Large-scale Column Research Articles

Behavior of ultra-high performance fiber reinforced concrete columns under pure axial loading

This paper presents the results of a study examining the axial load performance of ultra-high performance fiber reinforced concrete (UHPFRC) columns. As part of the experimental program six large-scale columns were tested under pure axial loading to examine the effect of UHPFRC and transverse reinforcement detailing on column performance. The results demonstrate that the provision of closely-spaced and well-detailed transverse reinforcement allows for the development of excellent ductility in UHPFRC columns. The results also indicate that spacing and configuration of transverse reinforcement are important factors affecting the axial strength and toughness of UHPFRC columns. The analytical investigation examines the suitability of using existing high-strength concrete and fiber reinforced concrete confinement models to predict the axial response of the columns tested in this research program. The results indicate the need for the development of UHPFRC-specific confinement models.

Influence of a compost layer on the attenuation of 28 selected organic micropollutants under realistic soil aquifer treatment conditions: Insights from a large scale column experiment

Soil aquifer treatment is widely applied to improve the quality of treated wastewater in its reuse as alternative source of water. To gain a deeper understanding of the fate of thereby introduced organic micropollutants, the attenuation of 28 compounds was investigated in column experiments using two large scale column systems in duplicate. The influence of increasing proportions of solid organic matter (0.04% vs. 0.17%) and decreasing redox potentials (denitrification vs. iron reduction) was studied by introducing a layer of compost. Secondary effluent from a wastewater treatment plant was used as water matrix for simulating soil aquifer treatment. For neutral and anionic compounds, sorption generally increases with the compound hydrophobicity and the solid organic matter in the column system. Organic cations showed the highest attenuation. Among them, breakthroughs were only registered for the cationic beta-blockers atenolol and metoprolol. An enhanced degradation in the columns with organic infiltration layer was observed for the majority of the compounds, suggesting an improved degradation for higher levels of biodegradable dissolved organic carbon. Solely the degradation of sulfamethoxazole could clearly be attributed to redox effects (when reaching iron reducing conditions). The study provides valuable insights into the attenuation potential for a wide spectrum of organic micropollutants under realistic soil aquifer treatment conditions. Furthermore, the introduction of the compost layer generally showed positive effects on the removal of compounds preferentially degraded under reducing conditions and also increases the residence times in the soil aquifer treatment system via sorption.

Does vegetation affect the methane oxidation efficiency of passive biosystems?

It is often reported in the technical literature that the presence of vegetation improves the methane oxidation efficiency of biosystems; however, the phenomena involved and biosystem performance results are still poorly documented, particularly in the field. This triggered a study to assess the importance of vegetation in methane oxidation efficiency (MOE). In this study, 4 large scale columns, each filled with sand, topsoil and a mixture of compost and topsoil were tested under controlled conditions in the laboratory and partially controlled conditions in the field. Four series of laboratory tests and two series of field tests were performed. 4 different plant covers were tested for each series: Trifolium repens L. (White clover), Phleum pratense L. (Timothy grass), a mixture of both, and bare soil as the control biosystem. The study results indicated that up to a loading equal to 100gCH4/m2/d, the type of plant cover did not influence the oxidation rates, and the MOE was quite high (⩾95%) in all columns. Beyond this point, the oxidation rate continued to increase, reaching 253 and 179gCH4/m2/d in laboratory and field tests respectively. In the end, the bare soil achieved as high or higher MOEs than vegetated biosystems. Despite the fact that the findings of this study cannot be generalized to other types of biosystems and plants and that the vegetation types tested were not fully grown, it was shown that for the short-term tests performed and the types of substrates and plants used herein, vegetation does not seem to be a key factor for enhancing biosystem performance. This key conclusion does not corroborate the conclusion of the relatively few studies published in the technical literature assessing the importance of vegetation in MOE.

