Large-scale Column Research Articles

Effect of aquatic worms and straw amendments on the geotechnical and biogeochemical properties of oil sands tailings

Aquatic Oliogochaete worms ( Lumbriculus variegatus) combined with straw led to improved geotechnical properties of fluid fine tailings (FFT) and thickened tailings (TT) in large-scale column studies. Gravity settling caused 19.9% and 20.6% consolidation of FFT and TT over 125 and 127 days, while the addition of straw and worms increased consolidation to 22.0%–24.3% for FFT and 28.1%–28.9% for TT. Solids content and yield stress were up to 1.1x and 6.6x higher in straw and worm columns, with greatest improvements seen in the top tailings layers where worm tunnels were visually observed. Surviving worms were only found in one column, suggesting the worms provide benefits extending past their depth of penetration and lifespan. The addition of straw stimulated methanogenic activity, decreasing pH, increasing alkalinity, and creating strictly anaerobic conditions (−300 mV), which may have impacted the survivability of the worms but provided another bioconsolidation pathway.

Rubberized reinforced concrete columns under axial and cyclic loading

The experimental study presented in this research was conducted to understand the performance of rubberized concrete columns under axial loads and numerically analyze the conduct of rubberized reinforced concrete (RRC) columns under cyclic loads. Twelve large-scale columns with square and circular cross sections were utilized to carry out experimental testing. Under axial loading, fine aggregate was replaced in percentages of 0%, 10%, and 15% with crumb rubber (CR). Square RRC columns were examined by a finite element program (ABAQUS) under cyclic loading. The experimental results indicated that the columns with crumb rubber had a lower load capacity than those without crumb rubber when exposed to axial loads. The numerical results were in good alignment with the experimental results, indicating that the simulated model may simulate the behavior of rubberized concrete columns under both axial and cyclic loads. According to the numerical analyses, the lateral displacement was significantly improved for rubberized reinforced concrete columns with 10% and 15% replacement of fine aggregates compared to columns without CR. Adding 10% and 15% of crump rubber to the fine aggregate in reinforced concrete columns increased the displacement ductility. The equivalent viscous damping ratio was enhanced by 33.67% when increasing crumb rubber (CR) from 0% to 10%, and when crumb rubber (CR) replacement became 15%, the damping ratio increased to 44.02%.The rubberized reinforced concrete columns showed a more ductile reaction than the traditional reinforced concrete columns, as evidenced by their softer post-peak response.

Effects of enhanced confinement on cyclic behavior of concrete bridge columns with partially unbonded seven-wire steel strands

The effects of enhanced confinement on the proposed bridge columns under lateral cyclic loading were investigated in this research by testing large-scale column specimens. The proposed column used nonprestressed partially unbonded seven-wire strands as elastic elements to increase the post-yield stiffness of the column to reduce the residual displacement under seismic loads. The enhanced confinement included rectilinear transverse reinforcement with an increased amount (specimen CSCR) and reduced spacing or innovative five-spiral reinforcement (specimen CSCS). Test results showed that all the specimens exhibited a positive post-yield stiffness ratio of 3.5–6.4 %. However, the enhanced confinement reduced the post-yield stiffness by 42–45 % but increased the lateral strength of the column, which is beneficial for controlling the residual displacement. The enhanced confinement did not affect the drift ratio when the positive post-yield stiffness ended (6 %) but significantly increased the deformation capacity by 15–31 % and the energy dissipation capacity by 37–63 % of the column. Even with a smaller amount of transverse reinforcement, the specimen with the innovative five-spiral reinforcement showed deformation and energy dissipation capacities better than the other specimens with conventional rectilinear transverse reinforcement. A pushover analysis model was developed and modified to better account for the effect of the enhanced confinement and the strand slip, and to consider the end point of positive post-yield stiffness. The comparison with the test result showed that the proposed pushover model well captured the envelope responses of the specimens. Finally, a simplified method was proposed for estimating the moment strength of the proposed column.

