Membrane Elements Research Articles

A new membrane finite element based on the strain approach

Membrane elements with in-plane rotation are applicable for modeling thin planar structures that are only stressed by volume and surface loads acting in their plane. In this paper a new finite element designed for static and free vibration analysis, featuring a four-node configuration is presented. Each node incorporates two engineering displacements and a fictive rotation, aligning with strain approach principles. The displacements field of this element is based on the assumed functions for the various strains satisfying the compatibility equations. This developed element passed all benchmark tests in the case of bending and shear problems. In static analysis, the displacements, strains, and stresses are calculated, while the free vibration analysis aims to determine natural frequencies, including both axial and fundamental frequencies. The proposed membrane element is validate through a series of selected examples, demonstrating its effectiveness and accuracy. The results consistently indicate that the new element exhibits high performance and exactitude in both types of analysis.

Использование компьютерной программы «ПРОЕКТ ВПУ» для проведения технологического расчета и анализа технологий обессоливания воды на ТЭС и АЭС

There are many viable options of desalination schemes that allow us to obtain purified water of the required quality. To conduct process design of a water treatment plant, thermal power plants and nuclear power plants use special software provided by manufacturers of ion exchangers and membrane elements. However, these software programs consider individual water treatment technologies and are attached to filter and membrane materials of a specific manufacturer. They do not provide the ability to calculate complete water desalination schemes, as well as determine the performance indicators of the water treatment plant. It is relevant to develop a software program that allows us to conduct process design of complete water treatment schemes, which include various water treatment technologies, and to determine technological, environmental, and technical-economic indicators. Multivariate calculations with different initial data will allow us to identify the advantages and disadvantages of scheme solutions and determine areas of their rational use. The method of mathematical modeling of chemical and technological processes of water treatment at thermal power plants and nuclear power plants has been used. An application software program “PROJECT WTP” has been developed. It is designed for process design of various water treatment schemes, which are visually assembled from individual elements, and allows one to determine the technological, environmental, and performance indicators of the operation of water treatment plant. Computation data on the auxiliary need coefficient has been obtained for the main water desalination schemes and under condition of different mineralization of the source water. The developed software program can be used for process design of various water treatment schemes and assessment of the degree of improvement of water desalination technology.

Inverse design of V-shape feed spacer for batch and semi-batch reverse osmosis

In recent years, batch and semi-batch reverse osmosis (RO) processes have received wide attention because of their internal staging feature. However their performance is severely compromised by salt retention induced by incomplete flushing, which leads to elevated salt concentration, uplifted peak pressure, and extra power consumption. Herein we adopt transient three-dimensional computational fluid dynamics to systematically analyze the effect of the V-shape feed spacer geometries on hydrodynamics and mass transfer characteristics. After a sensitivity analysis of all geometric parameters, a heuristic optimization framework is proposed for inverse design of the feed spacer. Using the optimized feed spacer, flushing efficacies after one displacement volume are 0.936, 0.962, 0.969 and 0.974 respectively for one, three, five and seven membrane elements connected in series (whereas 0.884, 0.926, 0.942 and 0.952 for commercial spacers), which help to mitigate membrane scaling and fouling. Moreover, the optimized spacer has a pressure drop per meter 73 % lower than that of the commercial spacer. If used in conjunction with high permeability membranes, batch RO and semi-batch RO could save 29.9 % and 24.1 % specific energy consumption relative to conventional one-stage seawater RO.