Greedy column subset selection for large-scale data sets

In today’s information systems, the availability of massive amounts of data necessitates the development of fast and accurate algorithms to summarize these data and represent them in a succinct format. One crucial problem in big data analytics is the selection of representative instances from large and massively distributed data, which is formally known as the Column Subset Selection problem. The solution to this problem enables data analysts to understand the insights of the data and explore its hidden structure. The selected instances can also be used for data preprocessing tasks such as learning a low-dimensional embedding of the data points or computing a low-rank approximation of the corresponding matrix. This paper presents a fast and accurate greedy algorithm for large-scale column subset selection. The algorithm minimizes an objective function, which measures the reconstruction error of the data matrix based on the subset of selected columns. The paper first presents a centralized greedy algorithm for column subset selection, which depends on a novel recursive formula for calculating the reconstruction error of the data matrix. The paper then presents a MapReduce algorithm, which selects a few representative columns from a matrix whose columns are massively distributed across several commodity machines. The algorithm first learns a concise representation of all columns using random projection, and it then solves a generalized column subset selection problem at each machine in which a subset of columns are selected from the sub-matrix on that machine such that the reconstruction error of the concise representation is minimized. The paper demonstrates the effectiveness and efficiency of the proposed algorithm through an empirical evaluation on benchmark data sets.

Packing of large-scale chromatography columns with irregularly shaped glass based resins using a stop-flow method.

Rigid chromatography resins, such as controlled pore glass based adsorbents, offer the advantage of high permeability and a linear pressure-flow relationship irrespective of column diameter which improves process time and maximizes productivity. However, the rigidity and irregularly shaped nature of these resins often present challenges in achieving consistent and uniform packed beds as formation of bridges between resin particles can hinder bed consolidation. The standard flow-pack method when applied to irregularly shaped particles does not yield well-consolidated packed beds, resulting in formation of a head space and increased band broadening during operation. Vibration packing methods requiring the use of pneumatically driven vibrators are recommended to achieve full packed bed consolidation but limitations in manufacturing facilities and equipment may prevent the implementation of such devices. The stop-flow packing method was developed as an improvement over the flow-pack method to overcome these limitations and to improve bed consolidation without the use of vibrating devices. Transition analysis of large-scale columns packed using the stop-flow method over multiple cycles has shown a two- to three-fold reduction of change in bed integrity values as compared to a flow-packed bed demonstrating an improvement in packed bed stability in terms of the height equivalent to a theoretical plate (HETP) and peak asymmetry (As).

Effect of fine particles on the hydraulic behavior of interlayer soil in railway substructure

The conventional railway substructure in France was built by emplacing ballast directly on subgrade. Over years of operation, the interpenetration of ballast and subgrade created a soil layer between them. Under different conditions, this naturally formed layer, namely interlayer, can contain different quantities of fine particles, becoming more or less sensitive to changes in water content. As the water content changes are governed by the hydraulic behavior of the interlayer soil, assessing the influence of fine particle content on the hydraulic behavior of interlayer soil is of importance. To this end, the hydraulic behavior of an interlayer soil taken from Sénissiat (near Lyon, France) was investigated using two infiltration columns, a large-scale column equipped with tensiometers and a time domain reflectometer (TDR) for suction and volumetric water content measurements, respectively, and a smaller column equipped with high-capacity tensiometers only. Different fines contents were considered and wetting–drying cycles were applied to the soil specimens. The hydraulic conductivity was determined by applying the instantaneous profile method. The results obtained showed that (i) hysteresis exists for both the soil water retention curve and the hydraulic conductivity changes with suction; (ii) the effect of wetting–drying cycles is insignificant; (iii) adding 10% fine particles to the natural interlayer soil gives rise to changes in the soil water retention curve but does not induce significant changes in hydraulic conductivity; (iv) the unsaturated hydraulic conductivity of interlayer soil with 10% fine particles added is close to that of soil sieved at 2 mm, suggesting that the unsaturated hydraulic conductivity of interlayer soil is mainly governed by fine particles through the suction effect. By contrast, in a saturated state, the value for the interlayer soil with 10% fine particles added was found to be higher, suggesting that in this case the hydraulic conductivity is mainly governed by the water transfer through macropores.

