Column Mode Research Articles

Experimental and numerical study on influence of impact mass and velocity on failure mode of RC columns under lateral impact

Reinforced concrete (RC) structures may encounter impact loads during service life, such as vehicle collisions, ship strikes, and explosions. Limited existing impact tests on RC columns and piers have yet to fully reveal the column impact performance and its relationship with structural or load parameters. To explore the effects of impact mass and velocity, which determine the impact energy, on the impact performance of RC columns, pendulum impact tests on nine RC columns were performed utilizing a specially designed loading setup. The test variables included the impact mass and velocity of the pendulum, as well as the slenderness ratio and stirrup ratio of the columns. During the tests, the impact force and velocity of the pendulum, as well as the axial force, displacement, and acceleration of the columns, were measured. Additionally, the damage evolution of each specimen was recorded using a high-speed camera. One-side shear failure, two-side shear failure near the impact point, and shear failure at the column bottom end were observed during the tests. The results indicated that, under similar impact energy, as the impact velocity increased, the specimens with the low stirrup ratio transitioned from one-side shear failure to two-side shear failure. An enhancement in the impact resistance of the columns was observed when the stirrup ratio was increased, or the slenderness ratio decreased. For the enhanced columns, shear failure was avoided at lower impact velocities; however, at the maximum impact velocity, end shear failure or one-side shear failure yet occurred. Additionally, a parametric analysis using LS-DYNA finite element software further clarified the effects of impact velocity and mass on the dynamic response and failure mode of RC columns.

Experimental investigation on the seismic performance of square concrete/ECC filled stiffened high-strength steel tubular columns

Seismic action can lead to severe damage in the plastic hinge zone of concrete-filled steel tubular (CFST) columns, such as the localized buckling of the steel tubes and the crushing of the core concrete. Despite the numerous proposed cross-sectional configurations for CFST columns, the core concrete exhibits substantial damage under intense seismic action, making post-earthquake maintenance challenging. To mitigate the spalling of the core concrete under seismic action, this paper proposes the utilization of engineered cementitious composites (ECC), which is a cement-based composite material, for a certain height within the plastic hinge zone as a substitute for common concrete. Six square concrete/ECC-filled stiffened high-strength steel tubular (CFSHST) columns were fabricated and subjected to quasi-static tests. The effects of the yield strength of the steel tubes, cross-sectional configurations, and axial compression ratio on the seismic performance and failure modes of the CFSHST columns were investigated. Subsequently, a numerical analysis of these columns was conducted to discuss the effects of the compressive strength of the core concrete, the yield strength of the steel tubes, and the axial compression ratio on the seismic performance of the columns. Finally, a design formula for the load-bearing capacity of this type of column was established, and its accuracy was verified using experimental results and numerical model results. The results showed that the CFSHST columns with the ECC in the plastic hinge zone exhibited only minor cracks and no evident ECC spalling occurred. Moreover, the longitudinal steel bars were beneficial in alleviating the spalling issue of the core concrete in these columns. The proposed design formula for the load-bearing capacity can accurately predict the peak load of CFSHST columns.

Sustainable Banana-Waste-Derived Biosorbent for Congo Red Removal from Aqueous Solutions: Kinetics, Equilibrium, and Breakthrough Studies

This study investigates the adsorption of Congo red (CR) dye from wastewater using banana peel biochar (BPBC) in both batch and fixed-bed column modes. BPBC was characterized using FTIR, SEM, XRD, TGA, and BET analysis, revealing a predominantly mesoporous structure with a surface area of 9.65 m2/g. Batch adsorption experiments evaluated the effectiveness of BPBC in removing CR, investigating the influence of the BPBC dosage, initial CR concentration, and solution pH. Results showed optimal CR removal at pH levels below 4, suggesting a favorable electrostatic interaction between the adsorbent and the dye. Furthermore, a pseudo-first-order kinetic model best described the adsorption process. The Freundlich isotherm provided a better fit compared to the Langmuir and Dubinin–Radushkevich (D-R) models, implying a heterogeneous adsorption surface. The calculated maximum adsorption capacity (Qm) from the Langmuir model was 35.46 mg/g. To assess continuous operation, breakthrough curves were obtained in fixed-bed column experiments with varying bed heights (1–3.6 cm). The results demonstrated efficient CR removal by BPBC, highlighting its potential for wastewater treatment. Finally, this study explored the feasibility of BPBC regeneration and reuse through four adsorption–desorption cycles.

