Channel Section Research Articles

Test, numerical investigation and design of perforated advanced high-strength steel I-shaped built-up compression members

This study investigates the effects of perforations on the buckling behavior and load-bearing capacity of advanced high-strength steel I-shaped built-up compression members. The built-up section was fabricated by connecting two identical lipped channel sections made of complex phrase steel HC700CP980 using pull rivets. The perforations were classified into two groups: holes in web and holes in both web and flanges. A comprehensive parametric study, combining both experimental results and finite element analysis, demonstrated the decrease in load-bearing capacity caused by the presence of perforations, particularly noticeable in specimens featuring holes in both web and flanges. The extend of the reduction is closely linked to the quantity and dimensions of the holes, with a higher hole-element width ratio resulting in a more substantial loss of load-bearing capacity. Additionally, the obtained test and FE results were used to evaluate the accuracy of direct strength method (DSM) for the examined advanced high-strength steel I-shaped built-up compression members. The evaluation findings highlight the limitations of the DSM in the design predictions for built-up columns featuring multiple web holes and holes on both web and flanges. Therefore, a modified calculation method was proposed, which integrated strength reduction factors to consider the influence of the position of holes relative to the flexural buckling axis of built-up sections. The modified method has shown notably improved design accuracy and consistency for the perforated advanced high-strength steel I-shaped built-up sections.

Numerical and Experimental Analysis of Buckling and Post-Buckling Behaviour of TWCFS Lipped Channel Section Members Subjected to Eccentric Compression.

The paper presents a static analysis of the buckling and post-buckling state of thin-walled cold-formed steel (TWCFS) lipped channel section beam-columns subjected to eccentric compression. Eccentricity is taken into consideration relative to both major and minor principal axes. An analytical-numerical solution to the buckling and post-buckling problems is described. The solution is based on the theory of thin plates. Equations of equilibrium of section walls are derived from the principle of stationary energy. Then, to solve the problem, the finite difference (FDM) and Newton-Raphson methods are applied. Linear (buckling) and nonlinear (post-buckling) analyses are performed. As a result, pre- and post-buckling equilibrium paths are determined. Comparisons of the obtained numerical results, FE simulation results, and experimental test results are carried out and presented in comparative load-shortening diagrams. Additionally, a comparison of the buckling forces and buckling modes obtained from theoretical analysis and experiments is presented.

Thermal instability and vibration characteristics of laminated composite struts with Graphene reinforcements: An analysis of distribution patterns and geometrical imperfections

This study explores the effect of local buckling on the compressive performance of slender structural elements, particularly those with thin-walled sections. The phenomenon of local buckling significantly reduces the axial compressive stiffness, leading to a notable decrease in the load-bearing capacity of these elements. The main goal of this research is to examine how the post-buckling characteristics of polymeric composite channel section struts can be improved under thermal loading by incorporating multi-layer graphene reinforcements. The solution methodology incorporates the von Karman geometrical nonlinearity and is based on the layerwise third-order shear deformation theory (LW-TSDT). To ascertain the precision and computational performance of the results derived from LW-TSDT, a three-dimensional (3D) finite element model is created in ABAQUS for comparative evaluation. An extensive analysis of nonlinear thermal instability in perfect and geometrically imperfect FG-GRC laminated channel section struts is undertaken to discern the graphene distribution patterns that are most and least effective in elevating the critical buckling temperature and natural frequencies through pre- and post-buckling conditions. The comparative analysis indicates that employing the FG-X graphene distribution pattern across the thickness of the web and flanges in channel section struts leads to a projected increase of 12 % in the critical buckling temperature for clamped channel section struts, in contrast to those that adopt the FGO graphene distribution pattern. For cases with simply-supported boundary conditions, this increase is noted to be approximately 9 %. Moreover, findings confirm that incorporating an asymmetric graphene distribution pattern (FGV) or introducing geometrical imperfections in the flanges and web that generate a bending moment within the structure from the beginning of thermal loading effectively prevents the primary natural frequencies of FG-GRC channel section struts from declining to zero close to the critical buckling temperature. This is significantly different from scenarios involving perfectly structured and symmetrically reinforced graphene distribution patterns such as FGX.

