# 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/ρIso) mm/min for wood fibre
ρIso = density of wood fibre

European Technical Assessment ETA-11/0137

## Effective charring depth surface element

def = dchar + dred

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

## Effective charring depth surface element isolated

def = dchar + dred

Example:
ti = 25 mm
def = 31 mm for REI30 = 30 min ⋅ 0.8 mm/min + 7 mm

Example:
ti = 40 mm, wood ρIso = 40 kg/m3
def = 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:

AAkustik (mm2) = perforation area
dAkustik (mm) = perforation area
bAkustik (mm) = position of perforation in relation to the timber web
ti (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 = AAkustik / dAkustik . 103 / (bAkustik 1.5 . ti)

β1 = 0.22 ⋅ k + 0.72

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

β2 = 0.9 . √(450 / ρAbsorber)

## Effective charring depth

def = dchar + dred

Example:
Acoustics type 2, ti = 31 mm, hi = 40 mm, ρAbsorber = 110 kg/m3, AAkustik = 707 mm2, dAkustik = 75 mm, bAkustik = 25 mm => k = 2.43, β1 = 0.22 ⋅ k + 0.72 = 1.26 mm/min
def = 48 mm for REI30 = 24 min ⋅ 1.26 mm/min + 6 min ⋅ 1.82 mm/min + 7 mm

## Effective charring depth

def = dchar + dred

Example:
Acoustics type 2, t= 31 mm, hi = 40 mm, tii = 33 mm, ρAbsorber = 110 kg/m3, AAkustik = 707 mm2, dAkustik = 75 mm, bAkustik = 25 mm => k = 2.43, β1 = 0.22 ⋅ k + 0.72 = 1.26 mm/min
def = 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.