Column Model Research Articles

Axial stress strain behavior of FRP-confined rectangular rubber concrete columns with different aspect ratio

At present, the mechanical properties of FRP-confined rectangular rubber concrete columns have not been studied. To fill this gap, thirty-six concrete columns were prepared and tested under axial compression in this study. The effects of the aspect ratio (1, 1.25 and 1.5), rubber volume replacement ratios of fine aggregates (0 %, 40 % and 60 %) and FRP layer number (2 and 3) on the failure state and stress–strain relationship were investigated. The test results showed that with increasing section aspect ratio and rubber volume replacement ratio, the damage zone of the specimen increased, and the compressive strength decreased. As the number of FRP layers increasing, the damage zone and compressive strength of the specimens both showed an upward trend. Based on the test results, the stress–strain model, compressive strength model and ultimate strain model of FRP-confined rubber concrete columns were proposed. The proposed models can accurately predict the stress–strain relationship, compressive strength and ultimate strain of FRP-confined rectangular rubber concrete.

Enhancing Friction Models for Starting Up Water Installations Containing Trapped Air

Starting up water installations is typically a task that falls within the purview of water utility companies. These operations involve the presence of two separate fluids (water and air) that can be analyzed in terms of consideration two distinct behaviors (hydraulic and thermodynamic). During a filling process, trapped air pockets exhibit a trend of declining volume, generating pressure surges that are typically not addressed under current worldwide regulations. This research introduces an innovative mathematical approach based on physical equations to investigate filling operations in water installations involving trapped air, incorporating an unsteady friction model (using the Brunone friction coefficient), in combination with the rigid water column model. The validation of the proposed model is carried out in an experimental facility measuring 7.36 m in length. The proposed model is then applied to a case study involving a 460 m long pipeline with an internal pipe diameter of 150 mm, featuring an undulating profile composed of three branches, to demonstrate how the gravity term should be calculated in real-world water installations. The results showed that the proposed model, considering an unsteady friction model, is suitable for simulating the start up of water pipelines for the experimental facility analysis and the case study. The Swamee–Jain formula yielded the best results compared to other formulations for computing the friction factor.

Buckling Analysis of a New Type of Double-Steering Prestressed Plate Column

A new type of dual-steering prestressed plate column is introduced. Compared to the previous prestressed strut column, this proposed column considers both bending and constraints at ends. The calculation results indicated that the support plate significantly improves the stable bearing capacity and buckling performance of the core steel column. When compared to the proposed column, the bearing capacity of the three-transverse prestressed beam column is 1.51 times smaller, the single-transverse prestressed beam column is 2.43 times lower, and the non-prestressed column is 4.51 times smaller. Moreover, this study examines the influences of effective length, buckling mode, stress nephogram detail, and prestress value. It explores the possibility of implementing this new type of dual-steering prestressed plate column in practical engineering. In addition, the variety and mechanical models of prestressed columns are expanded and refined.

Pattern Recognition of Food Security in Indonesia Using Biclustering Plaid Model

Biclustering come in various algorithms, selecting the most suitable biclustering algorithm can be a challenging task. The performance of algorithms can vary significantly depending on the specific data characteristics. The Plaid model is one of popular biclustering algorithms, has gained recognition for its efficiency and versatility across various applications, including food security. Indonesia deals with complex food security challenges. The nation's unique geographic and socioeconomic diversity demands region-specific food security solutions. Identifying province-specific food security patterns is crucial for effective policymaking and resource allocation, ultimately promoting food sufficiency and stability at the regional level. This study assesses the performance of the Plaid model in identifying food security patterns at the provincial level in Indonesia. To optimize biclusters, we explore various parameter tuning scenarios (the choice of model, the number of layers, and the threshold value for row and column releases). The selection criteria are based on the change ratio of the initial matrix's mean square residue to the mean square residue of the Plaid model, the average mean square residue, and the number of biclusters. The constant column model was selected with a mean square residue change ratio of 0.52, an average mean square plaid model residue of 4.81, and it generates 6 overlapping biclusters. The results show each bicluster has unique characteristics. Notably, Bicluster 1 that consist of 2 provinces, exhibits the lowest food security levels, marked by variables X1, X2, X4, and X7. Furthermore, the variables X1, X4, and X7 consistently appear across several biclusters. This highlights the importance of prioritizing these three variables to improve the food security status of the regions.