Formulating strain-based quadrilateral membrane finite elements with drilling rotations

Membrane finite elements with drilling degrees of freedom have sparked interest in many research works since they can be conveniently combined with plates to form shell elements. This study presents two non-conforming strain-based four-node quadrilateral membrane elements, SBQ13 and SBQ13E, for static analysis. SBQ13 partially satisfies the equilibrium equations, while SBQ13E completely fulfils the force balance equations. Both elements carry drilling rotations at each node. One difficulty when formulating quadrilateral elements is the singularity in the transformation matrix, which is addressed in this study by utilising the properties of singular matrices. Both quadrilateral elements were tested in several benchmark problems. It has been found that both elements passed the higher-order patch test but failed the constant stress patch test. Nevertheless, SBQ13 produced accurate responses in most numerical tests, but SBQ13E unreasonably overestimated the solution. Solving the eigenvalue problem revealed that the SBQ13E element has a near-zero energy deformation mode, which might explain the anomaly. Although fulfilling equilibrium does not always enhance solution accuracy, it is essential to overcome volumetric locking. Apart from the newly developed elements, this paper presents several new ideas that may apply to strain-based element formulations.

Lupeol protect against LPS-induced neuroinflammation and amyloid beta in adult mouse hippocampus.

Neuroinflammation includes the activation of immune glial cells in the central nervous system, release pro-inflammatory cytokines, which disrupt normal neural function and contribute to various neurological disorders, including Alzheimer's disease (AD), Parkinson's disease, multiple sclerosis, and stroke. AD is characterized by various factors including amyloidogenesis, synaptic dysfunction, memory impairment and neuroinflammation. Lipopolysaccharide (LPS) constitutes a vital element of membrane of the gram-negative bacterial cell, triggering vigorous neuroinflammation and facilitating neurodegeneration. Lupeol, a naturally occurring pentacyclic triterpene, has demonstrated several pharmacological properties, notably its anti-inflammatory activity. In this study, we evaluated the anti-inflammatory and anti-Alzheimer activity of lupeol in lipopolysaccharide (LPS)-injected mice model. LPS (250ug/kg) was administered intraperitoneally to C57BL/6 N male mice for 1 week to induce neuroinflammation and cognitive impairment. For biochemical analysis, acetylcholinesterase (AChE) assay, western blotting and confocal microscopy were performed. AChE, western blot and immunofluorescence results showed that lupeol treatment (50 mg/kg) along with LPS administration significantly inhibited the LPS-induced activation of neuroinflammatory mediators and cytokines like nuclear factor (NF-κB), tumor necrosis factor (TNF-α), cyclooxygenase (COX-2) and interleukin (IL-1β). Furthermore, we found that LPS-induced systemic inflammation lead to Alzheimer's symptoms as LPS treatment enhances level of amyloid beta (Aβ), amyloid precursor protein (APP), Beta-site APP cleaving enzyme (BACE-1) and hyperphosphorylated Tau (p-Tau). Lupeol treatment reversed the LPS-induced elevated level of Aβ, APP, BACE-1 and p-Tau in the hippocampus, showing anti-Alzheimer's properties. It is also determined that lupeol prevented LPS-induced synaptic dysfunction via enhanced expression of pre-and post-synaptic markers like SNAP-23, synaptophysin and PSD-95. Overall, our study shows that lupeol prevents memory impairment and synaptic dysfunction via inhibition of neuroinflammatory processes. Hence, we suggest that lupeol might be a useful therapeutic agent in prevention of neuroinflammation-induced neurological disorders like AD.

Long-Term Performance Evaluation and Fouling Characterization of a Full-Scale Brackish Water Reverse Osmosis Desalination Plant

Water scarcity in Tunisia’s semi-arid regions necessitates advanced brackish water desalination solutions. This study evaluates the long-term performance and fouling characteristics of the largest brackish water reverse osmosis desalination plant in southern Tunisia over a period of 5026 days. The plant employs two-stage spiral-wound membrane elements to treat groundwater with a salinity of 3.2 g L−1. The pre-treatment process includes oxidation, sand filtration, and cartridge filtration, along with polyphosphonate antiscalant dosing. Membrane performance was assessed through the analysis of operational data, standardization of permeate flow (Qps) and salt passage (SPs), and the calculation of water (A), solute (B), and ionic (Bj) permeability coefficients. Over the operational period, there was an increase in operating pressure, pressure drop, and permeate conductivity, accompanied by a gradual increase in SPs as well as in the solute B and ionic Bj permeability coefficients. The average B increased by 82%, reflecting a decrease in solute rejection over time. Additionally, the ionic permeability coefficients for both SO42− and Cl− ions increased, with Cl− showing an 88% increase and SO42− showing an 87% increase. The produced water’s salinity increased by 67%, indicating a significant loss of membrane performance. To identify the cause of these problems, membrane characterization was analyzed using visual inspection, X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR). The characterization revealed the complex nature of the foulants, with a predominant presence of calcium sulfate, along with minor quantities of calcite, dolomite, and silica. The extent of CaSO4 deposition suggests poor antiscaling efficiency, highlighting the critical importance of selecting an effective antiscalant to mitigate membrane fouling.