Axial compressive behavior and load carrying capacity prediction of prefabricated UHPC tube filled with seawater sea-sand coral aggregate concrete

To reduce construction costs, seawater, sea sand, and dead coral are often used in concrete buildings on distant islands. Such seawater-sea sand coral aggregate concrete (SSCAC) typically has insufficient mechanical properties and high chloride ion content. In this paper, a novel composite column, named SSCAC-filled ultra-high performance concrete (UHPC) tube (SFCT), is proposed and studied. The SFCT column combines a prefabricated fiber reinforced polymer (FRP) hoop reinforced thin-walled UHPC tube with the infill SSCAC. A total of 36 relative large-scale columns were conducted for axial compression tests. The SFCT columns showed a multi-crack failure mode on the surface of the tube without obvious peeling-off of the UHPC cover in the whole loading process. The test results reveal that the UHPC tube in the composite system effectively takes on the additional load released by the inner SSCAC during compacting due to the porous nature and low strength of coral aggregates. Therefore, the compressive behavior of the pre-peak stage of SFCT column is effectively improved compared with existing SSCAC confined by FRP tube or hoops, especially important is increased the axial stiffness. The proposed composite system effectively combines the ultra-high compressive performance of UHPC and the lateral confining effect from FRP hoops. A model was also proposed for predicting the axial load carrying capacity of SFCT columns. The analysis results indicate that selecting relatively thinner UHPC tube in SFCT composite system and using relatively flexible and low-cost basalt FRP (BFRP) and glass FRP (GFRP) hoops instead of carbon FRP (CFRP) hoops as the lateral confining component are economical and could be reasonable measures for manufacturing the composite columns.

Arsenic Adsorption on Designed Packed Bed Column using Chemically Modified PAN Fiber- A Simulation and Modeling Studies.

The efficiency of Chemically modified PAN Fiber (CM-PAN) as an adsorbent for the removal of As(III) from groundwater performed. For polluted water, many techniques have been developed recently to remove arsenic from it, such as chemical precipitation, adsorption, ion exchange, membrane processes, and others. Adsorption is the most often used technique because of its high arsenic performance and low cost. Arsenic (III) was removed from the aqueous solution in this study that use an adsorption technique with chitosan/iron oxide coated PAN Fiber as the adsorbent. In this work, Aspen AdsimV11 was used to create a steady-state model of a fixed bed column in the impact of various process factors. We created a small scale column of 2-cm-diameter and with various bed depths such as 1, 2 & 3cm. By an up-flow rate of 1, 2 & 3 mL/min and large scale column 8-cm-diameter and with various bed depths such as 8cm and by an up-flow rate of 512, 1024 & 1536mL/min. The amount of polluted water that was react towards the breakpoints where adsorption capacity was 91%of As(III) in a concentration of 0.0004004 mol/liter, 88%of As(III) in a concentration of 0.000269 mol/liter and 85% in a concentration of 0.0001335 mol/lit. By increasing starting concentration and bed depth and, total As (III) uptake decreased with increasing flow rate. Bed depth service time (BDST), mass transfer, first order kinetics, and regression analysis of equilibrium data were used to simulate the dynamics of the adsorption process and fit the Langmuir isotherms. The water quality of the treated effluent is adequate for home use, according to the findings. Ion exchange and physiosorption on the adsorbent surface appeared to be the mechanisms for As(III) removal in the CM-PAN column. For arsenic removal from groundwater, this appropriate module would be generate by using these results.