Assessment of residual resistant capacity of cold-formed Q1100 ultra-high strength steel channel section stub column with corrosion

Experiment and numerical analysis were conducted in this study to reveal the residual resistant capacity of the cold-formed Q1100 ultra-high strength steel (UHSS) channel section stub column with grooving corrosion. Based on the results of tensile coupon test, the strength properties of the Q1100 UHSS were barely changed by the cold-forming process. A clear reduction in the ductile properties was observed, after the cold-forming process. The load-end shortening curve of the cold-formed Q1100 UHSS channel section stub columns with different grooving corrosions were obtained through the axial compressive experiment. The initial resistant stiffness was reduced by the grooving corrosion significantly, because of the reduction in the cross-section area. Decrease in the corrosion angle and increment in the corrosion length enhanced the adverse effects of grooving corrosion on the resistant capacity. Local buckling was observed in the flange and web. The flanges near the corrosion weakening area were more prone to local buckling, because of the stress transfer from web to flange. A numerical modelling method was proposed to simulate the resistant performance of the cold-formed Q1100 UHSS channel section stub columns with different grooving corrosions, which was validated by the comparison in load-end shortening curve, ultimate resistance and failure mode. Effects of corrosion angle, corrosion length, and corrosion location on the resistant capacity and failure mode were investigated through the parametric study. Compared with corrosion location, the corrosion angle and corrosion length exhibited more significant effects on the resistant capacity of the cold-formed Q1100 UHSS channel section stub columns.

A multifractal model for predicting the permeability of dual-porosity media with rough-walled fractures and variable cross-sectional pore channels

The seepage of rock strata is greatly influenced by the pore network and fracture network; however, the prediction of permeability becomes challenging due to the changes in the cross section of pore channels and the morphology of fractures. In this study, a novel pore-fracture permeability model based on a fractal theory is proposed, and the analytical solutions of the model are given. In contrast to the traditional smooth parallel plate and uniform cross section straight capillary, this model not only considers the roughness of the fracture surface, but also the cross section variation and tortuosity of the pore channel. The comparisons between the calculated results and the experimental data verify the reliability of this model. The quantitative analyses of microscopic parameters indicate a positive correlation between the permeability and the fractal dimension, size, and proportion of pores and fractures. Conversely, there is a negative correlation with roughness, tortuosity, and cross-sectional changes. The range in which the seepage contribution of pores cannot be ignored is determined. Two logarithmic relationship expressions for permeability are presented. This study contributes to explore the effects of the geometry and morphology of the pore-fracture media on seepage and supplements the studies on the permeability models.

Вплив геологічних структур на характер русел правобережних приток річки Дністер

The proposed study aims to determine the influence of geological structures on the features of the channels of the largest right-bank tributaries of the Dniester River - the Stryi, Bystrytsia, and Limnytsia rivers. For this purpose, we conducted zoning of the river based on morphometric and hydrological characteristics. Three parts were identified: mountainous, pre-mountainous area and plain area, which differ significantly in channel properties, their changes over time, and deformation processes. Objective. Based on remote sensing images of various resolutions, the use of historical maps over time, and specialized maps, to investigate the nature of the channels of the right-bank tributaries of the Dniester: Stryi, Limnytsia, and Bystrytsia, from their sources to the estuarine part where they flow into the Dniester River, depending on the geological and lithological features of the surface. The main research methods involve the transformation of various materials from remote sensing, historical, and special maps for the purpose of studying specific phenomena of river processes. The methodology involves the preparation of input materials, including historical topographic maps, geological maps, satellite images, maps and images georeferencing, satellite image processing, river channel vectorization, analysis of river channels depending on geological structures. Results. Considering the morphology, valley width, manifestation, and development of channel processes, the Stryi, Bystrytsia, and Limnytsia rivers were categorized into three sections: mountainous, pre-mountainous and plain area with developed accumulative forms. In the mountainous section, all three rivers have single channels, while in the pre-mountainous section, multichannel patterns are observed, which have decreased from the 19th to the 21st century in terms of the width of multichannelity and the number of channels. This indicates a decrease in the flow modulus. For the plain sections of channels with undeveloped accumulative forms, a clear tendency towards dependence of channel type on structural-lithological features is traced. Originality. The paper has established the dependence of channel processes of right-bank tributaries of the Dniester River on geological and sedimentological structures of the Skole Beskids and Subcarpathian Depression. Practical significance. The results of monitoring channel processes need to be considered in addressing a range of tasks, including the construction of hydraulic structures, designing power transmission networks at river crossings, developing gas pipelines, determining flood zones, assessing the consequences of erosion after floods, land reclamation, establishing water protection zones, managing recreational and border lands, and establishing interstate borders along rivers.