Exploring the Significance of the Protection Column Model of Senior Professional and Technical Talents in Hospitals

Senior professional and technical personnel into the hospital senior, due to focus on administrative management, so that the mastery of professional skills cannot be carried out. What's more, some of them have gradually lost their ideals and beliefs after moving to leadership positions, and have inevitably become the key "hunting" objects, and finally slipped into the abyss of illegal and criminal offenses. For the country, medical field, hospitals, individuals, patients and society, this is a great loss. This paper focuses on the strategic long-term development of hospitals, based on the need to adapt to the development of medical and health care, mainly for the "protection of senior professional and technical personnel, value their existence, analysis and discussion of the significance of the protection of senior professional and technical personnel, to achieve the non-administrative mode of senior professional and technical personnel" to discuss.

Comparison of Load-Sharing Responses Between Graded Posterior Cervical Foraminotomy and Conventional Fusion Using Finite Element Modeling.

Following the diagnosis of unilateral cervical radiculopathy and need for surgical intervention, anterior cervical diskectomy and fusion (conventional fusion) and posterior cervical foraminotomy are common options. Although patient outcomes may be similar between the two procedures, their biomechanical effects have not been fully compared using a head-to-head approach, particularly, in relation to the amount of facet resection and internal load-sharing between spinal segments and components. The objective of this investigation was to compare load-sharing between conventional fusion and graded foraminotomy facet resections under physiological loading. A validated finite element model of the cervical spinal column was used in the study. The intact spine was modified to simulate the two procedures at the C5-C6 spinal segment. Flexion, extension, and lateral bending loads were applied to the intact, graded foraminotomy, and conventional fusion spines. Load-sharing was determined using range of motion data at the C5-C6 and immediate adjacent segments, facet loads at the three segments, and disk pressures at the adjacent segments. Results were normalized with respect to the intact spine to compare surgical options. Conventional fusion leads to increased motion, pressure, and facet loads at adjacent segments. Foraminotomy leads to increased motion and anterior loading at the index level, and motions decrease at adjacent levels. In extension, the left facet load decreases after foraminotomy. Recognizing that foraminotomy is a motion preserving alternative to conventional fusion, this study highlights various intrinsic biomechanical factors and potential instability issues with more than one-half facet resection.

Experimental research and finite element analysis on blast resistance of RRACFST columns

In order to research the dynamic response of rectangular recycled aggregate concrete-filled steel tubular (RRACFST) columns under blast loads, three contact blast experiments were carried out on three column models, and their different failure modes, dynamic strain rates and acceleration rates were determined. The numerical model was established using the arbitrary Lagrangian-Eulerian method and the fluid–solid coupling algorithm available in the explicit nonlinear finite element software LS-DYNA™, and the reliability and validity of the numerical model were verified by the experimental results. On this basis, the numerical model was used to analyze the parameters, as well as the effects of the replacement rate of recycled aggregate, column height, steel tube thickness and steel strength on the contact explosion resistance of RRACFST columns. Also, the advantages and disadvantages of overall refinement and local refinement are compared. The study results show that the RRACFST columns had basically no overall response to the action of contact blast loads, producing only a small explosion crater in the detonation area, without breaking the steel tube, and with no recycled aggregate concrete (RAC) overflows. The steel tube thickness was the decisive factor affecting the blast resistance performance of the RRACFST columns. In addition, for the numerical simulation of contact explosion, the local refinement was better than the overall refinement.

