Column Wall Research Articles

Failure analysis on abnormal damage and corrosion of methanol distillation column in MTBE production plant

Methyl tert-butyl ether (MTBE) is a commonly used gasoline additive that improves combustion and reduces pollutant emissions. The methanol distillation column is an integral part of the recovery system in MTBE production plants, used to separate and recycle unreacted methanol from water through distillation. During regular maintenance, severe damage to the support ring and abnormal perforations in the column were discovered. Despite repair welding, the column still leaked. Various investigations were conducted to determine the root cause of the failure. The chemical composition, metallurgical structure, and hardness of the support ring and column materials were examined, and the medium in the column was characterized. The medium at the bottom of the column was unexpectedly subjected to an undesirable excessive acidity (with a pH of approximately 3.8) dominated by the upstream etherification reaction deacidification, and provided common basic conditions for localized pitting and uniform corrosion of low carbon steel. What's more, the appearance of clean and smooth corrosion pits and scour traces on the perforated column wall, as well as honeycomb pits and arc-shaped layered traces on the support ring, revealed that the corrosion failure was intensified due to the interaction of selective erosive corrosion and medium concentration accelerated corrosion caused by multiple corrosion types of the acidic medium. In addition, the unpolished surface from incomplete repair welding was another significant factor. Based on these findings, specific countermeasures were implemented and proved effective.

Simulation of the liquid flow distribution in laboratory-scale additively manufactured structured packings

This article introduces a technique to simulate the liquid flow inside different additively manufactured structured packings with enclosing column wall on laboratory scale using the software OpenFOAM. The physical problem is handled by means of a periodic setup and makes use of common numerical discretization techniques of the software. The periodic setup reduces the required computational resources while permitting simulations of the liquid distribution in a large part of the column even for complex packing structures. A novel post-processing tool is used for a systematic evaluation of the liquid distribution. When optimizing packing structures, these computational fluid dynamics simulations eliminate the necessity to manufacture every developed geometry. As a proof of concept, this work simulates the liquid flow inside two additively manufactured packing structures. The results are validated with experimental data and show, that an improved liquid distribution can be obtained inside laboratory-scale packing structures.

Experimental and numerical investigations of tensile behavior of slip-critical blind bolts anchored in concrete-filled steel tubes

This paper presents experimental and numerical investigations of a Concrete-Anchored Slip-Critical Blind Bolt (CASCBB) system, which can be used to connect a steel beam to a concrete-filled steel tube column to form a rigid moment connection. A series of pull-out tests of CASCBBs embedded in concrete-filled steel square hollow section (SHS) is conducted with varying parameters such as with or without concrete infill, types of bolts, threaded or non-threaded anchor stud, tube thickness and bolt edge distance. A connection with a sufficiently thick SHS flange benefits significantly from its direct contribution to the total resistance even well before the anchorage failure. If the tube flange is too thin, the connection will possess no ductility as the concrete cone failure mode governs and dominates. A finite element methodology that resolves the difficulties of modelling the behaviour of infill concrete housing an anchored bolt is able to closely replicate the experimental responses. It is found from the finite element analysis that the contribution of the steel tube’s flange is independent of its thickness-to-width ratio but is a function of its thickness and the bolt edge distance. Placing the anchored bolt close to the SHS web can double the stiffness compared to placing it in the middle of the flange due to the greater contribution of the steel tube. It can also increase the maximum load-carrying capacity significantly. The finite element analysis results suggest that threading the anchor stud does not have noticeable effects on the anchorage failure load and the connection’s stiffness, in contrast to the apparent test results. In order to enable the plate separation to take place (at a load slightly higher than the bolt pretension), the column wall must be sufficiently thick. The wall thickness controls the maximum tensile capacity, the elastic stiffness and the ductility, but does not affect the initial stiffness.

