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Thin-walled steel structures and their production: why are they a great advantage for the future of the Czech construction industry?

In the current trends in the design of load-bearing steel structures, thin-walled cold-formed sections are increasingly important, with applications in a wide range of different types of structures, from civil buildings to warehouse and industrial hall structures to technological structures. The pressure from investors to reduce construction costs due to material and energy consumption, especially with the current dynamic rise in material and energy prices, is driven by the desire to make design more efficient and thus save on material and energy costs. The systems used in practice, consisting of thin-walled beams (floor beams, purlins, purlins, frame cross-sections) and columns (frame uprights, racking system uprights), include a wide range of profiles of different cross-sectional shapes.

History

The advent of the use of cold-formed thin-walled sections in the construction industry began in the 1950s in the United States and Great Britain. Until the 1940s, the use of cold-formed steel sections was limited due to the absence of technical standards with relevant design procedures. Due to the wide variety of different sizes and shapes of cold-formed sections, it was a challenge to devise general design procedures for all the cross-sectional shapes encountered. It is only in the last three decades that cold-formed sections have gained popularity in the construction industry, where they are also used for primary load-bearing structures.

Production

Thin-walled profiles can be made from almost any type of steel that is rolled into strips and sheets. Carbon steels are common, but alloy steels, stainless steels, low-corrosion steels or Atmofix steels are also used. Cold forming also produces cross-sections from high strength steels, but sufficient ductility is required to form the bends.

Cold rolling is the most commonly used technology for the production of thin-walled profiles, which is a continuous production process and is particularly suitable for the production of profiles of the same cross-sectional shape in large quantities to cover the costly initial investment in profiling lines. Steel for the production of cold-rolled thin-walled profiles is supplied in coils.

Ocelové svitky ve výrobní hale společnosti auklan — Steel coils in Auklan's production hall

In the process, a strip of steel (unwound from a coil) passes continuously through a rolling line formed by successive pairs of opposing rolling wheels which gradually form the strip of steel into its final cross-sectional shape. The passage of a strip of steel through one pair of rolling wheels is called the rolling phase. The disadvantage of the older types of profiling lines was the considerable downtime required to change the geometry of the sets of rolling wheels when the dimensions of the profile being produced changed. Today's modern profiling lines allow automatic (computer controlled) adjustment of the rolling wheels within the production of one group of profiles of the same shape differing only in cross-sectional dimensions (stand height, web width).

Thin-walled steel structures and their production: why are they a great advantage for the future of the czech construction industry?

The steel strips can be cut to the required lengths before entering the profiling line, but more often the cutting of profiles takes place at the exit of the profiling line. As a rule, hydraulic shears are used to cut the profiles.

Source: article Konstrukce magazine July August

Authors. Martin Horáček, Ph.D., Ing. Petr Johanides

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