Steel Buildings in Europe

Part 7: Fire Engineering 7 - 28 the fire during the fire duration (for example a concrete slab put on the upper flange of the profile), the type of fire protection (according to the outline of the steel profile or in box)  Determine the thickness from the manufacturer’s data using the critical temperature and the section factor. Linear interpolation is permissible to determine thickness. The European Convention for Constructional Steelwork (ECCS) has developed so-called Euro-nomograms [13] , which relate for a given time of standard fire exposure, the temperature reached by insulated steel members to the factor ( λ p / d p )  ( A p / V ) depending on the fire protection characteristics ( λ p and d p ) and the section factor A p / V . Note that these Euro-nomograms are determined on the basis of the ENV version of the fire part of Eurocode 3. Also for this reason they should be used with some caution. Other nomograms based on EN 1993-1-2 have been recently developed [14] . 5.3.4 Design tables for composite members Design tables for composite members are given in EN 1994-1-2. They are applicable only to steel and concrete composite members (composite beams with partially or fully concrete encasement of steel beam, composite columns with partially or fully concrete encased profiles, composite columns with concrete filled rectangular or circular steel hollow sections). They use predefined values, based mainly on standard fire test results, improved with analytical investigation. The tables allow the designer to quickly obtain the member size (minimum dimensions of cross-section, the necessary reinforcing steel area and its minimum concrete cover) as a function of the load level for common standard fire resistances. The most important advantage of this method is the ease of application. However it is limited by a very strict set of geometrical rules and it gives more conservative results compared to other simple calculation models or advanced calculation models. As a consequence, it should only be applied for the pre-design of a building. Detailed information is given in EN 1994-1-2. 5.3.5 Simplified calculations models for composite members The following design methods have been developed to predict the resistance of individual members when exposed to a standard fire curve. Therefore they are not applicable to “natural” fires. Only the design methods for the most commonly used composite members in single-storey building (composite columns and partially encased concrete beams) are described here. Composite columns The simple design methods for columns allow the designer to assess the fire resistance of a composite column by calculating its buckling resistance using the temperature distribution through the cross-section and the corresponding reduced material strength defined at the required fire resistance time. This method is based on the buckling curve concept: the plastic resistance to axial compression N fi,pl,Rd and the effective flexural stiffness ( EI ) fi,eff , are used to derive a reduction factor for buckling. The method is applicable to all types of