Steel Buildings in Europe

Part 2: Concept Design 2 - 27 4.2.3 Vertical coordination The targ et floor-to-floor height is b ased on a floor-to -ceiling height of 2,5 m to 2,7 m for speculative offices, or 3 m for more prestige applications, plus the floor depth including services. The fo llowing target floor-to-floor depths should be considered at the concept design stage: Prestige office 4 – 4,2 m Speculative office 3,6 – 4,0 m Renovation project 3,5 – 3,9 m These targets permit a range of structural solutions. If, for planning reasons, it is required to lim it the overall building height, this can be achieved by use of slim floor or integrated beam systems. Integrated beam systems are often used in renovation projects where the fl oor–to-floor height is lim ited by compatibility with the existing building or façade. For a 12 m span composite beam, the structural depth is approxim ately 600 mm. The fire protection thickness (if needed) and an allowance for deflections should also be included (nominally 30 mm). Where the s tructural and service zo nes are sepa rated ver tically, the f ollowing should be added to the structural depth: Raised access floor 150 mm to 200 mm Air conditioning units 400 mm to 500 mm Ceiling and lighting 120 mm to 250 mm However, significant reductions in overall depth can be achieved by vertical integration of the structural and service z ones. This is par ticularly effective for longer span construction. For concept design of or thodox commercial m ulti-storey steel structures, the following ‘target’ floor depths may be used: Composite beam construction 800 mm – 1200 mm Cellular beams (with service integration) 800 mm – 1100 mm Precast concrete floors (7,5 m span) 1200 mm – 1200 mm Precast concrete floors (14 m span) 1450 mm – 1450 mm Slim floor or integrated beams 600 mm – 800 mm 4.3 Structural options for stability The structu ral system required for stab ility is prim arily inf luenced b y th e building height. For buildings up to eight storeys height, the steel structure may be designed to provide stability, but for taller buildings, concrete or braced steel cores are m ore efficient s tructurally. The following structural system s may be considered for stability.