Shape Of Column Research Articles

Effect of warping shape on buckling of circular and rectangular columns under axial compression

The structural stability of a column with rectangular and circular cross-section under axial compression is studied based on various higher-order shear deformation beam theories. This paper has two-fold objectives. One is to introduce a transition parameter to describe the direction of axial load from Engesser’s hypothesis to Haringx’s one, then a unified method is presented to determine the critical load. The other is to introduce new cross-section warping shapes of rectangular and circular columns, then the buckling loads are exactly calculated and compared for various warping shapes. A governing equation for buckling of a column under axial compression is first derived. The buckling loads of a prismatic column with typical ends such as clamped-clamped, pinned-pinned, and clamped-free columns are determined and an explicit expression is obtained in terms of the Euler buckling load. The effects of the warping shape of the cross-section on the buckling loads are analyzed. The Haringx buckling load is greater than the Engesser buckling load that gives a conservative estimate of the critical load. A comparison of these buckling loads with Euler loads is made. The obtained results indicate that Euler buckling loads are both significantly overestimated for short columns or those with weak shear rigidity. The buckling loads are nearly not affected for very slender columns or those with high shear rigidity. The Euler loads are recovered from the present ones for columns in the case of shear locking. The buckling loads are also dependent on the warping shape of the cross-section.

Deformation behaviours of TiZrCuNiBe bulk metallic glass in supercooled liquid region

In this work, the deformation behaviours of the Ti33Zr30Cu9Ni5.5Be22.5 bulk metallic glass (BMG) in the supercooled liquid region (SLR) were explored through a series of uniaxial compression experiments with a Gleeble 3500 thermal simulator at different strain rates. Results showed two main deformation modes in the SLR: plastic flow and brittle fracture. With increasing temperature and decreasing strain rate during the plastic flow process, the stress overshoot gradually disappeared, and the steady flow stress decreased. At 648 K, a transition from Newtonian flow to non-Newtonian flow was observed while the strain rate exceeded 1 × 10−3 s−1. The morphologies of the deformed BMG specimens changed with increasing temperature and consequently exhibited three profiles: asymmetric deformation, upright drum shape and uniformly flattened column shape. Studies of fracture behaviours showed that as the temperature increased from 618 K to 638 K, the critical strain rate of the fracture increased from 3 × 10−3 s−1 to 6 × 10−3 s−1. Moreover, the fracture angles increased from 46° to 57° due to the change in cohesive strength according to the Mohr–Coulomb criterion. Unlike the condition at room temperature, unique fracture morphologies, including fishbone-like characteristics and a large area of viscous flow layers, were formed under the high-temperature condition.

Photogrammetric Analysis of Orolabial Region in South Indians.

In lip reconstructive surgery, knowledge of orolabial dimensions and position according to ethnicity, age, and gender are important to obtain satisfactory results. Unfortunately, there is a dearth of information related to these values in South Indians. The objective of the present study was to quantify the orolabial dimensions and position in South Indians. Evaluation of orolabial features was performed on standardized frontal and lateral of 400 South Indian subjects (200 males and 200 females), aged 18 to 30 years. The measured parameters were evaluated by an independent t-test. Significant sexual dimorphism was found in 12 of 13 measurements. Except upper lip reference to E plane, all other linear measurements such as mouth width, philtrum width, lower lip reference to E plane, upper lip height, cutaneous upper lip, upper and lower vermilion height, cutaneous lower lip height, lower lip height, and labiotragial distance were significantly greater in males than females. Angular measurements, interlabial angle, and labiomental angle were significantly greater in females. Clinically significant sexual dimorphism existed for mouth width, labiotragial distance, interlabial angle, and labiomental angle (mean difference > 3 mm). Out of the four orolabial indices, only intercanthal/mouth width indices showed a significant sexual difference. In both sexes, the triangular shape of philtral column was most common. Comparative analysis between South Indians and North American whites revealed significant differences in all measurements and some resemblance to the Han Chinese. The knowledge of the obtained mean values might be useful in the maintenance of the functional and aesthetic quality of this region during surgical planning.

