Load Response Research Articles

Development and Application of an FSI Model for Floating VAWT by Coupling CFD and FEA

The emerging floating vertical axis wind turbines (VAWTs) are regarded as a preferred solution to overcome the challenges faced by the traditional horizontal type in open-sea environments. Numerous numerical models have been advanced for assessing this novel object. However, current fully coupled models predominantly rely on simplified theories, assuming a linear fluid load and a one-dimensional slender beam structure. Despite computational fluid dynamic and finite element (CFD-FEA) coupling being qualified for high precision, this technology remains limited to the fixed VAWT field. To predict the load and structural response accurately and comprehensively, this study aims to extend CFD-FEA technology to floating VAWTs. First, an aero-hydro-moor-elastic fully coupled model is developed, and this model is validated by comparing it with several model experiments. Subsequently, a full-scale floating straight-bladed VAWT is simulated with the geometry and numerical models introduced. Furthermore, load and structural responses in a typical case are analyzed in both time and frequency domains. Finally, the sensitivity analysis of each structure part in floating VAWTs to environmental parameters is conducted and discussed. The discovery highlights the intricate nature of tower structural response, which incorporates 2-node, 3-node, wind frequency, and wave frequency components. Distinct from blades or floating foundations, which are primarily influenced by a single environmental parameter, the tower response is significantly amplified by the combined effects of wind and waves.

An experimental study on the influence of wind-wave-current coupling effect on the global performance of a 12 MW semi-submersible floating wind turbine

Investigating the coupling effect between different marine environmental conditions is essential to understand the dynamic response of wind turbines. This paper presents the study findings from the model tests conducted in a wave basin, exploring the coupling effect of wind, waves, and currents on the global performance of a 1:70 scale model 12 MW semi-submersible floating wind turbine (FWT). A multi-blade large-scale wind generation system with a rectifier network was improved and fabricated to provide a reliable wind field for the experiment. The stiffness-matched and geometry-matched tower models were designed and fabricated, achieving an accurate simulation of the tower's flexibility and windward areas and their impact on the global dynamic response. Following the calibration of marine environmental conditions and the characterization of the model FWT system, the study focused on the operational and extreme responses of the FWT concept. The aerodynamic damping effect of wind in pitch and surge motions is remarkable, especially in pitch motion, primarily manifesting by reducing the standard deviation of motions. Mooring load responses are predominantly induced by the hydrodynamic effect, with the wave-frequency response gradually becoming dominant as wave parameters increase. Tower-top load responses are primarily induced by the hydrodynamic effect of waves and the aerodynamic load effect of wind. Furthermore, the phenomenon where the action of current strengthens the aerodynamic damping effect of wind is observed. The coupling effect between wind and current amplifies surge motion while diminishing pitch motion, effectively reducing the tower-top and tower-base load responses.

Quantification of the out-of-plane loading fatigue response of bistable CFRP laminates using a machine learning approach

This study proposes data-driven machine learning models to predict the nonlinear load-displacement response in constant amplitude high-cycle fatigue loading of unsymmetric, cross-ply bistable carbon fiber reinforced polymer composites. Four selected ML models are trained on experimental fatigue data with eleven unique frequency, temperature, and boundary conditions combinations. Stiffness and damage index values, which serve as additional evaluation metrics, are calculated using the predicted load data. The models capture the nonlinear load response with acceptable error for in-domain experimental conditions. Model expandability demonstrates the sensitivity of machine learning models to training features but suggests an economical alternative to extensive fatigue experiments.

Linear static, geometric nonlinear static and buckling analyses of sandwich composite beams based on higher-order refined zigzag theory

This study aims at developing finite element formulations based on higher-order refined zigzag theory (HRZT) to analyze sandwich composite beams under linear static bending, geometric nonlinearity and buckling. In HRZT, the higher-order terms associated with average shear strain and rotation due to zigzag are added based on refined zigzag theory (RZT). In linear static bending analysis, both C0 and C1 elements are developed. For the C0 element, an extra node is used in order to eliminate shear locking. For geometric nonlinear static analysis, the two-node C0 element is developed to solve the bending response with lateral loading and buckling response. The numerical results are compared with those calculated by 2D exact solutions, analytical solutions of HRZT and 2D models using commercial software. Various beam theories such as first-order shear deformation theory (FSDT), higher-order shear deformation theory (HSDT), RZT, and other types of higher-order zigzag theory are also introduced for comparisons. Through comprehensive comparisons with existing works on FEM or zigzag theories, the HRZT beam elements developed in this study exhibit superior accuracy and are free from shear locking in linear static analysis. Furthermore, the study also demonstrates that these elements achieve high accuracy in geometric nonlinear analysis and buckling analysis.

Hindfoot joint kinematics analysis after the resection of talocalcaneal coalition

BackgroundThe subtalar joint movement between the talus and calcaneus is restricted in patients with talocalcaneal coalition (TCC). When the motion of the subtalar joint is restricted, shock absorption in the foot decreases, leading to pain during walking. Resection methods to maintain subtalar motion by removing abnormal unions have been proposed. The purpose of this study was to analyze the joint kinematics of patients who underwent TCC resection and to quantitatively evaluate the results of the surgery based on the measured kinematics. MethodsJoint kinematics of five patients with TCC were obtained using a biplane fluoroscopic imaging system and an intensity-based two-/three-dimensional registration method. The joint kinematics of the tibiotalar and subtalar joints and the tibiocalcaneal motion during the stance phase of walking were obtained. From the kinematics of the hindfoot joints, the inversion/eversion range of motion (ROM) of the patients before and after resection was statistically analyzed using the Wilcoxon signed-rank test to test whether TCC resection improved the ROM. ResultsDuring the loading response period, the eversion ROM of the subtalar joint and tibiocalcaneal motion significantly increased postoperatively. In addition, a significant postoperative increase was observed in the subtalar and tibiocalcaneal inversion ROM during the pre-swing period. SignificanceTCC resection surgery increased the ROM of the subtalar joint, which in turn contributed to the increase in tibiocalcaneal ROM. Increased subtalar and tibiocalcaneal ROM could result in increased shock attenuation and may be a contributing factor to pain relief during walking.

Lateral load response and collapse probability of reinforced concrete shear walls retrofitted for repairability

AbstractThis paper demonstrates the efficacy of a new reinforced concrete shear wall seismic retrofit method through a series of nonlinear static and incremental dynamic analyses. Unlike traditional retrofit methods, the method investigated aims to convert conventional walls into self‐centering walls whose behavior is governed by rocking and flexure. The retrofit involves creating a cold joint at the foundation–wall interface, cutting some reinforcing bars to allow rocking, adding external post‐tensioning to enable self‐centering, and externally confining wall toes to prevent concrete crushing. The retrofit was applied to two building archetypes, each with two different shear wall designs. The four walls were retrofitted by varying retrofit parameters (portion of the vertical reinforcement bars cut, and external post‐tensioning amount). Nonlinear static and nonlinear response history analyses were performed using experimentally validated, computationally efficient models that simulate walls with fiber‐based beam–column elements. Incremental dynamic analysis was used to create collapse fragility functions for pre‐ and post‐retrofit walls. The results show that the retrofit is effective when some vertical reinforcement bars are left uncut across the foundation–wall interface. The retrofit is more effective for walls with vertical reinforcement distributed across cross‐section as compared to walls with reinforcement concentrated near boundary elements and for walls with structurally efficient amounts of reinforcement as compared to walls with higher amounts of reinforcement. This is attributed to the larger amount of reinforcement bars cut in walls with concentrated reinforcement layouts or heavy reinforcement amounts, leading to a larger loss of strength, recovery of which requires larger amounts of post‐tensioning.

