### Abstract

This study describes a time-to-failure calculation model
for wooden beams under a standard fire exposure. The
model is based on the linear theory of elasticity by
taking the effect of temperature and moisture on the
strength and stiffness of the wood into account. The
time-to-failure criterion is a tensile failure in a
finger joint (a glu-lam beam) or in a knot.
The bending and shear stress distributions in the
non-charred wooden cross section are calculated
analytically by dividing the cross section into several
layers with different materia! properties. The bending
moment and shear capacity are then calculated by summing
the capacities of the layers.
Finally, the calculation is compared with test results.
Beams are assumed to be of rectangular cross section and
exposed to fire on three or four sides. Some earlier
calculation methods are briefly reviewed.

Original language | English |
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Place of Publication | Espoo |

Publisher | VTT Technical Research Centre of Finland |

Number of pages | 58 |

ISBN (Print) | 951-38-4015-8 |

Publication status | Published - 1991 |

MoE publication type | Not Eligible |

### Publication series

Series | Valtion teknillinen tutkimuskeskus. Tiedotteita |
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Number | 1282 |

ISSN | 0358-5085 |

### Keywords

- calculations
- models
- fire resistance
- fire safety
- wooden structures
- timber construction
- beams (supports)
- structural members
- elastic properties
- temperature
- stiffnes
- moisture
- strength
- failure
- bending stress
- shear stress

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## Cite this

Majamaa, J. (1991).

*Calculation models of wooden beams exposed to fire*. VTT Technical Research Centre of Finland. Valtion teknillinen tutkimuskeskus. Tiedotteita, No. 1282