Low-cycle fatigue behavior on the tensile region of Hollo-bolted angle connections

This paper presents the results of an experimental program to evaluate the low-cycle fatigue-related characteristics of the tensile region of Hollo-bolted angle connections. A summary of a total of 40 tension tests of equivalent T-stub connections is reported. The geometric parameters vary with the bolt gauge width, the column wall's thickness, the bolt type, and the angle's thickness. Based on the experimental test results, the typical failure mechanisms, the hysteretic load-deformation relationship, and the response characteristics such as degradations of strength and energy dissipation capacity of the connections are examined. It is shown that the bolt gauge width and the angle's thickness have significant influences on the failure mode. Energy-based model is proposed to overcome certain geometric limitations and five commonly used damage models are used to predict the damage behavior of connections. Moreover, the low-cycle fatigue life test results are compared with the codified S–N curves through a transformation of the displacement range into the effective stress range. Furthermore, the cumulative damage mechanism is analyzed and the fatigue life formula is obtained. Finally, the results are evaluated and verified by regression analysis. The 90% confidence level was used to test the availability of the regression equation, and the equivalent level of fatigue strength of the tensile region of angle connections is not less than Category 40 (ΔσC = 40 N/mm2). The EC3, BS7608, and AISC-LRFD-1999 specifications are used to evaluate the low-cycle equivalent fatigue strength, and it is found that there is a certain safety reserve when using Category 36.

Optimal Bracing Type of Reinforced Concrete Buildings with Soil-Structure Interaction Taken into Consideration

This study aims to investigate the impact of soil-structure interaction (SSI) on the seismic behavior of reinforced concrete buildings. An advanced numerical model for SSI was developed and verified using ABAQUS software. The seismic response of a 12-story building on four types of soil (rock, dense soil, stiff soil, and soft soil) was examined using a Normalized Response Spectra based on the Moroccan paraseismic regulation RPS 2011. The global lateral displacement, inter-story drift, and period were compared for two types of bracing (column and shear wall). The results show that SSI has a significant impact on the seismic behavior of buildings, and the seismic responses of soil-structure systems with column and shear wall bracing are quite different. The research contributions of this paper include developing an advanced numerical model for SSI, examining the impact of SSI on the choice of bracing for reinforced concrete buildings, and providing guidance on the most reliable bracing method for structures of various heights and soil types. The study's findings have important implications for seismic design and can help improve the safety and reliability of buildings in earthquake-prone regions. The study also highlights the importance of considering SSI in seismic design and the need for guidelines that describe the bracing systems to be used based on the structure's height and type of soil. Doi: 10.28991/CEJ-2023-09-06-06 Full Text: PDF

Static behavior of TOBs bolted endplate connection to strengthened HSST with fixed thread length

Five thread-anchored one-side bolts connected endplate connections to Hollow Square Steel Tube (TOBEC-HSSTs) with various strengthening measures were tested to investigate the structural performance under monotonic loads. The thread anchored length was 1.2 times the bolt diameter for all specimens. The connection behaviour were influenced by the endplate thicknesses and the strengthening measures (i.e. the internal polygonal tube, the internal polygonal tube with infilled concrete, and the cross-H section stiffener with infilled concrete). The failure patterns, moment-rotation curves, and strain response of joints were obtained through tests. It was found that (1) 1.2 times the bolt diameter was taken as the safe thread assembled length, which can avoid the premature failure of hole threads not before the fracture of other components under monotonic loads. (2) The presence of the infilled concrete can improve the rigidity and strength of the connection by 84% and 23%, respectively, compared to the reference joint without the infilled concrete, and the thickness of the column wall can be reduced when the concrete was infilled into hollow steel tube. (3) For the connections with thin endplates, the cross-H section stiffener exhibited 8.8% and 3.5% higher preliminary stiffness and yield bending moment than the inner polygonal tube, but the cross-H section stiffener had 14.3% lower rotation capacity. (4) Thickening endplates can change the failure modes of the connections to beam plastic hinge formation, enhance the preliminary stiffness and yield bending moment of joints by 2.4% ∼11%, but decrease the rotation capacity of joints by 54% compared to thin endplates. Based on experimental results, the calculation methods of the bending moment bearing capacity for TOBEC-HSSTs considering the strengthening effect of internal stiffeners and infilled concrete under different failure patterns were proposed with errors no greater than 15%.

