Members of building structures are often made of wood. There are many advantages of using timber, such as quick erection time, good environmental influence and high energy efficiency. But the fire safety requirement is one of the most important issues concerning the design of timber structures. Safe use in structures depends on a proper knowledge and modelling of the chemical and physical reactions related to the increase of temperature inside the timber members. This paper presents a summary of results from numerical studies on the heat transfer through timber members exposed to fire from different sides. The finite element software SAFIR was used to make two-dimensional thermal models of the timber elements. Then the FE models were used to analyze the heat flow within the members under standard ISO-fire exposure interacting from different sides. On the basis of the 300 °C isotherms, residual crosssections were determined. Then, the load-bearing capacity of the elements exposed to fire from different sides was determined. The obtained results showed that the location of construction members against the fire has a significant impact of the temperature distribution in the cross-section and, as a result, on the load-bearing capacity of the timber members.

Connections are usually the weakest parts in most structures, especially in fire conditions. The load-bearing capacity of timber structures is often limited by the resistance of steel connection between timber structural members. The temperature distribution in the cross-section as well as the influence of steel fasteners on the charring of the timber members is necessary to predict the fire resistance of the connection. This paper presents a summary of results from numerical studies on the fire behaviour of the steel connections between timber structural members. To make the three-dimensional thermal models of the joints, the FE (finite element) programme SAFIR was used. Then, the finite element models of the connections were used to analyse the temperature distribution inside cross-sections under standard ISO-fire exposure. The failure modes from the literature were used to predict the load-bearing capacity of the steel connections at elevated temperatures. The reduction of the cross-section caused by charring, the reduction of embedment strength and the reduction of steel strength at fire conditions were taken into account in the calculations.

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The fire development in timber buildings may have a different intensity depending on the location in which the fire originated. The large-space timber buildings are characterized by a large area with a comparatively low height, which makes fire-gas evacuation and air circulation difficult. This paper presents an investigation on the influence of the fire source location on the load-bearing capacity of timber beam exposed to fire. The finite element software Fire Dynamics Simulator (FDS) was used for numerical fire modelling, specifying the time-varying spatial maps of the fire-plume-gas temperature on the basis of the equations taken from the fluid dynamics methodology with aerodynamic and thermodynamic variables. The obtained results from the FDS were used to determine the load-bearing capacity of timber beam using the SAFIR software. The results of numerical simulations showed that the fire source location has a significant influence on the load-bearing capacity of timber beam exposed to fire.

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