Angle Sections Research Articles

Built-up battened steel columns under impact loading: Experimental and numerical analysis

In this work, experimental and numerical investigations are employed to examine the performance of the built-up battened steel columns under lateral impact load. The columns consist of four equal angle sections connected using batten plates. Drop-hammer impact tests were performed on six specimens, in which 3 impact energies were employed. Modes of failure, impact force-time histories and permanent deformations were obtained in the test. Subsequently, finite element (FE) models were established using ABAQUS, in which the strain-rate effects of steel material and initial global imperfections were considered. In addition, the validated FE models were utilized to analyze the whole dynamic response and investigate the influences of key parameters, including the impact energy, impact location, boundary condition and axial-load level etc., on the impact behaviour. A further discussion on the non-dimensional parameter of the energy absorption capacity (EAC) was conducted to qualify the behaviour of the built-up battened steel columns under impact load.

Co-modification of epoxy based polyhedral oligomeric silsesquioxanes and polyaniline on graphene for enhancing corrosion resistance of waterborne epoxy coating

Firstly, polyaniline (PANI) was used to improve dispersibility of graphene (Gr) in water through π-π interactions. Then, the obtained Gr/PANI products was further decorated with the epoxy based polyhedral oligomeric silsesquioxane (EPOSS) to enhance the hydrophobic properties of hybrid materials and compatibility with epoxy resins, thus leading to the increase of corrosion protection properties. From the wettability test results, the contact angle of the cross section of the composite coating reached up to 112.7 ° after grafting EPOSS, indicating that the hydrophobicity of the coating was improved significantly. Besides, the tensile strength of Gr/PANI@EPOSS/epoxy (0.7%) increased to 25.6 MPa, which proves the increase of interface force due to the introduction of epoxy group. The results of electrochemistry test illustrated that the impedance of Gr/PANI@EPOSS/epoxy (0.7%) is still as high as 2.79×107 Ω cm2 after 60 days of immersion, which is much higher than that of other samples.

A large-eddy simulation study on the similarity between free vibrations of a flexible cylinder and forced vibrations of a rigid cylinder

The strip theory in hydrodynamics has been widely used for predicting complex vortex induced vibrations (VIV) behind bluff bodies, but the question of how accurate such predictions are has not been addressed adequately before. In order to corroborate the application of strip theory in VIV, we present a comparative study between free mono-frequency vibrations of a long flexible cylinder in both uniform and linearly sheared flow and corresponding forced vibrations of a rigid cylinder with prescribed sinusoidal motions. We employ the entropy–viscosity large-eddy simulation (LES) to resolve the vortical flow and the coupled cylinder response, which we validate by companion experiments of the same configuration. We then extract from LES, at the same Reynolds number, the values of the sectional vibration amplitude, frequency, and phase angle (between inline and crossflow motions), and use them as input parameters for the forced vibration case, for which we perform two-dimensional simulations. We show here by systematic simulation studies that the hydrodynamic coefficients exhibit strong similarities between the two cases, and the forced vibration closely resembles the sectional near wake of the free vibration.

Determinación de los coeficientes de arrastre y sustentación en un perfil angular de alas iguales con el empleo de simulación numérica

Determinación de los coeficientes de arrastre y sustentación en un perfil angular de alas iguales con el empleo de simulación numérica

Failure Analysis of a Cruciform-Leg Transmission Line Tower

Design of latticed steel power transmission towers is a challenging task, which involves lengthy modeling and detailing of significant amount of steel members and connections. The tower is analyzed and designed as a space truss and various members of tower are checked for Tension, Compression and Slenderness Ratio. Sometimes, due to unavailability of required sections or economical point of view, single angle sections are replaced by Cruciform Sections (made of two angles connected toe to toe). The cruciform section, when connected with single angle sections, generate bending moments due to eccentric loading at connection on application of loads on tower, which subsequently results failure of the tower. In the present work, a full-scale testing of a 400 kV tower with built-up leg (Cruciform Leg connected with Single-Angle Leg) has been conducted and the behavior of joint on application of loads has been studied. While testing, one of the legs buckled at the connection. The failure pattern of the leg has been validated using FEM analysis, and the reason of failure has been discussed. In order to confirm the quality of steel, mechanical testing of steel used in leg has been carried out using UTM and results have been explained in the papers. The paper also gives some suggestions for the connection of this type of built-up sections used in tower in order to avoid such failures.

