Shape Of Column Research Articles

CFD study of oscillatory motion effect on liquid flow distribution into structured packed divided wall column

Packed distillation columns are key equipment in natural gas pre-treatment process within LNG production process train operated at offshore. In this work, the impact of offshore operating conditions and that of divided wall column shape were explored via developing transient three-dimensional CFD model for a divided wall distillation column filled with structured packing. Inter-phase drag force, porous resistance force, mass transfer, and liquid dispersion were incorporated into volume averaged equations to map the distortion in liquid distribution in response to column oscillatory motion. The results show that introducing a dividing-wall into distillation column affects fluids partition and distribution. Column motions induce complex fluid flows in radial direction that result in oscillatory patterns around the steady-state solution of vertical column. Furthermore, liquid distributions in a divided wall column under influence of column motion differ with respect to column system positions throughout rotational axes, mass transfer also fluctuates according to column oscillations. A position with a dividing wall making an angle of 45˚ with rotational axis gives a scenario in which rolling motion resembles to pitching motion. The thereof position leads to moderate liquid maldistribution in comparison to liquid maldistribution from scenario with dividing wall parallel to rotational axis.

Punching Strength of Reactive Powder Reinforced Concrete Flat Slabs

This research is devoted to investigating experimentally the punching shear strength of reactive powder concrete slabs under monotonic loading. All slabs have the same flexural reinforcement and same dimensions (1000mm length,600mm width,50mm thickness). The experimental program includes casting and testing of sixteen slabs tested under monotonic loading. The major parameters adopted in the current research include the shape of column (circle, square), column size (twocolumn sizes), number of columns (one, two), and the distance between two columns (3d,5d,7d). Results showed that, the slabs with circular column sections have slightly higher ultimate load than those with square column sections. An increasing column area increases the load of punching shear failure. It was found that the ultimate failure load for slabs with two columns is greater than the slabs with one column. Related to the effect of distance between the two columns for monotonic, it was found that the slabs maximum load reaches the maximum value at distance between the two columns equal to(7d) for a circular section with a diameter of 85mm and 113mm and square section with dimensions of (100*100)mm. While the maximum failure load reaches the maximum value when the distance between two columns (d) for a square section with the dimension of (75*75)mm. Related to the crack patterns, it was noticed that for slabs with larger columns sections with the distance between columns equal to 7d, the failure zone extended (in a large direction) to the slab sides.

Characterizing oxygen atoms in perovskite and pyrochlore oxides using ADF-STEM at a resolution of a few tens of picometers

We present an aberration corrected scanning transmission electron microscopy (ac-STEM) analysis of perovskite (LaFeO3) and pyrochlore (Yb2Ti2O7 and Pr2Zr2O7) oxides and demonstrate that both the shape and contrast of visible atomic columns in annular dark-field (ADF) images are sensitive to the presence of nearby atoms of low atomic number (e.g. oxygen). We show that point defects (e.g. oxygen vacancies), which are invisible – or difficult to observe due to limited sensitivity – in x-ray and neutron diffraction measurements, are the origin of the complex magnetic ground state of pyrochlore oxides. In addition, we present a method by which light atoms can be resolved in the quantitative ADF-STEM images. Using this method, we resolved oxygen atoms in perovskite and pyrochlore oxides and propose this method to be suitable for other materials containing both light and heavy elements.

Seismic analysis of various combinations of irregularities in a structure

One of the important governing parameters of the seismic performance of a structure is its irregularities. There are many types of irregularities such as geometric irregularities, mass irregularities, irregularities due to varied column shapes and dimensions, etc. It is very evident that these irregularities are seen in every project in this contemporary world. We have to acknowledge that there is a tremendous scope for these irregularities to exist in combinations. Although there has been extensive literature on various irregularities and their combination, it was evident that authors restricted themselves to limited combinations. This paper investigates the seismic response of a multi-storeyed building induced with combinations of irregularities by varying the seismic parameters using STAAD Pro. Various configurations of mass and torsion irregularities in combination with other irregularities were induced in the structure and results of seismic response using response spectrum methods were assessed to arrive at novel solutions.