Investigation of intumescent coating on the fire endurance of concrete-filled steel columns with varied characteristics

Concrete-filled steel columns (CFSC) are becoming increasingly popular in contemporary construction, particularly for the construction of tall buildings and structures with large spans. These columns offer superior fire protection compared to concrete or steel-only columns. Furthermore, CFSCs offer significant structural benefits by enhancing properties such as high tensile and compressive strength, ductility, capacity for energy absorption, improved fire resistance, and thermal insulation. However, there remains a notable research gap pertaining to the comprehensive analysis of the temperature distribution in CFSC sections that are protected by intumescent fire coating (IFC). Particularly, there is a need to investigate the specific effects of various heating rates, intumescent coating thickness, and steel thickness on the temperature distribution within these sections. The current research involved the creation of a finite element model for analyzing heat transfer and fire resistance in columns. This model was used to examine how the columns would perform under different fire conditions, including Standard (ISO-834), Fast, Slow, and Smouldering fires. The model has been verified with the available literature. Core concrete, dry film thickness (DFT) of intumescent coating, and steel section thickness are the primary determinants of the temperature rise of the protected CFSC section under fire considered in the developed models. This study adds large-scale column specimens to the corresponding numerical database. The numerical results provide additional proof that a CFSCs coated with an intumescent fire coating can achieve high fire resistance. With efficient IFC insulation and core concrete heat absorption, the temperature increase of a CFSC can be greatly retarded.

Behavior of large-scale columns strengthened with basalt fiber-reinforced polymers sheets or bars and hybrid FRPs

Basalt fiber-reinforced polymers (BFRP) have recently become a widely used material for increasing the ultimate load capacity of reinforced concrete (RC) columns and improving their behavior throughout their entire life. So, an experimental program consisting of 19 large-scale RC columns of low strength has been prepared to examine the behavior of strengthened RC columns at all stages of loading. In this program, the columns were divided into two groups. The main parameters include the strengthening materials (BFRP wrap, BFRP bars, and carbon fiber reinforced polymers (CFRP) wrap), the strengthening techniques (fully or partially wrapping, the number and direction of layers), the cross-sectional shapes (square, rectangular, and circular), and the loading types (eccentric and concentric). The confinement of BFRP wraps significantly improved the service load and the ultimate failure load. The hybrid systems achieved an adequate level of confinement of the strengthened columns, increased the maximum load by 43.61 %, and absorbed energy by 477.2 % compared to the control column. BFRP bars used as a near-surface mounted material improved the behavior of the columns by up to 60 % and 411 % in maximum load and absorbed energy, respectively. The ACI and ECP codes predicted good estimates for the stress of columns strengthened with a single layer but underestimated for columns strengthened with a single layer and BFRP bars. Based upon the existing test data, BFRP-RC is recommended. Furthermore, this research can support using BFRPs as strengthening materials.

Removal of Mn (II) from aqueous solution via biosorption technology for a drinking water treatment plant: From laboratory-scale tests to semi-industrial scale predictions

Biosorbents have drawn increasing attention for removing pollutants on lab-scale systems. Although biosorbents are ecofriendly, their potential on large-scale columns has not been assessed yet. This study evaluated the potential of sugarcane bagasse (SB) for the removal of Mn (II) from aqueous media. Firstly, batch experiments were conducted to establish the equilibrium data and predominant adsorption mechanisms. Secondly, a mathematical model was proposed to predict the breakthrough curves in a fixed-bed column. Alternatively, lab- and pilot-scale removal experiments were performed to validate the accuracy of the proposed model. Once the model was validated on both scales, it was employed to predict breakthrough curves for a semi-industrial column under actual conditions of a drinking water treatment plant. Langmuir isotherm (qmax: 2.82 mg/g) and Langmuir kinetic model (R2>0.98 and x2<0.01) reproduced the experimental equilibrium and kinetic behavior. The mathematical model successfully replicated the lab- and pilot-scale breakthrough data (R2>0.95 and x2<0.1). Therefore, its prediction on the semi-industrial scale was reliable. However, short breakthrough and exhaustion times were obtained on this column, which hinders SB from applying in actual raw water. The described methodology can be employed to assess the potential of other biosorbents for industrial applications.

