Load capacity of cold-formed column members of lipped channel cross-section with perforations subjected to compression loading – results of more detailed parametric study and proposals of design code modifications

In this paper, a numerical investigation on the global buckling capacity of the axially compressed steel columns with hot-rolled I cross-section at elevated temperatures is presented. Geometrically and materially non-linear finite element model and the ABAQUS software were used to determine the buckling resistance. The numerical ABAQUS model was validated using experimental results available in the literature, and then the validated numerical model was used to generate a database of load-carrying capacity. The parametric study covered three different cross-section classes (class 1, 2 and 3), ten different non-dimensional slenderness ̄λ = 0.5, 0.6, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, 2.0), three different temperatures (400°C, 500°C, 600°C), and two stress-strain constitutive relations including (the nonlinear material model adopted in the European guidance for structural fire design EN1993-1-2, and a Bilinear material model), with and without residual stress. The influence of the model parameters on the load capacity of steel columns at elevated temperatures was evaluated. The results of the parametric study were compared with the results of the simplified calculation model presented in EN1993-1-2.

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Numerical and Theoretical Study of Performance and Mechanical Behavior of PEM-FC Using Innovative Channel Geometrical Configurations

Applied Sciences ◽

10.3390/app11125597 ◽

2021 ◽

Vol 11 (12) ◽

pp. 5597

Author(s):

Hussein A. Z. AL-bonsrulah ◽

Mohammed J. Alshukri ◽

Ammar I. Alsabery ◽

Ishak Hashim

Keyword(s):

Fuel Cell ◽

Cross Section ◽

Rectangular Channel ◽

Compressive Load ◽

Proton Exchange ◽

Channel Cross Section ◽

Channel Height ◽

Cross Sectional ◽

Triangular Channel ◽

Higher Power

Proton exchange membrane fuel cell (PEM-FC) aggregation pressure causes extensive strains in cell segments. The compression of each segment takes place through the cell modeling method. In addition, a very heterogeneous compressive load is produced because of the recurrent channel rib design of the dipole plates, so that while high strains are provided below the rib, the domain continues in its initial uncompressed case under the ducts approximate to it. This leads to significant spatial variations in thermal and electrical connections and contact resistances (both in rib–GDL and membrane–GDL interfaces). Variations in heat, charge, and mass transfer rates within the GDL can affect the performance of the fuel cell (FC) and its lifetime. In this paper, two scenarios are considered to verify the performance and lifetime of the PEM-FC using different innovative channel geometries. The first scenario is conducted by adopting a constant channel height (H = 1 mm) for all the differently shaped channels studied. In contrast, the second scenario is conducted by taking a constant channel cross-sectional area (A = 1 mm2) for all the studied channels. Therefore, a computational fluid dynamics model (CFD) for a PEM fuel cell is formed through the assembly of FC to simulate the pressure variations inside it. The simulation results showed that a triangular cross-section channel provided the uniformity of the pressure distribution, with lower deformations and lower mechanical stresses. The analysis helped gain insights into the physical mechanisms that lead to the FC’s durability and identify important parameters under different conditions. The model shows that it can assume the intracellular pressure configuration toward durability and appearance containing limited experimental data. The results also proved that the better cell voltage occurs in the case of the rectangular channel cross-section, and therefore, higher power from the FC, although its durability is much lower compared to the durability of the triangular channel. The results also showed that the rectangular channel cross-section gave higher cell voltages, and therefore, higher power (0.63 W) from the fuel cell, although its durability is much lower compared to the durability of the triangular channel. Therefore, the triangular channel gives better performance compared to other innovative channels.

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Flexural bearing capacity and failure mechanism of CFRP-aluminum laminate beam with double-channel cross-section

Science and Engineering of Composite Materials ◽

10.1515/secm-2021-0012 ◽

2021 ◽

Vol 28 (1) ◽

pp. 139-152

Author(s):

Teng Huang ◽

Dongdong Zhang ◽

Yaxin Huang ◽

Chengfei Fan ◽

Yuan Lin ◽

...

Keyword(s):