Experimental and numerical investigation of cross-shaped stub CFSTs under axial compression

The cross-shaped concrete-filled steel tube (CFST) is a new shape of column, which avoids convex corners and increases the interior area of the room. Cross-shaped CFSTs possess high bearing capacity, good seismic performance and efficient construction speed. In this study, cross-shaped stub CFSTs under axial loading were tested. The key parameter is the width/thickness ratio of the cross-section. Experiments revealed that local buckling could be delayed and section capacity enhanced by reducing the tube width/thickness ratio. Moreover, a finite-element model was established using the commercial program Abaqus to simulate the compressive performance of the specimens. The results were used to confirm the precision of the finite-element model. Further, a parametric study was completed to inspect the effects of the tube width/thickness ratio, concrete strength and steel yield strength on the mechanical properties of specimens. Relying on the constitutive theoretical model of restrained concrete, an equation is recommended to calculate the section capacity of cross-shaped CFSTs. Finally, the practical outcomes and the calculated outcomes obtained from different design codes (AISC, AIJ, EC4, CECS and GB) were compared. The comparison results revealed that all recommended design codes underrate the section capacity of cross-shaped CFSTs.

Performance Comparison of High Strength Reinforced Concrete Circular and Square Columns Subjected to Flexural Controlled Cyclic Loading

In existing design practices selection of circular or square column shape mostly depends upon architectural needs rather than structural behavior. The behavior of equivalent area (circular and square), high strength reinforced concrete columns is reported to be same under monotonic loading conditions but their behavior under fatigue loading is not well-established. This paper presents the comparison of high strength reinforced concrete circular and square equivalent area columns’ performance (load-deflection behavior) under fatigue loading. Columns were casted in four configurations: square and circular shapes and with and without shear stirrups. Experimental results showed that in case of columns without shear stirrups, the square column resisted 38% more loading cycles as compared to circular column while the maximum deflection was 78% more than the circular column. Similarly, in case of columns with shear stirrups, square shaped column resisted 55% more loading cycles with only 5% more maximum deflections as compared to circular column. The results show that the square columns might be considered more ductile as compared to circular columns under the application of cyclic loading conditions like wind forces or seismic forces. Therefore, it might be concluded that square columns should be recommended for highly seismic regions as compared to circular columns with equivalent area. Doi: 10.28991/cej-2021-03091639 Full Text: PDF

An approach for partial strengthening of circular RC columns using outer steel tube

This paper introduces an improved design equation to evaluate the resisting capacity of circular reinforced concrete (RC) columns partially strengthened with outer steel tube. When RC column members are required to be strengthened according to the change in the loadings considered and/or the deterioration progress in columns, wrapping up RC column with steel circular tube, which takes the form of concrete filled steel tube (CFST), has been popularly considered because of its structural advantage induced from the confinement effect. However, the relatively high construction cost of steel tube is restricting its use to the required region, while deriving the shape of a partial CFST column. To evaluate the resisting capacity of a partial CFST column, numerical analyses need to be performed, and a numerical model proposed in the previous study for the numerical analysis of full CFST columns is used to conduct parametric studies for the introduction of a design equation. The bond-slip effect developed along the interface between the in-filled concrete and the exterior steel tube is taken into consideration and the validity of the numerical model has been established through correlation studies between experimental data and numerical results for partial CFST circular columns. Moreover, parametric studies make it possible to introduce a design equation for determining the optimum length of outer steel tube which produces partial CFST circular columns.

Effect of Spacing between Stone Columns on the Behavior of Soft Soil

Soil improvement by stone columns is extensively used, especially for the soft ones. This is because of their efficiency and no environmental impact. Several factors affect its efficiency in improving the mechanical properties of the soil, and the most important of these factors are the spacing, length, and diameter of the stone columns. In this study, the finite element method was used to study the impact of the spacing between the stone columns on the amount of settlement and the bearing capacity of the soil. The study comprises three different spaces (s) that were taken in relation to the columns’ diameter (d), which are (s/d= 3, 4, and 5). In addition, three types of the sectional shape of column involved circular, rectangular, and square sections with different lengths of (L/d=2, 4, 6, 8, and 10). The results showed that the spacing between the stone columns is effective when the vertical load is greater than 30 kN/m2, and below this, there is no effect of the spacing. In general, the settlement decreases, and the bearing capacity increases with the decrease in the spacing between the stone columns. The spacing becomes a more pronounced effect with the longer length of the stone columns. All sections of the stone columns with a short length of (L/d=2) showed the same settlement of 271 mm at a distance (s/d=5), which decreases by 7.4, 6.6, and 8.9% at a distance (s/d=3) for the circular, rectangular and square sections respectively. In the case of long columns (L/d=10), the settlement at (s/d=3) improves by about 27.5% which drop to about 18% at (s/d=5). A slight improvement in the soil's bearing capacity is associated with decreases in the spacing between the stone columns. The improvements in the bearing of soil treated with short columns (L/d=2) are 6.0, 6.5, and 4.7% for circular, rectangular, and square sections, respectively, when changing the distance from (s/d=5) to (s/d=3). Whereas they become greater when increasing the columns’ length to (L/d=10) to be 7.9, 9.2, and 6.4%.