Reduced-Order Modeling and Control of Heat-Integrated Air Separation Column Based on Nonlinear Wave Theory

The process of low-temperature air separation consumes a significant amount of energy. Internal heat-integrated distillation technology has considerable energy-saving potential. Therefore, the combination of low-temperature air separation and heat-integrated distillation technology has led to the development of a heat-integrated air separation column (HIASC). Due to the heat integration and the inherent complexity of air separation, the modeling and control of this process poses significant challenges. This paper first introduces the nonlinear wave theory into the HIASC, derives the expression for the velocity of the concentration distribution curve movement and the curve describing function, and then establishes a nonlinear wave model. Compared to the traditional mechanical models, this approach greatly reduces the number of differential equations and variables while ensuring an accurate description of the system characteristics. Subsequently, based on the wave model, a model predictive control scheme is designed for the HIASC. This scheme is compared with two conventional control schemes: PID and a general model control. The simulation results demonstrate that MPC outperforms the other control schemes from the response curves and performance metrics.

Development of modular and reusable AI models for fast predicting fire behaviour of steel columns in structural systems

It is important to model the local failure of structural members as well as the global responses of a structural system when it is exposed to fire. The local failure of columns such as buckling requires high-resolution models, which could be not used for modelling a structural system for its computational cost. Inspired by the hybrid simulation technique, this paper aims to develop modular AI models as a first attempt to predict the local performance of a specific steel column exposed to fires and to enable the future communication with structural system model. Two kinds of machine learning methods namely artificial neural network (ANN) and support vector regression (SVR) are utilized to train AI models based on a large numerical dataset extended from a 3D detailed shell model of columns after validation against fire test results. The excellent prediction performance of AI models is shown regarding the mean squared error (MSE), mean absolute error (MAE), coefficient of the variation of the root mean square error (cvRMSE), variance accounting for (VAL) and coefficient of determination (R2). Moreover, the capability of AI models is demonstrated in predicting fire behaviour of columns in untrained steady heating and transient heating scenarios. A further demonstration is performed within a plane-frame structure simulated with a hybrid-scale model and considering standard fire heating on columns, which shows great potential of the AI models towards further implementation in hybrid simulation.

Critical circumferential wavelength of elastic buckling of longitudinal compressed thin-walled cylindrical shells

The classical theory of elastic critical buckling stress works well for slender columns and thin flat plates under compression; however, the situation is different for longitudinally compressed thin-walled circular cylindrical shells, and the issue has plagued us despite considerable efforts over the last 100 years. We noticed that all such buckling analyses thus far, both linear and nonlinear, in terms of the main philosophy, inherited and were confined to Euler’s pioneering solution for the slender column model that focuses on the longitudinal buckling deformation mode and should be classified as the ‘longitudinal open-loop’ eigenmode because the deformations of the two longitudinal ends are physically independent of each other. In view of this, for an ideal linear-elastic buckling model of a thin-walled perfectly circular cylindrical shell under uniform longitudinal compression on the foundation of the longitudinal open-loop eigenmode solution, it is also necessary to consider a ‘circumferential closed-loop’ eigenmode simultaneously to physically avoid violating the reality of its ideal periodic deformation on the entire perimeter and to mathematically redefine the biunique and precise relationship for each distinct eigenmode by the critical circumferential wavelength. Originating from such a case study, the mathematical uniqueness issue hidden in the general solution of the Donnell equation is further discussed. The authenticity of the competing eigenmode characterized by the Koiter circle is also discussed. Furthermore, a preliminary attempt was conducted to interpret the discrepancy between theoretical and experimental buckling loads, mainly initiated by the characteristic type of longitudinally generated circumferential local inward displacement in initial geometric imperfections, using the insights herein.

Cervical Column and Cord and Column Responses in Whiplash With Stenosis: A Finite Element Modeling Study.

Spine degeneration is a normal aging process. It may lead to stenotic spines that may have implications for pain and quality of life. The diagnosis is based on clinical symptomatology and imaging. Magnetic resonance images often reveal the nature and degree of stenosis of the spine. Stenosis is concerning to clinicians and patients because of the decreased space in the spinal canal and potential for elevated risk of cord and/or osteoligamentous spinal column injuries. Numerous finite element models of the cervical spine have been developed to study the biomechanics of the osteoligamentous column such as range of motion and vertebral stress; however, spinal cord modeling is often ignored. The objective of this study was to determine the external column and internal cord and disc responses of stenotic spines using finite element modeling. A validated model of the subaxial spinal column was used. The osteoligamentous column was modified to include the spinal cord. Mild, moderate, and severe degrees of stenosis commonly identified in civilian populations were simulated at C5-C6. The column-cord model was subjected to postero-anterior acceleration at T1. The range of motion, disc pressure, and cord stress-strain were obtained at the index and superior and inferior adjacent levels of the stenosis. The external metric representing the segmental motion was insensitive while the intrinsic disc and cord variables were more sensitive, and the index level was more affected by stenosis. These findings may influence surgical planning and patient education in personalized medicine.

