Channel Section Research Articles

Web crippling of pultruded GFRP built-up sections

Web crippling is a critical premature failure of pultruded glass fiber reinforced polymer (GFRP) composites. One solution is to combine several sections to form a built-up section to carry the web crippling load. However, there is no existing study on the web crippling behavior of built-up sections under transverse loading. This paper presents an experimental and analytical study on the web crippling behavior of built-up I-shaped sections. The I-shaped sections were made by connecting two single channel sections back-to-back. Two connections methods were used including adhesive bonding and mechanical bolting. The bolt arrangements including number of bolt rows in the longitudinal direction, bolt spacing were varied to understand their effects on the web crippling behavior. The built-up sections were tested under two loading conditions of ITF and ETF, and the failure modes, load–displacement curves, and web crippling capacities were reported. Finally a section integrity enhancement coefficient was introduced in the analytical model to predict the web crippling capacity of built-up I-shaped sections and the predictions agreed well with the experimental results. This study contributes to the understanding of web crippling behavior of built-up sections made with pultruded GFRP sections.

Structural behaviour of press-braked austenitic stainless steel slender channel section beam-columns

The present paper reports experimental and numerical studies of the structural behaviour and resistances of press-braked austenitic stainless steel slender channel section beam-columns under combined compression and minor-axis bending. An experimental programme, including initial geometric imperfection measurements and ten beam-column tests, was firstly performed. The test procedures, setups and results were fully reported. The experimental programme was accompanied by a numerical modelling programme, including a validation study, where finite element models were developed and validated against the test results, and a series of parametric studies, where the validated finite element models were used to generate further numerical data. The obtained test and numerical data were adopted to assess the current design interaction curves for press-braked austenitic stainless steel slender channel section beam-columns, as provided in the European code, American specification and Australian/New Zealand standard. The assessment results revealed that all the three codified design interaction curves led to conservative and scattered resistance predictions, due to the conservative compression and bending end points and inappropriate shapes. To address these shortcomings, a new design interaction curve has been proposed and shown to yield a higher level of design accuracy and consistency for press-braked austenitic stainless steel slender channel section beam-columns than the codified design interaction curves.

Testing, simulation and design of press-braked ferritic stainless steel slender channel section columns failing by local–flexural interactive buckling

This paper presents an experimental and numerical study of the local–flexural interactive buckling behaviour and resistances of press-braked ferritic stainless steel slender channel section columns. An experimental programme was firstly conducted, including initial geometric imperfection measurements and ten pin-ended column tests. Interaction between local buckling and flexural buckling was observed for all column specimens upon testing and discussed in detail. The test results were used in a parallel numerical modelling programme to validate finite element models, which were then adopted to perform parametric studies to generate additional numerical data over a wide range of cross-section dimensions and member effective lengths. Based on the test and numerical data, the relevant design rules for press-braked ferritic stainless steel slender channel section columns, as given in the American specification and European code, were evaluated. The evaluation results revealed that the American specification resulted in a good level of design accuracy, while the European code led to conservative and scattered interactive buckling resistance predictions. Finally, a revised Eurocode design method was proposed and shown to yield much more accurate and consistent interactive buckling resistance predictions for press-braked ferritic stainless steel slender channel section columns than its original counterpart.

Nutrient transport following water transfer through the world's largest water diversion channel

Nutrient levels in the artificial channel constructed for the Middle Route Project are significant indicators of water quality safety and aquatic ecological integrity for this large, inter-basin scheme. However, the distribution and transport of nutrients along the channel were poorly understood. Based on a time-series dataset as well as mass balance and material flow analysis methods, the water and nutrient transport fluxes in the Middle Route of the South-to-North Water Diversion Project were identified in this study. The results indicate that the nutrient concentrations varied considerably with time, but there was no significant difference among the 30 stations of the main channel. Seasonal temperature difference was the major factor in the large fluctuations of water quality indicators over time. The nutrient loadings varied with the water volume outputs from the main channel to the water-receiving cities. Atmospheric deposition was an important source of nutrients in the main channel, accounting for 9.13%, 20.6%, and 0.635% of the nitrogen, phosphorus, and sulfur input from the Danjiangkou Reservoir, respectively. In 2021, a net accumulation of 988 tons of N, 29 tons of P, and 2,540 tons of S, respectively, were present in the main channel. The increase of these external and internal nutrient loadings would cause water quality fluctuation and deterioration in some local sections of the main channel. Our study quantified the spatial and temporal patterns of nutrient transport in the Middle Route and revealed the ecological effects on the aquatic environment, assisting authorities on the project to develop effective water conservation strategies.

