disturbance at caisson-soil interface. This process gives rise to a certain degree of shrinkage within the soil stress boundary, ultimately affecting the overall stability of the structure.

Individual household load forecasting using bi-directional LSTM network with time-based embedding

Accurate individual household load forecasting is essential for effectively managing energy demand and promoting efficient energy consumption. This study evaluates the performance of various deep learning models for individual household load forecasting, specifically using the Smart Grid Smart City (SGSC) dataset. Feature engineering is conducted, producing two distinct sets of features, and the models’ accuracy in predicting individual household loads is assessed using both basic and derived feature sets. The results demonstrate that the T2VBiLSTM model outperforms other models, achieving an average mean absolute percentage error (MAPE) of 74.90% and a root mean square error (RMSE) of 0.433 kW. The incorporation of a wider range of features, including maximum load, minimum load, and load range over time, is emphasized to enhance forecasting accuracy. These features capture long-term load behavior, enabling the models to comprehend complex energy consumption patterns and generate more accurate and reliable predictions. Moreover, limitations in using MAPE as a loss function for load forecasting at the individual customer level are revealed, due to its sensitivity to scale, asymmetry, outliers, and uniform weighting assumption. Alternative loss functions like mean absolute error (MAE) are recommended, as they treat all errors equally and better capture data peaks. While this study focuses on the SGSC dataset, the findings have broader implications for efficiently managing energy demand and promoting energy consumption on a larger scale.