Polymeric Column Research Articles

Development of machine learning based seismic retrofit scheme for AFRP retrofitted RC column

A fiber reinforced polymer (FRP) column jacketing system can provide additional confining pressure on existing RC columns and enhance their lateral resisting capacities. This paper aims to develop machine learning-based fast running model predicting seismic performance of aramid FRP-retrofitted RC columns, and the fast-running model was utilized to establish optimum retrofit schemes with respect to confinement- and stiffness-related parameters. To develop a physics-based dataset, the loading and retrofit parameters were implemented to the finite element column models validated with the experimental study. The various machine-learning models were trained, validated and tested by using the dataset, and the best-fit model was selected based on each model’s performance. The best-fit model was utilized to predict the seismic performance varying the loading and output parameters, and the optimum retrofit scheme for confinement ratio, stiffness ratio and effective bond length was proposed. The optimum retrofit details need to be higher than the retrofitted length-to-total height of 0.20 and the confinement ratio of 0.15 regardless of the stiffness ratio.

Buckling critical load prediction of pultruded fiber-reinforced polymer columns and feature analysis by machine learning

Buckling critical load prediction of pultruded fiber-reinforced polymer columns and feature analysis by machine learning

Low-migration, deep photocuring thiobarbituric acid-based one-component visible photoinitiators for high-efficiency photopolymerization

The practical applications of thiobarbiturates in medicinal chemistry exemplifies their exceptional biosafety, which is crucial for developing high-efficiency photopolymerization and low-migration photoinitiators (PIs). In this study, five novel D-π-A visible PIs (ANs) were designed and synthesized via using aniline derivatives as the electron donor (D) and thiobarbituric acid as electron acceptor (A). EPR and steady-state photolysis display that the conjugated structure can be destroyed by intramolecular electron/proton transfer, leading to photobleaching. Real-time infrared (FT-IR) analyses have confirmed effective polymerization of 1,6-hexanediol diacrylate (HDDA) initiated by ANs and ANs/N-methyldiethanolamine (MDEA) under illumination. The experimental molar extinction coefficient (ε) aligns with the oscillator strength (f) calculated via DFT, while the high ε and f of AN-5 facilitate electron transfer and free radical generation, resulting in improved initiation efficiency. The conversion rate of independent initiating polymerization exhibits an impressive 78 %. Moreover, colorless polymer columns initiated by AN-5 and AN-5/MDEA display curing depths of 45 mm and 50 mm, along with photobleaching rates reaching up to 98.7 % and 100 %, respectively. Especially, AN-5 exhibits the mere 0.2 % extraction rate from polymerization films under illumination (60 min). These results indicated the great potential of thiobarbituric acid-based ANs in deep-curing materials, food packaging.

Experimental and finite element investigation on bolted connection in monolithic 3-dimensional cuff with pultruded box section

This article presents a concise and practical research study on the application of pultruded GFRP (Glass Fiber Reinforced Polymer) hollow sections in structural engineering. Experimental and computational investigations are conducted on the utilization of GFRP cuff components for joining tubular pultruded fiber-reinforced polymer (PFRP) beams and columns. Both adhesive bonding and bolted connections are explored for connecting PFRP box sections of beam-column interfaces. The study investigates twelve series of beam-to-column connections under monotonic loading conditions, varying cuff geometry. A finite element model is developed to represent the pultruded fiber-reinforced polymer box sections, columns, and cuff sections. The model’s accuracy in depicting frame stiffness and cuff damage patterns, considering different thicknesses and lengths of GFRP cuff connections, is validated against experimental test frame behavior. This research fills a gap in scientific inquiry regarding GFRP hollow profiles, providing valuable insights for structural engineering applications.

Study on design optimization of GFRP tubular column composite structure based on machine learning method.