Nanoindentation responses of NiCoFe medium-entropy alloys from cryogenic to elevated temperatures

NiCoFe alloy, a medium-entropy alloy, shows potential for applications in extreme environments. However, there is a theoretical barrier concerning the unclear understanding of its high-temperature dislocation motion mechanism. The load response exhibits distinct signatures relevant to thermal activation, most notably a decrease in critical force (i.e., softening) from cryogenic to elevated temperatures, e.g., from 200 to 1000 K. The onset of plasticity is characterized by the nucleation of stacking faults and prismatic loops at low temperatures, whereas the surface nucleation of Shockley partial dislocations dominates plasticity at elevated temperatures. We show that thermal effects lead to non-uniform atom pile-ups and control the rate of phase transformation with increasing indentation depth. The findings in this work extend the understanding of the mechanical response of NiCoFe alloys under indentation at different temperatures, shedding light on the underlying dislocation motion mechanisms and surface deformation characteristics. The observed transformation-induced plasticity mechanism has implications for the properties of medium-entropy alloys and their potential applications in extreme environments.

Lateral Load Response of Reinforced Concrete Buildings Constructed on Clay Soil with Weak Zones

Lateral Load Response of Reinforced Concrete Buildings Constructed on Clay Soil with Weak Zones

Nonlinear stability of ES-FG porous sandwich cylindrical shells subjected to axial compression in thermal environment

Stability analysis of cylindrical shells subjected to axial compression is a common problem in engineering applications. The phenomenon of instability can easily appear with thin cylindrical shells. Therefore, to increase the load-carrying capacity of this type of structure, the cylinders are increased in thickness by adding a porous core layer and reinforcing orthogonal stiffeners. In this study, the nonlinear buckling and postbuckling behavior of functionally graded (FG) porous sandwich cylindrical shells with orthogonal eccentrically stiffeners (ES) are investigated via analytical approach. The FG porous sandwich cylindrical shells are rested on Pasternak elastic foundations and subjected to axial compression load in a thermal environment. The reinforcement of the shells is achieved through closely spaced stringers and rings, with the material properties of both the shell and stiffeners graded continuously in the thickness direction. The governing equations are derived based on the Donnell’s shell theory with von Karman geometrical nonlinearity and the smeared stiffeners technique. The Galerkin procedure is employed to ascertain the critical load and post-buckling response, employing a three-term deflection solution. The study analyzed the effects of parameters such as porosity coefficient, material, temperature, dimensional parameters, stiffener, and foundation characteristics.

Numerical Investigation on the Effect of Partially-Inclined Reinforcement on the In-Plane Behavior of Shear-wall

A shear wall is a structural component commonly used in buildings to resist lateral loads such as wind and seismic forces. They are vertical elements typically made of reinforced concrete, masonry, or steel. The effectiveness of shear walls in resisting lateral loads depends on various factors including their size, material properties, connection details, and the overall structural design of the building. An innovative idea of a concrete shear wall with partial diagonal reinforcement was introduced in this paper. All specimens were modelled and analyzed with the finite element software ABAQUS. The investigation was carried out to investigate the global behaviour of the shear wall in terms of lateral load and story drift response, yielding of reinforcement, and plastic concrete strain by varying the angles of inclined reinforcement from 45° to 65°. The research shows that the seismic performance of the shear wall in particular its resistance to sliding shear, was improved through this layout of the inclined reinforcement. Compared to the other shear walls, the shear wall with 60° partial rebars has a maximum lateral strength.

Efficacy of hinged and carbon fiber ankle-foot orthoses in children with unilateral spastic cerebral palsy and drop-foot gait pattern.