Analytical calculation of the in-plane shear strength of fibre-reinforced concrete

Existing code prescriptions for determining the shear strength of fibre-reinforced concrete (FRC) elements are either empirical or rely on important assumptions that require further clarification. A mechanically based method is here proposed to determine the fibres and the shear reinforcement contributions to the in-plane shear strength of membrane elements. The method is derived from the comprehensive Cracked Membrane Model for FRC to determine in-plane shear strength of FRC panels and is suitably adapted to determine the shear strength of beam elements. The proposed methodology is compared to existing code formulations and validated against experimental results from 14 panels subjected to in-plane shear stresses and from 34 beams failing in shear. The average ratio between experimental and calculated shear strength is 1.00 for the panels and 1.11 for the beams, with coefficients of variation 11 % and 24 %, respectively. The proposed analytical methodology enables the determination of shear strength and failure modes in FRC elements, with or without shear reinforcement. Equations providing the fibre contribution and the compression field inclination are derived from mechanical considerations, emphasizing the key influencing variables. The proposed method can serve as a basis for code-like formulations for shear strength linked to the involved mechanics, but for which further levels of simplification are still required.

Comparative analysis of reverse osmosis and nanofiltration for the removal of dissolved contaminants in water reuse applications

The increasing demand for drinking water has led to the adoption of unconventional water sources, such as water reuse. Reverse osmosis (RO) and nanofiltration (NF) membranes are effective barriers against trace organic contaminants in potable water reuse applications. However, the use of RO is being challenged by NF, primarily due to NF's potential to achieve similar contaminant removal as RO but with higher productivity and lower energy requirements. This study compares NF and RO membranes in terms of contaminant removal and energy consumption for potable water reuse applications. RO (BW30XFR) and dense and loose NF (NF90 and NF270) membranes were tested in bench-scale systems, and RO (TW30) and NF (NF9) membrane elements were tested in an engineering scale system utilizing UF-filtered reclaimed wastewater. The highest solute passage was observed using NF270 membrane. There was no difference between NF90 and BW30XFR in terms of divalent ion passage, but NF90's total organic carbon and monovalent ion passages were higher. Both NF90 and BW30XFR highly rejected negatively charged trace organic contaminants (TOrCs), though rejections were lower for neutral and positively charged compounds. Furthermore, all compounds were highly rejected in the engineering-scale system by NF9 and TW30. These results highlight the potential of dense NF membranes as an energy-efficient barrier for contaminant removal.

Irregular ANCF model and experimental investigations of the irregular membrane structures with variable cross-section

The membrane spacecraft structures are widely used for deep space exploration and on-orbit operation, but the dynamic responses of them is more complex. To advance the state of membrane structures, in this paper, a new ANCF membrane element is established to model dynamic equations of the membrane structure precisely and efficiently. Firstly, the irregular ANCF membrane element is studied by considering anomalistic boundary and variable cross-section. The mapping relations between the sub-ANCF element and the parent-ANCF element are illuminated by the Jacobian matrix, which makes the strain of each irregular element accurately calculated with the same shape functions. It is helpful to improve the description accuracy of inherent attributes and reduce the element number of dynamic systems. Further, the nonlinear dynamic model for membrane spacecraft system is established by the virtual work principle. Finally, the numerical examples and experiments are analyzed to verify the correctness of the proposed method and discuss the influence of nonlinear geometry and distortion on the dynamic behaviors. The results from the time domain and frequency domain analyses demonstrate that the distinct irregular geometric boundary of the irregular spacecraft can be more accurately modeled using the presented method. However, the difference becomes more pronounced when the distortion is too large. The research outcomes of this paper can provide theoretical guidance for the irregular spacecraft system, which is of great significance and urgently needs to be studied.

