Steel Buildings in Europe

Part 2: Concept Design 2 - 40 5 FLOOR SYSTEMS In add ition to th eir pr imary load-r esisting f unction, f loors tr ansfer ho rizontal loads to the vertical bracing. In addition, floor slab, beams and columns have to satisfy a specified fire resistance (typically 60 to 120 minutes). Services may be integrated with the fl oor construction, or be suspended below the floor (as described in Section 4.6). In commercial buildings, raised floors allow services (particu larly electri cal and communicatio n services ) to be distributed easily. This sectio n describ es various f loor system s of ten used in m ulti-storey buildings. T he m ain ch aracteristics of each floor sys tem are described , with guidance on im portant design issues. Th is section does not contain detailed design procedures but directs the reader to the sources of design guidance. The following floor systems are covered:  Composite beams and composite slabs with steel decking  Long-span composite beams often with service openings  Cellular composite beams with composite slabs and steel decking  Integrated beams with precast concrete units  Composite and non-composite beams with precast concrete units. 5.1 Composite construction In the following sections, design appr oaches are presented for com posite construction. Decking may have a re-entra nt or trapezoidal profile – re-entran t decking uses m ore concrete than trap ezoidal decking, but has increased fire resistance for a given slab depth. T rapezoidal decking generally spans further than re-entrant decking, but the shear stud res istance is reduced due to th e influence of the profile shape. Generally, norm al weight concrete (NWC) is used, although lightweight concrete (L WC) is structurally effi cient and in som e countries w idely available. 5.2 Composite beams and composite slabs with steel decking 5.2.1 Description Composite construction consists of downstand steel beam s with shear connectors (studs ) welded to the top flange to enable the beam to act compositely with an in situ composite floor slab. The composite slab comprises profiled decking of various shapes that span 3 m to 4 m between secondary beam s. The ge neric deck profiles are illustrated in