Performance of RC Columns Affected by ASR. II: Experiments and Assessment

AbstractThis paper describes the structural performance and analytical methodology for large-scale column specimens with a lap splice and concentric axial loading affected by varying levels of alkali-silica reaction (ASR) under displacement-controlled monotonic loading. The lap-splice length in the specimens is typical of the Texas DOT practice for the bar size used and is conservative by code standards. The specimens with varying degrees of ASR showed no evidence of bond deterioration within the splice; had similar initial stiffness and behavior up to the first cracking; had a 25–35% increase in postcracking stiffness up to yielding; had a 5–15% increase in yield strength; and showed no overall detrimental effects on the structural response when compared with control specimens without ASR deterioration. This improved behavior can be explained by the resulting volumetric expansion of the concrete because of the ASR that engaged the longitudinal and transverse reinforcement—this is believed to have resulte...

Operation Diagnosis of an Industrial Flotation Column at the Xuehu Coal Preparation Plant

A large-scale cyclonic-static microbubble flotation column (FCSMC) was tested at the Xuehu coal preparation plant for processing of fine particles (−0.5 mm). A measure of the axial gas holdup profile provided reasons for the deteriorating performance of the FCSMC. The results showed that an excessive mass flow rate of the solids resulted in the loss of mineralized bubbles to the tailings stream, which was responsible for the drop in the combustible recovery and tailings ash. This phenomenon gives rise to the gas holdup profile inversion where the increase of gas holdup from bottom to top decreases. It was shown that the critical tailings velocity of gas holdup profile inversion is exactly the same with the inflection point of carrying capacity and combustible recovery, which demonstrates that it is feasible to diagnose the column operation through the measurement of the axial gas holdup profile.

Performance of HSC columns under severe cyclic loading

Experimental and analytical results of seismic investigation of high strength reinforced concrete columns performance is summarized in this paper. Twelve cantilever columns with different sizes and concrete compressive strengths were tested. The column sizes were \(325\times 325\) mm, \(520\times 520\) mm and \(650\times 650\) mm for the small, medium and large scale specimens, respectively. Concrete compressive strength was 80, 130 and 180 MPa. All specimens were designed in accordance with the Japanese design guidelines. It was noticed that spalling of cover concrete was very brittle for specimens made of 180 MPa followed by a significant decrease in strength independently of the column size. It was also observed that, while concrete compressive strength increases, the drift corresponding to the peak load decreases as well as the ductility of the specimen. Curvature was much important for the small size than for the medium size columns. Specimens with high concrete compressive strength showed a higher equivalent viscous damping at all drift angles. An equation was proposed for predicting the moment-drift envelope curves for the medium and large scale columns knowing that of the small scale columns. Experimental moment-drift and axial strain-drift histories were well predicted using a fiber model developed by the authors.

Experimental Study on Mechanical Property of Corner Columns Supported Reinforced Concrete Honeycombed-core Girderless Floor

In order to study the basic mechanical property of the new honeycombed-core girderless floor in cast-in-place reinforced concrete, and similarities and differences of the structural performance compared with traditional floor, we carried out the destructive stage loading test on large-scale corner columns supported reinforced concrete honeycombed-core girderless floor. And the thesis conducted finite element analysis in virtue of ANSYS software for solid slab floor, rib floor and honeycombed-core floor. The experiment indicates that honeycombed-core modules cement well with concrete around and participate in the load-carrying; the developing process, distribution and failure mode of crevice in honeycombed-core floor are similar to that of general solid girderless floor. The honeycombed-core girderless floor has higher bearing capacity and better plastic deformation capacity. The finite element analysis manifest that compared with solid slab floor, honeycombed- core floor’s dead load decreases on greater level while deformation increases little, and that compared with rib floor, honeycombed-core girderless floor has higher rigidity. So reinforced concrete honeycombed-core girderless floor is particularly suitable for long-span and large-bay building structure.