Cadmium and copper transport in alluvial soils in the Brazilian semiarid region: column percolation and modeling

ABSTRACT Regarding the Brazilian textile industry, part of the northeast region stands out as the second-largest textile manufacturing hub in the country. Despite its importance, this industrial activity has been bringing relevant environmental concerns regarding the disposal of textile effluents, especially from industrial laundries. This waste contains many chemicals and among them are various types of heavy metals. To assess environmental risks associated with heavy metals, pollutant transfer needs to be investigated. This study evaluated the retention and mobility of heavy metals Cd and Cu in alluvial soil, through soil column tests. The up-flow column percolation tests were performed using a nonreactive tracer (KBr) at a concentration of 0.3 mol L -1 and injecting a metallic solution containing Cu and Cd at 100 and 60 mg L -1 , respectively. The injection flow rate was 0.75 mL min -1 . The hydro-dispersive parameters were obtained by modeling the observed breakthrough curves with the convection-dispersion equation (CDE) and the two-region model, also referred to as the MIM (Mobile-IMmobile waters) model. The transport parameters were obtained from the two-site model (TSS). All elution curves were fitted to the models with the CXTFIT 2.0 program. The Two-Site Sorption Model was the best for the case studied, with R 2 of 0.985 and 0.995 for Cu and Cd, respectively. The values of R were considerably higher than the unit, presenting an average of 2.138 for Cu and 1.907 for Cd. This indicates a delay of these contaminants when leaving the column, which is caused by the interaction of these chemical compounds with the soil. The values obtained for parameter D were 3.469 for Cu and 5.205 for Cd. Thus, the metals in this study present a risk of groundwater contamination for the local alluvial aquifers. The main reason for that is the physicochemical features of the soil, such as high sand content (85 %) and low OM content (2.1 %). The results also indicated greater retention and less mobility for Cu than for Cd, pointing to a greater risk for Cd.

Experimental Design and Breakthrough Curve Modeling of Fixed-Bed Columns Utilizing a Novel 3D Coconut-Based Polyurethane-Activated Carbon Composite Adsorbent for Lead Sequestration

This study presents a novel polyurethane-activated carbon composite (PACC) as an effective and sustainable adsorbent for treating lead-ion-contaminated waters. The PACC was characterized using Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer, Emmett, and Teller (BET) surface area analyzer, X-ray Diffraction (XRD), and Thermogravimetric Analyzer (TGA) to evaluate its physicochemical and thermal properties. Furthermore, the PACC was employed in an experimental column adsorption setup to investigate its adsorption performance and to develop a dynamic method suitable for industrial implementation. Parameters such as bed height (50, 100, 150 mm), flow rate (4, 6, 8 mL min−1), pH (2, 4, 6), and initial metal-ion concentrations (10, 50, 100 mg L−1) were examined. The experimental data exhibited strong agreement with the Thomas and Yoon–Nelson models (R2 ≥ 0.96), indicating efficient adsorption mechanisms. Remarkably, the used adsorbent has the potential for facile regeneration without substantial loss in capacity. The PACC demonstrated excellent adsorption performance for lead ions in aqueous solutions in a fixed-bed column system. Thus, the novel PACC material holds the potential for scalable application in industrial settings to address water pollution challenges, especially in regions with uncontrolled effluent discharge.

The Axial Compression Behavior of Basalt Fiber-Reinforced Recycled Aggregate Concrete-Filled Circular Steel-Tubular Column

Recycled aggregate concrete (RAC) technology has received a lot of attention as a green environmental protection technology. However, the unsatisfactory mechanical behavior of RAC restricts its application in engineering practice. The structure of basalt fiber-recycled aggregate concrete-filled circular steel tubes (C-BFRACFST) can dually improve the mechanical behavior of RAC. To observe the axial compression behavior of the C-BFRACFST column, seven specimens were designed with recycled aggregate replacement ratio (0%, 50%, 100%), basalt fiber (BF) content (0 kg/m3, 2 kg/m3, 4 kg/m3) and length–diameter (L/D, 5, 8, 11) as variable parameters for axial compression tests. The failure mode, load–displacement/strain curve, axial compression deformation, ultimate bearing capacity, energy dissipation, and ductility of specimens have been analyzed. The derived constitutive relation of core basalt fiber-reinforced recycled aggregate concrete (BFRAC) constrained by the circular steel tube and the 3D finite element model of C-BFRACFST column have been established to simulate the whole process of compression. It is observed that instability or shear failure occurs in specimens under axial compression load. When the recycled aggregate replacement ratio was increased from 50% to 100%, the change in the energy-dissipation capacity of the specimens was not significant but the ultimate bearing capacity and displacement ductility coefficient decreased by 3.45% and 8.91%, respectively. When the BF content was increased from 2 kg/m3 to 4kg/m3, the change in the ultimate bearing capacity of specimens was not significant; the energy-dissipation capacity at the later stage of bearing increased, and the displacement ductility coefficient was noted to increase by 13.34%. When the L/D was increased from 8 to 11, the energy-dissipation capacity of specimens was decreased, and the ultimate bearing capacity and displacement ductility coefficient declined by 1.37% and 43.52%, respectively. The finite element simulation results are in agreement with the test results.

Buckling and critical temperatures of restrained H-section steel columns in fire considering dynamic effect

In this paper, a parametric analysis on the buckling and critical temperatures of restrained H-section steel columns in fire, considering the dynamic effect, is presented. The developed finite element model of steel columns was verified by test results. Then, the buckling and critical temperatures of steel columns, obtained by static and explicit dynamic analyses, were compared. Moreover, the effects of rotational and axial restraint stiffness ratios, as well as load ratios, were studied. It was found that as the rotational restraint stiffness ratio increased, the buckling and critical temperatures both rose, and the rotational restraint stiffness ratio affected the critical temperature more than the buckling temperature. Besides, when the axial restraint stiffness ratio and load ratio rose, the buckling and critical temperatures dropped significantly. Finally, by combining the findings of the research and existing calculation formulas in literatures, new simplified formulas for buckling and critical temperatures were proposed, respectively. The prediction results of the proposed calculation formulas agreed well with the parametric analysis results. The proposed formulas were further verified by test data. According to the comparative results, the proposed formulas could well predict the buckling and critical temperatures of steel columns in fire.

Model of Electrical Stimulation of Back Muscles in the Treatment of Scoliosis

The article presents a three-dimensional model of the tissues of the human back in the ZBrush and SolidWorks software packages. Modeling of the spinal column with a bend, muscles, adipose tissue and skin was performed. Using the COMSOL Multiphysics environment, the effects of electrical stimulation on biological objects are modeled, and characteristics are determined. When modeling, in the properties of each biological tissue, the values of electrical conductivity and relative permittivity were set, the electrodes were adjusted, a grid was created to divide the models into smaller parts and elements, and the required frequency was adjusted. To verify the simulation results, a study was carried out on the patient, the calculation and analysis of the results obtained. The developed models can be used in clinical medicine to determine the strength of the stimulating current and set the parameters of electrical stimulation. When building a model, one can change the thickness of adipose tissue, skin, muscle and bone sizes, change the size of the electrodes, and thereby select the most optimal parameters for electrical stimulation. Models can be used in the development of the most effective method of electrical stimulation and the scheme for applying electrodes for a certain type of scoliosis.

Modeling of a bubble column for CO2 removal by absorption with NaOH

CO2 capture experiments were carried out in a small-scale bubble column reactor using alkaline solutions of sodium hydroxide. The results of the experiments show that a higher NaOH content in the liquid phase and elevated CO2 concentrations in the gas mixture led to a higher CO2 removal efficiency. A mathematical model was developed to describe the CO2 absorption as a function of CO2 gas inlet and OH- concentrations at low CO2 and OH- concentrations. The CO2 uptake at high OH- concentrations (high pH) was accurately predicted by the model, whereas the CO2 uptake at lower OH- concentrations could not be predicted with the same accuracy.