Quantification of the effect of gas–water–equilibria on carbonate precipitation

The expanding geothermal energy sector still faces performance issues due to scalings in pipes and surface level installations, which require elevated operation pressure levels and costly maintenance. For facilities in the North Alpine Foreland Basin, the precipitation of {hbox {CaCO}}_{3} is the main problem which is a consequence of the disruption of the lime-carbonic acid equilibrium during production. The formation of gas bubbles plays a key role in the scaling process. This work presents experiments in a bubble column to quantify the effects of gas stripping on carbonate precipitation and an extension of PhreeqC to include kinetic exchange between a gas phase and water for the simulation of the experimental results. With the same hybrid model not only precipitation of {hbox {CaCO}}_{3} but also the dissolution of scalings by the injection of {hbox {CO}}_{2} could be quantified. The bubble column was filled with tap water and brine. By varying the ionic strength of the solution, a wider range of geothermal waters was covered. Air and {hbox {CO}}_{2} were introduced at the bottom. The precipitates built on the column wall were analyzed with Raman spectroscopy: injecting air into tap water at low ionic strength led to the formation of aragonite with 59.8% of the precipitates remaining at the column wall and the rest as particles in dispersion. At moderate ionic strength the dominant polymorph was calcite and 81.5% of the crystals were attached to the wall. At high ionic strength precipitation was inhibited. The presence of crystallization nuclei reduced the time for precipitation, but not the amount of scalings formed. Injecting {hbox {CO}}_{2} into the solution completely removed the scalings from the column wall. The model and its experimental backup lay the foundation for a process-based prediction of the scales (not only) in geothermal systems.

Wave diffraction and radiation studies of the array of the cylindrical bait boxes with porosities in the middle of the column wall surface under wave action

In this paper, we study theoretically wave diffraction and radiation studies of the array of cylindrical bait boxes with porosities in the middle of the column wall surface under wave action. The middle position of each cylindrical bait box column wall surface is the region with holes, and the upper and lower ends of the cylindrical bait box column wall surface are the region without holes. Under the assumption of the linear theory of potential flow, the eigenfunction expansion method, Bessel's function addition theory, and Darcy's law are used to investigate the wave diffraction and radiation of the array of cylindrical bait boxes with porosities in the middle of the column wall surface. Then, the related analytical expressions for velocity potential and free surface elevation are derived. After the validation process, a detailed parametric study is carried out. Porosity, spacing, porous area size, and incident wave angle are systematically adjusted, and their effects on wave force, added mass, radiation damping coefficient, and wave height are investigated. The related phenomena are also explored. It is found that the variation of porosity coefficient and porous area size greatly influence the cylindrical bait boxed, which can efficiently bait while reducing drag. The study results can help the designer/engineer to design the bait boxes with better structural performance and achieve more rational and better baiting.

Fluid dynamic and separation performance of foam loaded packed distillation columns

Foam formation in distillation columns leads to various negative effects such as reduced distillation throughput and reduced separation performance. In order to determine the influence of foam on distillation throughput and separation performance, measurements with chlorobenzene/ethylbenzene (CB/EB) and water/monoethyleneglycol (water/MEG) mixtures in a DN50 laboratory distillation setup were carried out. As internals, structured packings were compared to randomized packings with different materials. Results show that structured packings were more susceptible to foam and had greater losses in separation performance under the influence of foam as compared to randomized packings. However, in absolute terms, foam-loaded structured packings showed the highest separation efficiencies compared to randomized packings. An increase in column wall temperature above adiabatic conditions resulted in an increased foam loading and a decreased separation performance. Pressure drops were similar between packings, but foam loaded randomized packings showed a slightly lower pressure drop.

Cyclodextrin-NH-MIL-53 open tubular stationary phase for capillary electrochromatography enantioseparation.

A novel chiral group functionalized metal-organic framework, Cyclodextrin-NH-MIL-53, was synthesized and modified on the inner wall of a capillary column via a post-synthetic process. The prepared chiral metal-organic framework was utilized as a chiral capillary stationary phase and used in an open-tubular capillary electrochromatography method to enantioseparate several racemic amino acids. Excellent enantioseparation of five pairs of enantiomers was obtained in this chiral separation system (Resolutions of D/L-Alanine = 16.844, D/L-Cysteine = 3.617, D/L-Histidine = 9.513, D/L-Phenylalanine = 8.133, and D/L-Tryptophan = 2.778). The prepared Cyclodextrin-NH-MIL-53 and the Cyclodextrin-NH-MIL-53-based capillary columns were characterized by scanning electron microscopy, X-ray diffraction, Fourie-transform infrared spectroscopy, and circular dichroism. The chiral capillary electrochromatography conditions, such as separation conditions, amount of Cyclodextrin-NH-MIL-53, and electroosmotic flow, were optimized. This research is estimated to present a novel insight and method for the design and use of metal-organic framework-based capillaries for enantioseparation.