Flexural behaviour of stiffened and multi-cell L-shaped CFSTs considering different loading angles

Stiffened and multi-cell L-shaped concrete-filled steel tubular (CFST) members are often subjected to the loads from different loading angles as corner columns. Moreover, the flexural behaviour is the basis for the research of beam-columns and the determination of axial force-bending moment interaction curves. However, little work has been done on the flexural behaviour of these kinds of members at different loading angles. In this study, a total of 11 L-shaped CFST specimens with the variables of sectional type and loading angle were tested under pure bending. The failure mode, bending moment-deflection curves, moments-strain curves, deflection curves, flexural capacity and stiffness were investigated. It was found that the influence of loading angles is significant. The flexural capacity and stiffness of the specimens are highest at 135°, middle at 0° and 180°, and lowest at 45° and 225°. Setting longitudinal stiffeners or using multi-cell cross-section can improve the flexural capacity by about 20%. Then a finite element model was developed incorporating residual stress and cold-formed effect. Considering the effect of loading angles on the basis of the design model at 0°, the simplified formulas for flexural capacity of the stiffened and multi-cell L-shaped CFST members were proposed.

Semi-rigid behaviour of stainless steel beam-to-column bolted connections

Stainless steel is increasingly used in structural applications but there is still significant lack of experimental evidence on the moment-rotation (M-) behaviour of moment resisting beam-to-column connections. The current paper presents experimental test results obtained from full scale tests conducted on three widely used connection types i.e., double web angle (DWA), top seat angle (TSA) and top seat with double web angle (TS-DWA) connection. Considered beam, column and angle sections were fabricated using austenitic stainless steel plates and M20 high strength bolts were used for connection assembly. M- curves for all connections were carefully recorded and were used to determine initial stiffness (Ki) and moment capacity (M20mrad) for each of the connections. Eurocode 3 guidelines were used to check the classification i.e., whether or not the connections were semi-rigid in nature. Although the considered DWA connection failed to achieve partial-strength, both TSA and TS-DWA connections showed obvious semi-rigid nature despite the connection capacities were limited by bolts. In addition, extensive ductility of stainless steel ensured that all three connection types achieved a minimum connection rotation of 30 mrad, which is specified by FEMA as a requirement for earthquake design of ordinary moment frames.

Numerical Statistic Approach for Peak Factor of Non‐Gaussian Wind Pressure on Building Claddings

Wind‐induced pressures on high‐rise buildings claddings are mostly non‐Gaussian distribution, and there is a one‐to‐one relationship between a specified guarantee rate and its corresponding peak factor. In this study, a stepwise search method for calculating the peak factor of non‐Gaussian wind pressure and a gradual independent segmentation method for extracting independent peak values are proposed to determine the relationship accurately. Based on the pressure data of a high‐rise building obtained from a rigid model wind tunnel test, the peak factors of non‐Gaussian wind pressures on claddings are calculated and compared by using several typical methods. The value of the peak factor and its error rate calculated by several methods is compared with the observed average peak value, and the conversion between the guaranteed rate and the peak factor is discussed. Based on the reliability theory, the true distribution of wind pressure time history was approached infinitely through an efficient numerical method in the process of stepwise search. Compared with the classical Sadek–Simiu method, the proposed stepwise search method achieves improved overall accuracy and applicability. The non‐Gaussian features are found to be prominent at leading edge airflow separation on the crosswind side, the leeward corner cuts, the windward corner cuts, and the junction of two leeward surfaces at 45° wind direction angle of square section. The junction of two leeward surfaces at 45° wind direction angle exhibits stronger non‐Gaussian features than the crosswind surface at 0° wind direction angle. By giving the identical guarantee rate, the peak factors tend to be much larger in the regions with strong non‐Gaussian properties and vice versa.