Strengthening RC eccentrically loaded columns by CFRP at different levels of initial load

This paper presents results obtained from test carried out to investigate the behavior of columns strengthened with CFRP laminates subjected to eccentrically applied axial loading. It is noted that when strengthening existing structures, it is often not possible to fully unload them and as a result the structural elements being strengthened are pre-loaded. In this research 10 large scale column specimens, strengthened with CFRP are investigated. Attention is focused on investigating the effect of pre-loading acting at the moment of strengthening on the recorded behavior. Each sample is initially loaded with eccentrically applied axial force, equal to 30%, 50% and 70% of the ultimate capacity. Once strengthened, the specimens were incrementally loaded until the destruction, values of strains and deflections were recorded on each loading stage. Strength, deformability and ductility parameters of columns were determined and thoroughly analyzed. Comparative analysis was carried out and the effectiveness of the strengthening is determined. It was identified, that the higher levels of initial loading decrease the strengthening effect from 31.8% to 15 % when for 30% and 70% preloading, respectively. Also, for samples with high pre-loading level the ultimate displacement at ultimate load reduced. It is important to note the increase of stiffness and decrease of deflections due to CFRP-strengthening. The presence on initial loading slightly decreases the ductility of CFRP strengthened columns (by 9–12 %). Specific features of CFRP effectiveness should be taken into account in engineering practice.

Behaviour of Large Scale Columns Strengthened with Basalt Fiber-Reinforced Polymers

Behaviour of Large Scale Columns Strengthened with Basalt Fiber-Reinforced Polymers

Behaviour of Large Scale Columns Strengthened with Basalt Fiber-Reinforced Polymers

Behaviour of Large Scale Columns Strengthened with Basalt Fiber-Reinforced Polymers

Chromatographic Purification of Viral Vectors for Gene Therapy Applications.

Chromatography has been a mainstay in the downstream processing and purification of biopharmaceutical medicines. Until now, this has largely involved the purification of protein products such as recombinant enzymes and monoclonal antibodies using large-scale column chromatography methods. The development of advanced therapeutic medicinal products (ATMP) is heralding in a new era of therapeutics for a range of indications. These new therapeutics use diverse substances ranging from live stem cell preparations to fragments of nucleic acid enclosed in a viral delivery system. With these new technologies come new challenges in their purification. In this chapter, the challenges faced in producing and purifying viral vectors capable of delivering life-altering gene therapy to the patient will be discussed. Current methods of chromatography capable of adaptation to meet these new challenges and advancements that may be needed to increase the purification capabilities for these new products will also be discussed.

Study on the Effect of Gamma-Ray Irradiation on the Adsorption of 99Tc and Re by a Silica-Based Pyridine Resin.

A silica-based anion exchange resin was synthesized and used to remove 99Tc from real radioactive liquid waste. The adsorbent had a uniform particle size and exhibited good thermal stability up to 100 °C, which is promising for large-scale column experiments. In accordance with the chemical similarity with Tc, Re was used as a surrogate in this study. The N 1s high-resolution XPS spectra of the adsorbent before and after the adsorption of Re indicated that the ion exchange reaction was the controlling mechanism in the process. After γ-ray irradiation, the changing trend of the Kd was consistent, which showed that the competitive adsorption of NO3- led to a decrease in Kd. The adsorption capacity for the Re decreased slightly from 35.8 to 31.9 mg/g with the increase in the absorbed dose from 0 to 50 kGy. The separation and recovery of Re and the coexisting ions were achieved by chromatographic separation experiments, and the recovery percentage of Re was 86%. In real radioactive liquid waste, N3/SiO2 exhibited good selectivity toward 99Tc over the coexisting metals, namely, 90Sr, 137Cs, 241Am, and U, and the decontamination efficiency of 99Tc attained 65%.