Concept of an innovative plasma system for hole-cutting in linear profiles

In the letter, the concept of a plasma system for simultaneous cutting of holes in one pass is introduced. The system is designed for machining long linear profiles used in engineering steel structures. It makes it possible to cut on opposite walls of channel or hollow sections in one plane and in two mutually perpendicular directions. The system is part of an innovative technological line for automatic plasma cutting, circular saw cutting and welding with use of welding robots.

Testing Scale Models of Hydro-Reactor Profiled Ducts That Create Notable Net Head to Promote Hydroelectric Power from Currents

In this article, experimental results from the testing of four representative scale models of hydro-reactor profiled channels, which create a net head to promote the extraction of hydroelectric power from currents, are presented. The tested scale models include a narrower intermediate channel section of 300 mm diameter. The different profile models studied include an inlet compression chamber and an outlet depression chamber. A net head is created by the difference in pressure, with the head being higher the narrower channel’s zone than in the kinetic head of the outside stream velocity. Because there were no laboratory premises to test the constructed duct model sizes and to easily change the imposed steady current velocity, the experimental tests were performed by dragging the immersed models, attached to a raft in motion, in a place of steady water (the bay of a port). With this methodology, the same effect was obtained, making it possible to perform the testing for several current velocities (velocity of the raft relative to the steady water). Tests on free-flow to compare the difference in kinetic heads were performed. Furthermore, three loads obstructing different percentages of the channel’s narrower section were inserted to analyze the duct channel obstruction limits. The experimental results are validated by numerical results from finite element analysis.

A Novel Approach to Improve the Distortional Buckling Strength of a Stiffened Cold-Formed Steel Channel Section under Axial Compression

This study investigates the distortional buckling strength of a partially closed cold-formed steel (CFS) channel section with intermediate web stiffeners and outward lips under axial compression. Generally, a closed CFS cross section has higher torsional resistance when compared to an open cross section. However, an open cross section is more popular in the construction industry. Despite the popularity of CFS open sections, distortional buckling can reduce the load-carrying capacity of such open cross sections. To improve the distortional buckling strength of the proposed selected section, a simple spacer plate is added externally to the channel section in the transverse direction. Initially, a numerical model is developed using the finite element software ANSYS, which is then validated against the experimental results available in the literature. A detailed parametric study was also conducted to investigate the influence of thickness, depth, and spacing of spacer plates on the distortional buckling strength of stiffened CFS channel sections. From the results of the parametric study, it was found that the presence of spacer plates can increase the axial capacity of stiffened CFS channel sections by as much as 32%. Finite element results were compared with the design strengths calculated in accordance with the direct strength method (DSM).

Сравнение численных схем для задачи ламинарного течения во внезапно расширяющемся канале

The paper studies fluid flow in a two-dimensional channel with sudden expansion (x/h = 2). Calculations were made for the laminar flow mode based on numerical integration of the nonstationary Navier --- Stokes equations. Various flow characteristics were determined at Re = 100--800. Results were obtained for the longitudinal speed profiles in various channel sections and lengths of the primary and secondary vortices at various values of the Reynolds number after the step. The friction coefficient distribution on the channel lower side along its length is presented for various values of the Reynolds number. For the difference approximation of the initial equations, the control volume method was applied; relationship between speed and pressure was found using the SIMPLE procedure. For numerical solution of the problem, the following QUICK schemes were introduced: McCormack's second-order accuracy, Warming --- Cutler --- Lomax's third-order accuracy and Abarbanel --- Gotlieb --- Turkel's fourth-order accuracy. To confirm correctness, numerical results were compared with the experimental data taken from the literature sources

Experimental investigation of the sectional buckling of built-up cold-formed steel columns