Circular reinforced concrete wound glass fiber reinforced polymer (GFRP) columns and reinforced concrete filled GFRP columns are extensively utilized in civil engineering practice. Various factors influence the performance of these two types of GFRP columns, thereby impacting the whole project. Therefore, it is highly significant to establish the prediction models for ultimate displacement and ultimate bearing capacity to optimize the design of the two types of GFRP columns. In this study, based on the experiments conducted under different conditions on the two kinds of GFRP columns, automatic machine learning along with four other commonly used machine learning methods were employed for modeling to analyze how the column parameters (cross section shape, concrete strength, height of GFRP column, wound GFRP wall thickness, inner diameter of wound GFRP column) affect their performance. The differences in performance among these five machine learning methods were analyzed after modeling. Subsequently, we obtained the variation patterns in ultimate displacement and ultimate bearing capacity of the columns influenced by each parameter by testing the data using the optimal model. Based on these findings, the optimal design schemes for the two types of GFRP columns are proposed. The contribution of this paper is three-fold. First, AutoML sheds light on the automatic prediction of ultimate displacement and ultimate bearing capacity of GFRP column. Second, in this paper, two optimal design schemes of GFRP columns are proposed. Third, for AEC industrial practitioners, the whole process is automatic, accurate and less reliant on data expertise and the optimization design scheme proposed in the article is relatively scientific.

Load-carrying capacities of pultruded GFRP I-section columns under eccentric load

Pultruded fiber-reinforced polymers have been increasingly applied in engineering structures, and previous studies have focused on their axial behaviors. However, the axial load borne by the components of engineering structures is not ideal. This study presents an investigation of the behavior of I-section pultruded glass fiber-reinforced polymer (GFRP) columns subjected to eccentric loads via experiments and finite element analysis. The effects of load eccentricity around the major axis, as well as the slenderness ratio on the load-carrying capacity, were investigated. The results show that the load-carrying capacity of the GFRP column is dominated by column buckling followed by material crushing, and an increase in the eccentricity and slenderness ratio causes a decrease in the load-carrying capacity, with a progressive rate of decrease. The load-carrying capacity reduction coefficient was fitted considering the slenderness ratio and eccentricity within the scope of this study. The coefficient of determination (R2) for the fitted formula was 0.86. This study provides valuable references for designers in this field.

Fast photobleachable and low migration one-component green indole visible photoinitiators

Six symmetric D-π-A-π-D indole derivatives (IDs) have been investigated as visible light photoinitiators (PIs). The IDs, with different indole as the electron donor (D), C = C bond as the π-bridge and carbonyl group as the electron acceptor (A), are type II PIs owning to their intermolecular hydrogen abstraction. In the process of generating free radicals, the carbonyl transformed to hydroxyl alkyl radicals, which disrupted the large conjugation systems and resulted in the color fading. Real time infrared (RT-IR) indicated that IDs and ID/N-methyldiethanolamine (MDEA) effectively initiated the photopolymerization of 1, 6-hexanediol diacrylate under illumination. ID-HA containing acrylate double bonds is expected to be served as not only a PI but also a crosslinker with extremely high migration stability. The extraction rate of ID-HA from the polymer films following 30 min of illumination was 1.0 %. ID-HA has a lower energy in the excited triplet state (DFT calculations), which is favorable for electron transfer and radical generation. Therefore, the color of ID-HA in acetonitrile solution completely faded within 15 s under illumination, demonstrating the best photobleaching behavior. Meanwhile, the polymerization conversion initiated by it alone could reach as high as 81 %. Furthermore, 47 mm high (with 96.8 % whiteness bleaching ratio) and 55 mm high (with 94.5 % whiteness bleaching ratio) polymer columns were obtained respectively, by using ID-HA and ID-HA/MDEA as PI. Thus, their outstanding photobleaching performance, migration stability and thermal stability endow IDs potential applications in deep photopolymerization, food packaging and biomedicine.