A large column analog experiment of stable isotope variations during reactive transport: I. A comprehensive model of sulfur cycling and δ34S fractionation

This study demonstrates a mechanistic incorporation of the stable isotopes of sulfur within the CrunchFlow reactive transport code to model the range of microbially-mediated redox processes affecting kinetic isotope fractionation. Previous numerical models of microbially mediated sulfate reduction using Monod-type rate expressions have lacked rigorous coupling of individual sulfur isotopologue rates, with the result that they cannot accurately simulate sulfur isotope fractionation over a wide range of substrate concentrations using a constant fractionation factor. Here, we derive a modified version of the dual-Monod or Michaelis–Menten formulation (Maggi and Riley, 2009, 2010) that successfully captures the behavior of the 32S and 34S isotopes over a broad range from high sulfate and organic carbon availability to substrate limitation using a constant fractionation factor. The new model developments are used to simulate a large-scale column study designed to replicate field scale conditions of an organic carbon (acetate) amended biostimulation experiment at the Old Rifle site in western Colorado. Results demonstrate an initial period of iron reduction that transitions to sulfate reduction, in agreement with field-scale behavior observed at the Old Rifle site. At the height of sulfate reduction, effluent sulfate concentrations decreased to 0.5mM from an influent value of 8.8mM over the 100cm flow path, and thus were enriched in sulfate δ34S from 6.3‰ to 39.5‰. The reactive transport model accurately reproduced the measured enrichment in δ34S of both the reactant (sulfate) and product (sulfide) species of the reduction reaction using a single fractionation factor of 0.987 obtained independently from field-scale measurements. The model also accurately simulated the accumulation and δ34S signature of solid phase elemental sulfur over the duration of the experiment, providing a new tool to predict the isotopic signatures associated with reduced mineral pools. To our knowledge, this is the first rigorous treatment of sulfur isotope fractionation subject to Monod kinetics in a mechanistic reactive transport model that considers the isotopic spatial distribution of both dissolved and solid phase sulfur species during microbially-mediated sulfate reduction.

Batch and continuous (fixed-bed column) biosorption of Cu(II) by Tamarindus indica fruit shell

The feasibility of employing Tamarindus indica (tamarind) fruit shell (TFS) as low-cost biosorbent for removal of Cu(II) from aqueous solutions was investigated. Batch experiments were carried out as function of initial solution pH (2–7), contact time (10–240 min), initial Cu(II) concentration (20–100 mg L−1), biosorbent dose (0.5–5 g) and temperature (293–313 K). Biosorption equilibrium data were well described by the Langmuir isotherm model with maximum biosorption capacity of 80.01 mg g−1 at 313 K. Biosorption of Cu(II) followed pseudo-second-order kinetics. Gibbs free energy (ΔG0) was spontaneous for all interactions, and the biosorption process exhibited endothermic enthalpy values. To ascertain the practical applicability of the biosorbent, fixed-bed column studies were also performed. The breakthrough time increased with increasing bed height and decreased with increasing flow rate. The Thomas model as well as the Bed Depth Service Time (BDST) model was fitted to the dynamic flow experimental data to determine the column kinetic parameters useful for designing large-scale column studies. The Thomas model showed good agreement with the experimental results at all the process parameters studied. It could be concluded that TFS may be used as an inexpensive and effective biosorbent without any treatment or any other modification for the removal of Cu(II) ions from aqueous solutions.