Effect of microchannel cross-section geometry on the flow resistance with stainless steel flat-plate solar collectors

The stainless steel flat plate solar collector is a new type of collector that has a longer lifespan in high-temperature and high-humidity environments. When using stainless steel as the base material of the collector, the microchannel structure is typically employed to increase the heat transfer area and compensate for the lack of heat transfer coefficient of stainless steel. However, the shape of the channel section in microchannel structures affects the flow resistance of the heat transfer medium. This article presented the equation for the optimal feature size of the channel, obtained through fluid theory analysis of the stainless steel flat plate collector. The study analyzed the impact of different section parameters on the flow distribution and pressure drop characteristics of the medium in the channel through numerical simulation. The results showed that for a certain inlet flow rate, the cross-sectional geometry of the microchannel heat-absorbing plate determined the parameters such as the type of core cross-section, the degree of wall urgency, and the geometrical length of the microchannel, which in turn affected the distribution of the fluid in the flow channel and the energy loss. The optimal thermal performance of the stainless steel collector was observed when the width of the micro-channel was 8.7 mm and the corrugation height of the tube group was 3.00 mm.

Mathematical modeling of the transport characteristics of a PVDF-based cation-exchange membrane with low water content

New effective ion-exchange membranes are needed for a variety of applications, with a particularly pressing need for membranes used in fuel cells and membrane water electrolysis. PVDF-based membranes are promising for these and other applications. Two samples of such membranes with a low water content are studied. The interest in the behavior of these samples is that with an increase in the bathing NaCl solution concentration, the diffusion permeability decreases, whereas usually it increases along with increasing membrane conductivity. The hypothesis is that with increasing concentration, the water content decreases even more, which leads to a narrowing of the intercluster ion-conducting channels and a reduction in the effective mobility of coions, since the latter have to go around narrowed sections of channels. To simulate the concentration dependence of conductivity, diffusion permeability and transport numbers for the two above samples, the microheterogeneous model is extended to describe the loss of water with increasing external concentration and take into account the decrease of coion percolation through the membrane. The results of simulation are compared with the experimental data.