Influence of hybrid nano/micro particles on the mechanical performance of cross-ply carbon fibre fabric reinforced epoxy polymer composite materials

This study presents the flexural strength, compressive strength, and impact energy behaviour of graphene nanoplates and fly ash microparticle-loaded cement-based CFRP composites manufactured by the vacuum-assisted resin infusion method (VARIM). The composite structures consist of a fixed ratio of graphene nanoplates (2%), fly ash (2%), silica (2%), cement (2%), and sand (4%) particles filled into cross-plied carbon fibre-reinforced epoxy resin polymer composite beams and columns. Composites fabricated by hand lay-up methods because of infiltration problems. A three-point bending test through the width was used to measure the flexural strength of the graphene nanoplate (GnP)-filled CFRP composite beam. The low-velocity Izod impact and Charpy impact tests through the thickness were used to determine Charpy impact energy (3.46 J), Izod impact energy (2.5 J), and the dynamic fracture toughness of notch specimens under Charpy (28.5 KJ/m2) and Izod impact (25.0 KJ/m2). Also, the compressive test method was used to measure the compressive strength of hybrid particles and short glass fibre-reinforced epoxy resin composite square and circular columns. The results show compressive strength and flexural strength. Izod impact energy, Charpy impact energy, and dynamic fracture toughness of hybrid nano/microparticle-filled fibre composites have higher values than virgin fibre composites because of the influence of graphene nanoparticles and the perfect interface bonding between two dissimilar molecules of nano and microparticles, which improve the fracture toughness and absorb impact energy. Overall, the results show that molecules of nano/microparticle-filled carbon fibre and glass fibre-reinforced epoxy resin composites can be used in seismic wave resistance because of their improved mechanical properties compared to virgin fibre composites. In addition, SEM micrographs clearly show that nano- and microparticles are resistant to crack propagation and the debonding of matrix fibres.

Mechanical Performance of Hybrid Graphene Nanoplates, Fly-Ash, Cement, Silica, and Sand Particles Filled Cross-Ply Carbon Fibre Woven Fabric Reinforced Epoxy Polymer Composites Beam and Column

The main goal of this study is to reduce the brittleness of a fibre-reinforced cement base structure when exposed to the effects of graphene nanoplates, fly ash, silica, sand, and cement fillers to better understand the effect of hybrid nano/micro particle fillers on the mechanical performance of cross-ply carbon fibre reinforced epoxy resin composites. A three-point bending test through the width was used to measure flexural strength. The impact tests Izod at low impact velocity and Charpy through the thickness were used to determine the dynamic fracture strengths of pre-cracked and non-cracked composite samples. Also, the compressive test method was used to measure the compressive strength of hybrid particles and short glass fibre-reinforced epoxy resin composite square and circular columns. The results show compressive strength and flexural strength. Izod impact energy, Charpy impact energy, and dynamic fracture toughness of hybrid nano/microparticle-filled fibre composites have higher values than virgin fibre composites due to the influence of graphene nanoparticles and perfect interface bonding between two dissimilar molecules of nano and microparticles, which improve the fracture toughness and absorb impact energy. Overall, the results indicate that molecules of nano/microparticle-filled carbon fibre and glass fibre-reinforced epoxy resin composites can be used in aggressive environments because of the improved mechanical properties in comparison to the virgin fibre composites. In addition, SEM micrographs clearly indicate that nano- and microparticles are resistant crack propagation and deboned of matrix fibres.

In-Depth Performance Analysis and Comparison of Monolithic and Particulate Zwitterionic Hydrophilic Interaction Liquid Chromatography Polymer Columns.

The kinetic performance of different zwitterionic hydrophilic interaction liquid chromatography polymer columns is evaluated and compared in-depth. For this purpose, two lab-made monolithic columns, synthesized with different crosslinkers, and a commercial particle packed column are considered. It is found that performance evaluation techniques, such as comparing plate height curves or fitted A-, B- and C-terms, obtained by fitting experimental plate height data to a plate height model, are complicated by the determination of a reliable characteristic length. This is due to the very different morphology of these column types, and the heterogeneity of the monolithic columns. The occurrence of a convective flow through the packed particle column further complicates the interpretation of the obtained fitting parameters, as part of the C-term is wrongfully attributed to the A-term. Therefore, the use of the kinetic plot method is suggested for the comparative evaluation of these columns, as kinetic plots do not require the determination of a characteristic length, nor rely on any fitting parameters. With the kinetic plot method, it is demonstrated that the lab-made monolithic columns outperform the packed particle column for plate counts between 10,000 and 800,000. This is attributed to the higher column efficiency of these columns, due to their small domain and skeleton sizes, and their high permeability, resulting from their high external porosity and the occasional occurrence of preferential flow paths.