Sequestration of a food dye (sunset yellow) from wastewater using natural adsorbent: a kinetic, isotherm and interference study

Cocos nucifera, commonly known as coconut is rich in coir dust (CCD) at its outer surface, which is a very significant agri waste used as biosorbent for wastewater treatment. The current work addresses use of CCD for removal of hazardous Sunset Yellow dye (SY) FCF widely used as coloring agent in food industry, from wastewater. The uptake capacity in batch and column mode is 82 mg/g and 160 mg/g respectively. Characterization study including SEM, FTIR and BET results also supported the adsorption process. The comparative analysis with other natural biosorbents showed best results of biosorption with CCD. The output was better at high pH (10) and lower concentration of dye (5 mg/L). The kinetic study suggested pseudo second order rate revealing both adsorbate-adsorbent interdependency. The presence of covalent bonding or valence forces between the interfaces, suggested chemisorption as the rate limiting mechanism with valence forces, hydrogen bonding and pi-pi stacking being the chief forces responsible in binding of the dye molecules to the surface. The isotherm supported Langmuir model with monolayer and uniform adsorption at the interfaces. The interference test confirmed slight decrease in percent adsorption with interference from chloride and sulfate as dominating ions. The techno-economic feasibility highly recommended in field application of the substitute (net profit value, 1.256 Rs/m3, input cost, 0.052 Rs/m3). The industrial sample analysis with lab to land approach justified sustainability and commercial viability of the present work.

Torsion and Combined Torsion-Axial Load Behaviour of Concrete Filled Steel Tube Columns with and without ECC/CFRP Wrap

ABSTRACT Concrete-filled tube columns may experience coupled torsion and axial compression under seismic and wind loading. Fifteen square, rectangular, and circular concrete filled steel/aluminium tube (CFST/CFAT) are tested under pure torsion to understand the behaviour and develop/validate finite element (FE) models. Parametric studies under pure torsion are conducted using FE models to study the effect of geometric (tube cross-section, length, and thickness) and tube/concrete material parameters on torsional strength, stiffness, and tube-concrete composite interaction. FE models are used to study strength, stiffness, and failure modes of CFST columns under combined torsion and axial compression load at various preload levels of axial and torsion. Coupled torsional preloading and subsequent axial load reduce the axial load capacity significantly, while coupled axial preloading and subsequent torsional loading have shown no significant influence on the torsional strength of CFST columns. Implementation of FE models developed for CFST columns with engineered cementitious composite (ECC) and carbon fibre reinforced polymer (CFRP) wraps showed significant enhancement of axial strength and stiffness compared to control (without wrap) even under high torsional preload level. The energy absorption capacity and ductility of the CFRP wrapped CFST column are about 1.38 and 1.1 times higher than its counterpart with ECC wrap of same axial load capacity. Overall, the results suggest that use of both CFRP and ECC wrap is an effective approach to enhance the torsional behaviour and ductility of CFST columns under combined torsion and axial loading conditions. However, high crack resistance and better post-peak ductility of ECC wrapped CFST compared to sudden CFRP rupture failure in CFRP-wrapped counterpart should be taken into consideration for seismic applications.