Study on seawater corrosion resistance of copper alloy

Abstract The Marine environment is a very complex and corrosive environment. Marine corrosion environment can be generally divided into Marine atmospheric environment and seawater environment. Because the seawater is rich in a variety of free ions mixed with corrosive media, the main component is sodium chloride, in addition to containing magnesium, potassium, iodine, bromine, and other elements of salt, which has strong corrosion to metal materials, if serious, it will cause safety accidents. Therefore, ensuring the effectiveness of the anticorrosion system is very important for the safe and reliable operation of the offshore platform. pulse plating is used and the metal nickel coating and metal nickel-chromium coating are prepared to analyze the microstructure and corrosion resistance of each film layer. From the macroscopic, it can be found that three coatings have more or less corrosion phenomenon, there is obviously no nickel-chromium and nickel layer on the surface of nickel-chromium corrosion defects, and through scanning electron microscopic observation, microscopic level nickel chromium corrosion after corrosion phenomenon is the least of three layers, which suggests that nickel chromium seawater corrosion resistance is strong. The three layers are then electrochemical corroded to study the corrosion resistance of the three layers. The results show that the corrosion resistance of the nickel-plated layer, nickel-chromium coating, and nickel-iron chromium coating prepared in the copper substrate is improved successively, which shows the influence of different membrane elements on the corrosion resistance of copper substrate against seawater medium. Although the composition parameters of the various membrane layers vary, they experience the same corrosion mechanism-pitting; Nickel chromium and chromium, iron and other atoms are present in the nickel matrix in the form of solid solution and finally form the solid solution alloy coating. For nickel-chromium coating, the content of iron and chromium in the surface layer has a certain influence on the corrosion resistance of the metal coating. The electrochemical parameters of nickel plating are studied separately, and the comparison with the nickel-chromium alloy coating and the coating is conducted. The equivalent circuit is fitted and determines the largest impedance value and the largest phase Angle among the three membrane layers, which finally has the strongest seawater corrosion resistance.

Simulation and Experimental Study of Mooring Function Composite Fragile Cover

Abstract Under the requirement that the fragile cover does not eject debris during missile launches, and to meet the demands of rapid combat, there is an urgent need for a lightweight missile launching system. Enhancing the effective utilization area of the fragile cover is an effective way to realize the lightweight of the missile launching system. This paper utilizes the properties of carbon fiber composite materials to design a novel frangible cover with mooring functionality and establishes numerical models for the cover’s pressure and bursting dynamics. In the pressure finite element model, the Tasi-Wu failure criterion is employed for damage assessment. In the bursting dynamics finite element model, a cohesive element is used to simulate the elastic behavior and damage evolution of the weak area, while a membrane element is employed to simulate the mooring function. Comparative analysis of numerical results with experimental data reveals minor discrepancies, with errors of 5.44% for maximum deformation under pressure and 8.1% for bursting force, respectively, validating the model’s rationality and effectiveness. Results from both experimental tests and finite element analyses demonstrate the successful implementation of mooring functionality in the segmented body. The effective utilization area of the cover was increased by 71.13%. This research provides a feasible direction for subsequent studies on non-ejecting frangible covers.