In children with unilateral spastic cerebral palsy (USCP), ankle-foot orthoses (AFOs) are widely used to correct common gait deviations such as a drop-foot pattern. Most studies on this topic have investigated specific time points while omitting other parts of the gait cycle. This study investigated the separate effects of prefabricated carbon fiber AFOs and custom-made hinged AFOs compared with barefoot walking in children with USCP with a drop-foot gait pattern using statistical parametric mapping. Retrospective, cross-sectional, repeated measures study. Twenty ambulatory children (9.9 ± 2.5 years) with USCP and a drop-foot gait pattern were included. Kinematics, kinetics, and spatiotemporal parameters assessed during 3-dimensional gait analysis were compared between barefoot and AFO walking. Statistical parametric mapping was used to compare joint angles and moment waveforms. Kinematics, kinetics and spatiotemporal parameters assessed during 3-dimensional gait analysis were compared between barefoot and AFO walking for each AFO type but not between the 2 AFO types. Compared with barefoot walking, there was a steeper sole angle at initial contact, corresponding to a heel strike pattern, and an increased ankle dorsiflexion in swing with the use of both AFOs. The ankle plantar flexion moment during loading response increased. Ankle power generation during pre-swing decreased in the carbon fiber AFO group when walking with AFOs. Both AFOs were beneficial for improving a drop-foot gait pattern in these small patient groups and can, therefore, be recommended to treat this gait deviation in patients with unilateral cerebral palsy. However, the reduction in ankle power generation during push-off and additional goals targeted by AFOs, such as correction of structural or flexible foot deformities, should be considered for prescription.

Modal and vibration response characteristics of rotating support platform

In order to improve the strength and stability of the rotating support platform, modal and stress characteristics were simulated and calculated based on finite element analysis method. In Hypemesh, the model of the rotating support platform was established. In Abaqus, boundary conditions and loads were defined, and the natural frequencies and vibration modes of the first four orders were obtained. Based on the structure and stress characteristics of the crossbeam, different damping technologies were compared and analyzed, and rubber damping scheme was selected and designed. Through time mileage analysis, the load response and damping effect of damping scheme were verified. The results show that the rubber damping scheme can reduce the maximum stress by more than 15 % without changing the natural frequency substantially.

Analysis and research on the dynamic characteristics of shock absorber based on ADAMS

In order to effectively improve safety and stability during transportation, a shock absorber with buffering and self-locking functions was designed. Based on the rigid flexible coupling technology, the working state and dynamic response of the shock absorber were simulated and analyzed. The linear spring was treated as a flexible body, and the cam button, guide pillar, and base were treated as rigid bodies. The modal neutral files required for the rigid flexible coupling dynamic analysis were generated. Based on ADAMS, a dynamic simulation model was established, replacing a part of the rigid model with a flexible model and conducting load response analysis on it. To further improve the vibration reduction effect, the performance of the contact material of the shock absorber was analyzed. Through the calculation of dynamic characteristics, it could be known that the self-locking mechanism had no dead points, and the vibration reduction force response stability was high, meeting the working requirements.

Identification of pine wood nematode (Bursaphelenchus xylophilus) loading response genes in Japanese pine sawyer (Monochamus alternatus) through comparative genomics and transcriptomics.

Pine wood nematode (PWN; Bursaphelenchus xylophilus) is the causative agent of pine wilt disease (PWD), which is considered the most dangerous biohazard to conifer trees globally. The transmission of PWN relies on insect vectors, particularly the Japanese pine sawyer (JPS; Monochamus alternatus). However, the molecular mechanism underlying PWN-JPS assembly remains largely unknown. Here, we found that both geographical and gender could significantly affect the PCA (PWN carrying amount) of JPS; thus, JPS transcriptomes from diverse locations and genders were explored regard to PWN loading. Due to the shortage of genomes, we developed a full-length reference transcriptome for analyzing next-generation sequencing data. A comparative genomic study was performed, and 11 248 potential PWN-carrying associate genes (β) were nominated in JPS by using the reported genomes of PWN and non-PWN carrier insect species. Then, 151 differentially expressed transcripts (DETs), 28 of them overlapped with β, correlated with the PCA of JPS were nominated by RNA-Seq, and found that fatty acid β-oxidation might be the key factor that affected the PCA of JPS. Furthermore, JPS fatty acid β-oxidation rates were experimentally decreased using the inhibitor Etomoxir, leading to an increased PCA of JPS. Meanwhile, silencing MaCPT1 in JPS by RNA interference led to a decreased fatty acid β-oxidation rate and increased PCA of JPS. In conclusion, MaCPT1 was able to decrease the PWN-JPS assembly formation through the fatty acid β-oxidation of JPS. These results provide new insights for exploring the impact of PWN invasion on JPS. © 2024 Society of Chemical Industry.

