Column Surface Area Research Articles

Enhancing the Effectiveness of Strengthening RC columns with CFRP sheets

The column is the most important structural element were strengthening of columns became a demanding issue. In this paper, the effectiveness of strengthening reinforced concrete (R.C) columns with carbon fiber reinforced polymers (CFRP) wraps has been improved by increasing the contact area between the column’s surface area and CFRP. A new strengthening technique was hired for the purpose of enhancing the efficiency of CFRP jackets in improving the load capacity of R.C columns, especially columns with rectangular sections. The method is based on increasing the contact area between the CFRP jacket and the column's surface area. This was done by adjusting the profile of the col's cross-section to almost ellipsoidal. The experimental program in this research includes testing 13 columns to include all test parameters, the shape of the cross-section, and the cross-section profile. The results include axial stresses and corresponding axial strains, and lateral strains at the mid-height and quarter height of tested specimens. And also, the cracking load and maximum load with crack patterns are determined. The comparison involved the study of the effect of the traditional CFRP jacket wrapping of R.C columns with square, and rectangular sections and the newly developed strengthening technique. A theoretical study was also conducted. Where the capacity of the square and rectangular confined columns with different radius of curvature, R, of the ellipsoidal profile is determined by the predicted and design equations. The study revealed that the strengthening technique is expected to effectively enhance the efficiency of the CFRP strengthening technique, especially for columns with square and rectangular sections as the area of the well-known dead zone of these columns is reduced using the proposed technique. Also, the results proved that the efficiency of strengthening tested columns by CFRP jacket has been enhanced using the strengthening technique by about 80% of original RC columns, which exceeds the traditional method (Jacket) CFRP wrap by 60%.

3D modelling and analysis of encased steel-concrete composite column using ABAQUS

This research paper introduces the ABAQUS simulation of fully encased composite (FEC) columns and compared to reinforced concrete columns of different concrete strengths. Axial load capacity deformation, stress and strain patterns are determined for reinforced concrete columns and composite columns with I-section steel confinement. The behavior of composite columns and reinforced concrete columns can be determined by the Finite Element Method (FEM) using the ABAQUS software. Based on the results, it was shown that the reinforced concrete column has less resistance to ultimate axial load compared to fully encased composite columns. Due to structural steel in composite columns ultimate axial load resistance has improved. Stress-strain distributes across the column surface area during yield, but it gets concentrated in the pedestal area. A detailed parametric analysis was performed to study the behavior of axially loaded columns of FEC and RC in ABAQUS software. The geometric and material properties are varied, and their effects have been observed with respect to ultimate axial load with failure mode and overall column load-deformation responses are tabulated and plotted in the graphs.

Sa1658 - The Timed Barium Esophagram Surface Area Correlates with Symptom Improvement Better than Column Height Following Treatment in Achalasia

Introduction Timed barium esophagram (TBE) is an objective measurement of esophageal emptying in achalasia. Post-therapy reduction of residual barium column height correlates imperfectly with short term symptomatic outcomes. We hypothesise that surface area (SA) of the barium column may be more accurate than height; firstly, by incorporating improvement in esophageal width that often occurs post-therapy, but also by correcting for artificially higher height values due to esophageal contraction occurring. We aimed to compare the correlation of TBE outcome measures of height and SA with symptom improvement post-therapy. Method Achalasia patients who underwent therapy between 2015–6 and had TBE and Eckardt score (ES) performed at baseline as well as within 6 months post-therapy were included. TBE images were acquired 5 mins following ingestion of 200 mL barium. Barium height was measured between the gastro-esophageal junction and the superior extent of any residual barium column. After manually defining column boundaries, software was used to calculate SA. Adequate symptom relief was defined as ES reduction to ≤3. On TBE, metrics of adequate emptying evaluated were i) post-therapy column height 50% reduction in column height from pre to post-therapy and iii)>50% reduction in column SA from pre to post-therapy. Results Of 18 patients, 11 had dilatation and 7 POEM. Reductions with therapy of both 5 min barium column height (14.7±8.7 to 7.9±6.0 cm; p=0.01) and SA (52.7±43.5 to 24.5±26.0cm2; p=0.02) were noted. Symptoms also improved; median baseline ES 7 (IQR 5.25–8) improved to 0 (IQR 0–1) post-therapy. However there was poor concordance between post-therapy barium height and symptomatic relief (i.e. post-therapy column >5 cm despite ES ≤3 or vice versa), and the correlation (R) between these two variables was poor. Similar poor concordance was seen when adequate emptying was defined by >50% reduction in column height, but >50% reduction in SA paralleled symptom relief most closely. Conclusion In TBE performed on achalasia patients post-therapy, reduction in SA of the residual barium column compared with baseline values parallels symptomatic relief more closely than reduction of column height. Disclosure of Interest None Declared