Separation performance of the calix[8]arene functionalized with polyethylene glycol units for capillary gas chromatography.

In this paper, an amphiphilic calix[8]arene with polyethylene glycol unit branches (C8A-PEG) was synthesized and applied for capillary gas chromatography (GC). The C8A-PEG was coated on the inner wall of a capillary column by a static method with the column efficiency of 3165 plates/m and polar nature. As demonstrated, the C8A-PEG column has excellent physicochemical properties and separation performance since it has π-electron-rich 3D cavity which combines with polar PEG units. Compared with two columns corresponding to the construction units C8A and PEG, the C8A-PEG column shows distinctly advantageous performance for the mixture of 22 components with diverse types. Impressively, it shows satisfactory resolution for positional isomers and cis-/trans- isomers, especially the challenging isomers of toluidine and dimethylaniline. The outstanding distinguishing capability of the C8A-PEG stationary phase is mainly attributed to the abundant molecular recognition interactions, including van der Waals, dipole-dipole, H-bonding and π-π stacking interactions. This work has proved that the new GC stationary phases constructed by different units can complement each other's advantages, improve their physicochemical properties and separation performance, and have broad application prospects in chromatographic analysis.

Probabilistic progressive collapse assessment for RC framed-wall structure

Since the progressive collapse of structures could cause disastrous consequences for humans and society, therefore assessing and improving the vulnerability of our buildings against progressive collapse is urgently needed. The current research presents a high-fidelity simulation procedure for an existing RC framed-wall structure and aims to investigate the structure’s resistance to progressive collapse under column/shear wall removal scenarios at different levels through deterministic analysis. Based on the considered removal scenarios, the dynamic effect of the sudden column/shear wall removal is studied, and a simple procedure to predict the vertical reaction of the neighboring columns/shear walls to the removed one is proposed with a dynamic amplification factor (DAF) 1.80 and 2.40 for the column and shear wall removal, respectively. The results revealed that the sudden column/shear wall removal at the higher floor is more critical than the lower one; since more floors participate in absorbing the released energy in the latter. Moreover, in some cases, the horizontal displacement resulting from the sudden shear wall removal is found to be more critical than the vertical displacement. Since there are several sources of uncertainties that significantly affect the building resistance to progressive collapse and the deterministic analysis neglects these uncertainties; therefore, it cannot quantify the failure probability of the structures. Consequently, based on the deterministic analysis results, the critical removal scenario is selected to perform the stochastic analysis via the probability density evolution method (PDEM), where both the stochastic response and the instantaneous probability density function (PDF) can be obtained. Finally, the failure probability of the studied structure is assessed using the PDEM combined with the absorbing boundary condition. The stochastic analysis revealed that the maximum vertical displacement increased to roughly 1.6 times its value compared with the deterministic analysis. Simultaneously, a failure probability of approximately 40% is recorded through the stochastic analysis, while no global or even local collapse is observed in the deterministic analysis.

Enantiomeric Separation by Capillary Electro chromatography with a Novel β-cyclodextrin-hyperbranched Carbosilane–silica Polymer Coating

A new type of β-cyclodextrin-modified hyperbranched carbosilane (β-CD@HBC) stationary phase was synthesized by combining hyperbranched carbosilane with the -OH group of β-cyclodextrin, and then the β-CD@HBC was used as astationary phase to fix it on the inner wall of capillary column, application in chiral drug separation. The chromatographic behaviour of the stationary phase was studied. The preliminary test results showed that the β-CD@HBC coated OT column has the ability to separate a variety of enantiomers, such as clenbuterol, ibuprofen, enrofloxacin, hlorpheniramine, isoproterenol hydrochloride, epinephrine, Phenylalanine, and Ketoprofen. The β-CD@HBC coated OT column has good repeatability and stability. The relative standard deviations (RSD) between runs, between days, and between columns were less than 1.5%, 1.86%, and 4.83%, respectively. This paper shows that hyperbranched polymers have great potential and advantages in the application of capillary electrochromatography for chiral separation.