Recovery of the Properties of Spent Commercial Reverse Osmosis Membrane Elements and Ways of their Reuse

Recovery of the Properties of Spent Commercial Reverse Osmosis Membrane Elements and Ways of their Reuse

Mathematical modeling of reverse osmosis system design and performance

ABSTRACT Reverse osmosis (RO) is one of the most effective technologies for water desalination. However, the RO system's performance is contingent on its design parameters and operating conditions. In this study, a computational model for RO desalination performance prediction was developed. The study compares the performance parameters of the RO system utilizing various types of membranes with the established model using a single pressure vessel and seven membrane elements within the pressure vessel. This study looked at two different feed water concentrations. The first is for saltwater with a concentration of 40,000 mg/L, while the second is for seawater with a concentration of 32,000 mg/L. WAVE software assessed the findings of the generated model to the recovery ratio, feed pressure, salt rejection, and permeate concentration of each membrane element inside the pressure vessel. The results of the study show good similarity between the simulation model results and the results obtained by WAVE software as they are illustrated in Figures 4–7.

Comparative morphological and morphometric analysis of the structure of the wall of the calf venous collectors

Introduction. Development of venous pathology of the lower extremities is based on morphological changes in the vascular wall. Further structural restructuring of the vein wall in chronic venous insufficiency will depend on the initially present differences in the structure of their walls.Aim. To conduct a comparative analysis of morphological and morphometric features of the structure of the walls of the main venous collectors of the lower leg: the great saphenous vein, intramuscular veins, posterior tibia veins and poplitea vein.Materials and methods. Histological studies were carried out on autopsy material of the veins of 32 people who died from various causes aged 35 to 50 years and 10 amputated limbs. Morphological studies of the venous wall were carried out by light microscopy with digital photo processing.Results. A quantitative comparative analysis of morphological changes with the determination of the volume fraction of smooth muscle and connective tissue elements of various membranes of the venous wall, as well as measurement of the total thickness of the vascular wall and its ratio to the lumen of the veins showed statistically significant differences at a significance level of p < 0.05.Discussion. Despite the similarity of the general morphological picture of the structure of various venous collectors of the lower leg, structural differences were established, which concerned the volume fraction of the presence of both smooth muscle and connective tissue elements.Conclusion. The comparative qualitative and quantitative statistical analysis of morphological and morphometric features of the structure of the walls of the main venous collectors of the lower leg allows us to make an assumption about the unequal role of individual main venous collectors in the work of the muscular-venous pump of the lower leg as a whole.

RNA-sequencing suggests extracellular matrix and vasculature dysregulation could impair neurogenesis in schizophrenia cases with elevated inflammation

A subgroup of schizophrenia cases with elevated inflammation have reduced neurogenesis markers and increased macrophage density in the human subependymal zone (SEZ; also termed subventricular zone or SVZ) neurogenic niche. Inflammation can impair neurogenesis; however, it is unclear which other pathways are associated with reduced neurogenesis. This research aimed to discover transcriptomic differences between inflammatory subgroups of schizophrenia in the SEZ. Total RNA sequencing was performed on SEZ tissue from schizophrenia cases, designated into low inflammation (n = 13) and high inflammation (n = 14) subgroups, based on cluster analysis of inflammation marker gene expression. 718 genes were differentially expressed in high compared to low inflammation schizophrenia (FDR p < 0.05) and were most significantly over-represented in the pathway ‘Hepatic Fibrosis/Hepatic Stellate-Cell Activation’. Genes in this pathway relate to extracellular matrix stability (including ten collagens) and vascular remodelling suggesting increased angiogenesis. Collagen-IV, a key element of the basement membrane and fractones, had elevated gene expression. Immunohistochemistry revealed novel collagen-IV+ fractone bulbs within the human SEZ hypocellular gap. Considering the extracellular matrix’s regulatory role in SEZ neurogenesis, fibrosis-related alterations in high inflammation schizophrenia may disrupt neurogenesis. Increased angiogenesis could facilitate immune cell transmigration, potentially explaining elevated macrophages in high inflammation schizophrenia. This discovery-driven analysis sheds light on how inflammation may contribute to schizophrenia neuropathology in the neurogenic niche.