Experimental and analytical behavior of strengthened reinforced concrete columns with steel angles and strips

The need of strengthening reinforced concrete columns, due to loss of strength and/or stiffness, is an essential requirement due to variation of the loads and environmental conditions applied on these columns. Steel jackets around the reinforced concrete (RC) columns are usually made by means of steel plates covering all over the column surface area. For the value of engineering purposes, another technique was developed using steel angles at the corners of the RC columns connected with discrete steel strips. In this paper, an experimental program is designed to evaluate the improvement in load-carrying capacity, stiffness and ductility of strengthened RC columns, concomitant with steel angles and strips. Despite of prevailing a substantially increased loading capacity and strength a pronounced enhancement in ductility and stiffness has been reported. A need for experimental test results with low value of concrete strength to mimic the local old-age structures condition that required strengthening in local countries. Seven columns specimens are tested to evaluate the strength improvement provided by steel strengthening of columns. The method of strengthened steel angles with strips is compared with another strengthening technique. This technique includes connected and unconnected steel-casing specimens. The observed experimental results describe load-shortening curves, horizontal strains in stirrups and steel strips, as well as description of failure mode. The extra-confinement pressure, due to existence of steel cage, of the strengthened RC column can be also observed from experimental results. The code provisions that predict the load-carrying capacity of the strengthened RC composite column has a discrepancy in the results. For this reason, an analytical model is developed in this paper to compare the code limit with experimental observed results. The proposed model accounts for the composite action for concrete confinement and enhancement of the local buckling of steel elements. This adopted model is simplified and applicable to practical design field. In this respect, the experimental results and those of the analytical model showed a good agreement.

In situ measurement of odor compound production by benthic cyanobacteria

A simple technique was developed to make in situ measurements of emission rates of two common odorants, 2-MIB and geosmin, and was validated with different natural communities of benthic cyanobacterial mats in Hope Valley Reservoir (HVR), South Australia, and Kin-Men Water Treatment Plant (TLR-WTP), Taiwan. A pair of parallel columns was used to differentiate between emission and loss rates caused by biodegradation, volatilization, and other mechanisms. Experimental results indicated that the loss rates followed a first-order relationship for all cases tested, with biodegradation and volatilization being the key mechanisms. The loss rates were comparable to those reported in the literature for biodegradation and those calculated from two-film theory for volatilization. After accounting for the loss rates, the net emission of geosmin and 2-MIB was estimated from experimental data. Odorant emission rates on the basis of column surface area, cyanobacterial cell number, and chlorophyll a (chl-a) were 4.2-4.4 ng h(-1) cm(-2), 1.0-5.5 x 10(-6) ng h(-1) cell(-1), and 3.2-3.5 ng h(-1)microg-chl(-1), respectively for 2-MIB released from benthic mats in TLR-WTP, and, 18-190 ng h(-1) cm(-2), 0.053-1.8 x 10(-3) ng h(-1) cell(-1), and 48-435 ng h(-1)microg-chl(-1) respectively for geosmin from benthic mats in HVR. The method developed provides a simple means to estimate the emission rates of odorants and possibly other algal metabolites from benthic cyanobacterial mats.

Is barium column surface area a better predictor of primary achalasia disease severity than barium column height?

Is barium column surface area a better predictor of primary achalasia disease severity than barium column height?

Small‐Scale Variability in Solute Transport Processes in a Homogeneous Clay Loam Soil

Small‐scale variations in transport parameters may have a profound influence on larger scale flow processes. Fiber‐optic miniprobes (FOMPs) provide the opportunity to continuously measure solute resident concentration in small soil volumes. A 20‐channel multiplexed‐FOMP system was used in repeated miscible displacements in a repacked clay loam soil column (20 cm long and 10‐cm diam.) to examine small‐scale, point‐to‐point variability in convective–dispersive transport processes. Transport parameters, measured 10 cm below the surface, were compared at two drip irrigation point densities and two fluxes. Irrigation densities of one irrigation drip point per 4 cm2 and 11 cm2 of column surface area produced similar results. The breakthrough curves measured at 0.10 cm h−1 had a larger immobile phase than at a flux of 1.07 cm h−1 In the clay loam soil the mobile–immobile model fit the breakthrough curves better than the convective–dispersive equation (CDE), with r2 values of 99.6 and 97.1, respectively. This analysis demonstrated that dispersion and mass recovery were much more variable than pore water velocity in this repacked clay loam soil. However, even in the most variable transport conditions encountered, only 17 sampling points were necessary to describe the column average transport parameters within 20% of the mean.