Adsorptive removal of phosphate from aqueous solutions using low-cost modified biochar-packed column: Effect of operational parameters and kinetic study

Adsorption in the continuous mode plays a significant role in wastewater treatment. In this study, Mimosa pigra-derived biochar modified with 2 M AlCl3 salt was used to pack a lab-scale column to eliminate PO43− from aqueous solutions. The influence of the operational factors, such as inlet PO43− concentration (25–100 mg/L), flow rate (6–18 mL/min), and biochar bed height (1.5–4.5 cm), on the breakthrough curve was evaluated. The kinetic models of Adam–Bohart and Yoon–Nelson were utilized to analyze the experimental results. The best conditions were determined to be the influent PO43− strength of 50 mg/L, injection speed of 6 mL/min, and column height of 4.5 cm. These results can be applied in the design of large-scale columns for the sequestration of PO43− from wastewater.

Effect of the concrete cover thickness ratio on the post-yield stiffness of bridge columns with partially unbonded unstressed steel strands

A new self-centering concrete bridge column has been developed by the authors. The proposed bridge column uses unstressed partially unbonded seven-wire steel strands as elastic elements to reduce the residual displacement of the column after a strong earthquake. This research aimed to study the effect of concrete cover thickness ratio on the cyclic behavior of the proposed column. Four large-scale column specimens were tested using lateral cyclic loading. One column was the conventional concrete bridge column. The other three columns were the proposed self-centering bridge columns with varying concrete cover thickness ratios. Test results showed that partial unbonding effectively prevented the strands from yielding. The proposed columns showed post-yield stiffness ratios higher than the conventional column. The concrete cover thickness ratio did not significantly influence the hysteretic energy dissipation and the strain responses of longitudinal reinforcement. However, it had a significant impact on the post-yield stiffness ratio. The post-yield stiffness ratio of the proposed column tended to be inversely proportional to the concrete cover thickness ratio. A relationship was proposed between the concrete cover thickness ratio and the post-yield stiffness ratio for the preliminary design of the proposed column. Based on the relationship, the cover concrete thickness ratio should not exceed 5.1% to achieve a post-yield stiffness ratio of at least 5%, as recommended in the literature to control the residual displacement of a column.

Cyclic Behavior of Reinforced Concrete Columns with Unstressed Steel Strands as Longitudinal Reinforcement

The use of unstressed Grade 1860 MPa seven-wire steel strands as longitudinal reinforcement has the potential to reduce steel congestion in reinforced concrete members. However, no studies which use unstressed steel strands as the longitudinal reinforcement in concrete columns have been reported in the literature. Thus, in this study, five large-scale column specimens: four of which used unstressed steel strands and one which used conventional Grade 420 MPa deformed bars as longitudinal reinforcement were subjected to cyclic loading under constant axial load to investigate the effectiveness in using strands. Columns with unstressed steel strands as longitudinal reinforcement exhibited drift capacities ranging between 4.96% and 5.70%, which is well over the conventional expectation of 3.50% drift requirement for columns in special moment frames. Also, the specimens exhibited lower energy dissipation but enhanced recentering capability owing to the fact that the strands have significantly higher tensile yield capacity compared to deformed bars. A reduction in effective elastic stiffness was also observed as the postcracking stiffness of specimens with strands dropped due to the low longitudinal reinforcement ratio of 0.78% provided. The test results indicated the relative ineffectiveness of strands in compression than in tension, where the strand bulged and unwound once the surrounding confinement deteriorated. Despite this, strands did straighten up and continued to sustain tensile stresses under load reversal. Based on the experimental observations, two constitutive models, one which considers strain hardening and the other which assumes an elasto-perfectly plastic response in tension was proposed for strands. The constitutive model with strain hardening was able to produce reasonably accurate estimates of flexural strength when used in a detailed moment-curvature analysis. Both constitutive models when used in a simplified analysis, which used equivalent stress block for concrete, was able to consistently produce conservative estimates of flexural strength, which is suitable for design purpose.