A SIMPLE EVALUATION OF THE WALL AND COLUMN WALL RATIOS OF LOW-RISE RC BUILDINGS BASED ON ENERGY BALANCE FOR CONTINUED USE AFTER EARTHQUAKES

This paper examines the wall and column wall ratios of low-rise RC buildings to determine wall and column wall ratios that would limit the degree of building damage to a level no greater than slight damage for the purpose of continued use of the building after a mainshock, foreshock, or aftershock. Based on the energy balance in seismic response, a simple evaluation formula was derived to calculate wall ratio to a strength that would allow walls to withstand a level of damage up to shear cracking after an earthquake. The applicability of this formula was confirmed by comparing the wall ratio of actual buildings based on earthquake damage surveys with the results of this evaluation formula. The results indicated standards for wall and column wall ratios that enable buildings to withstand being hit by one to three earthquakes of an extremely rare level, as described in the notice, and still sustain a level of damage below shear cracking.

Management of Complex Acetabular Fractures by Using 3D Printed Models.

Background and Objectives: Using 3D printed models in orthopaedics and traumatology contributes to a better understanding of injury patterns regarding surgical approaches, reduction techniques, and fracture fixation methods. The aim of this study is to evaluate the effectiveness of a novel technique implementing 3D printed models to facilitate the optimal preoperative planning of the surgical treatment of complex acetabular fractures. Materials and Methods: Patients with complex acetabular fractures were assigned to two groups: (1) conventional group (n = 12) and (2) 3D printed group (n = 10). Both groups included participants with either a posterior column plus posterior wall fracture, a transverse plus posterior wall fracture, or a both-column acetabular fracture. Datasets from CT scanning were segmented and converted to STL format, with separated bones and fragments for 3D printing in different colors. Comparison between the two groups was performed in terms of quality of fracture reduction (good: equal to, or less than 2 mm displacement, and fair: larger than 2 mm displacement), functional assessment, operative time, blood loss, and number of intraoperative x-rays. Results: A significant decrease in operative time, blood loss, and number of intraoperative x-rays was registered in the 3D printed group versus the conventional one (p < 0.01), with 80% of the patients in the former having good fracture reduction and 20% having fair reduction. In contrast, 50% of the patients in the conventional group had good reduction and 50% had fair reduction. The functional score at 18-month follow-up was better for patients in the 3D printed group. Conclusions: The 3D printing technique can be considered a highly efficient and patient-specific approach for management of complex acetabular fractures, helping to restore patient′s individual anatomy after surgery.

Experimental and numerical study of self-locking adaptable inter connection for modular steel structures

Compared to conventional steel construction, modular steel construction (MSC) is different. Instead of having a high degree of connectivity, the modules are connected at their corners only by inter-modular connections (IMC), which are the most vulnerable points of failure and require extra operation spaces. An adaptable connection was proposed in this study, and the working mechanism of the proposed connection was presented. Three full-scale connections consisting of square hollow section (SHS) members were tested under monotonic and cyclic loads to determine the seismic performance. The results showed that reinforced joints sustained 80% of the limit of the rigid joint at an inter-story drift ratio of 0.04 radian and satisfied the condition for strong column weak beam joint mechanism. Non-linear Finite Element Analysis (FEA) was conducted on this adaptable connection with a parametric study to study more influences of other related parameters. The findings indicated that the gap produced between connection and column under higher displacement was sensitive to the outer bolt and spring pin. This gap could be further reduced by increasing the number of outer bolts and by reducing tolerance between adapter and column walls.

Seismic performance of TOBs bolted endplate connection to concrete-filled square steel tube with damaged hole threads repaired by using spiral wire inserts