ANALYSIS OF IMPOLITENESS COMMENTS OF NETIZEN ON NAJWA SHIHAB YOUTUBE CHANNEL

This study is entitled "Analysis of Impoliteness Comments of Netizens on Najwa Shihab YouTube Channel". This study aims to examine the types of impoliteness strategies used by netizens in speaking in the comments column of Najwa Shihab's YouTube channel on the show "Ganjar Pranowo Bicara Gagasan" based on Jonathan Culpeper’s theory. In this study, the research design used is a qualitative descriptive method to analyze the types of impoliteness strategies used by netizens in commenting on the comment section of Najwa Shihab's YouTube channel on the "Ganjar Pranowo Bicara Gagasan" video uploaded in September 2023. Data will be obtained from transcripts of printed materials related to incivility, with Culpeper's theory as the basis of analysis. The results of this study identified four types of impoliteness strategies from 100 comments studied contain impoliteness strategies on the video, the four categories of impoliteness identified include: Bald on Record Impoliteness (25%), Positive Impoliteness (22%) with Insukting Others (3%), Rejecting Similarities with the Listener (1%), Diverting Topics that are Sensitive or do not want to be Discussed (5%), Using Inappropriate Code (1%), Not Interested in Conversation (6%), Look For Differences Opinion (4%), and Using Unclear and Confidential Language (2%), negative impoliteness (26%), and Sarcasm or Mock impoliteness (27%), while Withhold Politeness is not found because it can only be found in oral speech. Based on the analysis, Sarcasm or Mock Impoliteness (27%) is the most dominant type of impoliteness strategy. From these findings, it can be concluded that Indonesian netizens often express meanings that are opposite to the words they actually say, which aims to criticize or make fun of their interlocutors in a subtle way.

Numerical studies on lutetium isotopic selective photoionization based on a three-step ionization scheme

Numerical studies of lutetium selective photoionization have been carried out based on a three-step photoionization scheme, 5d6s2 2D3/2 → 5d6s6p4Fo5/2 → 5d6s7s4D3/2 → (53,375 cm−1)1/2 → Lu+, by the density matrix theory. Atomic hyperfine structures and magnetic sublevels are considered in our photoionization dynamics model. To examine the effectiveness of this model, the simulated 176Lu ion strengths are compared with the experimental results, and the simulated excitation cross sections of 176Lu excitation channels are compared with the analytical and experimental results. Semi-quantitative agreements are acquired for these two cases. On this basis, selective photoionization processes of two lutetium isotopes are simulated and discussed. Considering the ionization probability and abundance of target isotope, the 8.5-9.5-8.5 two-step excitation channel is optimal for 176Lu enrichment from natural lutetium. The influences of laser parameters and atomic Doppler broadening are presented numerically and optimization excitation conditions are identified. For the co-propagating excitation lasers, extra-narrow laser bandwidth (at the magnitude of 0.1 GHz) and atomic Doppler broadening (smaller than 0.3 GHz) is required. A new time-delayed configuration is proposed to implement multiple counter-propagating laser exposures for high target isotope abundance at the larger atomic Doppler broadening.

Bed morphology and turbulent anisotropy in a curved flexible bed channel

ABSTRACT The present study analyzed the curved channel with the flexible bed for its morphology and structural turbulent anisotropy. The result of the bed morphology shows that erosion on the outer bend of the channel was prominent, and sediment deposition was pronounced in the inner bed of the channel. Erosion and sediment deposition rates increase with the flow rate and time. The analysis presents an anisotropy invariant (Lumley triangle) for flow turbulence at different channel sections. At the apex of the curved channel, a pancaked structure with a higher magnitude confirms the presence of helical flow in the apex region. The presence of a cigar-shaped structure with a high magnitude on the right side of the bend compared to the left side may be attributed to higher turbulence on the right side (outer bend), which may result in erosion at the outer bend and lesser turbulence on the left side (inner bank) may result in sediment deposition.

Experimental and numerical investigations of high-strength cold-formed steel multi-limb built-up section columns

This paper investigates the buckling behaviour and load-carrying capacity of G550 high-strength cold-formed steel multi-limb built-up section columns under axial compression. Each built-up section consists of multiple lipped and unlipped channel sections connected by self-tapping screws. The C3U1 section is formed by three C-sections (i.e. lipped channel section) and one U-section (i.e. unlipped channel section), while the C2U2 section is formed by two C-sections and two U-sections. The experimental programme involved tensile coupon tests, measurements of initial geometrical imperfection, and column tests on ten C3U1 and ten C2U2 multi-limb built-up section columns. The numerical modelling programme was then performed, with the nonlinear finite element models created and validated against the experimental results. The applicability of the codified Effective Width Method and Direct Strength Method for predicting the strengths of G550 high-strength cold-formed steel multi-limb built-up section columns, as specified in the American Specification and Australian Standard, was then evaluated. The evaluation results showed that the codified Effective Width Method led to rather conservative and less accurate failure load predictions for G550 high-strength cold-formed steel multi-limb built-up section columns, while the codified Direct Strength Method provided accurate and consistent failure load predictions and thus applicable to the design of G550 high-strength cold-formed steel multi-limb built-up section columns. Concerning the lack of design guidelines specifically for multi-limb built-up sections, a modified Direct Strength Method was thus proposed as an alternative design method and shown to provide accurate failure load predictions.