Simplified Procedure to Determine the Cohesive Material Law of Fiber-Reinforced Cementitious Matrix (FRCM)-Substrate Joints.

Fiber-reinforced cementitious matrix (FRCM) composites have been largely used to strengthen existing concrete and masonry structures in the last decade. To design FRCM-strengthened members, the provisions of the Italian CNR-DT 215 (2018) or the American ACI 549.4R and 6R (2020) guidelines can be adopted. According to the former, the FRCM effective strain, i.e., the composite strain associated with the loss of composite action, can be obtained by combining the results of direct shear tests on FRCM-substrate joints and of tensile tests on the bare reinforcing textile. According to the latter, the effective strain can be obtained by testing FRCM coupons in tension, using the so-called clevis-grip test set-up. However, the complex bond behavior of the FRCM cannot be fully captured by considering only the effective strain. Thus, a cohesive approach has been used to describe the stress transfer between the composite and the substrate and cohesive material laws (CMLs) with different shapes have been proposed. The determination of the CML associated with a specific FRCM-substrate joint is fundamental to capture the behavior of the FRCM-strengthened member and should be determined based on the results of experimental bond tests. In this paper, a procedure previously proposed by the authors to calibrate the CML from the load response obtained by direct shear tests of FRCM-substrate joints is applied to different FRCM composites. Namely, carbon, AR glass, and PBO FRCMs are considered. The results obtained prove that the procedure allows to estimate the CML and to associate the idealized load response of a specific type of FRCM to the corresponding CML. The estimated CML can be used to determine the onset of debonding in FRCM-substrate joints, the crack number and spacing in FRCM coupons, and the locations where debonding occurs in FRCM-strengthened members.

Low-Dose Radiation Therapy Impacts Microglial Inflammatory Response without Modulating Amyloid Load in Female TgF344-AD Rats.

Low-dose radiation therapy (LD-RT) has demonstrated in preclinical and clinical studies interesting properties in the perspective of targeting Alzheimer's disease (AD), including anti-amyloid and anti-inflammatory effects. Nevertheless, studies were highly heterogenous with respect to total doses, fractionation protocols, sex, age at the time of treatment and delay post treatment. Recently, we demonstrated that LD-RT reduced amyloid peptides and inflammatory markers in 9-month-old TgF344-AD (TgAD) males. As multiple studies demonstrated a sex effect in AD, we wanted to validate that LD-RT benefits are also observed in TgAD females analyzed at the same age. Females were bilaterally treated with 2 Gy×5 daily fractions, 2 Gy×5 weekly fractions, or 10 fractions of 1 Gy delivered twice a week. The effect of each treatment on amyloid load and inflammation was evaluated using immunohistology and biochemistry. A daily treatment did not affect amyloid and reduced only microglial-mediated inflammation markers, the opposite of the results obtained in our previous male study. Moreover, altered fractionations (2 Gy×5 weekly fractions or 10 fractions of 1 Gy delivered twice a week) did not influence the amyloid load or neuroinflammatory response in females. A daily treatment consequently appears to be the most efficient for AD. This study also shows that the anti-amyloid and anti-inflammatory response to LD-RT are, at least partly, two distinct mechanisms. It also emphasizes the necessity to assess the sex impact when evaluating responses in ongoing pilot clinical trials testing LD-RT against AD.

