Fire design of columns out of high strength concrete

How can reinforced concrete columns made of high-strength concrete be designed to resist fire?

The design methods according to EN 1992-1-2 apply to concrete up to strength class C90/105. However, the additional rules in Section 6 must be observed for high-strength concretes from a strength class of C50/60. The background to these additional rules is that the unbound water in high-strength concrete is difficult to escape in the event of fire due to the particularly dense structure - there are no capillary pores. Thus, without further measures, a vapor pressure builds up, which can lead to explosive spalling and exposure of the reinforcement in the event of a fire. In this respect, EN 1992-1-2 specifies further design rules for the reinforcement of high-strength concrete, such as a compacted reinforcement mesh or the addition of polypropylene fibers, which melt in the event of fire and create additional capillary pores.

In principle, according to Section 6 in EN 1992-1-2, the simplified design methods may also be used for columns made of high-strength concrete will. However, the required cross-section dimensions specified in the dimensioning tables must then be increased by a factor. This thwarts the idea of reducing the cross-sectional dimensions of the supports by using high-strength concrete.

How I can help you

In order to be able to build the columns from high-strength concrete as compactly as possible, I use the so-called fire design. Of course, the cross-sectional dimensions of columns made of high-strength concrete must not be arbitrarily small, otherwise the cross-section would heat up too quickly in the event of a fire. We therefore optimize the cross-sectional dimensions in such a way that the support maintains the cross-sectional dimensions required in the event of a fire. The fire design is usually based on the ISO standard fire.

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