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Plastic mechanisms for thin-walled cold-formed steel members in eccentric compression

Ungureanu V., Kotełko M., Grudziecki J.

Acta Mechanica et Automatica

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2016

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Vol. 10, no. 1

33--37

EN

The Eurocode 3 concerning thin-walled steel members divides members subjected to compression into four classes, considering their ductility. The representatives of the class C4 are short bars, for which the load-capacity corresponds to the maximum compression stresses less than the yield stress. There are bars prone to local buckling in the elastic range and they do not have a real post-elastic capacity. The failure at ultimate stage of such members, either in compression or bending, always occurs by forming a local plastic mechanism. This fact suggests the possibility to use the local plastic mechanism to characterise the ultimate strength of such members. The present paper is based on previous studies and some latest investigations of the authors, as well as the literature collected data. It represents an attempt to study the plastic mechanisms for members in eccentric compression about minor axis and the evolution of plastic mechanisms, considering several types of lipped channel sections.

2

Influence of corrugation depth on lateral stability of cold-formed steel beams of corrugated webs

Ungureanu V., Dubina D.

Acta Mechanica et Automatica

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2016

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Vol. 10, no. 2

104--111

EN

The beams of thin corrugated web afford a significant weight reduction compared with hot-rolled or welded ones. In the initial solutions, the flanges are made of flat plates, welded to the sinusoidal web sheet, requiring a specific welding technology. A new solution is proposed by the authors, in which the beam is composed by a web of trapezoidal cold-formed steel sheet and flanges of back-to-back lipped channel sections. For connecting flanges to the web self-drilling screws are used. The paper summarizes the experimental and numerical investigations carried out at the CEMSIG Research Centre (www.ct.upt.ro/centre/cemsig/) of the Politehnica University of Timisoara and, at the end, presents the influence of corrugation depth of web on the lateral stability of the beams.

3

Koiter asymptotic analysis of thin-walled cold-formed steel members

Ungureanu V., Dubina D., Crisan A., Madeo A., Zagari G., Zucco G., Zinno R.

Acta Mechanica et Automatica

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2015

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Vol. 9, no. 4

245--251

EN

An imperfection sensitivity analysis of cold-formed steel members in compression is presented. The analysis is based on Koiter’s approach and Monte Carlo simulation. If the modes interaction is correctly accounted, than the limit load and the erosion of critical buckling load can be easily evaluated. Thousands of imperfection can be analysed with very low computational cost and an effective statistical evaluation of limit performance can be carried out. The analysis is done on pallet rack uprights in compression, based on an intensive experimental study carried out at the Politehnica University of Timisoara.

4

Sensitivity to Imperfections of Perforated Pallet Rack Sections

Ungureanu V., Dubina D.

Mechanics and Mechanical Engineering

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2013

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Vol. 17, nr 2

207--220

EN

The paper analyses the influence of imperfections on the behaviour of perforated pallet rack members in compression using non-linear FE simulations. The effect of imperfections, perforations and buckling modes, reduces significantly the capacity of perforated members in compression, especially in the coupling range due to interaction. A sensitivity analysis done using calibrated and validated numerical models can be done in order to determine the most detrimental combinations of imperfections to be considered for numerical simulations. The ECBL approach can be successfully applied to perform a sensitivity analysis via numerical simulations, using a limited number of experimental tests.