CFD Simulation of Flow Characteristics on Semi-Submersible Platforms

In this paper we present the turbulent flow around a semi-submersible platform, modelled using Ansys Fluent. The computational domain is designed as a rectangular horizontal channel with the semi-submersible platform mounted inside the channel. The top, bottom, left and right walls of the channel are treated with no slip boundary condition. The front and back walls are specified with velocity inlet and pressure outlet boundary conditions. The semi-submersible platform is designed with of two pontoons, four square columns and two bracings. The problem is modelled as three dimensional, transient, incompressible flow and turbulence is modelled using Large eddy simulation (LES) turbulence model. The computational domain is meshed to 4,72,749 hexahedral mesh cells. Parametric study is performed by varying the Reynolds number (Re) in the range of 104 ≤ Re ≤ 106 and also the shape of the columns. The investigation is carried out by plotting stream function, velocity and pressure contours. We observe vortex shedding and flow separation between the front and back columns of the semi-submersible platform. As we increase the Reynolds number the intensity of flow separation also increases. The transient flow characteristics of the lift and drag forces are evaluated by plotting the coefficients of lift and drag for different Reynolds number and column shapes.

Superior design solutions of section sizes in steel buildings for different lateral frame systems and column shapes

Superior design solutions of section sizes in steel buildings for different lateral frame systems and column shapes

Hybrid simulation of bridges constructed with concrete-filled steel tube columns subjected to horizontal and vertical ground motions

This paper presents the application of multi-axis hybrid simulation for evaluating the seismic response of a rigid-frame bridge structure constructed with concrete-filled steel tube (CFST) columns subjected to combined horizontal and vertical ground motions. These types of bridges are believed to have superior seismic performance and better ability to withstand collapse when subjected to extreme multi-directional seismic loads. The case-study hybrid model was a 1:3 scaled bridge structure with three spans and double-column bents. The experimental element consisted of one CFST column while the rest of the bridge elements were modelled numerically in the computer. Two popular cross-section shapes of circular and square CFST columns were tested and compared. The structure was subjected to the horizontal (longitudinal) and vertical components of the Northridge ground motion with five increasing intensity levels to cover all scenarios ranging from frequent to very rare events during the lifecycle of the structure. A state-of-the-art hybrid testing facility, referred to as the multi axis substructure testing system, was used to simulate complex boundary effects on the physical specimen using mixed load/deformation modes. The bridge columns showed great levels of ductility and no sign of severe damage or loss of stability, while they were subjected to large axial force variations and lateral deformation demands during hybrid simulations. The superior seismic performance of CFST elements highlights their benefit in construction of more resilient bridges, particularly those with the vital roles in post-disaster operations.

Effects of column shape and configuration on the vortex-induced motions of semi-submersibles

The vortex-induced motions (VIM) of offshore floaters occur when the frequency of the vortex shedding is close to the natural frequency, and this phenomenon can severely affect the fatigue life of risers and moorings. During the design and operation stage of the semi-submersible (SS), VIM behavior has emerged as an important issue in offshore engineering. The shape of the columns, circular or square, and the wake interference, characterize the VIM of the SS. Numerical studies using the validated Detached Eddy Simulation (DES) method are carried out for parametric analysis of the VIM performance of various SS models consisting of different column shapes: with four rounded square columns, four circular columns and the mixed square-circular columns. The results show that the most significant transverse responses at 0∘ current incidence are observed for the SS with four circular columns and the one with two circular upstream columns. At a diamond configuration (i.e., 45∘ and 135∘), the SS models with a square upstream column all present the most pronounced VIM. The analysis shows that the vortex shedding characteristics of each column at different current incidence govern the VIM of the SS models. The square and circular columns both do large positive work on the transverse motions, and thus improve the VIM response at a certain current incidence. Therefore, the design of SS with square, circular and multi-shape columns can not mitigate the VIM behaviors efficiently. Designing a SS model with irregular polygon-shaped columns or twisted columns to avoid the strong vortex shedding may work.

