Steel Buildings in Europe

Part 4: Detailed Design 4 – 15 3 PRACTICAL GLOBAL ANALYSIS FOR ‘SIMPLE CONSTRUCTION’ 3.1 Introduction This Section provides guidance on the global analysis of a low or medium rise building, taking appropriate account of the specific aspects of frame behaviour addressed in Section 2. The Section addresses both persistent and transient design situations. Design for accidental situations is addressed in Section 6. 3.2 Actions and their combinations Buildings have to be designed for the combinations of actions set out in EN 1990 [5] , § 6.4.3.2; this aspect is discussed in more detail in Multi-storey steel buildings. Part 3: Actions [6] For the ultimate limit state, the basic combination of actions is given in expression (6.10) as:        i 1 Q ,i 0 ,i k ,i j 1 Q , 1 k , 1 p G , j k , j Q P Q G      6.10 This combination includes the permanent actions G k, j , the pre-stressing action P (not normally applicable in multi-storey steel building frames), the leading variable action Q k ,1 and the various accompanying variable actions Q k,i . Partial factors,  , are applied to the characteristic value of each action and additionally a factor  0 is applied to each accompanying action. Alternatively, for the STR and GEO Limit States (see EN 1990-1-1 § 6.4.1), EN 1990 [5] permits the use of the least favourable of the combinations of actions given in expressions (6.10a) and (6.10b) for the ultimate limit state .        1 Q, 0, k, 1 p Q,1 0,1 k,1 G, k, i i i i j j j Q Q G P       6.10a        1 Q, 0, k, 1 p Q,1 k,1 G, k, i i i i j j j Q G P Q      6.10b The first of these two expressions effectively treats all variable actions as accompanying the permanent action (and thus applies  0 to all variable actions) while the second considers the leading variable action as the primary action and allows a modest reduction in the design value of the permanent action. Although EN 1990 permits the use of equations (6.10a) and (6.10b) as an alternative to (6.10), the National Annex may give guidance regarding the combination that should be used. Recommended values of the partial factors and factors on accompanying actions are given in EN 1990 but these are confirmed or varied by the Nationally Determined Parameters (NDP) in the National Annex.