The comparative study of analyzing the T-shaped and square-shaped concrete columns

This study aims to analyze how much changes in column shape effect have on the strength of the column structure. This calculation is comparing a square-shaped concrete column with two different axis of a T-shaped column. Each sample is compared in terms of 6 different column dimensions, however, the cross-sectional area within the three samples ( Square, T-shaped axis1 and 2) has remained constant. The concrete quality (fc') is kept at 30 MPa while the reinforcement area used 1% and 5%. Column calculation analysis is using Hognestad stress-strain diagram relationship and finite difference method. The result shows, the greater the reinforcement ratio, the greater the difference of Mn value and the smaller the difference of Pn value, of T-shaped and square column for each area. The same cross-sectional area does not necessarily lead to the same behavior of a T-shaped column with a different axis

Finite Element Analysis (FEA) Based Frequency Optimization of Vertical Storage Column

The ethanol containing vertical storage column is typically a leak proof tank which is used to store the liquid and fine powder. To exploit the storing capability, these columns are generally precise high normally above 27meters with a circular cross section. The task arranged is that the agitator and the vertical pole are necessary to be on the equal podium. Due to this the pole is predisposed to vibrations from the Campaigner. This was needed to optimize the natural frequency of the column. Stiffeners /Support are fond of to the column plate to reinforce the column counter to pressure force, to minimize the vibrations of the plate and to become rigid plate against buckling. Stiffeners must be set apart at some suitable positioning so that plate stress is low than permissible stress. If column panel tallness or breadth is less than acceptable plate span then according to assumption column doesn’t requires stiffeners/support. Though if column lifted or handles in one piece then, some stiffening may be required to keep column shape. Rise the stiffness by growing stiffeners/supports leads to load increase so no actual variance in rate of recurrence. By reducing mass of column and that can be possible only by selecting proper material. The objective of entire effort is to design of the vertical column in such a way that the natural frequency of the column can be optimized. As number of supports (horizontal) are increasing the natural frequency of column is also increasing, but at same time weight is also increased. So in order to optimize design the weight of column provided by support must be reduced. After optimize the structure of support and carrying out pre stressed modal analysis the targeted natural frequencies (>16 Hz) is obtained in the structure.

Effect of Shape Modification on the Performance of Cfrp Confined Square Concrete Columns: A Review

Now a days fiber-reinforced polymer (FRP) confinement is one of the most important techniques used for the strengthening and repairing of concrete structures. In the case of columns, the square/rectangular columns show less effectiveness towards FRP confinement compared with circular columns due to their flat sides and sharp corners. So the strengthening of square/rectangular columns needs more attention than circular columns. The performance of square/rectangular columns can be improved by modifying the shape of columns before FRP wrapping. The researches show that varying the corner radius of non-circular columns improves the confinement area and thereby increase the confinement efficiency of FRP. Recently, curvilinearization technique was developed in which slightly curved sides are provided to existing square/rectangular sections before application of FRP. Circularization is also another shape modification method in which the existing square columns are modifying into circular sections by using segmental concrete covers before the FRP wrapping process. This paper mainly deals with these shape modification techniques in the carbon-fiber-reinforced polymer (CFRP) confined square columns.

Parametric investigation on the design of RBS moment connections with jumbo beams and columns

Recent experiments demonstrated that reduced beam section moment connections with some of the largest hot-rolled beam and column shapes (jumbo shapes) may not have sufficient ductility for high seismic applications if designed according to current design procedures. A parametric computational study was performed to evaluate potential changes to the design procedures to enhance the ductility of these connections with jumbo shapes. First, three-dimensional finite element models were developed and calibrated to match cyclic experimental results including load vs displacement response, panel zone deformations, and deformed shape. The models were then used to conduct parametric studies with inelastic monotonic loading to examine the effect of design parameters including beam flange reinforcing fillet weld size, panel zone strength and doubler plate location on fracture potential. The results showed that the size of the reinforcing fillet weld on the underside of the bottom flange has a significant impact on the local stresses and strains at the location of fracture initiation in the tests and that larger size fillet welds should be used with jumbo beams to mitigate the concentration of inelastic strains. The results also showed that joints with higher panel zone strengths lead to lower fracture potential and that moving the column web doubler plate outwards to the edge of the flange is another effective strategy to reduce local strain concentrations. The absence of local buckling in jumbo sections eliminates the strength degradation that limits demands on the welds and needs to be taken into consideration in their design.

