LOAD-BEARING CAPACITY ANALYSIS FOR STRUCTURAL COLD-FORMED MEMBERS SUBJECTED TO CENTRAL COMPRESSION

The main purpose of the research was a deep analysis and verification of the consistency and completeness of the design code relating to calculation of load-bearing structural members made from cold-formed profiles. The work has been done in close connection with the implementation on the territory of Ukraine of this design code. The article has discussed and investigated the load-bearing capacity of structural members made of cold-formed profiles subjected to the action of central compression. A system of constraints has been presented, in which the strength and buckling constraints for thin-walled cold-formed column members are formulated, taking into account their possible post-buckling behavior, namely, the ability to resist external loads and effects even after the occurrence of the local buckling and/or distortional buckling phenomenon. The performed load-bearing capacity investigation has shown that for the mono-symmetric cold-formed profiles, the flexural-torsional buckling is determinative. For such cold-formed profiles, the effect of the overall dimensions ratio (flange width to web height) on the load-bearing capacity of cold-formed profiles has been estimated. It has been shown that for the same cross-sectional area the load-bearing capacity of a column structural member made from cold-formed profile and subjected to axial compression can be significantly increased by assigning an optimal ratio of flange width to web height. The paper also has presented the results of the load-bearing capacities for the structural cold-formed members subjected to central compression, calculated according to the design standard DSTU-N B EN 1993-1-3: 2012 and according to the design code DBN V.2.6-198: 2014. It has been shown that in some cases the difference in the assessment of the load-bearing capacity for such structural cold-formed members reached 25%. A comparison of the load-bearing capacities for the action of the central compression has been made for structural cold-formed members made from a C-shaped profile and with a composite section of two C-shaped profiles. It has been shown that the load-bearing capacity of the structural cold-formed member of the composite section exceeds the load-bearing capacity of the member with single C-shaped profile by more than 3 times, while cross-section areas of these structural members differ only doubly.

Composite plate analysis made in an unsymmetric configuartion

The work presents a thin-walled plate element with the central rectangular cut-out which can be use as an elastic or load-bearing element. Plates were made of carbon epoxy laminate and subjected to uniform compression. Plates were simply supported on shorter edges, and loaded axial load. The study included analysis of the critical and weakly post-critical behavior using experimental and numerical methods. Numerical analysis was performed with using linear analysis of eigenvalue problem to determination critical loads. The second step connected nonlinear analysis of structure with initiated geometrically imperfection corresponding to the flexural-torsional buckling mode of the plate. To the numerical calculations the commercial ABAQUS program was used.

Fire buckling curves for torsionally sensitive steel members subjected to axial compression

PurposeBuckling should be carefully considered in steel assemblies with members subjected to compressive stresses, such as bracing systems and truss structures, in which angles and built-up steel sections are widely employed. These type of steel members are affected by torsional and flexural-torsional buckling, but the European (EN 1993-1-2) and the American (AISC 360-16) design norms do not explicitly treat these phenomena in fire situation. In this work, improved buckling curves based on the EN 1993-1-2 were extended by exploiting a previous work of the authors. Moreover, new buckling curves of AISC 360-16 were proposed.Design/methodology/approachThe buckling curves provided in the norms and the proposed ones were compared with the results of numerical investigation. Compressed angles, tee and cruciform steel members at elevated temperature were studied. More than 41,000 GMNIA analyses were performed on profiles with different lengths with sections of class 1 to 3, and they were subjected to five uniform temperature distributions (400–800 C) and with three steel grades (S235, S275, S355).FindingsIt was observed that the actual buckling curves provide unconservative or overconservative predictions for various range of slenderness of practical interest. The proposed curves allow for safer and more accurate predictions, as confirmed by statistical investigation.Originality/valueThis paper provides new design buckling curves for torsional and flexural-torsional buckling at elevated temperature since there is a lack of studies in the field and the design standards do not appropriately consider these phenomena.

Nonlocal Analysis of the Flexural–Torsional Stability for FG Tapered Thin-Walled Beam-Columns

This paper addresses the flexural–torsional stability of functionally graded (FG) nonlocal thin-walled beam-columns with a tapered I-section. The material composition is assumed to vary continuously in the longitudinal direction based on a power-law distribution. Possible small-scale effects are included within the formulation according to the Eringen nonlocal elasticity assumptions. The stability equations of the problem and the associated boundary conditions are derived based on the Vlasov thin-walled beam theory and energy method, accounting for the coupled interaction between axial and bending forces. The coupled equilibrium equations are solved numerically by means of the differential quadrature method (DQM) to determine the flexural–torsional buckling loads associated to the selected structural system. A parametric study is performed to check for the influence of some meaningful input parameters, such as the power-law index, the nonlocal parameter, the axial load eccentricity, the mode number and the tapering ratio, on the flexural–torsional buckling load of tapered thin-walled FG nanobeam-columns, whose results could be used as valid benchmarks for further computational validations of similar nanosystems.