Development of Noninvasive Method for the Automated Analysis of Nine Steroid Hormones in Human Saliva by Online Coupling of In-Tube Solid-Phase Microextraction with Liquid Chromatography–Tandem Mass Spectrometry

Accurate measurement of steroid hormones is crucial to elucidate new mechanisms of action and diagnose steroid metabolism-related diseases. This study presents a simple, sensitive, and automated analytical method for nine representative steroid hormones. The method involves on-line coupling of in-tube solid-phase microextraction (IT-SPME) with liquid chromatography–tandem mass spectrometry (LC–MS/MS). The steroid hormones were extracted and enriched on a Supel-Q PLOT capillary column using IT-SPME. Subsequently, they were separated and detected within 6 min using a Discovery HS F5-3 column and positive ion mode multiple reaction monitoring system via LC–MS/MS. Calibration curves of these compounds using each stable isotope-labeled internal standard (IS) showed linearity with correlation coefficients greater than 0.9990 in the range of 0.01–40 ng/mL, with limits of detection (S/N = 3) of 0.7–21 pg/mL. Moreover, intra- and inter-day variations were lower than 8.1 and 15% (n = 6), respectively. The recoveries of these compounds from saliva samples were in the range of 82–114%. The developed IT-SPME/LC–MS/MS method of steroid hormones is a highly sensitive, specific, and non-invasive analytical method that allows extraction and enrichment with no organic solvents, and enables direct automated online analysis by simply ultrafiltrating a small sample of saliva.

Eccentric Compression Performance of Core-Steel Tube with T-Shaped Steel Reinforced Concrete Column

This paper introduces a novel steel–concrete composite column referred to as the core-steel tube with T-shaped steel reinforced concrete (CSTRC) column, which is composed of a core steel tube with T-shaped steel embedded in a reinforced concrete column. To investigate the mechanical performance of the CSTRC column under eccentric compressive load, the load–deformation response, stress, and strain distribution of CSTRC columns under eccentric load are analyzed by finite element software. Furthermore, the effects of slenderness ratio, concrete and steel strength on the eccentric compression performance of CSTRC columns are also discussed. Finally, a set of formulas for predicting the ultimate strength of the CSTRC columns is proposed. The study results reveal that: (1) The established finite element model accurately predicts bearing capacity and strain development. (2) When the eccentricity is 0.2, the specimen exhibits characteristics indicative of small eccentricity failure. Conversely, when the eccentricity is 0.8, the specimen demonstrates traits associated with large eccentricity failure. Furthermore, as the eccentricity increases, there is a notable decrease in the bearing capacity of the specimen. (3) The slenderness ratio affects the failure mode of the CSTRC columns, with consideration for second-order effects necessary when the ratio exceeds 22. (4) Increasing the concrete strength, steel strength, and steel ratio significantly enhances the ultimate load values of the CSTRC columns. (5) A comparison between calculated and simulated values demonstrates good agreement, validating the accuracy of the proposed method.

ИЗВЛЕЧЕНИЕ БУТАДИЕНА ТРЕБУЕМОЙ ЧИСТОТЫ ИЗ БУТЕН-ДИВИНИЛЬНОЙ ФРАКЦИИ С ПОМОЩЬЮ ЭКСТРАКТИВНОЙ РЕКТИФИКА-ЦИИ

The operating modes of a distillation column with a fixed number of theoretical stages, ensuring the required extraction of butadiene from the butene-divinyl fraction, are considered

Dynamic behaviors of eccentrically loaded RC column under lateral low-velocity impact

This study aims to examine the influence of eccentric axial loads on the lateral low-velocity impact behaviors of RC columns. Firstly, the numerical simulation approach is validated by accurately reproducing the impact force, as well as the deflection, axial load and failure mode of columns in pendulum impact and eccentrically loading tests. Secondly, the effects of the axial load ratios and eccentric distances on the dynamic behaviors of RC columns are analyzed as follows: (i) Increasing the axial load ratio and the eccentric distance at the impact direction can reduce the deflection of RC columns when the axial load ratio is relatively low; (ii) the instability failure could occur on columns with large enough axial load and impact energy; (iii) the eccentric distance of axial loads on the fixed-supported RC column can be neglected since the induced boundary rotation is constrained by fixed supports; (iv) for RC columns with pinned-fixed or pinned-pinned supports, the eccentric distance at the impact direction should be considered, while the eccentric distance at the vertical impact direction can be neglected. Furthermore, the dynamic coupled flexural and shear resistance function of eccentrically loaded RC columns are established and validated. A 2DOF model is presented to predict low-velocity impact behaviors of RC columns with varying axial load ratios and eccentric distances. The failure modes transition mechanism induced by the axial load is further revealed. Increasing axial loads can enhance columns’ flexural resistance and tendency of failure mode from flexural to shear/flexure-shear. The P-δ effect is amplified by larger axial loads and deflections, causing the instability failure of columns. Finally, a theoretical impact energy of the critical instability of eccentrically loaded RC columns is proposed to assist the structural impact-resistant design.

A multi-strategy fusion identification model for failure mode of reinforced concrete column

Accurate identification of the failure modes of Reinforced Concrete (RC) columns based on the design parameters of the structural members is critical for earthquake-resistant design and safety evaluation of existing structures. Existing identification methods have some problems, such as high cost, incomplete consideration of influencing factors, and low precision or recall in identifying shear or flexural-shear failure. In this paper, the main factors for the failure modes of RC columns are first analyzed and studied. Then, the problem of class imbalance in data samples is investigated. To identify the failure modes of RC columns, oversampling of data (BSB-FMC), model ensembling (RFB-FMC), cost-sensitive learning (CSB-FMC) and a fusion model of three strategies (BSFCB-FMC) are proposed. And finally, the SHapley Additive exPlanations (SHAP) method is used to provide a better interpretation of the designed model. The results show that the developed strategies can improve the accuracy of identifying the failure modes of RC columns compared to the models using a single Artificial Neural Network (ANN), a Support Vector Machine (SVM), a Random Forest (RF), and Adaptive Boosting (AdaBoost). The overall accuracy of the developed BSFCB-FMC model reaches 97%, and the precision and recall for the three failure modes are both above 90%. The designed model provides a solution for fast, accurate and cost-effective identification of the failure modes of RC columns.

Seismic behavior test and plastic hinge theory for HRB500 prefabricated steel reinforcement cage-cast-in-situ concrete columns

An innovative method for constructing concrete columns has been proposed, namely utilizing the hot-forged double-lock mother combined mechanical sleeve connection for the HRB500 prefabricated steel reinforcement cage－cast-in-situ concrete (PRC-CISC) columns. The purpose of this method is to promote the industrialization of steel reinforcement projects and enhance the quality of structural construction. Two traditional reinforced concrete (RC) columns and four PRC-CISC columns were designed for quasi-static tests with design axial compression ratio (ACR) and reinforcement connection methods as parameters. Firstly, the results of the study showed that all specimens exhibited typical flexural failures, with well-rounded hysteresis curves, gradual stiffness degradation in the later stages, good ductility, and energy dissipation. Mechanical sleeve connections had a minor impact on the failure mode of PRC-CISC columns. Increasing the ACR improved the carrying capacity but reduced ductility, narrowed the hinge zone, and increased longitudinal bar stress. The effect of sleeve connection on energy dissipation, stiffness, ductility, and carrying capacity of the specimens was limited, and the overall behavior was stable and controllable. Furthermore, the carrying capacity and stress distribution of core area steel bars in traditional RC columns and PRC-CISC columns were further calculated to assess the differences. Finally, a two-stage plastic hinge calculation theory was formulated, which takes into account the influence of axial pressure, and construction recommendations for two types of PRC-CISC columns were provided.

Remediation of Cr(VI) using a radiation functionalized green adsorbent: Adsorption modelling, mechanistic insights and prototype water purifier demonstration

The work reports remediation of hexavalent Chromium (Cr(VI)) in water using a radiation functionalized cellulose based green adsorbent, fabricated via gamma radiation assisted Mutual Irradiation Grafting Process (MIGP), wherein poly(2-Trimethylammoniumethyl methacrylate chloride) (PTMAEMC) was grafted onto Woven Cotton Cellulose Fabric (WCCF). The grafted adsorbent “ChromClear” efficiently sequestered Cr(VI) from water and demonstrated a maximum adsorbent capacity of ∼55 mg.g−1, successfully curtailing Cr(VI) concentrations to <20 μg.L−1. Characterization of samples was performed using 13C NMR, XPS, SEM-EDS, FTIR, TGA, and BET analysis. The equilibrium adsorption, kinetic, and breakthrough curve data were analysed using various theoretical models to infer the adsorption mechanism and extract important process parameters. Artificial Neural Network (ANN) modelling was used to predict adsorption capacity and % Cr(VI) removal in continuous flow column mode under different operational conditions, with a high degree of agreement (R2 > 0.99) between experimental and modelled data. Density Functional Theory (DFT) calculations established the interaction between CrO42− and PTMAEMC groups of ChromClear to be occurring in a 1:2 ratio. ChromClear could be regenerated for over five recycled iterations with >88 % retention in adsorption capacity. Concept based prototype water purification systems were also developed for pump as well as gravity driven continuous flow operations, and successfully demonstrated for remediation of Cr(VI) contaminated ground water samples. The efficacy and simplicity of the process provides ample scope for further upscaling and deployment for community level water treatment applications, with a special emphasis on compliance with drinking water norms in affected areas.

Sodium hydroxide supported cellulose for efficient removal of cationic dyes from aquatic solutions in batch and column modes: Adsorption characteristics and mechanism study

Sodium hydroxide supported cellulose for efficient removal of cationic dyes from aquatic solutions in batch and column modes: Adsorption characteristics and mechanism study

Compressive Behaviour of Long Steel Tube Columns Filled with Recycled Large Aggregate Self-Compacting Concrete

One of the important directions for green development in the world today is to expand the application methods of recycled concrete, improve the utilization rate of waste aggregates, and slow down the consumption of natural resources. The column structure with a large length and slenderness ratio is the most widely used compression unit in practical engineering, which conforms to the principle of sustainable development. In this paper, we study the mechanical properties and failure modes of long columns fabricated from steel tubes filled with recycled large aggregate self-compacting concrete (RLASCC-ST-LC) under compression load. Moreover, we examine the influence of steel tube thickness, recycled large-aggregate particle size, the strength of self-compacting concrete, and the length-to-diameter ratio on the performance of the members through finite element modelling. The results indicated that RLASCC-ST-LCs exhibited different degrees of buckling damage, and the damage processes were basically the same as that of steel tube concrete. When the thickness of steel pipe increased from 4 mm to 5 mm, the ultimate bearing capacity of the component increased by 12.1%; when the strength of self-compacting concrete increased from 30 MPa to 40 MPa and 50 MPa, the ultimate loads of the component increased by 6.96% and 12.4%, respectively. However, the increase in the aspect ratio weakened the bearing capacity of the component, and the ultimate bearing capacities reduced by 4.78% and 10.51% when the aspect ratios were 8, 10, and 12. Finally, based on the existing design codes, the theoretical calculation formulas are proposed for the ultimate bearing capacities of RLASCC-ST-LCs. These findings have significant implications for the widespread application of RLASCC-ST-LCs.

Experimental and numerical research on the uniaxial behavior of the stiffened circular concrete-filled steel tube stub columns

In large-span bridges or high-rise buildings, CFST columns with large width-to-thickness ratio are often adopted, which require proper stiffening measures to improve the mechanical behaviors. This paper presents a comparative study of circular CFST stub columns with different stiffening methods, including longitudinal stiffeners (cross-shaped, T-shaped and ordinary type), additional reinforcement and headed studs. Axial compression tests have been conducted to investigate the effects of different stiffening methods on the failure mode, ultimate strength and ductility of the circular CFST stub columns. Finite element models are established to simulate the columns’ behaviors and conduct parametric studies. Based on test and simulation results, an axial bearing capacity prediction model for circular CFST stub columns stiffened by longitudinal stiffeners is proposed. It is demonstrated that the failure modes of the steel tube and core concrete are changed by the longitudinal stiffeners. The longitudinal steel stiffeners as well as reinforcing cage can effectively improve the axial bearing capacity and ductility of the columns. The latter is more efficient in promoting the bearing capacity while the former is more efficient in improving the ductility and residual strength. A combination of the additional stirrups and the ordinary stiffeners will be a more economical choice. In addition, the proposed formula gives better prediction accuracy compared to the equations in various design codes.

