A steel for every climate

Let's start at the upper end of the temperature scale: The highest air temperature ever recorded is 56.7 °C and was measured in the famous Death Valley in the USA. Stahl can only laugh about that, of course; depending on the alloy, its melting point is in the high three to four-digit range. Or?

In fact, it is not liquefaction that demands the attention of architects and engineers - unless they are designing a turbine - but rather the spatial expansion of a material as temperatures rise.

As you probably know, physical substances expand when heat is added and contract again when the temperature drops. The corresponding formula for linear expansion is:

𝑙₀ . 𝛼 . Δ𝑇 = Δ𝑙

where:

This means that the steel structure (α=12×10^-6) of a 100 meter long bridge will expand by 8.5 centimeters with a temperature change of 70 degrees. The Eiffel Tower, which is made of iron (α=11.8×10^-6) and is 330 meters long, is up to 30 centimeters higher on hot summer days than on cold winter days.

In practice, however, this physical phenomenon is easy to master: Steelworkers, structural and civil engineers, even tile and parquet layers always install so-called expansion joints in their constructions. These consist of an elastic material and, in addition to the expansion and contraction of the individual components, also compensate for other influences such as seismic activities.

In addition to the temperature, a standard weather report always includes the wind. So far we have been spared from hurricanes that devastate entire regions

in this country there can be hurricanes with wind speeds of over 160 kilometers per hour. The highest wind speed ever measured in our latitudes is even 335 kilometers per hour.

However, it does not have to be 10 Beaufort for wind to affect buildings. Even everyday air circulation is enough to cause buildings to sway. In the wind-stricken USA, for example, there is a regulation that a house may move sideways by a maximum of 0.5 percent of its height.

For an average single-family house ten meters high, that would be five centimeters. A real skyscraper like the Burj Khalifa in Dubai (at 828 meters it is still the tallest building in the world), on the other hand, should sway by a clearly visible 4.14 meters at its top.
Of course, engineers and architects try to prevent such extreme fluctuations. For example, by adapting the aerodynamics of their constructions accordingly. Or through measures such as in Taipei 101 (508 meters high, 1.3 meters effective fluctuation): There, between the 87th and 92nd floors, a huge steel ball suspended on ropes floats, which absorbs the fluctuations and is also intended to protect the building from earthquakes.

Which leads us straight back to the material steel. Because no matter how resourceful the designers are, the influence of the wind cannot be completely compensated. Therefore, the selection of the right steel grades is of crucial importance for your work:
Suitable steels for building construction are precisely standardized in relevant regulations, such as the Construction Products Ordinance (BauPV), the building inspection approval of the German Institute for Building Technology (DIBt) or the Euronorm with its CE mark. Two material properties play an important role here: On the one hand, the transition from elasticity (a material returns to its original state after a load) to plasticity (a material remains in the deformed state after a load); on the other hand, its rigidity – i.e. the resistance of a body to external loads.

The values ​​that a material must achieve in order to be suitable for a specific application are precisely regulated in the relevant regulations. So if you have set yourself the task of outstripping the Burj Khalifa, you can look it up there - or simply use our inquiry tool for your project and get advice from our experts.