Fire Protection of Steel Structures

When exposed to fire, all commonly used structural materials lose some of their mechanical strength. Heavily loaded steel will lose its designed safety margin at temperature around 550°C – regardless of the grade of steel. To protect the structural steel in your building, use PAROC fire protection slabs. Depending on the application, you can use one of three methods for fire protection: profile, box and solid.

The bigger volume of steel in the exposed area, the better fire resistance it has. How quickly the steel structure heats up in a fire can simply be described as the relation between the surface exposed to the fire and the steel volume of the profile. This relation is called the section factor A/V. A high section factor gives a quick temperature raise of the steel. In practice, this means that thin steel structures demand thicker protection.

Use tables 1 and 2 to find the fire class you need and the required product thickness for the most common steel profiles.

When the I profile has a height greater than 450 mm, install the insulation so that it matches the profile.

Sometimes columns in external walls can be protected from three sides. A 5mm thick RHS profile, at a critical temperature of 400⁰ – 600⁰C and with the required fire class R 60, can be protected from three sides with 20mm thick PAROC FPS 17. This only can be done in fire class R60 with two layers of plaster board on the internal side of the wall. The external side of the wall has to be covered with thick plaster board at least 9mm thick. The limitation is that the steel profiles can’t be located next to openings (windows and doors). The facade also has to be non-combustible.

Fire protection of steel profiles in partitions

Use plaster board layers in partitions for steel profile fire protection. Apply the following table for fire class R90:

Insulation thickness for square RHS profiles, critical temperature 450 °C

Steel thickness (mm)	Thickness of PAROC FPS 17 (mm)
	1 x 13 mm plaster board (1 layer on both sides)	2 x 13 mm plaster board (2 layers on both sides)
5	40	25
6.3	40	25
8.0	30	20
10.0	25	20

HSQ beams

HSQ profiles are often used together with concrete elements.
When deciding about what fire protection thickness you need, use the dimensions of the visible flange. The construction is tested with insulation slabs that have 50mm excess on both sides to simplify the installation.

Insulation thickness for square HSQ profiles, fire from 1 side

	t_s (mm)	A_i / V_s (mm^-1)	R 60		R 90		R 120
			450°C	500°C	450°C	500°C	450°C	500°C
HSQ 1	15	67	20	20	20	20	40	25
HSQ 2	10	100	20	20	40	25	60	40

Publish Date : 2017/01/30