Recent advances in flue gas desulfurization gypsum processes and applications - A review.

Face-to-face built-up cold-formed steel channel sections are becoming increasingly popular for column members in cold-formed steel structures; its applications include cold-formed steel trusses, space frames and portal frames. In such an arrangement, the independent buckling of the members is resisted by intermediate fasteners. In the literature, no research is available for such face-to-face built-up cold-formed steel columns. The issue is addressed herein. This paper presents the results of 36 experimental tests, conducted on face-to-face built-up cold-formed steel channel-sections covering a wide range of slenderness from stub to slender columns. A nonlinear finite element model is then described that shows good agreement with the experimental results. The finite element model includes material non-linearity, initial imperfections and modelling of intermediate fasteners. Both finite element and experimental results are compared against the design strengths calculated in accordance with the American Iron and Steel Institute (AISI), Australian and New Zealand Standards (AS/NZS) and Eurocode (EN 1993-1-3). The verified finite element model is used for the purposes of a parametric study comprising 90 models. The effect of fastener spacing on the axial strength was investigated. From the results of experiments and finite element investigations, it is shown that the design in accordance with the AISI & AS/NZS and Eurocode (EN 1993-1-3) is generally conservative by around 15%, however, AISI & AS/NZS and Eurocode (EN 1993-1-3) can be un-conservative by 8% on average for face-to-face built-up columns failed through local buckling.

Experimental and numerical investigation into the behaviour of face-to-face built-up cold-formed steel channel sections under compression

A combined CP theory and TCD for predicting fatigue lifetime in single-crystal superalloy plates with film cooling holes

This paper reports on experiments addressing the buckling and collapse behavior of common built-up cold-formed steel (CFS) columns. The built-up column consists of two individual CFS lipped channels placed back-to-back and connected at the web using two self-drilling screw fasteners at specified spacing along the column length. The experiments aim to quantify ultimate strength, composite action, member end fixity, and buckling interactions and collapse behavior for common built-up CFS members. The testing also explicitly explores the effect of sheathing, as typically employed in cold-formed steel framing, on the response. The experiments provide benchmarks for design that include specific considerations for both thin-walled buckling and fastener behavior. A total of 17 monotonic, concentric compression tests with a column length of 1.83 m (6 ft) are completed with an array of position transducers monitoring displacements at key locations. Tests are conducted with the built-up member seated in CFS tracks. Results indicate a large range of deformation behavior, with local-global interaction and flexural-torsional modes common in many of the unsheathed specimens. Columns sheathed with oriented strand board on both flanges behave as braced against global buckling in the plane of the wall, and local buckling induced failures prevail. The end condition for the tested built-up members seated in track is determined to be semi-rigid, but generally closer to fixed than pinned.

Experimental study on the composite action in sheathed and bare built-up cold-formed steel columns

This paper presents a numerical investigation and design of cold-formed steel built-up closed section columns with web stiffeners A finite element model (FEM), considering the initial geometric imperfections and nonlinear material properties, was developed to simulate the structural behaviour of fixed-ended built-up closed section compression members The comparison between the numerical results and the available test results show that this FEM can provide good predictions for both the ultimate strength and the failure modes of the test specimens The verified FEM was used to conduct an extensive parametric study for the investigation on the structural behaviour of cold-formed steel built-up closed sections with web stiffeners The parametric study was designed to investigate the effect of web stiffeners as well as to evaluate the current design method The column strengths obtained from the finite element analysis and the test results were compared with the design strengths calculated using the direct strength method in the North American Specification and the Australian/New Zealand Standard for cold-formed steel structures Design curves modified from the current direct strength method are proposed for flexural, local and distortional buckling The reliability analysis was used to assess the current design rules and the modified design curves It is shown that the modified direct strength method is generally conservative and reliable for the design of cold-formed steel built-up closed section compression members

Finite element analysis and design of cold-formed steel built-up closed section columns with web stiffeners

Ductile fracture of Q460 steel: Effects of stress triaxiality and Lode angle

Compression test and analysis of multi-limbs built-up cold-formed steel stub columns

Thirty specimens of built-up closed box sections consisting of two cold-formed steel channels of various cross sections (B92 and B143), lengths (3000, 1500, 450, and 270 mm), and thicknesses (1.2 and 1.5 mm) were tested subject to concentric and eccentric axial compression. Failure modes were analyzed and load vs. displacement curves were obtained. The test results indicate that the failure modes of long and medium columns subject to concentric axial compression are flexural buckling about the weak axis, whereas that of the short column is excessive local buckling; specimens subject to eccentric axial compression about the strong and weak axes exhibited flexural-torsional buckling and flexural buckling, respectively. Finite element (FE) models were established and verified. Detailed parameter studies were performed to evaluate the accuracy of code equations for a wide range of parameters. The FE analysis results indicate that the concentric axial compression strength of the columns decreased with an increase in the slenderness ratio of column or the web height-to-thickness ratio; increasing the flange width can significantly increase the stability and strength of the column; the eccentric axial compression strength of the column about the weak axis decreased faster than that about the strong axis. Finally, the effectiveness of the design methods, i.e., the effective ratio of width-to-thickness method in the Chinese code, effective width method, direct strength method, and load and resistance factor design in North American specifications to predict the strength of this type of built-up column is evaluated. For the B92 series columns and B143 series column with slenderness ratio of the column greater than 92, it is conservative to use design methods to calculate the concentric axial compression strength of the column. Additionally, it is conservative to use the design methods to calculate the eccentric axial compression strength of the columns.

Compressive behavior of built-up closed box section columns consisting of two cold-formed steel channels

Research on axial compression behavior of cold-formed triple-lambs built-up open T-section columns

In order to improve lateral stiffness and shear strength of cold-formed steel (CFS) framing wall, an innovative CFS wall with infilled lightweight flue gas desulfurization (FGD) gypsum is presented in this paper. For this purpose, six full-scale specimens were tested under cyclic lateral loads. The density and compressive strength of the infilled gypsum were varied to investigate their impacts on lateral stiffness and shear strength of the walls. The failure modes, load-displacement responses, deformability, and energy absorption capacity of the specimens were also investigated. Test observations showed that the infilled gypsum behaved as a diagonal bracing along with wall frames to resist shearing forces. In addition, the failure modes of the infilled walls were characterized by bond-slip cracks between infilled gypsum and wall frames, as well as compressive failure at the corners of gypsum pieces. The peak loads of the infilled specimens were improved by 1.72–2.54 times compared with the unfilled. Besides, the improvement in shear capacity and lateral stiffness of the infilled walls were obtained by increasing compressive strength of the infilled gypsum. When filling identical gypsum into the walls, one with the bigger stub spacing and the stronger sheathing material had the greater lateral stiffness and shear capacity. In addition, a method for determining the resistance factor γR of the infilled specimens was proposed in the paper, which can be used for seismic design.

Tianhua Zhou

Papers

Ductile fracture of Q460 steel: Effects of stress triaxiality and Lode angle

Compression test and analysis of multi-limbs built-up cold-formed steel stub columns

Compressive behavior of built-up closed box section columns consisting of two cold-formed steel channels

Research on axial compression behavior of cold-formed triple-lambs built-up open T-section columns

Cold-formed steel framing walls with infilled lightweight FGD gypsum Part I: Cyclic loading tests