Buckling strengths of cold-formed built-up cruciform section columns under axial compression

This paper describes experiments addressing the buckling and collapse behaviour of cold-formed stainless steel cruciform section columns. Doubly symmetrical flanged cruciform section columns were built using six individual press-braked plain channels made of austenitic grade EN 1.4307 assembled back-to-back. Three different column lengths were tested – namely, short (600 mm), intermediate (1200 mm) and long (2400 mm) lengths, and two channel geometries were used in all tests – with cross-section depths of 200 mm and 100 mm. Tests were carried out under pure axial compression and with fixed end support conditions. Tests were repeated two times for each length. It was observed that the buckling patterns were affected both by the global slenderness and by the spacing between the fasteners. Stocky columns experienced local buckling of the individual channel sections. The plastic failure mechanism was dependent on the fasteners spacing. Intermediate slenderness columns were characterised by interaction between global torsional buckling and local buckling whereas more slender columns failed predominantly through torsional buckling. For the latter, the spacing between the fasteners had a minor influence on the ultimate capacity.

Numerical investigation of cold formed steel sleeve connection for channel sections subjected to combined bending and shear

This study focuses on the behaviour of the sleeve connection to ensure proper distribution of moment at the location of discontinuity between two channel sections subjected to combined bending and shear using finite element (FE) modelling. The FE model was validated with the experimental data from previous authors studies and was found. A total of 180 simulations were carried out as part of the parametric study, by varying the depth, thickness, length of sleeve connector, length of the test specimen, and bolt configuration. Two modes of failure were identified based on sleeve length (Ls) and combination of sleeve length and channel thicknesses. The Ls/D ratios were suggested to achieve a similar strength and stiffness of sleeve specimen when compared with control specimen. The influence of sleeve length on the ultimate moment resistance was studied for combination of sleeve length and channel thickness. The increase in the channel thickness from 2 mm to 2.5 mm led to as significant increase in the ultimate moment resistance. An equation was proposed to calculate the nominal moment capacity of sleeved specimens and reliability analysis of this equation was carried out. The conservativeness of the proposed design procedure was checked by comparing it with the AISI S100 [1] interaction curve.

Tidal, density and wind-driven subtidal circulation in a hypersaline coastal lagoon

Subtidal circulation patterns were studied along an elongated hypersaline system. Month-long data were collected using three acoustic Doppler current profilers. These profilers were moored at depths of around 15 m in three locations: 10 km inland from the mouth of the lagoon, within the central region, and near the head of the lagoon. The variability of temporal and spatial subtidal circulation was explored using Empirical Orthogonal Functions analysis, which explained 93% of the variability through the first three modes. The first mode was influenced by tidal advection, resulting in a tidally-driven residual circulation for elongated channels, with inflows occurring over the shoals and outflows in the deeper channel sections. During the neap-tide cycle, inverse density gradients became relevant, coinciding with the peaks of mode 2 amplitude that accounted for 15% of the total variability. The gravitational circulation exhibited its highest intensity near the head, characterized by a vertically sheared flow with inflow occurring near the surface and outflow underneath. Predominant onshore wind stresses had a significant impact on the subtidal circulation and displayed a strong correlation with the mode 3 amplitude, explaining 11% of the total variability. Wind-driven circulation exhibited a vertically sheared profile, characterized by downwind near-surface flow and upwind flow underneath in the lagoon mouth and head, and a homogeneous downwind profile in the central part of the lagoon. It is concluded that tidal stresses governed the subtidal circulation, followed by density gradients, and wind stresses modified spatial circulation patterns induced by tides and density gradients. This research provides new observational evidence on tidal residuals in long channels and contributes to the understanding of the interactions between the main subtidal circulation drivers in hypersaline lagoons.