Selective recovery of boron, cobalt, gallium and germanium from seawater solar saltworks brines using N-methylglucamine sorbents: Column operation performance

The European Union (EU) identified a list of Critical Raw Materials (CRMs) crucial for its economy, aiming to find alternative sources. Seawater is a promising option as it contains almost all elements, although most at low concentrations. However, to the present, the CRMs' recovery from seawater is technically and economically unfeasible. Other alternatives to implement sea mining might be preferred, such as reverse osmosis brines or saltworks bitterns (after sodium chloride crystallisation). The CRMs' extraction in a selective way can be achieved using highly selective recovery processes, such as chelating sorbents. This study focuses on extracting Trace Elements (TEs) from solar saltworks brines, including boron, cobalt, gallium and germanium, using commercial N-methylglucamine sorbents (S108, CRB03, CRB05). The application of these sorbents has shown potential for boron recovery, but their selectivity for cobalt, gallium, and germanium requires further investigation. This research aims to assess these sorbents' kinetics and column mode performance for TEs recovery from synthetic bitterns. Boron and germanium were rapidly sorbed, reaching equilibrium (>90 %) within 1 h, except for S108, which took 2 h. In column mode, 20–25 pore volumes of bittern were treated to remove boron and germanium, but competition from other elements reduced treatment capacity. An acidic elution (1 M hydrochloric acid) allowed to elute them (>90 %), reaching concentration factors for germanium and boron of 35 and 11, respectively, while cobalt and gallium had less affinity for the sorbents. In addition, the experiments performed were fitted by a mass transfer model to determine the equilibrium constants and selectivities. Therefore, bittern mining has been proven as a secondary/alternative source to obtain CRMs, which can lead the EU to a position in which its dependence on other countries to obtain these raw materials would be decreased.

Research into arsenic (III) effective catalytic oxidation in an aqueous solution on a new active manganese dioxide in a flow column

Groundwater in many places on Earth contains arsenic compounds. Arsenic (III) compounds must be oxidised to purify water containing arsenic effectively. The subject of this study is oxidation of arsenic (III) compounds in an aqueous solution. Today’s most common industrial arsenic oxidation method using aggressive oxidising agents such as chlorine or ozone has a number of serious disadvantages. The most problematic of these include extremely high risks to human health and the environment, the cost and overall complexity of the process. Catalytic oxidation of arsenic (III) compounds using atmospheric oxygen is an alternative free from the above disadvantages, yet, to date, no information about effective catalysts for this process has been presented in the literature. The arsenic (III) catalytic oxidation process is studied in an aqueous solution on a new active manganese dioxide (NAMD) synthesised by the author. A comparative experimental analysis is performed with other known modifications of manganese dioxide. It is shown that the new active manganese dioxide (NAMD) has high catalytic activity towards arsenic (III), this being confirmed experimentally in both a limited volume and a flow column mode. Some theoretical aspects of the mechanism for catalytic oxidation of arsenic (III) with oxygen on active manganese dioxide in an aqueous solution are also discussed on the basis of the research results. Experimental work is required at pilot plants in the field for successful industrial implementation of the technology for catalytic oxidation of arsenic (III) compounds on NAMD. Further laboratory research is necessary for developing a detailed theoretical basis for catalytic oxidation of arsenic in aqueous solutions. The results of this research are of interest to industrial companies specialising in removing arsenic compounds from water, to scientists and researchers studying catalytic oxidation of arsenic (III), as well as heterogeneous catalytic oxidation with oxygen in general.

Experimental study of energy‑absorbing and support characteristics of glass microsphere-filled steel tube columns under uniaxial compression.