Inspection of the TFT Devices Using the Low-Energy Electron Beam Emitted from the Microcolumn

The inspection of the TFT device for the LCD panel has been usually carried out by the large-scale electron column where the kinetic energy of the electron beam is higher than 10 kV, which has many disadvantages for the inspection. In this work, we replaced the bulky electron column with a tiny microcolumn and carried out the inspection of the TFT device. The result shows that the low-energy e-beam inspection can clearly observe the physical defects of the devices and also identify the abnormal electrical behavior caused by the defects in the device.

The influence of design parameters on clogging of stormwater biofilters: A large-scale column study

A large-scale laboratory study was conducted to test the influence of design and operating conditions on the lifespan of stormwater biofilters. The evolution of hydraulic conductivity over time was studied in relation to a number of key design parameters (media type, filter depth, vegetation type, system sizing, etc). The biofilters were observed to clog over time, with average hydraulic conductivity decreasing by a factor of 3.6 over the 72 weeks of testing. The choice of plant species appears to have a significant effect on the rate of decrease in permeability, with plants with thick roots (e.g. Melaleuca) demonstrating an ability to maintain permeability over time. Other species studied, with finer roots, had no such beneficial effects. As expected, small systems relative to their catchment (and thus which are subjected to high loading rates) are more prone to clogging, as increases in hydraulic and sediment loading can lead to extremely low hydraulic conductivities. Sizing and the appropriate choice of vegetation are thus key elements in design because they can limit clogging, and therefore, indirectly increase annual load treated by limiting the volume of water bypassing the system.

Behavior of Large-Scale Concrete Columns Wrapped with CFRP and SFRP Sheets

AbstractCircumferential wrapping of fiber-reinforced polymer (FRP) sheets is one of the most common applications for repair and rehabilitation of large-scale columns. Common types of fibers used for wrapping are carbon FRP (CFRP), glass FRP (GFRP), and aramid FRP (AFRP). Recently, steel FRP (SFRP) has been introduced as a new class of composites for strengthening applications. Up to now, there has been no experimental data available on the behavior of large-scale columns wrapped with SFRP sheets. Thus, in this paper, the behavior of nonreinforced and reinforced large-scale columns (300×1,200 mm) wrapped with CFRP and SFRP sheets is examined and compared with that of unwrapped columns. The experimental results include stress-strain behavior, ultimate stress, ultimate strain, dilation, and ductility of large-scale columns. This study presents the first ever insight into the strain variation of large-scale circular columns wrapped with CFRP and SFRP sheets using the digital image correlation technique (DICT...

Water Treatment Residual as a Bioretention Amendment for Phosphorus. II: Long-Term Column Studies

Bioretention is an EPA-designated best management practice developed to mitigate negative ecological effects from urban storm-water. However, while these facilities perform well for the removal of a multitude of pollutants, in many cases they are ineffective in treating excessive storm-water nutrients such as phosphorus (P) that may induce surface water eutrophication. This work builds on the results of a previous paper, which describe initial studies on the use of aluminum-based water treatment residual (WTR) as a bioretention soil media (BSM) amendment. A 5% WTR-, 3% triple-shredded hardwood bark mulch-amended loamy sand BSM was investigated in a large-scale (0.9 m) column to determine the media P adsorption performance under varying hydrologic and pollutant concentration conditions. Results indicate that the WTR-amended media adsorbed 88.5% of the applied P mass, relative to a non-WTR-amended control media for which effluent P mass increased by 71.2%. The amended media consistently produced total phosp...

Theoretical model for slender FRP-confined circular RC columns

An important application of fiber-reinforced polymer (FRP) composites is to provide confinement to reinforced concrete (RC) columns to enhance their load-carrying capacity. However, this application is generally restricted to short columns as existing design guidelines do not contain provisions for the design of FRP jackets for slender columns. This situation has been due to both the scarcity of test data and the lack of rigorous theoretical studies into the behavior of slender FRP-confined RC columns. This paper presents a theoretical model for slender FRP-confined circular RC columns based on the numerical integration method; Lam and Teng’s stress–strain model is employed to describe the behavior of FRP-confined concrete in the column. Predictions from the theoretical column model are compared with existing test results, which demonstrates that the theoretical model is reasonably accurate in reproducing the experimental results of FRP-confined circular RC columns. These comparisons also demonstrate the need to conduct careful tests on large-scale columns to eliminate some uncertainties associated with the existing test data to enable a more conclusive verification of the proposed theoretical column model.