Computational analysis of INVELOX wind turbine to analyze the venturi velocity by change the parameter of diffuser

Wind power harnessing in omnidirectional wind turbines is clean and non-polluting renewable energy sources to produce power. INVELOX is a revolutionary concept in omnidirectional wind turbines, collecting wind from all directions to ground level for safe, powerful and cost-effective operation. It increases the flow inside the section of venturi which is eventually extended and released via diffuser to the ambient atmosphere. In this analysis, the power output of this omnidirectional wind turbine was improved by optimizing the geometrical parameter of the diffuser exit and the variation of velocity on the throat area is discussed. The wind turbine efficiency was examined for various diffuser section angles based on the venturi segment and computationally simulated to test the increase in power output to determine the effective turbine for multiple incoming velocities.

СТІЙКІСТЬ РУХУ СЕКЦІЇ МАШИНИ ДЛЯ ОБРОБКИ ПАРІВ В ПОЗДОВЖНЬО-ВЕРТИКАЛЬНІЙ ПЛОЩИНІ

One of the tasks of using the black fallow in agricultural production is the weed control and the moisture conservation in the soil. Application of the most advanced soil cultivation technologies ensures preservation of no more than 75% of precipitations in the soil. To improve the state of this issue, we have developed a special machine for processing the black fallow. A mathematical model has been developed that describes the dynamics of the movement of the harrow section in a longitudinal-vertical plane, and its solution is given, which allows investigation of the impact of this or that design parameter upon the dynamics of the angle of rotation in time. The adequacy of the developed mathematical model is confirmed by special laboratory and field investigations of the created experimental machine. With rational design parameters the rotation angle of the harrow section in a longitudinal-vertical plane will not exceed – 3º, and the time of its exit to the equilibrium position will not exceed 16...17 s.

INVESTIGATION OF LONGITUDINAL STABILITY PROCESS AT ROLLING WITH STRIP TENSION

Earlier in the works, a qualitative construction of the diagram of changes in longitudinal normal stresses in the case of thin-sheet rolling with strip tension was proposed.. On the basis of the proposed stress distribution, the internal longitudinal forces were determined in a dimensionless form. Knowing these values, it is possible to determine the average resultant longitudinal force of the plastically deformed metal during rolling with the strip tension. It is shown that the value of the mean resulting internal forces is a more stringent boundary condition for the rolling process than the equality of the angle of the neutral section to zero.In this work, the influence of the strip tension mode on the ultimate stability of the metal in the rolls was determined, as well as the limiting condition of rolling, the change in the moment in the deformation zone and the angle of the neutral section. The theoretical analysis was carried out proceeding from the solution of the equilibrium equation with the specific friction forces specified by the Coulomb model. Using the technique proposed in previous works, we studied the effect of the magnitude and mode of strip tension on the longitudinal stability of the sheet during continuous rolling. It is shown that the rear tension has a significant effect on the average resultant longitudinal internal forces, and thereby predetermines the boundary conditions of the rolling process. The boundary conditions of deformation in a steady-state process presented in this work and generally accepted in theory differ significantly, which should be taken into account when developing a technology for continuous sheet rolling.

Features of the analytical solution of the problem of displacement cantilever steel beams with variable flange depth

