Numerical modelling of timber connections under fire loading using a component model

Published Date
August 2009, Vol.44(6):840–853, doi:10.1016/j.firesaf.2009.03.013

Author 

Paulo B. Cachim ^a,,

Jean-Marc Franssen ^b

aDepartment of Civil Engineering/LABEST, University of Aveiro, DECivil, 3810-193 Aveiro, Portugal

bDepartment ArGEnCo, University of Liege, 1 Chemin des chevreuils, B-4000 Liege 1, Belgium

Received 31 July 2008. Revised 25 March 2009. Accepted 27 March 2009. Available online 5 May 2009. 

Abstract

This paper describes a component model for dowelled timber connections under fire loading. The component model of the dowelled connection is first developed and calibrated for room temperature. The constitutive relations for dowel–timber interaction are detailed and compared with experimental results. In the fire situation, a two-step approach is used: first, three-dimensional (3D) thermal analysis of the connection is performed using a conductive model with timber properties defined in Eurocode 5 in order to calculate the temperatures in the fasteners and timber; afterwards, the mechanical analysis using a component model is carried out using mechanical properties of the steel dowel and of timber adjusted to the temperatures obtained by the thermal analyses. These properties are reduced according to Eurocode 3 and Eurocode 5, respectively. Numerical simulations are presented that allow evaluation of the model behaviour and performance. Obtained results show good agreement with available experimental data, indicating that regardless of its simplicity, the component model has the capability to accurately model timber connections under fire loading.

Keywords

Component model

Timber

Fire

Dowel

Connections

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Nomenclature

α

angle to the grain (when used as subscript it is replaced by 0 when parallel to grain and by 90 when perpendicular to the grain)

f_y

steel yield stress (N/mm²)

P_α

property at an angle α to the grain

f_h,_α

embedding strength at an angle α to the grain (N/mm²)

F_y,_α

yield strength at an angle α to the grain (N/mm)

F_u,_α

ultimate strength at an angle α to the grain (N/mm)

k₉₀

parallel/perpendicular strength ratio

ρ_k

characteristic density of timber (kg/m³)

d

fastener diameter (mm)

n₉₀

ratio between η₀ and η₉₀

p_y,_α

yield displacement at an angle α to the grain (mm)

p_u,_α

ultimate displacement at an angle α to the grain (mm)

η_α

ratio between F_u,α and F_y,α

K_1,α

initial stiffness at an angle α to the grain (N/mm²)

K_2,α

post-yielding stiffness at an angle α to the grain (N/mm²)

ζ₉₀

ratio between k_1,0 and k_1,90

K_fc (θ)

reduction factor for strength

K_Ec (θ)

reduction factor for stiffness

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 Table 1

Table 1.

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 Table 2

Table 2.

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 Table 3

Table 3.

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 Table 4

Table 4.

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