Bioleaching - An Alternate Uranium Ore Processing Technology for India

Abstract Meeting the feed supply of uranium fuel in the present and planned nuclear reactors calls for huge demand of uranium, which at the current rate of production, shows a mismatch. The processing methods at UCIL (DAE) needs to be modified/ changed or re-looked into because of its very suitability in near future for low-index raw materials which are either unmined or stacked around if mined. There is practically no way to process tailings with still some values. Efforts were made to utilize such resources (low-index ore of Turamdih mines, containing 0.03% U3O8) by NML in association with UCIL as a national endeavor. In this area, the R&D work showed the successful development of a bioleaching process from bench scale to lab scale columns and then finally to the India's first ever large scale column, from the view point of harnessing such a processing technology as an alternative for the uranium industry and nuclear sector in the country. The efforts culminated into the successful operation of large scale trials at the 100 kg and 2ton level column uranium bioleaching that was carried out at the site of UCIL, Jaduguda yielding a maximum recovery of 69% in 60 days. This achievement is expected to pave the way for scaling up the activity to a 100ton or even more heap bioleaching trials for realization of this technology, which needs to be carried out with the support of the nuclear sector in the country keeping in mind the national interest.

CO2 -porewater-rock reactions–Large-scale column experiment (Big Rig II)

This study focused on the reactions between carbon dioxide (CO2), porewater and host rock during geological CO2 storage in deep reservoirs. The aim of this work was to provide a well-constrained laboratory experiment reacting known quantities of minerals with CO2-rich fluids, to simulate situations where CO2 is being injected into lithologies deep underground. The experiment was undertaken using a Ti-column, 100 cm long, held within a large pressure vessel. The column was packed with a simplified mineral assemblage. The reactant fluid was equilibrated with CO2 at a temperature of 130 °C and a pressure of 300 bar, before being pumped into the column held under the same conditions. Fluid was passed along the column at a constant flow rate for approximately 3.5 months. Fluids collected from the outlet end of the column were analysed to provide data on the fate of the dissolved species. On completion of the experiment, the column was then examined for mineralogical changes. The experimental results can be used as a test case for predictive geochemical computer modelling. Such models will help improve our ability to predict the long-term fate of CO2 stored underground.

Formation of Secondary Containment Systems Using Permeation of Colloidal Silica

U.S. Environmental Protection Agency (USEPA) regulations require the capture of spills from liquid tanks containing hazardous chemicals by using a secondary containment system. Compacted clay or geomembrane liners are commonly used in secondary containment systems, but they are cumbersome when used in conjunction with existing liquid tanks because of pipeline networks surrounding the tanks. This study evaluates the formation of hydraulic barriers for secondary containment through the permeation of colloidal silica grout. A sim- plified infiltration model is presented to predict the downward movement of the colloidal silica grout into a soil layer, considering the time- dependent increase in dynamic viscosity of the colloidal silica for different concentrations of an electrolyte accelerator. Because the simplified infiltration model cannot predict the soil-grout interaction or the permeation of the colloidal silica by fingering, its results were calibrated by using the observations from a large-scale column test involving the permeation of colloidal silica into sand. The predicted position of the wetting front was found to match that of the experiment when the parameter governing the change in viscosity of the colloidal silica was increased by a factor of 30. The infiltration model calibrated with observations from column infiltration experiments provides a simple approach to the design of the secondary containment systems using permeation of colloidal silica. DOI: 10.1061/(ASCE)EE.1943- 7870.0000345. © 2011 American Society of Civil Engineers.