This paper presents an experimental program investigating the local and/or distortional (sectional) buckling of built-up cold-formed steel sections subjected to pure compression. The experiments were designed to study the influence of key parameters, including buckling mode, cross-section geometry and fastener spacing, on the ultimate sectional capacity of built-up columns. Three singly- or doubly-symmetric built-up sections were considered with two sets of component lipped channel sections, one buckling predominantly in the distortional mode and one buckling in the local mode. The component sections were connected using self-drilling screws at three different spacings. Material properties, geometric imperfections and residual stresses of the specimens were measured prior to testing. A total of 36 specimens with a length of 1 m were tested under concentric compression between fixed ends, which was achieved through a special end plate connection. The specimens failed in either distortional or the interaction of local and distortional buckling modes. Compared to the sum of the capacity of component sections, the ultimate capacity in built-up columns with distortional buckling mode increased significantly with the reduction of screw spacing, whereas the increase was minor for specimens that failed through local-distortional interaction. The ultimate strength of the specimens was predicted using the current Direct Strength Method, where either conservative or overly unconservative predictions were obtained depending on the considered composite action level in the elastic buckling analysis.

Behavior of Stainless-Steel Hot-Rolled Channel Section Beam–Columns: Testing, Modeling, and Design

This paper presents a testing and numerical modeling program on the global stability and resistance of stainless steel hot-rolled channel section beam–columns under combined compression and minor-axis bending. The testing program comprised material tests, imperfection measurements, and 18 beam–column tests. Following the testing program, systematic numerical simulations were conducted; finite-element models were developed to simulate the test observations and conduct parametric studies to obtain more numerical data. The obtained experimental and numerical results were analyzed and used to perform a design analysis, in which the accuracy of interaction curves prescribed in the US and European design codes for stainless steel hot-rolled channel section beam–columns was assessed comprehensively. The results of the design analysis generally revealed that both the US and European interaction curves yield unduly inaccurate and scattered resistance predictions due to the use of inappropriate curve shape and inaccurate end points. A new design interaction formula is proposed using a more appropriate curve shape and more-accurate end points. The new interaction curve was shown to be capable of offering greatly improved design accuracy and consistency compared with the US and European curves.

Effect of corrosion on the buckling behaviour of cold-formed steel channel section columns under axial compression

Effect of corrosion on the buckling behaviour of cold-formed steel channel section columns under axial compression

DIFUSI INOVASI PROGRAM MASYARAKAT PEDULI TB TANJUNG GADANG (MASPETTAG) DI PUSKESMAS TANJUNG GADANG KABUPATEN SIJUNJUNG

The aim of study to describe the diffusion of innovations in the Tanjung Gadang TB Care Community (Maspettag) program at the Tanjung Gadang Health Center, Sijunjung Regency. The background of this research is about health problems, one of which is TB disease or commonly known as Tuberculosis. The study used M. Rogers's theory of innovation diffusion with four variables including the innovation, communication channels, time, and a social system. The method used in this research is descriptive qualitative. Data collection techniques were carried out by interviews and documentation. Selection of informants using purposive sampling technique. Data analysis was carried out by grouping data, reducing data, presenting data, and drawing conclusions. For the validity of the data using source triangulation. The results of this study indicate that the innovation diffusion of the Tanjung Gadang TB Care Community (Maspettag) program has been going well. This can be seen from the innovation of the Maspettag program that has met the indicators of the theory of diffusion of innovation. Although there are still obstacles experienced by cadres when they go to the field due to rejection from the community. The innovation communication channel section, the Maspettag program does not use social media and only uses interpersonal channels to spread innovation to the public. The time variable for the spread of innovation is quite fast, it can be seen from the increasing number of suspected TB discoveries. Finally, the social system variable of the Maspettag program innovation fulfill indicators of the social system.

Structural Performance of Cold-Formed Steel Face-to-Face Built-Up Channel Sections under Axial Compression at High Temperatures through Finite Element Modelling

This paper studies the structural performance of cold-formed steel (CFS) face-to-face (FTF) built-up channel sections subjected to axial compression at high temperatures. The material properties of G250 and G450 CFS channel sections at room and high temperatures were acquired from the literature, and the range of temperatures was from 20 to 700 °C. The influences of the section thickness, member length, screw number, and high temperature on the structural performance of such channel sections were examined via a comprehensive parametric analysis involving 576 validated finite element models. As the temperature increased from 20 to 700 °C, the mean axial capacity of the CFS-FTF built-up unlipped and lipped channel sections decreased by 88.9% and 90.2%, respectively. Based on the results of the parametric study, new design equations for the axial capacity of CFS-FTF built-up channel sections at high temperatures were proposed. The mean ratio of the EWM strengths calculated using the American standard (AISI 2016) and Australian/New Zealand standard (AS/NZS 2018) to the FE strengths was 0.77, while the mean ratio of the proposed design strengths to the FE strengths was 1.01. Finally, a reliability analysis was conducted, and it was found that the proposed equations could come close in predicting the axial capacity of CFS-FTF built-up channel sections at high temperatures.