Energy Characteristics in the Flow Channel of the Shaft-Type Tubular Pumping Station Considering Tides

The shaft-type tubular pumping station has the remarkable characteristics of a large flow rate and high efficiency. It can realize the functions of irrigation, pumping, and drainage through pumping and generating conditions considering tides. Moreover, it is widely used in the plain area of eastern China and the tidal area along the marine region. Due to the different topological features of the airfoil of the impeller, the energy evolution characteristics of the shaft-type tubular pumping station during pumping and generating conditions remain unclear. The entropy generation theory was introduced to numerically simulate the flow pattern and energy characteristics in the shaft-type channel, impeller, and straight channel in operation conditions. The results show that the flow pattern is stable when the shaft-type channel and the straight-type channel are used as the inlet channel under pumping and generating conditions, and a low-pressure region occurs in the contraction section of the shaft-type channel. The velocity of sections of the inlet and outlet and the middle section of the impeller in the generating condition is larger than that in the pumping condition. In addition, the difference in the static pressure on the blade surface nearby the hub is large. With a change in the position of the wingspan, the difference gradually decreases from the small flow condition to the large flow condition. There is a high-entropy production rate zone in the channel contraction section and the shaft-type wall surface of the shaft-type flow channel. When the straight-type channel is used as the outlet flow channel, a high-entropy production region appears near the inlet water surface. In the pumping condition, a high-entropy production area is found at the inlet of the impeller, the blade groove channel, and the inlet of the guide vane. In the generating condition, a high-entropy production area is found at the out-of-impeller outlet, the blade groove channel, and the outlet of the guide vane. These research achievements have some reference value for the design of the shaft-type tubular pumping station considering tides and the study of hydraulic performance, along with the energy characteristics of the channels.

Two-stage channels can enhance local biodiversity in agricultural landscapes

Field drainage causes habitat loss, alters natural flow regimes, and impairs water quality. Still, drainage ditches often are last remnants of aquatic and wetland habitats in agricultural landscapes and as such, can be important for local biodiversity. Two-stage channels are considered as a greener choice for conventional ditches, as they are constructed to mimic the structure of natural lowland streams providing a channel for drainage water and mechanisms to decrease diffuse loading. Two-stage channels could also benefit local biodiversity and ecosystem functions, but existing information on their ecological benefits is scarce and incomplete. We collected environmental and biological data from six agricultural stream systems in Finland each with consequent sections of a conventional ditch and a two-stage channel to study the potential of two-stage channels to enhance aquatic and riparian biodiversity and ecological functions. Biological data included samples of stream invertebrates, diatoms and plants and riparian beetles and plants. Overall, both section types were highly dominated by few core taxa for most of the studied organism groups. Riparian plant and invertebrate communities seemed to benefit from the two-stage channel structure with adjacent floodplains and drier ditch banks. In addition, two-stage channel sections had higher aquatic plant diversity, algal productivity, and decomposition rate, but lower stream invertebrate and diatom diversity. Two-stage channel construction did not diversify the structure of stream channels which is likely one explanation for the lack of positive effects on benthic diversity. However, both section types harbored unique taxa found only in one of the two types in all studied organism groups resulting in higher local gamma diversity. Thus, two-stage channels enhanced local biodiversity in agricultural landscapes. Improvements especially in aquatic biodiversity might be achieved by increasing the heterogeneity of in-stream habitat structure and with further efforts to decrease nutrient and sediment loads.