Electrodeposition of Li Metal onto an Ulta-Micro-Electrode

Li metal is very attractive candidate for a negative electrode of next-generation rechargeable batteries because Li metal has very large theoretical capacity and the lowest standard electrode potential. In order to utilize Li metal for negative electrode, it is indispensable to control the morphological variation during charging and discharging. However, Li metal forms dendrites very easily in the electrodeposition process. In general, the distribution of the current density will induce the dendrite formation in the electrochemical system. In addition to that, SEI (solid electrolyte interphase) should play an important role for the morphological variation of the electrodeposited Li metal. Many researches were conducted based on the surface chemistry in order to reveal the relationship between the nature of SEI layer and the morphology of electrodeposited Li metal. However, the localization of the electrodeposition sites is an obstacle for the quantitative analysis in order to discuss the dendrite initiation and growth.In this study, ultra-micro-electrode was utilized to observe the morphological variation of the electrodeposited Li metal. Constant current electrodeposition was conducted to observe the electrodeposited Li metal. All electrochemical experimental was done in super dry room. The dewpoint of the room was kept lower than 213K. After the electrodeposition, the ultra-micro-electrode was rinsed with some solvents very carefully, and transferred to FE-SEM or TEM with transfer vessel without air exposure. Ex-situ SEM and TEM observation was done to discuss the electrolyte effects to the morphology of electrodeposited Li metal. For SEM observation, not only the observation of morphology but also the chemical composition of SEI layer was analyzed by EDS spectra. The SEM observation was conducted in room temperature. For TEM observation, the sample was cooled to be about 100 K in order to minimize the electron beam damage. STEM-EELS analysis was also conducted for analysis of SEI layer on the electrodeposited Li metal.The electrodeposited Li metal onto a ultra-micro-electrode in 1M LiPF6-EC:DEC=1:1 electrolyte was very smooth and uniform column shape. The chemical composition of the SEI layer on the electrodeposited Li metal was confirmed to be mainly LiF and Li2O by SEM-EDS and STEM-EELS analysis. In this presentation, we would like to discuss the relationship between the SEI layer and morphological variation based on the SEM and TEM observation results.

Experimental investigation and finite element analysis of cold-formed steel channel columns with complex edge stiffeners

Abstract Presented in this paper are results obtained from experimental and numerical investigations on the axial behavior of cold-formed thin-walled steel channel columns with complex edge stiffeners, which are referred to as G-section columns. In the experimental investigation, a total of 36 G-section columns, with and without perforations, were tested under pin-ended boundary conditions, and their structural behavior was described. In these tests, the perforations were found to affect the ultimate strength and deformed shape of the G-section columns. In the numerical investigation, finite element models for G-section columns with and without perforations were developed with use of ABAQUS. The models were validated based on the test results. The calibrated finite element model was subsequently adopted for an extensive parametric study by varying the dimensions and locations of perforations. The numerical results indicated that increasing the perforation dimension resulted in a greater reduction on the column ultimate strength than changing the perforation location. But the location of the perforation could affect the deformed shape of the column significantly. Based on the results obtained from the parametric analysis, it is recommended that the spacing of circular holes is between three and six times the nominal diameter of the hole for engineering practice.

Measurements of current loads on side-by-side semi-submersibles in a wind tunnel

Numerous multi-body coupled systems are adopted in offshore operations to improve the accommodation environment and work efficiency. The current loads on a multi-body system are complex due to environmental sheltering and greatly affect operation safety and feasibility. This paper presents experimental studies on current loads, particularly the longitudinal and transverse forces acting on two side-by-side semi-submersibles in a wind tunnel. The influences of separation distance, spacing ratio, shape of columns, and draft of production platform on current loads are investigated. When the accommodation platform is upstream, the twin-body interference can generally increase the longitudinal force acting on the vessel and decrease the transverse force. The shielding effect appears when the vessel is downstream, significantly decreasing the mean transverse load coefficient by up to 80%. When separation distance decreases, the interference becomes more distinct and there is nearly a linear relationship between distance and force reduction. Once the accommodation platform turns and is shielded, the reduction in mean load coefficients becomes more noticeable as the spacing ratio decreases. The shielding effect is insensitive to drafts except for the 90°. The production platform with square columns has greater interferences (about 1.2–1.8 times) than that with cylindrical columns.