The article is devoted to the problem of generalization of the influence of the variability of stiffness of elastic steel elements on thedisplacement and angles of rotation in the Cartesian coordinate system when placing the origin ofthe coordinates in the center of gravity of the largest cross section. Cantilever elastic I-beam steelbeam with variable flange depth is considered.The obtained formulas are shows the influenceof the variability of the I-beam cross-section on themoment of inertia in two main axis. This made itpossible to write the differential equation of beambending as a linear equation with variable coefficients.The solution of the differential equation makesit possible to obtain analytical formulae for determining the displacements and angles of rotation ofthe cross section of cantilever I-beams with variable flange depth. To confirm the obtained analytical expressions in the transition to the definition ofdeflections and angles of rotation of the I-beamswith a constant cross-section, the Lopital-Bernoullirule was used. A variant of the formula for theconsequences of the second remarkable (special)boundary in the disclosure of uncertainty is obtained.This makes it possible to prove by an analyticalapproach the coincidence of the obtained solutionswith the solutions for constant cross-section Ibeams. Numerical studies also confirmed the obtained result. This approach can be applied to Ibeams with variable flange depth under differentsupport conditions.The obtained displacement formulas make itpossible to check the stiffness of cantilever steel Ibeams with a linear change in their stiffness of thebeams according to the deflection limits. The obtained results can also be used for research of Ibeams with variable flange depth under differentsupport conditions. The obtained displacementformulas make it possible to check the stiffness ofcantilever steel I-beams with a linear change intheir stiffness of the beams according to the deflection limits. The obtained results can also be usedfor research of I-beams at linear change of stiffness, including a change of the modulus of deformation of steel at limited plastic work deformations on different sections of a beam.

Radiobiological effectiveness of iodouracil and the influence of atomic giant resonance

Hadron therapy combined with nanotechnology has been proposed as an elegant alternative for cancer treatment. Internal amplification of electron emission causing radiobiological effectiveness in nanoinserted biomolecules is of prime importance and has been measured here for the iodouracil molecule. Our experiment involves the measurement of angle and energy resolved double differential cross section (DDCS) of electron emission from iodouraciil and uracil (and also water) in collisions with fast ${\mathrm{C}}^{6+}$ ions. The electron emission from iodouracil is substantially enhanced over that from uracil or water. The enhancement is much larger than the state-of-the-art model for Coulomb ionization based on the continuum distorted wave-eikonal initial state (CDW-EIS) approximation. The electron sensitizing factor ($\ensuremath{\approx}2.4$) is in excellent agreement with the strand-breaking sensitizing factor ($\ensuremath{\approx}2.0$) for metal nanoparticle embedded in a DNA. The enhancement is explained in terms of collective excitation of strongly correlated 4d electrons, known as atomic giant dipole resonance (GDR) in I atoms. The GDR contribution to the enhancement is derived, which is in excellent agreement with recent theoretical prediction, thereby providing conclusive experimental evidence of the crucial role of collective excitation in radio sensitization.

Colonic Stent as “Bridge to Surgery” and Its Complications: A Case Report

Introduction: Endoluminal colonic stents can be used as a palliative solution in case of neoplastic subocclusions of the bowel and in some cases, they have been proposed as a temporary solution, in place of the derivative stoma, waiting for radical surgery. The "bridge to surgery" solution however can be complicated by perforations or dislocations that can make the patient's cancer treatment more complex. Case Presentation: A seventy-nine-year-old female patient presented a medium sigma adenocarcinoma that was treated initially with a stent to solve the bowel subocclusion. The procedure was complicated by a perforation that leaded to a modification of the TNM stage and consequently of the oncological therapeutic attitude. Conclusion: Self expandable stents could be used to solve the bowel occlusion to replace the derivative stoma performed in urgency. These procedures guarantee a better quality of life and generally less morbidity. However, an accurate assessment of the risks resulting from the positioning of the stents is necessary, avoiding the implant of the stent in tortuous or angled sections of the bowel with a high risk of decubitus and consequently of micro or macro perforations.

