Steel Buildings in Europe

Part 4: Detailed Design 4 – 2 2 BASIC CONCEPTS 2.1 Introduction EN 1993-1-1 [1] provides a very flexible, comprehensive framework for the global analysis and design of a wide range of steel frames. This section introduces the basic concepts that underpin the design approaches for economic low and medium-rise multi-storey frames. 2.2 Simple construction As discussed in Multi-storey steel buildings. Part 2: Concept design [3] , the greatest economy for low and medium rise braced multi-storey frames will be achieved by the use of ‘simple construction’. The analysis assumes nominally pinned connections between beams and columns; resistance to horizontal forces is provided by bracing systems or concrete cores. Consequently, the beams are designed as simply supported and the columns are designed only for any moments arising from nominal eccentricities of connections of the beams to the columns (in conjunction with the axial forces). As a further consequence, it is not necessary to consider pattern loading to derive design forces in the columns. This design approach is accommodated by the EN 1993 [1] ‘simple’ joint model, in which the joint may be assumed not to transmit bending moments. This approach may be used if the joint is classified as ‘nominally pinned’ according to EN 1993-1-8, § 5.2.2. This classification may be based on previous satisfactory performance in similar cases. The joint configurations discussed in Section 3.3 assume a pinned connection and that the beam reactions are applied eccentrically to the columns. The widespread and successful use of these types of connection in many parts of Europe provide the evidence of satisfactory performance required by EN 1993-1-8, § 5.2.2. For braced frames designed in accordance with EN 1993-1-1 [1] , the global analysis model may therefore assume pinned connections between the columns and the beams, provided that the columns are designed for any bending moments due to eccentric reactions from the beams (see Section 3.3).