Longitudinal muscular column in the prostatic urethral wall: Its form, shape, and possible function based on mathematical simulation in ejaculation.

The shape and function of the longitudinal muscular column (LMC) of the prostate have not been established in detail. The present study was undertaken to elucidate the roles of the LMC of the posterior wall of the prostatic urethra (PSU) in the emission phase of ejaculation by investigating the form and muscular arrangement of the LMC. Prostates and urinary bladders were obtained from 14 Korean adult cadavers. Nine specimens were histologically analyzed using hematoxylin and eosin, Masson's trichrome, and Verhoeff-van Gieson staining. Two specimens were scanned using microcomputed tomography (micro-CT), and all scanned images were reconstructed into a three-dimensional model. At the proximal level of the prostate, the ejaculatory ducts (EDs) and prostatic utricle (PU) together were surrounded by circular smooth-muscle fibers. However, at the seminal colliculus (SC) where the EDs and PU opened, they were mainly surrounded by an abundance of longitudinal fibers. The longitudinal fibers posterior to the EDs and PU formed a distinctive LMC in the posterior urethral wall. In histologic sections and micro-CT images, the LMC extended distally from the level of the SC to the level of the membranous urethra (MBU). We simulated a potential mechanism of LMC using a mathematical model of its movements. Comprehensive analyses based on in-depth assessment of histologic characteristics and micro-CT images demonstrated extension of the LMC from the level of the SC to the level of the MBU, enabling a better understanding of ejaculation physiology involving the LMC. These results suggest that the LMC in the posterior wall of the PSU is a critical component of ejaculation by facilitating the ejection of seminal vesicle fluid into the PSU via well-coordinated contractions.

The Effect of Shape on Chloride Penetration of Circular Reinforcement Concrete Columns and Its Durability Design

The reinforced concrete (RC) circular element is usually simplified as slab one on the issue of chloride diffusion simulation, without considering the effect of the geometrical shape. In the paper, a modified slab diffusion model is proposed for circular section. A formulation for estimating the error caused by neglecting the effect of shape on chloride diffusion is derived. The formulation demonstrates that radius significantly affect the error. When shape is neglected, the effects of model parameters, including the diffusion coefficient, radius, cover concrete thickness and age factor, on the corrosion initiation time are investigated. The result shows the radius has a slight effect on calculating the corrosion initiation time compared with other model parameters. Furthermore, the influence of shape on estimating on reliability index for different service time is also discussed. A guideline is proposed for properly using the modified slab diffusion model instead of the original one to predict service life. Finally, the impact of the shape of the RC circular column on the durability design against chloride corrosion is studied. The design result when the column is simplified as a slab element indicates a lower required minimum concrete cover thickness. The minimum thickness should be improved by 5 mm as a conservative choice based on the result of the slab element.

Prediction of liquid jet trajectory in supersonic crossflow and continuous liquid column model