РОЗРАХУНОК КОНСТРУКТИВНИХ ТА СИЛОВИХ ПАРАМЕТРІВ ГРАВІТАЦІЙНО-КАСКАДНОГО СЕПАРАТОРА

У сільському господарстві для сепарування зерна використовують різні типи сепараторів. Сепарування в основному проводять за фізико-механічними та аеродинамічними властивостями зернової маси. До перспективних конструкцій сепараторів зернової маси відносяться гравітаційні сепаратори. У цих сепараторах енергія не витрачається на сепарування. У статті запропоновано гравітаційно-каскадний сепаратора ножичного типу. Конструкція гравітаційно-каскадного сепаратора відноситься до рамних конструкцій ножичного типу. Для забезпечення сепарування зерна в такому сепараторі, необхідно встановити сепарувальні секції під заданим кутом до горизонтальної площини, що визначається властивостями сировини. Для встановлення секцій сепаратора в задане положення в конструкції сепаратора пропонується використовувати передачу “гвинт-гайка”. Для усунення можливості самовільного переміщення роликів сепаратора необхідно розрахувати утримуюче зусилля. Крім того, для обґрунтування силових та конструктивних параметрів сепаратора необхідно було провести теоретичні дослідження. Дослідження дозволили встановити взаємозв’язок між параметрами сепаратора і передачі “гвинт-гайка”. Також використовуючи принцип можливих переміщень було отримано залежність для визначення зусилля, що необхідне для утримання секцій сепаратора в заданому положенні із урахуванням маси сепаратора та сировини, а також кута нахилу секцій до горизонтальної площини.

Reliability and uncertainty quantification of the net section tension capacity of cold-formed steel angles with bolted connections considering shear lag

In cold-formed steel members under tension and connected with bolts, the resistance capacity of the net section should be calculated, taking into account the shear lag phenomenon. This is done through the net section reduction coefficient, Ct. Different Standards show different equations for Ct. In this work, experimental laboratory data of cold-formed steel angles from the authors are used for the evaluation of the accuracy of the predictions of the net section capacity of members under tension. Such predictions are given by the equations of AISI, Eurocode-3, Brazilian standard NBR 14762, and also by a predictive equation previously proposed by the authors. The paper shows how each equation predicts the tension member resistance capacity in front of the experimental data. Most of the equations in the design standards have good predictions when more sections of the steel angles are connected. The results show that the AISI standard presented the best resistance capacity prediction and lower standard deviations of the output response upon uncertainty.

Geometry optimization of double pass solar air heater with helical flow path

Solar air heaters (SAH) have been widely studied due to their extensive applications in solar energy extraction. This research is in line with the previous study of the authors of this article in which the energy efficiency and heat transfer performance of a double pass solar air heater with helical flow path (HFP) were experimentally and numerically explored in a triangular cross-section channel. Here, the effect of different geometric parameters of this SAH on heat transfer performance is numerically investigated. The optimization procedure was also carried out by the differential evolution (DE). The results of this study were developed by referring to the grid independency and validation of the previous work of the authors. Finally, the effects of triangular section angles and dimensions and the location of the entrance section of each channel were investigated and optimized. The results indicated that optimized geometry resulted in a considerably higher thermo-hydraulic performance as compared with reference geometry for all Reynolds numbers which showed a minimum increment of t 16.5% upon optimization. The inactive vortices produced at the edge of entrance flow passage were reduced in each channel due to optimization which also declined the pressure drop.

Pin-ended press-braked S960 ultra-high strength steel angle section columns: Testing, numerical modelling and design

The structural performance and compression resistances of pin-ended press-braked S960 ultra-high strength steel (UHSS) angle section columns have been studied based on experiments and numerical modelling, and are reported in the present paper. An experimental programme was firstly performed on two series of press-braked S960 UHSS angle section column specimens, with each series containing six specimens of the same cross-section dimension but different member lengths, and included initial torsional and global geometric imperfection measurements and pin-ended column tests. The detailed pin-ended column test setup, procedures and results, including the failure loads, deformations at the failure loads, load–mid-height lateral deflection curves and failure modes, were fully reported. It is worth noting that two distinct flexural buckling orientations about the minor principle axis were observed from the tests, namely ‘C’ orientation (indicating that the failed column specimens buckled towards the angle corners) and ‘reverse C’ orientation (signifying that the failed column specimens buckled towards the angle tips). A numerical modelling programme was then followed; finite element (FE) models were firstly developed to replicate the test responses, and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member lengths. Given that the current design codes for steel structures, as used in Europe, Australia/New Zealand and North America, are only applicable to members and joints with material grades up to S700 (or S690), the relevant codified design provisions for press-braked S700 (or S690) high strength steel angle section columns were evaluated for their applicability to press-braked S960 UHSS angle section columns, based on the obtained test and numerical data. The evaluation results revealed that the European code yields unduly conservative and scattered compression resistance predictions when applied to press-braked S960 UHSS angle section columns, while the Australian/New Zealand standard and North American specification lead to a higher degree of design accuracy and consistency, on average, when used for press-braked S960 UHSS angle section columns, though some of the compression resistance predictions are unsafe for those failing by flexural buckling in the ‘C’ orientation.

