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Fire resistance

Residual section after fire load

All the following information and calculations are based on the assumptions stated here:

• one dimensional charring
• charring rate β₁ at the layers = 0.8 mm/min
• charring rate β₂ at the webs around the insulation
• layer accounting for loss of strength dred = 7 mm

β₁ = 1.6 mm/min for rockwool
β₂ = 0.9 ⋅ √ (450/ρ_Iso) mm/min for wood fibre
ρ_Iso = density of wood fibre

Effective charring depth

d_ef = d_char + d_red

d_ef = 31 mm for REI30 = 30 min ⋅ 0.8 mm/min + 7 mm
d_ef = 55 mm for REI60 = 60 min ⋅ 0.8 mm/min + 7 mm
d_ef = 79 mm for REI90 = 90min ⋅ 0.8 mm/min + 7 mm

Effective charring depth

d_ef = d_char + d_red

Example:
t_i = 25 mm
d_ef = 31 mm for REI30 = 30 min ⋅ 0.8 mm/min + 7 mm

Example:
t_i = 40 mm, wood ρ_Iso = 40 kg/m³
d_ef = 77 mm for REI60 = 50 min ⋅ 0.8 mm/min + 10 min ⋅  3.0 mm/min + 7 mm

Residual section of acoustic element after fire load

The charring rate β₀ of the acoustic slat can be described based on the following parameters:

A_Akustik (mm²) = perforation area
d_Akustik (mm) = perforation area
b_Akustik (mm) = position of perforation in relation to the timber web
t_i (mm) = thickness of the acoustic slat

The factor k summarises the resulting influence of the parameters. The charring rate β₁ can be calculated depending on the factor k. 

k = A_Akustik / d_Akustik . 10³ / (b_{Akustik ^1.5} . t_i)

β₁ = 0.22 ⋅ k + 0.72

The charring rate β₂ at the webs around the wood fibre absorber depends on the density ρ_Absorber (kg/m³).

β₂ = 0.9 . √(450 / ρ_Absorber)

Effective charring depth

d_ef = d_char + d_red

Example:
Acoustics type 2, t_i = 31 mm, h_i = 40 mm, ρ_Absorber = 110 kg/m^3, A_Akustik = 707 mm², d_Akustik = 75 mm, b_Akustik = 25 mm => k = 2.43, β₁ = 0.22 ⋅ k + 0.72 = 1.26 mm/min
d_ef = 48 mm for REI30 = 24 min ⋅ 1.26 mm/min + 6 min ⋅ 1.82 mm/min + 7 mm

Effective charring depth

def = d_char + d_red

Example Acoustics type 2:
 ti = 31 mm, hi = 40 mm, tii = 33 mm, ρ_Absorber = 110 kg/m3
A_Akustik = 707 mm2, d_Akustik = 75 mm, b_Akustik = 25 mm
=> k = 2.43, β1 = 0.22 ⋅ k + 0.72 = 1.26 mm/min
d_ef = 89 mm for REI60
= 24 min ⋅ 1.26 mm/min + 22 min ⋅ 1.82 mm/min + 14 min ⋅ 0.8 mm/min + 7 mm

Joint detail under fire load

Basic boundary conditions for space-enclosing and heat insulation effects must be met in the event of fire. LIGNATUR floors and roofs with fire resistance class REI30, REI60 and REI90 have to be installed according to ETA-11 / 0137 with the appropriate joints, shown on the right. They already reach EI30, EI60 or EI90, so that floor and roof structures can be chosen freely without further requirements.