The trajectory of the spray is studied theoretically and experimentally when a round liquid jet is injected into a supersonic crossflow vertically. A solid model of continuous liquid column is established in three-dimensional space. The cross-section deformation equation of the continuous liquid column along the injection direction is established using a method of micro-element analysis. The stress analysis of cross section is simplified into a two-dimensional droplet. The shape of the cross section is considered to continuously change from circular to elliptical shape. And the bow shock wave in front of the jet column is simplified into an oblique shock wave with a known shock angle. Based on this, the calculation of aerodynamic force is greatly simplified. A dimensionless parameter named effective deformation time of liquid column (the logogram is <inline-formula><tex-math id="M300">\begin{document}${t_{\rm valid}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200903_M300.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200903_M300.png"/></alternatives></inline-formula>) is defined and used to judge the end point of the liquid column quantitatively. The liquid jet trajectory and cross-section deformation can be calculated using MATLAB software. The instantaneous images of continuous liquid columns in supersonic crossflow are captured using high-spatial-resolution microscopic imaging methods. The microscopic imaging system is composed of a double pulse solid-state laser, computer, CCD camera, synchronous controller, microscope lens and laser diffuser. After passing through the laser diffuser, a plane background light with uniform distribution is formed on the scattering plate. The mean filtering method is used to filter the original image. After filtering, the range of gray distribution in the background area is obviously reduced. The distribution of gray value is more concentrated, and the background of the image is more uniform. Then the image edge detection function is used to obtain the near-field jet trajectory. The parameter variables studied include liquid injection pressure drop (1–2 MPa), liquid nozzle diameter (0.5 mm/1.0 mm), and liquid gas momentum ratio (3.32–7.27). The results show that the continuous liquid column model can better predict the jet trajectory on the center plane and the shape of the liquid column in three-dimensional space. It is indicated that the predictive result matches well with the experimental result. This study is of great significance for establishing the solid-particle coupling model of liquid jet in supersonic crossflows.

Steel Stiffeners for Enhancement of Slab-Column Connections

This paper introduced a strengthening technique for flat plates using steel stiffeners. In this paper, the effectiveness of steel stiffeners with different arrangements and numbers on the punching shear strength. The strengthening steel stiffeners were installed around the column and extended to the slab and acted as a column capital and designed with the equivalent of a concrete column capital. The study was divided into two lines, the first line was the experimental study involves the molding three reinforced concrete flat slab models strengthening with different dimensions and the molding three reinforced concrete flat slab models strengthening with different dimensions and numbers of steel stiffeners, where the dimensions of steel plates changed as shown for specimen SS1 (100×100mm), SS2 (200×200mm), and SS3 (300×300mm) in addition to reference model without strengthening. The second line that numerical modeling through the ABAQUS finite element program was introduced. Effect of the steel stiffeners' size and the effect of the column's shape (rectangular and circular) that's deal with steel stiffeners were studied experimentally and numerically. A good agreement was obtained between the experimental and theoretical results.

The Shape of Philtrum Column in Jordanian Population for Its Application in Geometric

The Shape of Philtrum Column in Jordanian Population for Its Application in Geometric

Field test and emergency reinforcement evaluation for an ancient wood pagoda

SummaryAncient wood pagodas, as the excellent representative of ancient China, play an important role in Chinese historical, art, and scientific aspects. Because most pagodas are lacking maintenance for a long time and the long term reinforcement measure has not been determined, it is necessary to carry out an emergency reinforcement method to avoid further damage. This paper presents a design guideline of emergency reinforcement method for ancient wood pagodas. Field tests based on pulsating method were carried out to identify the dynamic characteristics, structural stiffness, and structural damages. The modal frequency, modal shape of different columns and stiffness of each story indicate that the second apparent story is the weak point of the whole structure. To effectively analyze the nonlinear performance of the second apparent story and verify the superiority of the emergency reinforcement method, three elaborated finite element models of the second apparent story in undamaged, and current and reinforced states are established. The buckling analysis shows that the emergency reinforcement method could improve the critical load 89% nearby compared with the current structure. In addition, the seismic analysis proves that the emergency reinforcement method has positive effects on strengthening the weak point to against the earthquakes.

Three-dimensional architecture of a mechanoreceptor in the brown planthopper, Nilaparvata lugens, revealed by FIB-SEM.

Trichoid sensilla are the most common mechanoreceptors in insects; depending on their distribution, they can act as either exteroceptors or proprioceptors. In this study, the internal structure of the trichoid sensillum from Nilaparvata lugens was studied, using focused ion beam scanning electron microscopy (FIB-SEM). We reconstructed a three-dimensional (3D) model derived from the FIB-SEM data set. The model displayed characteristic mechanosensory sensilla components, including a hair inserted in the socket, a dendrite going through the laminated cuticle, and an electron-dense tubular body at the dendrite terminal. The detailed 3D model showed the relationship between the microtubules within the tubular body and those outside of the tubular body. We also found an autocellular junction in the tormogen cell, indicating that the tormogen cell grows around the dendrite sheath to form a hollow column shape during sensilla morphogenesis.

