Column Mode Research Articles

Dynamic and mass-exchange parameters of scandium recovery by TVEX-TBP in column mode from the solution after salt chlorinator cake leaching

The paper deals with scandium extraction with Levextrel-type resin named TVEX contained tributyl phosphate (TVEX-TBP) in the column mode from the clarified solution formed after leaching salt chlorinator cake formed at Zaporozhye Titanium & Magnesium Combine Ltd. It was found that TVEX-TBP featured high extraction parameters. Total dynamic exchange capacity was defined. Mass-exchange parameters were calculated for scandium extraction in the column mode taking into account the impact of external diffusion kinetics: time to form the equation concentration front, front parallel transfer time, concentration and kinetic recovery factors, kinetic factor of external diffusion, linear speeds of the solution in the column and the equilibrium concentration front motion. The calculated mass-exchange parameters may be used to design the column cascade for scandium extraction from the clarified leaching solution of the salt chlorination cake in column mode. There are the following advantages of scandium extraction with TVEX-TBF in the column mode in comparison with its recovery in a reactor cascade: simpler hardware design and process control, the possibility to better wash TVEX from impurities, getting a strippant higher Sc concentration, reduced TVEX abrasion.

Rhenium recovery from highly concentrated sulfuric media using AMR anionite in column mode

The paper deals with the study of rhenium recovery by AMR anionite from model high-acidic sulfuric solution as well as its desorption by ammonia solution in column experiments. Total dynamic exchange capacity was calculated. Experimental data were processed using the Thomas, Yoon-Nelson and Bed Depth Service Time models, basic parameters were calculated. It was found that total dynamic exchange capacity calculated by Thomas fit was the closest to the experimental value. Rhenium desorption was examined using ammonia solution. Rhenium recovery degree and concentration factor were calculated. The elution curve featured a clear peak that allows producing eluate with high rhenium concentration. The presented results may be used when designing technologies for rhenium sorption from different process solutions and during recycling rhenium-containing alloy wastes.

Dynamic behavior of concrete-filled steel tube cantilever columns stiffened with encased carbon fiber reinforced plastic profile subjected to lateral impact load

The impact behavior of building and bridge structures is already a growing concern due to the frequent occurrence of vehicle collision accidents. Concrete-filled square steel tube stiffened with encased I-shaped carbon fiber reinforced plastic profile (CFST-CFRP) is suitable for building and bridge structures due to its high bearing capacity and small section size. Thus, this study experimentally and numerically presents the dynamic responses for CFST-CFRP columns under lateral impact to evaluate their impact resistance. Firstly, three CFST-CFRP columns and one CFST column were tested in a rigid vehicle impact device, with variations in impact velocity, impact type, impact impulse of the rigid vehicle, and CFRP profile. The impact force-displacement curve and failure mode of CFST-CFRP columns were obtained. Additionally, finite element analysis (FEA) models were built by ABAQUS and verified against tested results. Then, the working mechanisms of CSFT-CFRP columns under impact load were further revealed in-depth by analyzing displacement, impact force, inertia force, bending moment, shear force, and dissipated energy. Based on the working mechanisms, the effect of the CFRP profile on the dynamic response of CFST-CFRP member subject to different parameters was discussed. The results indicated that all the specimens fail at the support. With the additional CFRP profile in the CFST column, the failure pattern of the steel tube was transformed from fracture to local buckling. CFRP profiles enhance the impact resistance of CFST columns (incremented by 17%), and the increasing ratio rises with the decreasing steel ratio and steel strength of members. Steel tubes can share 72% and 78% of energy absorption and bending moment, which is the main impact-resistant component. For this study, valuable experimental data can be supplied for CFST-CFRP columns subjected to vehicle collision. Meanwhile, a theoretical reference for impact resistance design in the future is also provided.

Post-fire performance of axially-loaded elliptical concrete-filled steel tubular stub columns

This paper investigates the post-fire performance of elliptical concrete-filled steel tubular (CFST) columns by a series of post-fire axially-loaded stub column tests and numerical analysis. The test parameters included target temperature, high temperature duration time, section type and section size. A post-fire stress-strain relationship model of core concrete applicable to the elliptical CFST column was proposed according to the test data, and finite element analysis (FEA) model of the elliptical CFST column was established. Based on the FEA model, the temperature and deformation developments, failure mode, stress and load distributions of elliptical CFST columns were analyzed and discussed, and parametric analysis was further conducted to identify the key influencing factors on the post-fire ultimate bearing capacity and residual bearing capacity index of elliptical CFST columns. Finally, a simplified formula was proposed to calculate the post-fire residual bearing capacity index of elliptical CFST columns.