Global Buckling Experiments of Cold-rolled Aluminium Alloy Downturn Lip Channel Beams

The paper is aimed to describe an experimental program of cold-rolled aluminium alloy downturn lip channel beams undergoing global buckling. Cold-rolled aluminium sections can be seen as new products of BlueScope Permalite, and the downturn lip channel section is in the form of the channel section with a modification of the bottom lip direction. A series of four tests with two lengths were carried out at The University of Sydney. The experiments were driven by a dual-actuator loading system to ensure the applied load was in the upward direction through the shear centre of the investigated section specimens while testing. Global buckling failures were seen in all specimen tests. The obtained test results will be the base for the calibration of a finite element model and the proposal of new design guidelines for these section beams subjected to global buckling modes in further studies.

The exact Riemann Solver to the Shallow Water equations for natural channels with bottom steps

The Shallow Water equations model is commonly used to reproduce a wide variety of environmental flows. Its applications include river hydraulics and flood forecasting.Therefore, an algorithm to solve the Riemann problem for the Shallow Water equations can be a considerable asset for the development of numerical schemes devoted to the solution of such equations. Nevertheless, for real world applications, it becomes mandatory to consider the influence of the irregular shape of the cross section of natural channels in the solution.This work presents an energy based exact Riemann solver for the Shallow Water equations for channels with an arbitrarily shaped cross section with the presence of a non flat bottom and dry states.The procedure for solving the Riemann problem involves the solution of a system of non linear algebraic equations, for which a CPU time efficient solution strategy based on nested Newton-Raphson methods is presented.The proposed solver can be used to develop Finite Volume or Discontinuous Galerkin schemes, based on the Godunov method. For a non flat bottom, the Shallow Water equations are a non conservative system, once the bottom elevation is included in the state variables. Many available schemes take advantage of this fact to use approximate path-conservative Riemann solvers. In other cases, the term related to the non flat bottom is treated as a source term. The use of this exact solver avoids the necessity of considering the bottom topography as a source term and of reverting to approximate solvers. These strategies can in facts pose numerical problems in situations such as transonic rarefactions and flows approaching abrupt changes in bottom topography.The solver is tested by reproducing the solution of Riemann problems with a Godunov finite volume scheme. An analysis of the performance of the solver shows that it requires less computational time than path-conservative schemes and that it has better stability and convergence properties, especially in situations involving resonant waves, such as transonic flows across a bottom step.

NUMERICAL STUDY ON BEHAVIOUR OF COLD-FORMED STEEL UNLIPPED CHANNEL SUBJECT TO AXIAL COMPRESSION

Innovation in obtaining construction materials that are efficient and applicable to various conditions is a challenge for researchers. Cold-formed steel is a material breakthrough in construction that has advantages over hot-rolled steel. Many studies have been carried out on Cold-formedsteel subjected to various loadings to examine the behavior and capacities of the sections. This study aims to investigate the behavior and section capacity of cold-formed steel unlipped channels due to axial compression loads. This research begins with conducting a literature study, then carrying out numerical analysis using the finite element method in ABAQUS, numerical test, and calculation of section capacity based on existing research in the literature. The calculation of section capacity is carried out based on SNI 7971-2013 or AS/NZS 4600:2005. The results of the numerical analysis can be seen from the behavior and capacities of the sections of the unlipped channel, the section capacity from the numerical test will be compared with the section capacity obtained from the calculation based on SNI 7971-2013 or AS/NZS 4600.

Influence of the bevel and steeple triggers on crashworthiness of carbon fiber-reinforced composite channel section structure

To induce the progressive crushing of composite channel section structure (CCSS), the bevel and steeple trigger are proposed and designed. A nonlinear damage model considering both damage initiation and evolution of intra-ply and inter-ply is developed. The damage initiation and stiffness degradation processes of intra-ply are predicted by the maximum stress criterion and an exponential evolution law, respectively. The adhesion behavior between adjacent plies is modeled following the surface-based cohesive contact method, and the delamination failure behaviors of inter-ply are predicted using the traction-separation model. The effects of different configurations of bevel and steeple trigger on the energy absorption characteristics of CCSSs subjected to quasi-static axial loading are compared and analyzed. The results show the initial peak load of CCSS using the bevel and steeple trigger has a negative correlation function with the bevel angle. The steeple trigger can induce progressive crushing of the structure and significantly enhance the specific energy absorption (SEA).

