Steel Buildings in Europe

Part 7: Fire Engineering 7 - 9 Member analysis Analysis of part of the structure Global structural analysis Figure 3.1 Different design approaches for mechanical response of structures in fire Member analysis is easy to use particularly with simplified calculation methods and therefore largely used under standard fire condition. The analysis of the whole structure or its subassemblies considers at least several structural members together, so that the interaction effect between them will be directly dealt with. In this way, load redistribution from heated parts (weakened parts inside fire compartment) to cold parts (stronger parts outside fire compartment) can be taken into account in accurate way and global analysis provides therefore a much better understanding of overall behaviour of structure under fire condition. According to the Eurocodes, three types of design methods can be used to assess the mechanical behaviour of structures under fire situation in the different design approaches explained above. Fire design can be carried out by means of:  A simple calculation method, based on predefined tabulated data, as given in EN 1994-1-2 [3] . This method is only applicable to steel and concrete composite structures. The tables were evaluated by numerical models and experiments for basic types of structures, such as slabs, beams and columns, for certain time of fire resistance, for heating according to the nominal fire curve and for defined level of loading. The tables are easy to use and safe but cover only a limited range of section types.  Simple calculation models. This type of design method can be divided into two different families. The first one is the critical temperature method widely applied to steel structural member analysis. The second is the use of simple mechanical models (verification in strength domain) developed for both steel and composite structural member analysis. Models have been developed for standard structural elements, e.g. slabs, beams, and columns.  Advanced calculation models. This kind of design method can be applied to all types of structures and the models are, in general, based on either finite element method or finite difference method. They should provide a realistic analysis of structures. The results of the analysis are generally obtained in terms of deformation of structure during the whole fire period. Structural models will be briefly detailed in following chapters.