An innovative energy-absorbing and bearing structure was proposed, which incorporated the coupling of glass microspheres with a metal tube. Glass microsphere-filled steel tube (GMFST) column, consisting of external steel tube and inner glass microspheres, was expected to give full play to the energy-absorbing and load-bearing capacities of the particle while restricting particle flow from collapsing, thereby enhancing the overall structural strength. Four groups of steel tubes and the GMFST specimens were designed and subjected to axial compression tests at four different loading rates to investigate the performance of the structure. These tests aimed to analyze the deformation mode, mechanical response, and energy absorption capacity of the GMFST columns under quasi-static to low-speed compression conditions. The results indicated that the deformation process and failure mode of GMFST columns were similar to those of hollow steel tubes, albeit with a different post-buckling mode. Filling the steel tubes with glass microspheres reduced the load fluctuation range, moderated load-displacement curves, and exhibited a strain rate strengthening effect. The GMFST columns demonstrated superior energy absorption capacity, with significant increases in crush force efficiency, the averaged crush force, and the total absorbed energy, particularly in terms of subsequent support capacity. The load-increasing reinforcement properties enabled GMFST columns to overcome the limitations associated with the unstable post-buckling path of energy‑absorbing damping structure, exhibiting outstanding load-bearing performance and stability in the later stages. The results provided valuable guidelines for designing and engineering high-performance GMFST columns, serving as a new type of energy-absorbing and supporting structure.

Reduction-orientated selective removal of selenate by thiourea-functionalized polystyrene material

Efficient removal of trace selenate [Se(VI)] from contaminated water is still challenging because of the inevitable interference from the coexisting anions toward the adsorption or ion-exchange process. Herein, a bifunctional material (NCS@CMPS) was proposed for selective removal of Se(VI) from a complex matrix. NCS@CMPS was subtly prepared by grafting a chloromethylated polystyrene substrate (CMPS) with thiourea, resulting in reductive groups (C-SH and C=S) and adsorptive sites (–NH-, –NH2, and C=NH2+) anchored on the skeleton of CMPS. Batch studies demonstrated an excellent removal efficiency and anti-interference capabilities of NCS@CMPS toward Se(VI), even with very high levels of competing anions (chloride, sulfate, phosphate, nitrate, and bicarbonate) over a wide pH range (3 ∼11). The in-situ reductive removal and the unique pH-buffering effect of NCS@CMPS were responsible for the high selectivity and the wide applicability. The XPS analyses identified the removal mechanisms of concentrating, reducing, and sequestrating of Se species inside NCS@CMPS, where the majority of Se species was reduced to Se(IV) (80.9%). In column mode, NCS@CMPS can treat over 10,000 bed volumes (BV) of a simulated Se(VI) wastewater ([Se]ini = 200 μg/L) to below 10 μg/L, whereas the capacity of its substrate (i.e., CMPS) was only 28 BV. Additionally, the exhausted NCS@CMPS can be regenerated by NaBH4-NaOH-HCl treatment for repeated use. Moreover, the effectiveness of NCS@CMPS in treating actual industrial Se(VI) wastewater was also validated.

Machine learning tools to improve nonlinear modeling parameters of RC columns

Modeling parameters are essential to the fidelity of nonlinear models of concrete structures subjected to earthquake ground motions, especially when simulating seismic events strong enough to cause collapse. This paper addresses two of the most significant barriers to improving nonlinear modeling provisions in seismic evaluation standards using experimental data sets: identifying the most likely mode of failure of structural components, and implementing data fitting techniques capable of recognizing interdependencies between input parameters and nonlinear relationships between input parameters and model outputs. Machine learning tools in the Scikit-learn and Pytorch libraries were used to calibrate equations and black-box numerical models for nonlinear modeling parameters (MP) a and b of reinforced concrete columns defined in the ASCE 41 and ACI 369.1 standards, and to estimate their most likely mode of failure. It was found that machine learning regression models and machine learning black-boxes were more accurate than current provisions in the ACI 369.1/ASCE 41 Standards. Among the regression models, Regularized Linear Regression was the most accurate for estimating MP a, and Polynomial Regression was the most accurate for estimating MP b. The two black-box models evaluated, namely the Gaussian Process Regression and the Neural Network (NN), provided the most accurate estimates of MPs a and b. The NN model was the most accurate machine learning tool of all evaluated. A multi-class classification tool from the Scikit-learn machine learning library correctly identified column mode of failure with 79 % accuracy for rectangular columns and with 81 % accuracy for circular columns, a substantial improvement over the classification rules in ASCE 41-13.