Cationised Fibre-Based Cellulose Multi-Layer Membranes for Sterile and High-Flow Bacteria Retention and Inactivation.

Low-cost, readily available, or even disposable membranes in water purification or downstream biopharma processes are becoming attractive alternatives to expensive polymeric columns or filters. In this article, the potential of microfiltration membranes prepared from differently orientated viscose fibre slivers, infused with ultrafine quaternised (qCNF) and amino-hydrophobised (aCNF) cellulose nanofibrils, were investigated for capturing and deactivating the bacteria from water during vacuum filtration. The morphology and capturing mechanism of the single- and multi-layer structured membranes were evaluated using microscopic imaging and colloidal particles. They were assessed for antibacterial efficacy and the retention of selected bacterial species (Escherichia coli, Staphylococcus aureus, Micrococcus luteus), differing in the cell envelope structure, hydrodynamic biovolume (shape and size) and their clustering. The aCNF increased biocidal efficacy significantly when compared to qCNF-integrated membrane, although the latter retained bacteria equally effectively by a thicker multi-layer structured membrane. The retention of bacterial cells occurred through electrostatic and hydrophobic interactions, as well as via interfibrous pore diffusion, depending on their physicochemical properties. For all bacterial strains, the highest retention (up to 100% or log 6 reduction) at >50 L/h∗bar∗m2 flow rate was achieved with a 4-layer gradient-structured membrane containing different aCNF content, thereby matching the performance of industrial polymeric filters used for removing bacteria.

Experimental Evaluation of Shape Memory Alloy Retrofitting Effect for Circular Concrete Column Using Ultrasonic Pulse Velocity

The seismic performance of a concrete column retrofitted with an iron-based shape memory alloy (Fe-SMA) was evaluated under cyclic loading. In addition to structural behavior, internal damage was monitored using an ultrasonic pulse velocity test. The round shapes of three reinforced concrete (RC) columns were tested: a non-retrofitted RC column as a control, a carbon fiber-reinforced polymer (CFRP) column, and an Fe-SMA retrofitted column. During the cyclic loading test, the degradation of the column was defined based on the decrease in compressional wave velocities. The experimental results demonstrated a maximum improvement of 175% in seismic performance of the Fe-SMA retrofitted RC column compared with the controlled column. This is primarily owing to the active constraints of the SMA, which were quantified based on ultrasonic velocities. Furthermore, the surface degradation process was identified using external cracks, which were not visible in the CFRP retrofitted RC column.

Application of Porous Layer Open Tubular Columns: Beyond Permanent Gases

Porous layer open tubular (PLOT) columns are traditionally built with particles that are adhered to the tubing walls. These columns have unique selectivity and provide a great alternative when gaseous samples need to be separated, but these columns also have been used to separate higher boiling point analytes. There are many different commercially available stationary phases of PLOT columns, including alumina-based columns, molecular sieves, and porous polymers. Alumina-based columns have an aluminum oxide stationary phase that is then deactivated with different salts. These columns have high capacity, superior loading ability, and produce symmetrical peaks. Molecular sieve columns are designed specifically for permanent gas separations because the columns have high retention. Porous polymer columns are highly hydrophobic, making them more applicable to analyzing a wider range of samples.

Acylamino-functionalized hyper-cross-linked polymers for efficient adsorption removal of phenol in aqueous solution