Investigating SARS-CoV-2 virion material trafficking in syrian hamster neocortecal neurons

Introduction. Taking into account the experience on the new coronavirus infection COVID-19 pandemic, the relevance of studies assessing the cellular processes of SARS-CoV-2 virus assembly and transport to justify the choice of pharmacological action points has now markedly increased. The study was aimed at analyzing morphologically assessed events of SARS-CoV-2 life cycle in neocortical neurons using electron microscopy based on its traced wide prevalence in vivo and ability to penetrate the blood-brain barrier accounts. Materials and methods. Patient-derived SARS-CoV-2 virus was obtained and accumulated in Vero(B) cell culture. An electron microscopy study (EMR) of the viral particle transport was carried out in male Syrian hamsters. Animals were inoculated intranasally with 26 μl of virus culture in an amount of 4 × 104 TCID50/ml. Animals were euthanized on day 3, 7, and 28 post-infection. The extracted brain was prepared for EMR according to methods previously described in the literature. The results were recorded using an FEI Tecnai G2 Spitit BioTWIN electron microscope. Results. Using EMR, the morphological equivalents of virus transport variants in neocortical neurons were traced dynamically during infectious process in Syrian hamsters. After synthesis, viral membrane proteins are included in transport vesicles in the endoplasmic reticulum (ER) terminal tubules and enter the intermediate compartment (IC), a collection of smooth-walled membrane vesicles between the endoplasmic reticulum (ER) and the Golgi apparatus (AG). In the first 3 days post-infection, viral copies are included in the Ag in PC membrane-formed transport vesicles. Due to the large size, viral particles are restricted to the expanded ends of the mobile AG tanks. Morphologically, destruction of AG membranes was revealed on day 7 post-infection, which indicates an interaction between PC vesicles and preserved AG membrane elements or the implementation of their independent transport function to deliver SARS-CoV-2 virus to the cell periphery and further into the intercellular space. In the neuronal processes, the transport of mature SARS-CoV-2 viral particles associated with cytoskeletal elements was observed, which was not detected in other loci of virus persistence. Conclusion. Based on data obtained, it is possible to hypothesize about a cumulative importance for progression and persistence of SARS-CoV-2 infection in cortical neurons. Early signs of neuron infection are represented by characteristic changes in the nuclei, ER hypertrophy and formation of “viral factories” based on the ER, PC and AG. The formation of viral biomass occurs inside neurons; virion exit from target cells is more accompanied by cell death rather than if a virus becomes incorporated in the lysosomal-endosomal system.

A clear view of biofouling in spacer filled membrane filtration channels: Integrating OCT and CT for improved visualization and localization

Spiral wound membrane elements for reverse osmosis (RO) seawater desalination are increasingly important to produce clean water to cope with the rising global freshwater scarcity. Spiral wound elements are prone to biofouling development which can be monitored in-situ using optical coherence tomography (OCT). Although OCT has emerged as a dominant technology for nondestructive monitoring of membrane fouling, the application of OCT to study fouling on feed spacers has been limited because image processing of spacers is complex. In this study, an automated image processing algorithm was developed for visualization and quantification of fouling in spacer filled channels. The spacer shadow was used to estimate the location of the spacer in the OCT image. Subsequently, a computed tomography (CT) scan of the same spacer type was overlaid, providing a clear indicator of the spacer position. The spacer position was used to i) correct the distortion below the spacer, ii) visualize fouling in 3D with reference to the membrane and spacer, and iii) reproducibly and precisely locate images to make time series and compare parallel experiments. The results showed that the addition of a spacer geometry as a solid object in a 3D representation of an OCT-scan greatly improves visualization, because fouling and the spacer can be distinguished and the position of fouling relative to the spacer and membrane can be clearly seen. Moreover, the ability to select a dataset relative to the orientation of the spacer will enable objective and automated quantitative analysis in future work.

