IntroductionGroup of authors made series of experiments on cold formed steel sections where is shown that geometrical imperfections significantly effect on bearing capacity of the elements. Same conclusion has been made for carbon steel elements. We have to consider those factors during designing cold formed steel elements. Having that on mind we have made numerical and experimental analysis of cold-formed centrally compressed elements aspiring to show more accurate method of calculation.Experiments have been made on five series, each containing six samples with different slenderness. Cold-formed steel (CFS) members are created by the working of sheet steel using stamping, rolling, or presses to deform the sheet into a usable product, at room temperature. This production technology effect on mechanical characteristics of the elements. We have presented the results of the effect of production technology on mechanical characteristics of rolling steel mean values in the summary diagram. In corners, changes are most pronounced and yield points are between 560-606 MPa, and on the straight parts of the profile the same value is 302 -320 MPa.The strength of elements used for design is usually governed by buckling. Cold-formed steel sections tend to be more sensitive to local buckling effects than typical hot rolled sections. Cross sections are generally stiffened to improve resistance to local buckling.Results gain from experiments and with numerical analysis are compared to European buckling curves showing that they are to conservative for cold formed steel sections.
The use of lightweight concrete in timber-concrete composite structures for the purposes of reconstruction, upgrading, and strengthening has increasing application potential. The correct combination of mechanical properties of both materials can preserve the beneficial aspects of timber in tension and concrete in compression, while reducing the weight of the structure. This paper experimentally evaluated the slip modulus of screw connectors as one of the key issues in the structural design of these types of composite structures. The results of four groups of push-out tests, which were performed on composite samples, are presented. All of the samples had identical cross sections, but each group was made with a different lightweight concrete density class according to Eurocode 2. The obtained results were compared with the values recommended by Eurocode 5. The analysis showed that the code recommendations yielded slip modulus values that were considerably higher than the ones obtained experimentally, which could lead to unsafe timber and lightweight concrete structures.
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