Numerical study on the flow and heat transfer performance of SCO2/molten salt in Z-type printed circuit heat exchangers

The utilization of a PCHE in conjunction with a SCO2 Brayton cycle and molten salt thermal storage demonstrates a high efficiency. Investigating the flow and heat transfer characteristics of SCO2 and molten salt within a Z-type PCHE is essential. However, this particular aspect has not been explored by previous researches. This study employs a Z-type PCHE to analyze the heat transfer and flow characteristics of SCO2 and molten salt under different inlet temperatures, mass fluxes, and outlet pressures. Furthermore, the heat transfer efficiency of a Z-type PCHE is evaluated and compared to that of a conventional straight-type PCHE. The results indicate that the flow pattern of SCO2 exhibits periodic behavior due to the periodic bending structure of Z-type PCHE, while the flow of molten salt is minimally affected. Furthermore, different SCO2 conditions lead to divergent patterns in flow and heat transfer efficiency compared to molten salt. Z-type channels help alleviate the decline in heat transfer that typically happens in the inlet section of straight channels. Nu for a dual working fluid in a straight-type PCHE is only 1.1 times greater than that of a single working fluid. In Z-type PCHE configuration, the ratio of the dual working fluid to the single working fluid Nu is 1.4. The sensitivity of SCO2/molten salt dual working fluid to the heat exchanger structure is significant, with Z-type PCHE demonstrating superior heat transfer capabilities. The results outlined in this study offer the prospect of improving the design and deployment of Z-type PCHE in molten salt energy storage systems that operate within SCO2 Brayton cycle.

A numerical study on a novel demountable cold-formed steel composite beam with profiled steel sheeting

Cold-formed steel composite beams are known for their unique advantages, like being lightweight and ease of installation. The use of profiled steel sheeting in cold-formed composite beams reduces construction time and costs by acting as a permanent formwork in the composite beams. The current study presents a 3D finite element model of cold-formed steel composite beam specimens comprising a cold-formed double-lipped channel section, profiled steel sheeting, concrete slab, and bolted shear connector. Employing bolted shear connectors, structural components can be deconstructed and replaced after their service life expires or if they are damaged. The characteristics of the materials obtained from an experimental program were assigned to the finite element model. Geometric characteristics, material nonlinearities, and loading procedures were attentively simulated, and a dynamic explicit procedure was employed for the numerical analyses. A comparison of the results obtained from the finite element models and the available experimental results validated the precision of the models. Then, numerical studies were conducted to investigate the effects of various parameters, including compressive strength of concrete, thickness of concrete slab, height and grade of cold-formed steel section, thickness of profiled steel sheeting, number and diameter of shear connectors, on the behavior of the composite beam. The results showed that the height and grade of the cold-formed steel section and compressive strength and thickness of the concrete slab have a significant effect on increasing the capacity of the composite beam.

Computation of shear buckling stress of thin-walled sections using constrained spline finite strip method

The direct strength method (DSM) design for shear incorporates the elastic shear buckling stress of the cross-section to evaluate the ultimate shear capacity of thin-walled members. To calculate the shear buckling stress using the finite strip method (FSM), the shape functions for longitudinal interpolation are an issue, while capturing the phase change of displacements along the plate strip. This paper presents a novel constrained spline finite strip method (cSFSM) that eliminates the phase change of displacements. Although constrained buckling analysis for shear stresses is reported in the literature based on FSM, the present study is unique in determining pure buckling stresses for simply supported members subjected to shear edge stress. The formulation also provides an accurate representation of the variation of shear stress along the longitudinal and transverse directions of the plate. Hence, coarse discretization of cross-section is sufficient to obtain the accurate shear buckling stress. The formulation is demonstrated on channel sections with lips subjected to shear edge stresses, and elastic buckling stresses are compared with results available in the literature and also with the finite element method (FEM). Illustrative examples are presented on lipped channel members with different end conditions and longitudinal stiffeners on flanges and webs, to calculate the pure elastic buckling stresses under shear edge stresses. The calculation of buckling stresses for members subjected to longitudinal variation of shear and flexural stresses is also presented to calculate coupled and uncoupled buckling stresses.