Chemically functionalized hyper-cross-linked polymers (HCLPs) with high Brunauer-Emmett-Teller (BET) surface area (SBET) and pore volume (Vtotal) are efficient polymeric adsorbents for the adsorption of polar phenolic substances. Herein, chloromethylated polystyrene (CMPS) was used as the raw material and two consecutive Friedel-Crafts reactions were adopted to prepare the acylamino-functionalized HCLPs, and they were used to adsorb phenol in aqueous solution. In the first reaction, considerable acylamino groups were successfully loaded on the polymers, and the N and O contents were measured to be 1.03 wt% and 3.59 wt%, respectively. In particular, a great deal of rigid methylene joined the polymer chains in the second reaction as using dichloromethane as the novel external cross-linker, and hence acylamino-functionalized HCLPs with high SBET (up to 914 m2/g) and Vtotal (up to 1.01 cm3/g) were prepared. The resulting HCLPs exhibited excellent adsorption of phenol, the fitted maximum capacity (qmax) was measured to be 318.6 mg/g, and the adsorption reached the equilibrium within 120 min. The dynamic adsorption demonstrated that up to 79 BV (bed volume, 1 BV = 8 mL) of phenol could be removed at the initial concentration of 1000.5 mg/L and the dynamic capacity was scaled to be 316.1 mg/g, and ethanol could desorb phenol from the polymer column completely. The adsorption mechanism revealed that hydrogen bonding, π–π stacking, micropore-filling were the main driving forces for the adsorption.

On the occurrence of very low intra-particle diffusion rates in zwitterionic hydrophilic interaction liquid chromatography polymer columns

Intra-particle diffusion is investigated in particle-packed and monolithic zwitterionic hydrophilic interaction liquid chromatography (HILIC) polymer columns. For this purpose, plate heights are first measured over a broad range of velocities for polar compounds with zone retention factors between k″ = 2 and 10 on all column types, multiplied with the corresponding velocity, and extrapolated to zero velocity. The thus obtained B-term coefficients are additionally verified via peak parking experiments and indicate a very low degree of longitudinal diffusion in all columns, that moreover seems to be independent of the zone retention factor. This is in contrast to earlier observations on reversed-phase liquid chromatography columns and bare silica HILIC columns. To obtain more insight into the reasons for these low levels of longitudinal diffusion, the experimentally obtained effective diffusion coefficients are modeled to equations derived from the effective medium theory, such as the models developed by Torquato and Jefrey & Hashin. It is, however, demonstrated that these models fail to adequately describe effective diffusion in the studied zwitterionic HILIC columns, due to the low degree of intraparticle diffusion in these stationary phases. Fitting the experimental effective diffusion coefficients to the two limiting cases of the effective medium theory, i.e., the pure parallel-connection and pure serial-connection case, it is observed that to stay within these limits, intraparticle diffusion must be extremely low, i.e., Dpz/Dm ≤ 0.01, indicating that the diffusion inside the pores is at least 100 times smaller than the bulk diffusion coefficient. There are several possible explanations for these low intraparticle diffusion coefficients, such as a strongly hindered diffusion in the polymer matrix, extremely low surface diffusion rates in the aqueous layer adsorbed onto the stationary phase and/or the occurrence of slow localized adsorption events.

Effect of an oscillating magnetic field in polymeric columns with magnetic nanoparticles

Magnetite magnetic nanoparticles (MNP) exhibit superparamagnetic behavior, which gives them important properties such as low coercive field, easy superficial modification and acceptable magnetization levels. This makes them useful in separation techniques. However, few studies have experimented with the interactions of MNP with magnetic fields. Therefore, the aim of this research was to study the influence of an oscillating magnetic field (OMF) on polymeric monolithic columns with vinylated magnetic nanoparticles (VMNP) for capillary liquid chromatography (cLC). For this purpose, MNP were synthesized by coprecipitation of iron salts. The preparation of polymeric monolithic columns was performed by copolymerization and aggregation of VMNP. Taking advantage of the magnetic properties of MNP, the influence of parameters such as resonance frequency, intensity and exposure time of a OMF applied to the synthesized columns was studied. As a result, a better separation of a sample according to the measured parameters was obtained, so that a column resolution (Rs) of 1.35 was achieved. The morphological properties of the columns were evaluated by scanning electron microscopy (SEM). The results of the chromatographic properties revealed that the best separation of the alkylbenzenes sample occurs under conditions of 5.5 kHz and 10 min of exposure in the OMF. This study constitutes a first application in chromatographic separation techniques for future research in nanotechnology.

Monotonic loading performance of GFRP beam-column joints connected with slotted-hole bolts.

