Reference : Calculation of internal forces in axially and rotationally restrained beams under nat...
Dissertations and theses : Master of advanced studies dissertation
Engineering, computing & technology : Civil engineering
Calculation of internal forces in axially and rotationally restrained beams under natural fire
[fr] Calcul des efforts internes induits par un feu naturel dans une poutre restreinte axialement et en rotation
Hanus, François [Université de Liège - ULiège > Département Argenco : Secteur SE > Struct. en béton, struc. en bois et résist. au feu >]
Université de Liège
Diplôme d'Etudes Approfondies en Sciences Appliquées
Franssen, Jean-Marc mailto
Dotreppe, Jean-Claude mailto
Jaspart, Jean-Pierre mailto
Vassart, Olivier mailto
[en] Natural fire ; Axial and rotational restraints
[en] When a constituent of a frame is subjected to fire, the thermal dilatation and bowing of this element is limited by the action of the surrounding frame. The reduction of steel mechanical properties and restrained thermal deformations induce a new distribution of internal forces in the frame. Generally, the stability of structures is calculated by the use of recommended temperature-time curves that do not considered the cooling phase of the fire. After being submitted to high compressive forces and experiencing significant plastic deformations, heated elements become in tension. As it was observed experimentally, the failure of bolts due to an excess of tensile forces may occur during the cooling phase of the fire.

That is the reason why a research project on the design of connections subjected to natural fire (COSSFIRE) has been funded by the Research Fund for Coal and Steel (RFCS). The objective of this project is to provide experimental data and to propose guidelines for designing the joints including both the heating and cooling phases.

This work describes a part of the contribution of the University of Liège in the project COSSFIRE. It is focused on the determination of the internal forces experienced by axially and rotationally restrained beams submitted to a natural fire. This preliminary step is essential for an optimised design of connections in similar conditions.

This work is subdivided three parts. Firstly, some experimental tests have been modelled numerically with the homemade finite element software SAFIR in order to validate it and the models used to analyse this type of problem. Secondly, a set of parametrical analyses have been performed in order to better understand the influence of several factors on the induced internal forces and provide some reference results for the last part of the work. Finally, some simplified methods, based on Wang’s method, have been defined to allow determining the internal forces in a given case without requiring any numerical simulation in finite element packages.
Research Fund for Coal and Steel

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