Thread-anchored One-side Bolts bolted Endplate Connections to Concrete-Filled Square Steel Tube (TOBEC-CFSSTs) have a great potential in steel structures for its excellent behavior and ease of construction, but the hole threads of the column wall are easily damaged on account of non-standard operations of workers in the installation process. Thereupon, this paper proposes a novel thread repairing method, i.e. Spiral wire inserts, to repair the damaged hole threads, which ensures the safety of TOBEC-CFSSTs. Tests on seven specimens were conducted to investigate the seismic behavior of the hole threads-repaired connections with inner stiffeners under cyclic loading. The experimental parameters contained the inner stiffener type, the thread anchored length, the anchorage detail of bolt and the endplate thickness. The performance of the connections with repaired threaded holes were analyzed and compared in terms of failure modes, strength and rigidity, the ductility and the energy dissipation capacity. It was found that the connections using spiral wire inserts to repair the hole threads can exhibit a comparable mechanical property to that with intact hole thread. Besides, the presence of the epoxy adhesive in bolted endplate connections made the assembly of components more flexible without considering the concrete cast sequence, which revealed that the TOBEC-CFSSTs with repaired threaded holes would present extensive application prospects in prefabricated or built-up modular steel buildings. • Spiral wire inserts were used to repair threaded holes for Thread-fixed One-side bolts (TOBs). • TOBs bolted Endplate Connections under cyclic loads were tested. • Moderate strengthening component can enhance ductility and energy dissipation capacity. • Effects of concrete cast sequence on connection seismic behavior were presented.

The effect of moisture transfer on heat transfer of roof-wall corner hygrothermal bridge structure

Due to effects of moisture transfer, the hygrothermal bridge could be developed at building corners, and increase the thermal conductivity of building materials. Three different types of roof-wall corners (ring beam, double beam column and shear wall structure) were studied. When considering moisture transfer, effects of different air states, structural types and wall materials on the thermal performance of the hygrothermal bridge were evaluated and heat losses of the structure were compared. Given the periodic boundary conditions, the dynamic thermal response of the hygrothermal bridge after moisture transfer was analysed. Among three types of corners, the increase of heat flow through the most detrimental point of the ring beam structure corner was the largest (34.7%) after considering moisture transfer. The heat flow loss rate of the shear wall structure was the lowest (15.2%). When clay brick was used at the corner rather than aerated concrete for walls, a lower proportion of latent heat flow and higher (8.6%) heat flow loss rate were shown after considering moisture effects. Furthermore, the dynamic thermal response was influenced by multi-dimensional and moisture effects. The time lag was reduced with increasing humidity, while the thermal bridge effects increased the deterioration of the time lag.

Numerical simulation of gas–liquid flow in the bubble column using Wray–Agarwal turbulence model coupled with population balance model

In this paper, an improved computational fluid dynamic (CFD) model for gas–liquid flow in bubble column was developed using the one-equation Wary–Agarwal (WA) turbulence model coupled with the population balance model (PBM). Through 18 orthogonal test cases, the optimal combination of interfacial force models, including drag force, lift force, turbulent dispersion force. The modified wall lubrication force model was proposed to improve the predictive ability for hydrodynamic behavior near the wall of the bubble column. The values simulated by optimized CFD model were in agreement with experimental data, and the errors were within ± 20%. In addition, the axial velocity, turbulent kinetic energy, bubble size distribution, and the dynamic characteristic of bubble plume were analyzed at different superficial gas velocities. This research work could provide a theoretical basis for the extension of the CFD–PBM coupled model to other multiphase reactors..

A Generalized Analytical Model for Thermal and Bulk Comptonization in Accretion-powered X-Ray Pulsars

We develop a new theoretical model describing the formation of the radiation spectrum in accretion-powered X-ray pulsars as a result of bulk and thermal Comptonization of photons in the accretion column. The new model extends the previous model developed by the authors in four ways: (1) we utilize a conical rather than cylindrical geometry; (2) the radiation components emitted from the column wall and the column top are computed separately; (3) the model allows for a nonzero impact velocity at the stellar surface; and (4) the velocity profile of the gas merges with Newtonian freefall far from the star. We show that these extensions allow the new model to simulate sources over a wide range of accretion rates. The model is based on a rigorous mathematical approach in which we obtain an exact series solution for the Green’s function describing the reprocessing of monochromatic seed photons. Emergent spectra are then computed by convolving the Green’s function with bremsstrahlung, cyclotron, and blackbody photon sources. The range of the new model is demonstrated via applications to the high-luminosity source Her X-1, and the low-luminosity source X Per. The new model suggests that the observed increase in spectral hardness associated with increasing luminosity in Her X-1 may be due to a decrease in the surface impact velocity, which increases the PdV work done on the radiation field by the gas.