Optimal operation of multiple energy system considering load management approach and uncertainty

In recent years, the advancement of technology has led to the development of energy networks' infrastructure, resulting in the transformation of conventional networks into smart networks. By incorporating communication equipment, each component of the network can now exchange information with other components, creating an environment where innovative ideas can be implemented. One such idea is the utilization of multi-carrier energy systems, also known as Energy Hubs. Integrating energy hubs into traditional networks used to be a challenging task. However, with the expansion and enhancement of smart networks, the potential for incorporating and locating energy hubs within the power grid has significantly increased. In these systems, the focus shifts from optimizing a single energy carrier to ensuring the optimal operation of a system that encompasses multiple energy carriers, such as natural gas, electric grid, and thermal energy. Energy hubs act as intermediaries between energy supply companies and various consumers, including residential, commercial, and industrial sectors. These energy suppliers can encompass different energy networks, such as electricity, gas, and local heating. The integration of residential and commercial energy hubs has become a crucial aspect of modern energy systems, particularly in the context of load response applications. This paper proposes a novel approach for effectively utilizing residential and commercial energy hubs, taking into account the time of use (ToU) load response program. In the proposed system, the inherent uncertainties of the system are addressed using the two-point estimation method of the model. To achieve the desired objective, the Cuckoo optimization algorithm, a well-established meta-heuristic algorithm for solving optimization problems, is employed. This algorithm aids in determining the optimal scheduling of energy resources while considering ToU tariffs and load management plan signals. The results demonstrate that the proposed approach can significantly reduce energy costs for the energy system.

Development of a high temperature and high pressure downhole string dynamic load monitor

Due to the uncertainty of the formation and the complexity of downhole tubular string loads and deformations, the existing tubular string static theory is difficult to explain and lacks support from measured data of tubular string dynamic loads. Therefore, a dynamic loads monitor for oil and gas tubular string is developed, which can synchronously measure the internal pressure, external pressure, axial force, and vibration acceleration for the string during the whole operation process. The monitor realizes simultaneous monitoring of tubular string load and vibration response parameters while meeting the requirements of various sensor placement spaces and structural strength safety, simplifying the on-site test process. By adding a power control circuit to the circuit system, the working time of the monitor is extended. The high temperature calibration test of the monitor is carried out, and the maximum calibration error is 0.10%, which meets the requirements of measurement accuracy.

Continuous fiber path optimization in additive manufacturing: A gradient-based B-spline finite element approach

Additive manufacturing of continuous fiber enables the control of local material distribution and mechanical characteristics. This localized control is realized through fiber path generation and optimization, which is one of the core problems in the additive manufacturing of continuous fiber. Current fiber path generation and optimization methods mostly try to infill topology-optimized parts or align the fiber with the maximum stress directions, which may lead to sub-optimality or time-consuming computations. This paper provides a different approach to optimize the fiber path directly by parameterizing it with B-splines and manipulating its control points. A finite element model with B-spline fiber parameterization is established, with an analytical fiber-in-element probability. This framework streamlines the computation of local and global stiffness and mass matrices, enabling effective and efficient prediction of loading responses, stiffness, and natural frequencies. The probability framework also allows efficient calculation of the gradients of the stiffness and mass matrices, leading to a gradient-based fiber path optimization. The effectiveness and accuracy of both the finite element and optimization methods are verified with simulation and experiment case studies. Results demonstrate enhancements in stiffness and strength with less fiber usage compared to a commonly adopted principal stress direction method.

Efficient criticality oriented service brokering policy in cloud datacenters

Cloud service provider (CSP) offers a huge number of datacenters and virtual servers to the users for processing their workloads in an infrastructure as a service (IaaS) cloud computing environment. Due to the heterogeneous volume of these resources and the immense number of user workloads arriving simultaneously in the cloud, it is necessary to use an effective load distribution technique for scheduling the resources to achieve high performance and high user satisfaction. Service brokering policy and load balancing techniques are the two crucial areas to be focused on while selecting the datacenters and virtual machines, respectively. In this study, we have proposed a dynamic efficient criticality-oriented service brokering policy for load allocations among datacenters by considering task criticality, datacenter proximity, and traffic, the size of the datacenter, its present load and makespan value. The proposed methodology is examined against the current policies in the CloudAnalyst simulation tool and the analysis report confirms that our proposed policy gives priority to processing the urgent loads and chooses the optimum datacenter to diminish the load response time, datacenter processing time, minimizes the cost, achieves optimum resource utilization and workload balancing among resources.