Nowadays there are many types of glass fiber reinforced polymer(GFRP) composite beam and column joints, such as standard connection, bolted through connection, angle steel connection, tube connection and so on, most of which connected by high-strength bolts with round holes. In this paper, monotonic loading tests on GFRPcomposite beam and column joints connected by slotted-hole bolts were conducted. To compare the performance of different joints, two groups of specimens were used in this study; one of group was the beam-column joints connected by the angle steel, and other group was connected by the tube connection. Specimens with different bolt holes, side plate reinforcement condition, and different bolt pre-tightening forces were studied. Failure modes, bending moment curves, plastic rotation, and yield stiffness of the two groups of joints were compared. Results showed thatthe ultimate bending moment bearing capacity of specimens with side plates could be increased by 30%. Under the same conditions, the bearing capacity of the tube joints was about 10% larger than that of the angle steel joints. Although the bearing capacity of joints was not increased by using slotted holes, plastic rotation capacity and yield stiffness of joints with slotted-hole bolts were 1.1 times than that of the ordinary round-hole bolts joints.

Rapid and ultra-trace levels analysis of 33 antibiotics in water by on-line solid-phase extraction with ultra-performance liquid chromatography-tandem mass spectrometry

A method was developed for the determination of 33 antibiotics belonging to 4 different antibiotic groups, including sulfonamides (16), fluoroquinolones (12), macrolides (1), and tetracyclines (4) in water samples using on-line solid-phase extraction-ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (on-line SPE-UPLC-MS/MS). The enrichment and analysis conditions were optimized for the determination of trace concentrations (nanogram per liter). Aliquots of the water samples (5 mL) were filtered through a membrane and enriched on an on-line polymeric column with hydrophilic–lipophilic balance (HLB). The analyte was eluted by the mobile phase during on-line SPE and separated on an Acquity BEH130 column, detected by tandem mass spectrometry, and quantified using an external standard method. The optimization of the analytical methods was discussed, which included optimization of pH of the sample, filtration membrane, Na2EDTA, chromatographic column, formic acid and aqueous ammonia in mobile phase. The detection limit for all test compounds by this method was in the range of 0.2–1.5 ng/L, with recoveries of 76.6–118%. The precision of the method, as indicated by the relative standard deviation, was 2.4–7.9%. Results of analysis of surface water samples demonstrated the ability of the proposed method to analyze ultra-trace levels of antibiotics, without the need for complex manual pretreatment.

Low-Cycle Reverse Loading Tests of the Continuous Basalt Fiber-Reinforced Polymer Column Filled with Concrete

The continuous basalt fiber-reinforced polymer column filled with concrete (BFRPC composite column) can well resist the erosion of the external environment, improve the durability of the structure, and reduce the life-cycle cost of the project. To evaluate the mechanical behaviors of the BFRPC composite column under cyclic lateral loading, laboratory low-cycle reverse loading tests were implemented on a BFRPC composite column specimen, a prestressed reinforced concrete (PRC) tube column specimen, and a prestressed high-strength concrete (PHC) tube column specimen. The failure features, hysteretic curve, and skeleton curve for these three types of column specimens were compared and analyzed through the load–displacement hysteretic curve. The results indicated that the BFRPC composite column possesses the better bearing capacity and deformation performance. The horizontal bearing capacity of the BFRPC composite column is at least three times better than that of PHC and PRC tube columns. Finally, the functional expression of the skeleton curves for the BFRPC composite column is fitted by the rational function fitting method.

Ultra-Compact Full-Angle-Range Direction-Distinguishable Tilt Sensor Based on Fiber in-Line Polymer Microcavity

We propose an ultra-compact full-angle-range direction-distinguishable tilt sensor based on a polymer column working as a Fabry–Perot (FP) microcavity fixed between two sections of single-mode fibers (SMFs). The directional tilt angle from −90 deg to +90 deg can be demodulated by monitoring the wavelength shift of interference fringe, based on the deformation of the polymer column under the effect of the gravity force. The sensitivity of the sensor can be adjusted by changing the shape and size of the polymer column that is fabricated by the single beam illumination with high efficiency and low cost. The sensor can satisfy the engineering requirements owing to its small size, flexible structure, cost-effective performance, large measurement range, and direction-distinguishable ability.