The Efficiency of Steel Brace Strengthening of School Buildings according to the Failure Mode of Columns

The Efficiency of Steel Brace Strengthening of School Buildings according to the Failure Mode of Columns

Flexural strengthening of full-scale RC columns with Adhesively-bonded longitudinal CFRP plates: An experimental investigation

Conventional method of flexural strengthening of RC columns using carbon fiber reinforced polymer (CFRP) composites is transverse wrapping. However, for rectangular columns, this method is not effective or requires modification of column geometry. In this paper, a new configuration of rectangular RC column flexural strengthening system is investigated. The new system includes prefabricated CFRP plates vertically attached on column surfaces, and a short concrete jacket to prevent debonding of the CFRP composites. Five full-scale rectangular RC columns strengthened by either concrete jacket or vertical CFRP plates were tested under cyclic loading. Cyclic performance of the strengthened columns, and strain distribution of CFRP composites on the tension side were investigated. Test results showed that failure modes of rectangular RC columns were changed by application of CFRP composites. Vertical CFRP plates are effective in improving ultimate capacity and stiffness of rectangular RC columns under cyclic loading.

Influence of support interface on the lateral performance of rocking columns in traditional Chinese timber structures

This study investigates the influence of support interface on the lateral performance of rocking columns in traditional Chinese timber structures. Six half-scaled timber column specimens, characterized by stone bases or timber bases, were reversed cyclically tested. Typical damage modes were identified, the load–displacement curves of the specimens were evaluated and compared with those of rigid rocking bodies. Theoretical analysis was further conducted based on a trilinear model. The experiments indicated that with the decrease of support stiffness, the damage mode of timber rocking columns shifted from slight parallel to grain deformation at column bottom to significant perpendicular to grain deformation at timber beams. The support stiffness significantly influenced the lateral performance of timber rocking columns. The peak load of a column resting on a stone base was about 80% of that of corresponding rigid rocking body, the column’s hysteretic loops overlapped each other with strength degradation coefficients greater than 0.95. However, with softer timber beams as support, the peak load of a column was reduced to 46% of that of corresponding rigid rocking body, the column’s hysteretic curves prominently pinched and the strength degradation coefficient decreased up to 0.1 with the increase of loading amplitude. The model-based theoretical analysis well captured the load–displacement curves of timber rocking columns on stone bases, and it further indicated when calculating the load–displacement relationship of timber rocking columns on timber beams with lower support stiffness, the local compression effect and hardening effect perpendicular to grain should be considered.

Study on Eccentric Compressive Behavior of Concrete Columns Reinforced with NPR735 High-Strength Steel Bars

In this paper, eccentric compressive tests and theoretical studies of grade 735 MPa reinforced concrete columns were conducted. The eccentric distance and strength of the longitudinal reinforcement were used as experimental parameters to investigate the bearing capacity, failure mode, and strength of eccentric compressive behavior of NPR735 high-strength steel bars. When the load eccentricity of the reinforced concrete columns was small or longitudinal, the reinforcement ratio was large, and small eccentricity failure occurred. The results were similar to the failure mode of ordinary concrete columns with traditional steel bars. When the load eccentricity decreased, the bearing capacity increased, but the deflection and ductility of the specimen decreased. When the strength of the longitudinal reinforcement increased, the bearing capacity of the specimen increased slightly. Finally, according to current design methods in the concrete structure design code, the bearing capacity of the eccentric compressive column was obtained, and the calculated results were compared with the experimental results to verify the applicability of the concrete structure design code GB50010-2010 to concrete columns with grade 735 MPa reinforcement.

Residual seismic resistance of CFDST columns after a close-in explosion: Experimental study

This paper examines the residual seismic resistance of a concrete filled double-skin steel tube (CFDST) column after a close-in explosion experimentally. First, six 1/4 scaled CFDST columns were fabricated and tested under a close-in explosion with scaled distances ranging from 0.116 m/kg1/3 to 0.232 m/kg1/3. After that, the failure mode and seismic behaviours of the CFDST columns, including one intact specimen, three postblast specimens, and three postblast specimens with retrofitting, were investigated via the cyclic loading test. Additionally, a modified composite damage index was proposed. The results showed that: (i) The CFDST column exhibited a combined localized crater and overall deformation under a close-in explosion, which became more severe as the scaled distance decreased. (ii) As the initial damage degree of the specimen increased, the likelihood of a plastic hinge developing in the blast-induced crater region to consume the hysteretic energy increased. (iii) A weak hinge formed at the crater caused by slight blast damage can assist the plastic hinge induced by the repeated lateral loading to enhance the energy dissipation capacity of the specimen. (iv) In the cyclic loading test, the lateral loading capacity, initial stiffness and energy dissipation of the specimens decreased with the increase in the initial degree of the blast-induced damage. (v) The deformation of the inner steel tube had an unfavourable influence on the stiffness and energy dissipation capacity of the postblast specimen with and without retrofitting. (vi) Among all the specimens, the retrofitted columns exhibited the worst lateral loading capacity, ductility, and energy dissipation capacity due to weld joint failure at the column foot. (vii) When the damage index is less than 0.5, the postblast CFDST column should be retrofitted for further use. In particular, the inner steel tube should be repaired. When the damage index exceeds 0.5, demolishing the postblast CFDST column is suggested.

Classification method for failure modes of RC columns based on class-imbalanced datasets

In order to overcome the limitation that traditional machine learning (ML) techniques cannot accurately classify the failure modes of reinforced concrete (RC) columns due to the imbalance class distribution in datasets, an efficient classification method for four types of failure modes of RC columns based on class-imbalanced datasets was proposed. A new treatment method for class-imbalanced datasets was proposed first by combining the synthetic minority over-sampling (SMOTE) with the Tomek Links technique. Then an efficient classification method for four types of failure modes including flexure failure (F), flexure-shear failure (FS), shear failure (S) and splitting failure (SF) for RC columns was developed based on the gradient boosting decision tree (GBDT) algorithm. Finally, the proposed method was validated by comparing with untreated method and four traditional treatment methods for class-imbalanced datasets and six typical machine learning methods based on a total of 423 sets of experimental data for RC columns (including 253 sets of F, 65 sets of FS, 53 sets of S and 52 sets of SF). The results show that F1 scores and Kappa coefficients of the minority classes (e.g., FS, S and SF) were increased about 12% and 0.14 respectively when comparing with untreated method and four traditional treatment methods for class-imbalanced datasets, while F1 scores and Kappa coefficients of the minority classes were increased about 19% and 0.17 respectively when comparing with six typical machine learning methods. The proposed class-imbalance treatment method is a hybrid sampling method, which overcomes the limitation of both over-sampling and under-sampling techniques.

Experimental study on the seismic behavior of RC columns with high axial compression ratios retrofitted by large rupture strain fiber-reinforced polymer

Fiber-reinforced polymer (FRP) composites being utilized to retrofit reinforced concrete (RC) columns has been well documented. However, the axial compression load of the FRP retrofitting RC columns was relatively limited. Aiming to analyze the applicability of FRP retrofitting RC columns with higher axial compression loads, this paper presents an experimental study on the seismic performance of RC columns retrofitted by the Polyethylene Terephthalate (PET) FRP composites. A total of twelve 1/3 scale RC columns were fabricated, including four control specimens and eight PET FRP retrofitting columns with two retrofit schemes. All the columns were tested under combined high axial compression load and cyclic lateral displacement excursions, and the maximum axial compression ratio reaches 1.1. The seismic performance of RC columns retrofitted by PET FRP was analyzed detailedly from the failure mode, shear force and deformation capacity, energy dissipation and ductility. The test results showed that PET FRP retrofitting changed the failure mode of RC columns from brittle to more ductile. The post-peak strength degradation of the columns was more rapid with the increase of axial compression ratio, but the strength degradation of the PET FRP retrofitting columns was more gradual. PET FRP retrofitting significantly improved the ductility and lateral deformation capacity of the columns even under the high axial compression ratio. PET FRP retrofitting can be applied for the RC columns with serous demand of deformation capacity due to the lighter change of shear-loading capacity and stiffness. Contrastively, the improvement of the seismic capacity of the RC columns retrofitted by the laterally wrapped scheme is higher than that of the striped wrapped scheme. Conclusions from this study provide useful references for the seismic retrofitting of RC structures.

Seismic behavior of RC cross-shaped column under combined torsion loading: Experiment and simulation finite element

The seismic behavior of the reinforced concrete (RC) cross-shaped columns under the combined action of compression, bending, shear, and torsion were studied by experiment and numerical simulation. The effects of torsion-bending ratio (T/M) and axial compression ratio (n) on the seismic indexes, i.e., failure modes, skeleton curves, hysteretic curves, strength, ductility and stiffness were studied. Experimental results suggested that the T/M ratio determines the failure modes of RC cross-shaped section columns. Both the damage length and crack angle increase with the raise of the T/M ratio. The displacement ductility factor and elastic–plastic drift ratio are higher than 3.0 and 0.02, respectively, indicating that the RC cross-shaped columns exhibit good ductility and deformation capacity under combined torsion loading conditions. The normalized shear-displacement hysteretic model and the torque-twist angle hysteretic model were established. Based on the experimental results, as well as the finite element model for RC cross-shaped columns under combined torsion, was proposed. The results derived from the hysteretic models and finite element simulation are in good agreement with the experimental results.

Electroblown titanium dioxide and titanium dioxide/silicon dioxide submicron fibers with and without titania nanorod layer for strontium(II) uptake

Nuclear power is a clean alternative to fossil fuels. However, the use of nuclear energy generates hazardous fission products of which 90Sr is the second most important. To remove Sr2+ from aqueous solutions, we synthesized submicron TiO2 and TiO2/SiO2 composite fibers with Ti : Si molar ratios of 3 : 1 (3TiO2–1SiO2) and 1 : 1 (1TiO2–1SiO2) utilizing a novel electroblowing technique. After calcination at 500 °C, the TiO2 and 3TiO2–1SiO2 fibers had a predominantly anatase TiO2 structure with portions of rutile and brookite but the crystallites in the 3TiO2–1SiO2 fibers were smaller due to the SiO2 component. The 1TiO2–1SiO2 fibers were quasi-amorphous. Rutile TiO2 nanorods were grown on the fibers by a hydrothermal method. The rods seemed to grow only on the TiO2 domains of the fiber surface, which affected their size and morphology. In batch adsorption experiments all the fibers had excellent Sr2+ uptake with the hydrothermally modified TiO2 fibers having the highest distribution coefficient (Kd) of 3,490,000 mL g−1. The results show that both anatase and rutile TiO2 can efficiently adsorb Sr2+ from an aqueous environment. Hardly any damage was observed in the nanorods on the TiO2 fibers in a column operation test with flow rates up to 74 mL h−1 which is promising for the use of the fibers in industrial column mode wastewater treatment.

Experimental and Numerical Investigation into the Stability Behaviour of Cable-Stiffened Steel Columns.

A cable-stiffened steel column (CSSC) possesses superior stability behaviour compared to ordinary compression columns. In the past, the research emphasis has focused on the behaviours of stiffened columns under axial compression; investigations into their behaviour under eccentric loading is scant. This study aims to examine the buckling behaviour of CSSCs under eccentric loading using experimental and numerical investigations. The effects of pretension in cables and eccentricity on stability behaviours were studied. According to the current investigation, it can be demonstrated that the capacities of CSSCs are higher than those of ordinary compression columns. It has also been illustrated that both the buckling loads and modes of CSSCs can be changed by changing the load eccentricity; however, the modes of ordinary columns cannot be changed. These results could be of theoretical and engineering significance in the exploration of the behaviours of cable-stiffened columns.

Experimental Study on the Seismic Performance of Hollow Columns with Fiber Lightweight Aggregate Concrete

To study the seismic performance of hollow columns with fiber lightweight aggregate concrete, a quasi-static test on eight hollow columns with fiber lightweight aggregate concrete under lateral low-cycle reversed loading and axial force is presented in this article. The effects of the dosage of plastic-steel fibers (0, 3, 6 and 9 kg/m3, respectively), steel fibers (25, 50 and 75 kg/m3, respectively) and the axial compression ratio (0.4 and 0.6, respectively) on the seismic mechanical properties such as capacity under lateral load, stiffness, ductility and energy dissipation were investigated, and the main failure morphology and force mechanism of hollow columns with fiber lightweight aggregate concrete under lateral low-cycle reversed loading were revealed. The results showed that (1) the failure modes of hollow columns could be divided into shear failure, bending-shear failure and bending failure; (2) compared with the specimens without fiber, the increase in ductility coefficient of specimens with plastic-steel fiber was 2~33.7%, and that with steel fiber was 30.8~125.7%; the increase in cumulative energy dissipation of specimens with plastic-steel fiber was 5.3~43.7%, and that with steel fiber was 88.9~203.8%, thus indicating that the seismic performance of the specimens could be improved effectively via the incorporation of fibers. The formula of shear capacity under lateral load was proposed, and its calculation results were more reliable when compared with the actual project. A foundation for further research on the seismic performance of hollow columns with fiber lightweight aggregate concrete is provided.

Impact of background strains and diet on metabolic profile in mouse model of Alzheimer’s disease

AbstractBackgroundGenetic background is known to significantly affect the behavioral and molecular phenotypes in mice and has been well documented over many disease areas including Alzheimer’s disease (AD). However, how different background strains and their interaction with environmental factors such as high fat diet (HFD) could have an impact on metabolic phenotypes in AD not known.MethodTo determine how genetic background, diet, sex and age contributes to the metabolic profile in AD, 2.5 months old male and females 5xFAD mice on C57BL/6J (B6) and B6D2 background were fed either normal chow diet, or 45% high‐fat diet till 6 or14 months of age and compared to their age matched non‐transgenic littermate controls. Blood plasma samples were collected and a four‐mode discovery metabolomics approach on a Q‐Exactive Orbitrap coupled to an ultra‐high‐performance liquid chromatography (UHPLC) system was used to analyze metabolic changes.ResultFollowing the quality assessment of spectral data, the dataset contained a total of 21,746 features across C18 and HILIC columns run with negative and positive ionization. After further filtering for named metabolites, removing duplicates, and a Fragment Ion Search (FISh) Score > 10, a total of 3,199 unique metabolites with high confidence MS2 fragmentation remained. Using linear regression analysis on these unique metabolites, we found that diet has a substantial impact (of all the factors tested including diet, sex, age, background strain, genotype) on plasma metabolites in both the strains with and without 5XFAD genotype, both in positive and negative mode of C18 and HILIC columns. Further on examining the interactive effects of different factors, we found a stronger interaction effect of sex by diet on metabolic phenotype. Interestingly, background strain had a moderate influence on collective metabolites irrespective of sex and age of mice.ConclusionOur initial results suggest that HFD is a major factor in defining the metabolic profile in AD mice above background strain, that could affect AD pathophysiology. We are currently looking into various classes of metabolites altered following HFD feeding and performing metabolic pathway analysis to understand the underlying disease mechanisms.

Оптимізація процесу перегонки спиртової бражки

Criteria for optimization of the distillation process of the distillated liquor are qualitative composition of the liquor distillate, concentration of ethyl alcohol in the distillate and bard and specific flow rate of heating steam in the distillation column. These characteristics depend on the quality composition of the mash, the number and type of plates, the hydraulic mode of their operation, the temperature mode of the distillation process, the method of heating the column, the degree of decarbonization of the mash and the effectiveness of automation of control and monitoring of technological parameters. An important optimization factor is increase of the con-tact time of steam and mash on the column plates in order to achieve a phase state close to equilibrium. The authors proposed an energy-saving technology for distillation of the mash in the mode of controlled cycles of its delay and overflow, developed a design of distillation column for the implementation of the innovative method and hardware-technological scheme of inclusion it to work. Under production conditions, the optimal technological parameters and hydraulic operating modes of the experimental column of cyclic action are established. It is proved that the innovative way allows to prolong time of contact of steam and mash on each plate to 35—40 s and to reduce time of its overflow from plate to plate to 1.5—1.7 s, due to this the concen¬tration of ethyl alcohol in the distillate increased by 33% (up to 60% vol.), the column capacity — by 17% (from 15000 to 18000 dm3/h) and specific consumption of heating steam for distillation process decreased by 60% (from 25 to 10 kg/dl in terms of anhydrous alcohol, introduced to the feed plate). In order to achieve the above-mentioned indicators, it is sufficient to install 24 flake plates with variable free cross-secti¬on, which allows reducing the metal-intensity of the technological equipment.

A reinforcing protection for steel parking-structure column under vehicular impact and design method

Previous studies manifest that steel parking-structure columns have an inferior impact resistance. The main objective of this research is to present and design a reinforcing protection (RP) for the existing columns to prevent structural damage under vehicular impacts. The failure modes of the parking-structure column were disclosed based on the validated numerical methods and reduced vehicle model. According to the failure modes, a novel RP was proposed which has the virtues of easily assembling and without taking extra land. Subsequently, numerical analyses were conducted to explore the behaviour of the column equipped with an RP. The results demonstrate that the RP is effective at reducing lateral deformation, particularly local deformation. More significantly, they show that diverse RPs will cause the reinforcing columns to exhibit various failure modes wherein failure mode II where two plastic hinges appear at the column middle is an expected pattern for the ideal design. To better design the RP, the analytical study was carried out to describe the relationship of PR’s sectional parameter and then a procedure was given for a rapid optimal design. Eventually, the well-designed RPs were applied to the different columns and their universality and effectiveness were validated. The RP with a good design can efficiently and feasibly improve the impact resistance of the existing column, which can be utilized and promoted in the steel parking structure.

Local–distortional buckling mode of steel cold-formed columns: Generalized direct strength design approach

Cold-Formed Steel (CFS) members are highly susceptible to several structural instability phenomena, involving either individual (Local — L, Distortional — D and Global — G) or interaction (LD, LG, DG, and LDG) buckling modes. The buckling mode interaction of CFS columns and beams may lead to strength erosion compared to isolated modes and must be considered in structural design. The North American, Australian/New Zealand and Brazilian standards incorporated the Direct Strength Method (DSM) that provides accurate design approach for columns and beams affected by L, D, G, and LG buckling modes. However, the coupled LD, DG, and LDG buckling modes are not currently considered in the DSM and many recent research projects have been focused on these topics. The procedure adopted by DSM estimates the CFS member strength through experimentally calibrated design strength equations and curves, based on the relationship between the member elastic stability and the steel yielding property, respectively the elastic critical buckling load and the plastic load, represented by the slenderness factor. The more accurate the buckling load, the more improved will be the result of the column strength by the DSM equations. In this context, the present paper presents the main results of the investigation, based on both experimental and finite element method numerical results, that conducted to calibrated strength curves for CFS unstiffened sections columns without holes covering LD interaction buckling mode. To take into account the effect of the LD buckling, the proposed procedure for design purposes incorporates the slenderness factor ratio RλDL=λD/λL as the main variable, and λL, λD, λG as the local, distortional and global slenderness factors, respectively.

Adsorption of Cr(VI) by Mesoporous Pomegranate Peel Biowaste from Synthetic Wastewater under Dynamic Mode

This study aims to eliminate hexavalent chromium Cr(VI) ions from water using pomegranate peel (PGP) powder. Dynamic measurements are carried out to examine the influence of the operating factors on the adsorption efficiency and kinetics. The analyzed PGP is found to be amorphous with relatively high stability, contains hydroxyl and carboxyl functional groups, a pH of zero charge of 3.9, and a specific surface-area of 40.38 m2/g. Adsorption tests indicate that PGP exhibits excellent removal effectiveness for Cr(VI) reaching 50.32 mg/g while the adsorption process obeys the Freundlich model. The thermodynamic study favors the exothermic physical adsorption process. The influence of operating parameters like the flow rate (1 to 3 mL/min), bed height (25 to 75 mm), concentration (10 to 30 mg/L), and temperature (298 to 318 K) on the adsorption process are investigated in column mode. To assess the performance characteristics of the column adsorption data, a non-linear regression has been used to fit and analyze four different kinetic and theoretical models, namely, Bohart-Adams, Thomas model, Clark, and Dose response. The obtained experimental results were found to obey the Dose Response model with a coefficient of regression R2 greater than 0.977. This study proved the excellent efficiency in the treatment of chemical industry effluents by using cost-effect abundant biowaste sorbent. This research demonstrated great efficacy in the treatment of chemical industrial effluents by using an abundant, cost-effective biowaste sorbent, thereby achieving the UN SDGs (UN Sustainable Development Goals) primary objective.