PEEK columns for open-tubular liquid chromatography with electroosmotic flow

A surface treatment method was developed for bonding a hydrophobic layer on the inner surface of poly(ether ether ketone) (PEEK) capillaries for electroosmotically driven open-tubular liquid chromatography (LC). The inner wall of the PEEK capillaries was treated with a dilute chlorosulfonic acid solution. This treatment increased the column surface area and thus improved the phase ratio and, at the same time, activated the surface for the subsequent reaction with alkylamines. Capillary columns prepared in this manner showed retention characteristics similar to reversed-phase LC. The column performance was evaluated using neutral compounds as analytes; with a 65-μm-inside-diameter capillary, separation efficiencies were 4.77×104 plates/m for an unretained solute, but those for retained solutes were lower. ©1999 John Wiley & Sons, Inc. J Micro Sep 11: 693–700, 1999

Method for determination of the chromatographic surface area of reversed-phase surfaces

A method for determination of the chromatographically accessible area of a reversed-phase column is developed. The electrostatically modified linear adsorption isotherm, in combination with the solution of the linearized Poisson-Boltzmann equation, forms the theoritical basis of the developed method. The column's surface area is calculated by applying this theory to measured adsorption isotherms of charged amphiphiles. The consistency of the method is tested for different negatively charged amphiphiles using mobile phases of different ionic strengths, pH values and different methanol content. It is found that the chromatographically accessible column area is unchanged for different amphiphilic solutes and when buffer solutions of different compositions are used as the mobile phase (222–230 m 2/g). The surface area increases to approximately 250 m 2/g when the mobile phase contains 5 or 10% methanol. The developed method can be used by column manufacturers and by the practising chromatographer to characterize reversed-phase columns. The method is also of theoretical interest since it can be used to calculate the column's phase ratio, which is needed to obtain adsorption entropies.

Evolution of the Mt. Pinatubo aerosol over Antarctica inferred from sage II extinction measurements

This study focuses on the evolution and stratospheric settling of the Mt. Pinatubo volcanic aerosol. The volcanic aerosol characteristics are inferred from the Stratospheric Aerosol and Gas Experiment (SAGE) II extinction measurements using a modified randomized minimization search technique (RMST) between 13–30 km in the radii range between 0.10–0.80 μm. The temporal span of this study is between the date of eruption to early 1994 at latitudes poleward of 50°S. The 1991 eruption of Mt. Pinatubo resulted in the enhancement of the derived quantities with the existence of a large particle mode superimposed on the small background mode. This resulted in an order of magnitude increase in column number concentration, a 5-fold increase in column surface area, and greater than 20-fold increase in column mass loading (luring the austral summer of 1992. The averaged column effective radius is around 0.25 μm in 1994, still greater than the 0.15 μm observed in 1991 (background). The column mass loading has decreased 25 mg m −2 over two years between 1992–1994. Column bi-modal size distributions were evident from austral spring 1991 through the austral summer of 1994 with small mode radii ⩽ 0.20 μm and large mode between 0.30 – 0.60 μm. Effects of the polar vortex are observed during each austral spring since the eruption. Aerosol settling and decay in the presence of horizontal and vertical transport is observed during each austral spring. Column number concentrations have reached pre-eruption background levels whereas mass loading, surface area, and mean effective radius are still elevated as of early 1994.

Correlation between column surface area and retention of polar solutes in packed-column supercritical fluid chromatography

The retention of organic acids, amines, aminophenols, and amides was directly proportional to the surface area of Diol coated silica particles. Surface area was measured in situ using the method of Hong and Parcher [ Anal. Chem., 62 (1990) 2313–2317]. Linear regression analysis was performed on the results from four pore diameters (100, 300, 500 and 4000), plus the origin. Correlation coefficients between retention and surface area were as high as 0.9991. Both the surface area of the chromatographic support and solute retention changed by more than 14 times. All the solutes tested behaved similarly, indicating that changing the surface area is a viable means of retention control. The smallest pore diameter tested (100 Å) produced the same efficiency as some of the larger pore sizes ( i.e., 300 and 500 Å) suggesting that still smaller sizes, like 60 Å, might be useful for supercritical fluid chromatography. Particles with 4000 Å pores produced poor efficiency, due to peak tailing, which suggests that deactivation was inadequate.

Axial dispersion and enterainment of particles in wakes of bubbles

The entrainment and dispersion of solid particles in bubble columns was investigated experimentally and heoretically. A mechanistic model for the dispersion caused by entrainment in wakes of large solitary bubbles was developed. The dispersion coefficient was found to be dependent on the bubble size, bubble frequency, particle settling velocity and column surface area. Experimental tests were conducted in a rectangular bubble column. The system consisted of air, water and copper powder. Spherical cap bubbles were produced by a single nozzle. Significant entrainment of particles in wakes of rising bubbles observed in the lower region of the column, whereas, turbulence seemed to dominate the dispersion in the upper region of the tank. Calculated particle distributions were found to be in good agreement with experimental data.