Flexural behavior of a novel high-strength RCFST column-to-column connection

Brittle fracture is one of the principal disincentives to limit the use of ultrahigh-strength steels in tall buildings. This paper proposes a novel column-to-column connection without full penetration welding in reinforced concrete-filled steel tubular composite columns. The paper describes an experimental investigation into the flexural behavior of the proposed RCFST column-to-column connection, in which the steel was manufactured using ultrahigh-strength steel grades H-SA700 and USD 685. Four specimens with varying configurations of reinforcing steel bars (separated type or gathered type) and column shapes (square or circular) were tested under four-point bending to evaluate the failure modes, flexural capacity, and deformation capacity. The results show that the gathered type of configuration of reinforcing steel bars can effectively improve the flexural capacities while having a negligible effect on the strain distribution of steel tubes or steel bars. Besides, the column type was found to significantly influence the strain distribution of the steel tube. The design formulae show accuracy and reliability and could be applied to assess the yield and ultimate strength of the proposed new connections.

Punching strength behavior of reinforced concrete slabs with chips waste tire rubber

Every year waste in millions tons are accumulated in the globe and much of it is non-biodegradable in nature, e.g. waste vehicle tires. In addition, waste recycling is energy consuming and pollution producing. Moreover, in this research, an experimental study is carried out to explore the behavior of chips rubberized concrete (CRC) in punching shear of flat plates. The experimental program comprises 10 specimens designed to fail by punching. The investigated parameters were the model type column, chips rubber ratio that used instead of coarse aggregate. Two cases are classified according to shape of column; square and rectangular. Each case consists of five specimens, the first specimen casted by normal strength concrete (NSC) and the other casted with CRC, by 5%, 10%, 15%, and 20%. The experimental results present that increasing chips rubber instead of coarse aggregate in two cases studies (square, and rectangular column) from zero to 20% shows a drop in the punching shear capacity by range of 13.54%, and 18.52%, and a reduction in the initial and secant stiffness by (16.06%, 25.19%), and (24.44%, 26.88%) respectively. Also, using 20% chips waste rubber increased the central deflection of two cases at service load by (37.39%, 47.28%), and increased the central ultimate deflection of the plates by about (24%, 24.58%) respectively. Furthermore, 20% replacement of coarse aggregate by rubber increased the ductility by (20.38%, 15.60%), and increased the energy absorption index significantly by 41.41%, and 28.75%, and led to decrease cracks width at service load by 36.11%, and 44.12% for the two cases respectively. From comparison between theoretical and experimental results one can get three equations relate the deficiency of punching shear capacity and chips rubber ratio, and concluded that the optimal replacement was by using 10% to15%. It can be inferred that the experimental results for square columns (S-R) specimens at all replacement percentages from zero to 20% less constrictive than ACI-code equations, whereas for rectangular columns (R-R) specimens the ACI-code equations can be used to replace 15%, after that the correction factor must be applied

The effects of cross-sectional shapes on the axial performance of concrete-filled steel tube columns

Concrete-filled steel tubular (CFST) columns have been used in the construction of modern structures such as high-rise buildings and bridges as well as infrastructures as they provide better structural performance than conventional reinforced concrete or steel members. Different shapes of CFST columns may be needed to satisfy the architectural and aesthetic criteria. In the study, three dimensional FE simulations of circular, square, hexagonal, and octagonal CFST stub columns under axial compression were developed and verified through the experimental test data from the perspectives of full load-displacement histories, ultimate axial strengths, and failure modes. The verified FE models were used to investigate and compare the structural performance of CFST columns with different cross-section shapes by evaluating the overall load-deformation curves, interaction stress-deformation responses, and composite actions of the column. The extent of the ultimate-axial-strength enhancement due to enhanced steel yield strength and concrete compressive strength was evaluated through the parametric studies. At last, the accuracy of available design models in predicting the ultimate axial strengths of CFST columns were investigated. Research results showed that the behaviors of hexagonal and octagonal CFST columns were generally similar to that of the square CFST column as their overall structural performance was relatively improved.