Corrosion Behavior of Corrosion Resistant Steel Reinforcements in Normal-Strength and High-Performance Concrete: Large-Scale Column Tests and Analysis

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Cyclic behavior of shear-critical concrete columns with unstressed steel strands as longitudinal reinforcement

The significantly higher tensile capacity of seven-wire steel strands compared to the conventional Grade 420 (MPa) deformed bar can effectively reduce reinforcement congestion in concrete columns. As no previous studies have been reported in the literature, the realization of the above objective necessitates the critical evaluation of the flexural and shear behavior of columns. Thus, this study focused on the shear behavior of concrete columns where unstressed seven-wire Grade 1860 (MPa) steel strands were used as longitudinal reinforcement in place of conventional deformed bars. As shear behavior was under consideration, two types of transverse reinforcement layouts in rectilinear ties and multi-spiral transverse reinforcement were also considered. The experimental program consisted of the cyclic testing of six large-scale column specimens subjected to constant axial load. The tests indicated that the specimens with strands as longitudinal reinforcement failed in shear as intended in the design. Furthermore, the multi-spiral transverse reinforcement layout was more effective than the rectilinear tie layout in confining the core concrete and restraining the steel strands. Finally, both the ACI-318 simplified and detailed shear strength prediction methods were able to estimate the shear strength of the test specimens conservatively. Compared with the ACI-318 simplified method, shear strength prediction by the ACI-318 detailed method was able to produce safer estimates with less variation. In addition to the ACI method to estimate steel contribution to shear strength, modified discrete computational shear strength (mDCSS) model was also used for columns with multi-spiral transverse reinforcement. The mDCSS method provided more accurate results with less variation than the ACI method.

Using 3D printed formworks for the creation of steel fibre reinforced concrete-plastic columns

A concept of steel fibre reinforced concrete–plastic columns was proved and discussed in the paper. Plastic was playing the role of stay-in-place 3D printed formwork. Seven cross-sections representing different types of shapes of columns (from circular to fractal-based) were created. 3D printed plastic stay-in-place formworks were filled with steel fibre reinforced concrete. After ordinary curing, the specimens were loaded. During the tests load–strain characteristics were recorded. Both the destruction characteristics and the energy dissipated during the loading up to 3.5% strain were of special interest. The achieved results were analysed and discussed. Columns with traditional circular and square cross-section were characterized by sudden destruction of the formworks. Specimens with fractal-based cross-sections were characterized by a very smooth destruction process associated with significant deformations of formworks. All steel fibre reinforced concrete–plastic columns in question were characterized by highly quasi-plastic behaviour. The achieved results proved that it is feasible to replace traditional formwork and ordinary concrete (reinforced by steel bars and stirrups) by much more automatized 3D printing of plastic and steel fibre reinforced concrete based solution. The future aims of the much needed research should cover both large scale column specimens and other structural elements.

Cyclic behavior of bridge columns with partially unbonded seven-wire steel strands to increase post-yield stiffness

A new method of increasing post-yield stiffness of bridge columns to reduce the residual displacement after large earthquakes is proposed. In the proposed method, partially unbonded unstressed seven-wire steel strands are used as elastic element to increase the post-yield stiffness of the column. Three large-scale column specimens were tested using lateral cyclic loading to investigate the seismic performance of the proposed column. Test results showed that the use of the unstressed partially unbonded steel strands effectively increased the post-yield stiffness ratio of a conventional bridge column from −0.3% to 6.4%, which exceeded the 5% post-yield stiffness ratio that has been shown in the literature to reduce the residual displacement significantly. Test results also showed that the post-yield stiffness could not be maintained when the strands started to bulge in compression. The ultimate drift was slightly reduced from 5.76% to 4.77%. The use of fully bonded strands further increased the post-yield stiffness ratio to 8.8%. However, the ultimate drift ratio was greatly reduced to 2.84%. To predict the behavior of the proposed column under lateral load, a pushover model was developed. The strain of the partially unbonded strand was calculated based on deformation compatibly with the longitudinal deformed steel bar. The effect of anchorage slip was considered. Comparison with the test results showed that the proposed model captured well the envelope response of the proposed column.