Horizontal deformation of skeletal muscle thick sections visualised by confocal microscopy.

Certain morphological parameters of the skeletal muscle tissue can be better understood via 3D considerations. Fluorescent confocal microscopy of thick tissue sections is a well-established method for visualising and measuring skeletal muscle fibres and surrounding capillaries in 3D. However, thick tissue sections are prone to deformations which may significantly influence some stereological and morphometric results like muscle fibre diameter and capillary length, but not dimensionless parameters like object number and Euler-Poincaré characteristics. To better understand this phenomenon, we studied the horizontal deformation of thick (100µm) transverse skeletal muscle sections, by comparing the muscle fibre diameters measured on thick sections to muscle fibre diameters measured on thin (10µm) sections of the same sample. Diameter changes were further correlated with shrinkage in the Z direction (axial shrinkage) and deviation of the muscle fibre preferential axis from the Z-axis. We showed that the thick sections dilated in horizontal and shrunk in Z direction, and that the magnitude of horizontal dilation was associated with the magnitude of shrinkage in the Z direction. The latter was more pronounced in transversely than obliquely cut tissue sections. The results emphasise that even when shrinkage in the Z direction can be corrected using calibration, it is important to optimise histological protocols to minimise the Z-axis collapse that could cause horizontal dilation. LAY DESCRIPTION: In skeletal muscle research, 3D analysis is especially important for studying the microvasculature. Laser scanning confocal microscopy of skeletal muscle thick tissue sections is a well-established method for visualising and measuring skeletal muscle fibres and surrounding capillaries in 3D. However, such sections are prone to deformations which may significantly influence the study results. To better understand this phenomenon, we studied the horizontal deformation of thick transverse skeletal muscle sections. We compared the average muscle fibre diameters measured on thick skeletal muscle sections, thin fixed skeletal muscle sections and immunohistochemically stained thin skeletal muscle sections with the muscle fibre diameters measured on thin native skeletal muscle sections of the same sample, with the latter condition serving as the standard diameters (ie the control condition). We further studied the association among muscle fibre diameter changes, shrinkage of the thick skeletal muscle sections in the Z direction and their sectioning angle. We showed that the thick skeletal muscle sections dilated in the horizontal direction and shrunk in the Z direction, and that the magnitude of horizontal dilation was associated with the magnitude of shrinkage in Z direction. The shrinkage in the Z direction was more pronounced in transversely than obliquely cut tissue sections. These results emphasise that even when shrinkage in the Z direction can be corrected using Z-axis calibration, it is very important to optimise histological protocols to minimise the Z-axis collapse that could cause horizontal dilation in order to enhance the integrity of study results.

Design and optimization of a cavitating device for Congo red decolorization: Experimental investigation and CFD simulation

The aim of this work is to perform design and optimization of a cavitating device based on CFD simulation. A set of operational and geometrical parameters such as convergence angle, divergence angle, length of throat, and inlet pressure that can affect the hydrodynamic cavitation phenomenon generating in a Venturi are evaluated through CFD simulation and experimental approaches. Response surface methodology (RSM) was employed to achieve the optimum geometrical configuration. The CFD results show that the maximum cavitation zone in the Venturi can be obtained when half angle of the convergence section, throat length and half angle of the divergence section are 22.7°, 4 mm, and 6.5°, respectively. A maximum decolorization of 38.8% has been obtained using the designed Venturi at cavitation number (Cv) of 0.12. Additionally, the results were compared to that of various orifice plates. A decolorization of 26.2% using 33 holes orifice plate and 11.55% in one hole orifice plate approved the superiority of the designed Venturi.