A new strain-based pentagonal membrane finite element for solid mechanics problems

Polygonal finite elements remain an attractive option in finite element analysis due to their flexibility in modeling arbitrary shapes compared to triangles. In this study, a pentagonal membrane element was developed with the strain approach for the first time. The element possesses invariance, and the equilibrium constraint was applied to the assumed strain field using corrective coefficients. Inspired by the advancing front technique, a pentagonal mesh was generated, and the mesh quality was enhanced with Laplacian smoothing. The performance of the developed pentagonal element was assessed in a few numerical tests, and the results revealed its suitability in modeling the bending of beams. Besides, the numerical results are enhanced when pentagonal elements are used in mesh transitions along boundaries to smoothen curved edges and capture distributed loads.

Membrane fouling in engineering nanofiltration process for drinking water treatment: The spatial and chemical aspects

Nanofiltration (NF) has become an established process for advanced treatment of drinking water, while membrane fouling remains as the main issue slowing the widespread application of the process. In this study, the key foulants were identified, and their spatial distribution and potential interactions were investigated based on a two-stage NF engineering project for municipal drinking water treatment. Over half a year of operation showed that the membrane fouling was mostly chemically reversible. Characterizations of the cleaning waste revealed that inorganic fouling dominated at both stages, which was mainly caused by the deposition of Al, Ca, and Si. While the overall fouling was much more severe at Stage 2, the organic fouling was the reverse. Autopsy of one full-size membrane element from each stage indicated that in addition to Al, P and humic acid-like compounds were abundant in the fouling layer for both stages despite the spatial differences. The spatial distribution of foulants was influenced by both concentration effects and presence of feed channel spacers. For the free membrane area, inorganic foulants and humic acid-like compounds had higher contents at Stage 2 than Stage 1. While for the membrane area contacting with spacers, Al and P at Stage 1 were 0.74 and 1.51 times higher than those at Stage 2, respectively. Moreover, statistical analysis, complexation experiments and engineering operation strongly supported that the residual Al and natural organic matter (NOM) were key foulants for the NF process, mainly by forming Al-NOM complexes. Besides the Al-NOM complexes, condensed phosphate, primarily sourced from the dosed phosphate-containing antiscalants, might also co-precipitate with Al or Al-NOM complexes.

Over-sampling for data augmentation in data-driven models for the shear strength prediction of RC membranes

Complex reinforced concrete (RC) structures are generally assessed as a group of individual membrane elements subjected to in-plane combined stresses; however, an accurate prediction of the shear strength of such elements is still a complex task. In addition, the limited availability of experimental data of RC panels, which also presents an unbalanced statistical distribution towards lower strength values, limits the development of data-driven models. Thus, it is crucial to explore data augmentation techniques with a view to supporting the development of more accurate and generalizable predictive models in structural engineering. This paper evaluates over-sampling techniques for data augmentation and their use in the creation of an explainable, data-driven model for the shear strength prediction of RC panels. A dataset of 195 experimental tests of RC panels under different loading conditions is initially collected. Five over-sampling techniques are implemented to extend the original dataset and to reduce the imbalance. Three ensemble models (Random Forest, AdaBoost, and XGBoost) are trained with each of the generated datasets. It is observed that all the over-sampling techniques produced predictive models with better performance than the original dataset; however, the results show that by applying the Random Over-Sampling (ROS) the performance metrics of the model can significantly increase (around 39% for some metrics) compared to the model with the original dataset, without any overfitting issues. This strategy allowed to develop an accurate XGBoost model (with a value of R2 = 0.97 for the testing set). The explainability of the final predictive model (XGBoost model obtained from ROS) is evaluated using the SHAP (SHapley Additive exPlanations) analysis. The proposed predictive model outperformed traditional mechanics-based models (improvement of approximately 27% over SMCS and 33% over MCFT for some performance metrics) and with a more controlled error distribution over the range of variables. The proposed model was also more accurate (mean prediction ratio of 0.98) than sophisticated finite element analysis (mean prediction ratio of 0.84) for six specimens of the original dataset.