Fire Resistance of Steel Framed Car Parks

Steel-framed car parks have been rigorously fire tested in a number of countries (Table 3). These tests demonstrate that most unprotected steel in open sided steel-framed car parks has sufficient inherent resistance to withstand the effects of any fires that are likely to occur. Table 3 lists the maximum temperatures reached in open sided car park tests in four countries. These can be compared with the characteristic failure temperatures for beams carrying insulating floor slabs and columns of 620oC and 550oC respectively.

Open sided car parks are defined in Approved Document B to the Building Regulations 1991 for England & Wales as having open ventilation of at least 5% of the floor area at each level, at least half of which should be in opposing walls.

The fire resistance requirements for open sided car parks in the United Kingdom and Ireland are outlined in Table 4. The dominant period is 15 minutes. Most Universal Beams and Columns will achieve 15 minutes fire resistance without added protection although a small number of sections at the lower end of the range, will do so only when less than fully loaded.

In general, where a section does not have 15 minutes inherent fire resistance, it is usually more efficient to increase the section size than to fire protect.

Full scale fire tests

Maximum measured steel temperature

Country

Beam

Column

UK

275oC

360oC

Japan

245oC

242oC

USA

226oC

-

Australia

340oC

320oC

Table 3. Fire tests in various countries

 

Requirements from regulations

Height of top floor

Up to 30 metres

Over 30 metres

England & Wales

15 minutes * +

60 minutes

Scotland

15 minutes

15 minutes

Northern Ireland

15 minutes * +

Not permitted

Republic of Ireland

15 minutes *

Not permitted

* Increased to 60 minutes for compartment walls separating buildings
+ Increased to 30 minutes for elements protecting a means of escape

Table 4. Fire resistance requirements for open sided car parks