Experimental and multiphase modeling of small vertical-axis hydrokinetic turbine with free-surface variations

Vertical-axis hydrokinetic turbines are promising option to harness the low velocity currents. However, limited investigations have been carried out considering the interactions between the turbine rotor and the channel section, including the free-surface. Thus, a vertical-axis turbine model has been designed and manufactured, to be tested in an open channel. Also, a three-dimensional multiphase simulation has been carried out, using the volume of fluid (VOF) model, to capture the air–water interface and to investigate the free-surface variations effects on the turbine output. Experimentally, the turbine model has been characterized under different flow conditions and free-surface levels. The peak power coefficients are found to increase with the upstream velocity. This effect is directly linked to the blockage ratio and the Froude number. A reasonably good match has been found between the experimental and the numerical results. The VOF model is able to simulate the free-surface longitudinal variations, and the effect of the turbine blockage of the channel. The velocity field and the pressure coefficient distribution, around the turbine rotor, have been studied and correlated with the free-surface variations from upstream to downstream of the turbine. Finally, the vortex street generated by the blade–plate interaction has been analyzed.

Моделирование русловых процессов в створе канала

An erosion mathematical model of a sand channel coastal slope, which occurs under the influence of passing flood wave, is formulated. The model includes the equation of motion of a quasi-steady hydrodynamic flow in the channel section. The movement of the bottom and bank surface of the channel is determined from the solution of the Exner equation, which is closed by an original analytical model of the movement of traction sediments. The model takes into account transit, gravitational and pressure mechanisms of movement of bottom material, and does not contain phenomenological parameters. The movement of the free surface of a hydrodynamic flow is determined from the interpolation of experimental data. The model takes into account changes in the average turbulent viscosity along the alignment when the channel alignment changes. The influence of quasi-steady hydrodynamic flow on mass loss in the channel section was studied. A criterion has been introduced to determine the disequilibrium of the channel flow. It is shown that to model channel deformations in this case, it is necessary to take into account a non-zero gradient of sediment movement along the channel axis. Numerical calculations have been carried out demonstrating the qualitative and quantitative influence of these features on the process of determining the turbulent viscosity of the flow and the erosion of the coastal slope of the channel. Data comparison on coastal deformations obtained as a result of numerical calculations with known flume experimental data showed their good agreement.

Pulsating flows of viscous fluid in flat channel for given harmonic fluctuation of flow rate

In research work, it is pointed out the issue of a pulsating flow of a viscous incompressible fluid in a flat channel for a given harmonic fluctuation of the fluid flow rate. The study of the generation of pulsating current is used in biological mechanics, in particular, in the use of microchip systems. In addition, to ensure a constant flow of liquid, pneumatic micropumps that periodically squeeze liquid from empty volumes are widely used. In such systems, the installation of pulsating flow is shown to be economically beneficial. The transfer function of the amplitude-phase rate response is determined; with the help of these functions, the ratio of the tangential shear pressure on the channel fence to the average acceleration over the channel section is determined. In Figure 1, it can be seen that the ratio of KH = 0 of in τHC/τ0KC is close to one and α02 is less than one. If α02 takes on values greater than unity, then the ratio of to KH = 0 to τHC/τ0KC is greater than unity, and it has been shown to increase with increasing frequency of dimensionless oscillation. It was shown that in an unsteady flow of liquid, even in cases where liquid acceleration is equal to zero, it was studied that the stress on the wall of the channel exceeds its quasi-stationary value. τHC/τ0KC with the increase of the ratio KH, the increase of the parameter is explained by the fact that the change of the tensile stress on the wall advances in phases concerning the average speed along the section. Calculations determine that the non-stationary shear pressure on the channel fence increases non-monotonically with the acceleration of the liquid particle at low oscillation frequencies. The shear pressure reaches its maximum value, then decreases with increasing dimensionless oscillation rate, and asymptotically approaches the values without accelerated flow.