Effects of column imperfections on capacity of steel frames in variable loading

The presence of column initial imperfections in a steel frame can increase deflections and decrease its load carrying capacity. A method is proposed for evaluating the lateral stiffness, inter-storey displacement and deflected column shapes in a semi-braced, semi-rigidly connected planar storey frame subjected to gravity loading and column initial imperfections. An equation is proposed for calculating the inter-storey displacement, which contains the notional load associated with out-of-plumbness imperfections, in addition to a new notional load term associated with out-of-straightness imperfections. Additionally, when the lateral stiffness calculated by the proposed method diminishes, the frame is considered unstable. Different gravity loading scenarios can exist that equally result in the various criteria of capacity being reached defined as either instability, the maximum permissible deflection associated with structural integrity, or the onset of yielding in columns. The proposed method extends the variable loading approach to identify the worst- and best-case scenarios of gravity loading for this to occur. Unlike traditional proportional loading analyses, loads are varied independently of each other in the variable loading approach. Numerical models for the frame subjected to variable loading with accounting for the presence of column initial imperfections are established. It is demonstrated that although the presence of column initial imperfections does not affect the buckling loads of frames, it increases deflections and can significantly reduce the capacity even if the frames are constructed within the allowable tolerances for initial imperfections.

In-plane deformation monitoring of a cylindriscal specimen using a simple approximate method combined with two-dimensional digital image correlation.

This paper presents a quick-to-implement and simple approximate method that uses a single camera system to measure the relatively small surface deformation of a cylindrical specimen in the context of triaxial tests in geotechnical engineering. Digital images of a speckled cylindrical specimen before and after loading were obtained from only one perspective view. For each acquired image, there are geometric distortions and speckle losses, which are mainly caused by both perspective projection and column shape. Based on particular prior knowledge, we attempted to back-project the raw perspective images onto a cylindrical curved surface to reconstruct the speckle feature scene. These back-projected images were subsequently analyzed by the two-dimensional digital image correlation method to reveal the surface deformation information of the region of interest on the surface of the test specimen. Finally, a test case and a finite element study were, respectively, given to validate the effectiveness of the method. This feasibility study demonstrates the potential of extending this method to handle a wide range of regular cylindrical specimens with a relatively small deformation which are analyzed without taking out-of-plane motion into consideration.

Study on three-dimensional flow structures of a sweeping jet using time-resolved stereo particle image velocimetry

The three-dimensional flow structures that were induced by a sweeping jet emitted from a sweeping jet actuator to an open space were examined experimentally using stereo and two-dimensional PIV (particle image velocimetry) measurements. A new method was proposed to obtain phase-averaged flow field based on proper orthogonal decomposition, which is more robust to local flow fluctuations than existing methods. The jet Reynolds number (Re) was fixed to 8000 and the jet exit had a square shape with a hydraulic diameter (Dh) of 10 mm. The three-dimensional time-averaged flow fields of the sweeping jet were first reconstructed using multiple two-dimensional flow fields along various planes. In the time-averaged flow field, the jet flow distribution generally showed a V-shape pattern, which consisted of two inclined jet columns with an angle of approximately 90°. As the jet traveled away from the jet exit, the shape of jet column also changed from an elliptical shape to a circular shape because of the confinement effect of the jet exit. Stereo-PIV measurements were then conducted at two cross-sectional planes with distances of 3Dh and 8Dh away from the jet exit. In the plane 3Dh from the jet exit, one pair of counter-rotating vortices formed during the switching period when the jet swept from one side to the other. This is because the jet switching motion can enhance the jet shear layer, as in the case of a jet in crossflow. On the other hand, on the plane 8Dh away from the jet exit, the counter-rotating vortices dissipated quickly owing to the strong turbulence and weak switching motion.