Concrete-filled steel tube columns of different cross-sectional shapes under axial compression: A review

This paper presents a review on the axial compression behavior of different cross-sectional shaped concrete-filled steel tube (CFST) columns such as circular, rectangular, square, elliptical, hexagonal, octagonal and round-ended. A discussion on some special shapes like triangular, D-shape, ¼ circular, fan shape etc. is also done in this paper. Confinement offered by the varying cross-sectional shape steel tubes to concrete core, material strength limits and slenderness limits available in different codes of practices and the proposed yield slenderness limits for rectangular, elliptical and octagonal cross-sections are discussed. The failure modes encountered during the axial compression test on CFST columns are mentioned. An analysis on the parameters that influence the behavior of the columns, design equations in the current codes of practice, modifications made on the code design equations, equations proposed on the determination of compressive strength of different cross-sectional shapes of CFST columns is done. Unified formulas for two different cross-sectional shapes and solid and hollow concrete-filled steel tubes are also included. Conclusions are finally made based on the discussion done.

Discrimination and application of the properties of the in-seam seismic wave in the collapse column of the working face

During in-seam wave seismic exploration of working face, the anomaly has serious diversification, and sometimes it is difficult to accurately determine the nature of the anomaly. Due to the large differences in the collapse column shape of the working face, especially when there are multiple sets of collapsed columns, it is difficult to effectively distinguish its nature. This has been an unresolved problem since the tunnel wave earthquake was introduced. Based on the analysis of the characteristics of the collapse column in the working face, the forward simulation analysis of the collapse column is carried out. Based on the field application case, the BPT algorithm and the SIRT algorithm in the calculation process of the energy attenuation coefficient tomography overlay inversion calculation are studied. Through analyzing the amplitude and frequency dispersion characteristics of the verification of the collapse column anomaly, a method for identifying the seismic properties of the working face collapse column groove wave is proposed, which effectively improves the accuracy of the in-seam wave seismic detection.

Deformation and regimes of liquid column during water exit of a partially submerged sphere using the front-tracking lattice Boltzmann method

When a solid sphere exits water at a given velocity, the liquid column is pulled out of a liquid reservoir. The present study focuses on the dynamic deformation of the liquid column and on the identification of the liquid column regime on the Weber number and dimensionless time (We-t*) map. The three-dimensional model of water exit has been established on the basis of the lattice Boltzmann method. A mass tracking algorithm was incorporated to capture the free surface, where the liquid–gas​ two-phase flow is simplified to a single-phase free surface flow. The surface tension is included by adding a perturbation term and the gravity as a body force is introduced in form of calculating the equilibrium distribution with an altered velocity. The contact angle condition in numerical simulation is not considered. The accuracy of the numerical results is demonstrated through the comparisons with the prior numerical and the experimental results in the literature. A parametric study has been conducted numerically on the radius and volume and of liquid column. Besides, the relationship between the pinch-off time of a liquid column and the Froude number has been obtained. Moreover, the evolution of the liquid column shape with a wide range of the Weber number and time scales are discussed based on the number of ligaments and droplets. The liquid column exhibits different characteristics and has been divided into three regimes. The transition between different regimes has been analyzed and the critical Weber number is given.

MEASUREMENT OF PLASMA PARAMETERS BY OPTICAL DIAGNOSTICS IN THE VISIBLE SPECTRUM RANGE AT THE SECOND STAGE OF PHYSICAL START-UP OF THE TOKAMAK KTM

The article describes the characteristics of optical diagnostics of the tokamak KTM and the results of measuring the plasma parameters of the tokamak KTM obtained with their help. The measurements of the parameters of the plasma discharge were carried out as part of the work at the second stage of the physical start-up of the tokamak KTM. Based on the obtained experimental data the elemental composition of the plasma was estimated by measuring line radiation in the visible range (380–700 nm), the moment of plasma breakdown was determined and the position and shape of the plasma column was estimated.

Circular and square columns strengthened with FRCM under concentric load

Fiber-reinforced cementitious matrix (FRCM) systems have recently emerged as an innovative technique to strengthen and retrofit reinforced concrete structures. These non-corrosive systems involve the use of high strength reinforcing textiles sandwiched between layers of cementitious mortars. This paper aims to study the effect of retrofitting newly constructed short columns with FRCM using PBO type of textiles. The experimental program consisted of testing 4 rectangular columns and 4 circular columns under concentric loading. All columns had a reinforcement ratio of 0.02 and were cast with concrete of 30 MPa compressive strength. For each type of cross-section, columns were wrapped with 1, 2 or 4 layers of PBO FRCM. Overall, the strengthened columns exhibited higher load carrying capacity than their control unwrapped counterpart with an increase ranged between 5.1% and 36%. The confining effect of FRCM layers was more pronounced in the circular columns than in the square ones. It was also noticed that all columns exhibited similar responses in terms of load -strain relationship irrespective of the column shape and the number of FRCM layers used. Furthermore, the displacement levels increased as the number of layers increased which indicated an increase in ductility of columns wrapped with FRCM.