Fire safety for steel structures

Steel doesn't burn, but...

Steel is a non-combustible building material. Then fire protection shouldn't be a problem, right? Unfortunately it's not that simple. Indeed steel only melts at temperatures between 1425°C and 1540°C. But due to its very high thermal conductivity, it heats up very quickly. As a result, its stiffness and strength rapidly decrease in the event of a fire. Therefore, without further measures, steel supports quickly buckle in the event of a fire and girders sag severely. All in all, unprotected steel constructions fail quite quickly in the event of a fire.

This can be problematic for many buildings because they have to withstand a standardised course of fire over a certain period of time. The more complicated the escape and rescue from a building, the longer it takes. For example, the supporting structure of high-rise buildings has to withstand a fire much longer than the supporting structure in an industrial hall. This time is the so-called fire resistance class.

How can the fire protection of steel structures still be implemented?

Possibility 1: constructive fire protection

Steel structures can be provided with protective materials. These include, for example, plasterboard, mineral wool and intumescent coatings. What do these materials have in common? They have low thermal conductivity, so that the steel member is protected from rapid heating. These measures are summarized under the term constructive fire protection.

Possibility 2: simplified design methods for unprotected steel

It is also possible to verify unprotected steel structures by calculation. There are simplified design methods in the so-called "hot" Eurocodes. As a rule, however, fire design is only successful if the steel member is only slightly utilized at room temperature.

Possibility 3: fire design, possibly with natural fires

Finally, it is possible to consider more realistic fires instead of the ISO standard fire . It is far on the safe side for many buildings. If the actual fire loads are taken into account, so-called natural fires can be taken into account. This means that it is often possible to use a so-called fire design to verify unprotected steel structures in the event of a fire. This last option is my passion. Feel free to contact me if you would like to provide evidence of a specific project in the event of a fire.