A comparison of Eulerian and Lagrangian methods for vertical particle transport in the water column

Abstract. A common task in oceanography is to model the vertical movement of particles such as microplastics, nanoparticles, mineral particles, gas bubbles, oil droplets, fish eggs, plankton, or algae. In some cases, the distribution of the vertical rise or settling velocities of the particles in question can span a wide range, covering several orders of magnitude, often due to a broad particle size distribution or differences in density. This requires numerical methods that are able to adequately resolve a wide and possibly multi-modal velocity distribution. Lagrangian particle methods are commonly used for these applications. A strength of such methods is that each particle can have its own rise or settling speed, which makes it easy to achieve a good representation of a continuous distribution of speeds. An alternative approach is to use Eulerian methods, where the partial differential equations describing the transport problem are solved directly with numerical methods. In Eulerian methods, different rise or settling speeds must be represented as discrete classes, and in practice, only a limited number of classes can be included. Here, we consider three different examples of applications for a water column model: positively buoyant fish eggs, a mixture of positively and negatively buoyant microplastics, and positively buoyant oil droplets being entrained by waves. For each of the three cases, we formulate a model for the vertical transport based on the advection–diffusion equation with suitable boundary conditions and, in one case, a reaction term. We give a detailed description of an Eulerian and a Lagrangian implementation of these models, and we demonstrate that they give equivalent results for selected example cases. We also pay special attention to the convergence of the model results with an increasing number of classes in the Eulerian scheme and with the number of particles in the Lagrangian scheme. For the Lagrangian scheme, we see the 1/Np convergence, as expected for a Monte Carlo method, while for the Eulerian implementation, we see a second-order (1/Nk2) convergence with the number of classes.

Seismic behavior of concrete-filled double-skin thin-walled steel box columns stiffened with PBL

Concrete-filled double-skin thin-walled steel box (CFDTSB) columns stiffened with PBL are a new type of columns formed by setting longitudinal ribs on an inner wall of outer and inner steel boxes of CFDTSB columns. Quasi-static tests on one CFDTSB column without PBL and two CFDTSB columns stiffened with PBL were carried out to investigate their seismic performance. The damage modes, hysteresis curves, envelope curves and strain distribution on outer steel boxes of different specimens were compared and analyzed. Then, FE models of CFDTSB columns stiffened with PBL and without PBL were established and parametric analysis was conducted to investigate the effects of cross-sectional hollow ratio, thickness of outer steel boxes and height of PBL ribs. At last, calculation methods for load bearing capacity of the two types of columns were proposed. It is found that, the arranging of PBL ribs significantly improves the local buckling of outer steel boxes, enables steel boxes to fully participate in bearing the axial load and bending moment, and enhances the interaction between steel boxes and sandwich concrete, so the bearing capacity, deformation capacity, and energy dissipation capacity of CFDTSB columns stiffened with PBL are improved a lot, compared with CFDTSB columns without PBL. That is to say, the seismic behavior of CFDTSB columns stiffened with PBL is good. The proposed method could consider the local buckling of steel boxes, steel-concrete interaction and effect of PBL ribs on them rationally, thus predicting the load-carrying capacity of the two types of columns.

Experimental study on spatial evolution of mode-I and mode-II fracture toughness of cemented paste backfill under external sulphate attack

ABSTRACT External sulphate attack (ESA) interferes with spatial changes in fracture toughness of cemented paste backfill (CPB) and affects its mechanical stability. Large-scale curing column models are developed to investigate the spatial evolution of mode-I and mode-II fracture toughness (i.e. KIC and KIIC) under seepage- and diffusion-induced ESA. It has been found that the seepage-induced ESA leads to spatial changes in KIC and KIIC of CPB at advanced ages and higher extent of degradation of fracture toughness is measured at a deeper position in CPB. Comparatively, KIc can be used as a reliable quantity to estimate KIIc under the diffusion-induced ESA.