Carbon Fiber ◽

Bearing Capacity ◽

Failure Mechanism ◽

Cross Section ◽

Failure Criterion ◽

Failure Modes ◽

Channel Cross Section ◽

Fiber Layer ◽

Flexural Bearing Capacity ◽

Double Channel

Abstract In this study, the flexural bearing capacity and failure mechanism of carbon fiber-reinforced aluminum laminate (CARALL) beams with a double-channel cross-section and a 3/2 laminated configuration were experimentally and numerically studied. Two types of specimens using different carbon fiber layup configurations ([0°/90°/0°]3 and [45°/0°/−45°]3) were fabricated using the pressure molding thermal curing forming process. The double-channel CARALL beams were subjected to static three-point bending tests to determine their failure behaviors in terms of ultimate bearing capacity and failure modes. Owing to the shortcomings of the two-dimensional Hashin failure criterion, the user-defined FORTRAN subroutine VUMAT suitable for the ABAQUS/Explicit solver and an analysis algorithm were established to obtain a progressive damage prediction of the CFRP layer using the three-dimensional Hashin failure criterion. Various failure behaviors and mechanisms of the CARALL beams were numerically analyzed. The results indicated that the numerical simulation was consistent with the experimental results for the ultimate bearing capacity and final failure modes, and the failure process of the double-channel CARALL beams could be revealed. The ultimate failure modes of both types of double-channel CARALL beams were local buckling deformation at the intersection of the upper flange and web near the concentrated loading position, which was mainly caused by the delamination failure among different unidirectional plates, tension and compression failure of the matrix, and shear failure of the fiber layers. The ability of each fiber layer to resist damage decreased in the order of 90° fiber layer > 0° fiber layer > 45° fiber layer. Thus, it is suggested that 90°, 0°, and 45° fiber layers should be stacked for double-channel CARALL beams.

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Fractal-induced 2D flexible net undulation

Scientific Reports ◽

10.1038/s41598-021-86418-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Michael Joon Seng Goh ◽

Yeong Shiong Chiew ◽

Ji Jinn Foo

Keyword(s):

3D Reconstruction ◽

Cross Section ◽

Channel Cross Section ◽

Time Varying ◽

Blockage Ratio ◽

Transient Time ◽

Cross Sectional ◽

Velocity Fluctuations ◽

Square Grid ◽

Multilength Scale

AbstractA net immersed in fractal-induced turbulence exhibit a transient time-varying deformation. The anisotropic, inhomogeneous square fractal grid (SFG) generated flow interacts with the flexible net to manifest as visible cross-sectional undulations. We hypothesize that the net’s response may provide a surrogate in expressing local turbulent strength. This is analysed as root-mean-squared velocity fluctuations in the net, displaying intensity patterns dependent on the grid conformation and grid-net separation. The net’s fluctuation strength is found to increase closer to the turbulator with higher thickness ratio while presenting stronger fluctuations compared to regular-square-grid (RSG) of equivalent blockage-ratio, σ. Our findings demonstrate a novel application where 3D-reconstruction of submerged nets is used to experimentally contrast the turbulence generated by RSG and multilength scale SFGs across the channel cross-section. The net’s response shows the unique turbulence developed from SFGs can induce 9 × higher average excitation to a net when compared against RSG of similar σ.

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Closure to “Improved Channel Cross Section with Two-Segment Parabolic Sides and Horizontal Bottom” by Said M. Easa

Journal of Irrigation and Drainage Engineering ◽

10.1061/(asce)ir.1943-4774.0000246 ◽

2010 ◽

Vol 136 (9) ◽

pp. 667-670 ◽

Cited By ~ 2

Author(s):

Said M. Easa

Keyword(s):

Cross Section ◽

Channel Cross Section ◽

Horizontal Bottom

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Long waves in a straight channel with non-uniform cross-section

Journal of Fluid Mechanics ◽

10.1017/jfm.2015.147 ◽

2015 ◽

Vol 770 ◽

pp. 156-188 ◽

Cited By ~ 5

Author(s):

Patricio Winckler ◽

Philip L.-F. Liu

Keyword(s):

Boundary Layer ◽

Wave Propagation ◽

Cross Section ◽

Three Dimensional ◽

Channel Cross Section ◽

Cross Sectional ◽

New Model ◽

One Dimensional ◽

Uniform Channel ◽

The Cross

A cross-sectionally averaged one-dimensional long-wave model is developed. Three-dimensional equations of motion for inviscid and incompressible fluid are first integrated over a channel cross-section. To express the resulting one-dimensional equations in terms of the cross-sectional-averaged longitudinal velocity and spanwise-averaged free-surface elevation, the characteristic depth and width of the channel cross-section are assumed to be smaller than the typical wavelength, resulting in Boussinesq-type equations. Viscous effects are also considered. The new model is, therefore, adequate for describing weakly nonlinear and weakly dispersive wave propagation along a non-uniform channel with arbitrary cross-section. More specifically, the new model has the following new properties: (i) the arbitrary channel cross-section can be asymmetric with respect to the direction of wave propagation, (ii) the channel cross-section can change appreciably within a wavelength, (iii) the effects of viscosity inside the bottom boundary layer can be considered, and (iv) the three-dimensional flow features can be recovered from the perturbation solutions. Analytical and numerical examples for uniform channels, channels where the cross-sectional geometry changes slowly and channels where the depth and width variation is appreciable within the wavelength scale are discussed to illustrate the validity and capability of the present model. With the consideration of viscous boundary layer effects, the present theory agrees reasonably well with experimental results presented by Chang et al. (J. Fluid Mech., vol. 95, 1979, pp. 401–414) for converging/diverging channels and those of Liu et al. (Coast. Engng, vol. 53, 2006, pp. 181–190) for a uniform channel with a sloping beach. The numerical results for a solitary wave propagating in a channel where the width variation is appreciable within a wavelength are discussed.

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