# RF-/STEEL EC3 Version 5/8

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# 8.2 Fire Resistance

This example describes the fire resistance design for a steel column, using the National Annex of Germany.

 Figure 8.3 Column cross-section: HE-B 300, steel S 235System: hinged column, β = 1.0System height: 3 mLoading: GK = 1200 kN, QK = 600 kN
Ultimate limit state design for room temperature
Flexural buckling about minor axis (⊥ to z-z axis)

→ Design for flexural buckling must be performed.

cross-sectional geometry: h/b = 1.00 ≤ 1.2; structural steel S 235; t ≤ 100 mm

• [1] Table 6.2, row 3, column 4: buckling curve c
• ⇒ αz = 0.49   ([1] Table 6.1)

Design ratio

Results of RF-/STEEL EC3 calculation
 Iz 8560.00 cm4 Effective member length Lcr,z 3.000 m Elastic flexural buckling force Ncr,z 19712.9 kN Slenderness λz 0.4215 > 0.2 6.3.1.2(4) Buckling curve BCz c Tab. 6.2 Imperfection factor αz 0.490 Tab. 6.1 Auxiliary factor Φz 0.643 6.3.1.2(1) Reduction factor χz 0.886 Eq. (6.49) Flexural buckling resistance Nb,z,Rd 2821.80 kN Eq. (6.47) Design ratio η 0.893 ≤ 1.0 Eq. (6.46)
Fire resistance design

After a fire exposure of 90 minutes according to the standard temperature-time curve, the mean steel temperature is 524 ℃.

A box-shaped GRP encasement (glass-reinforced plastic) is used as fire resistance material, having the following properties:

 Specific weight: ρp = 945 kg/m3 Thermal conductivity: λp = 0.2 W/K Specific heat capacity: cp = 1700 J/kgK Thickness: dp = 18 mm
Determination of reduction factors
 ky,Θ = 0.704 [10] Table 3.1 kE,Θ = 0.528 [10] Table 3.1

Imperfection factor α:

Non-dimensional relative slenderness ƛΘ:

Auxiliary factor:

Reduction factor for flexural buckling in fire situation:

Buckling resistance of structural component subjected to compression: