Steel Buildings in Europe

Part 2: Concept Design 2 - 35 4.5.3 Features of long span construction Long span beams have gained in popular ity in the comm ercial building sector because they offer the following benefits in design and construction:  Internal columns are elim inated, leading to m ore f lexible and efficient use of internal space  Services ca n be integ rated with in the depth of the struc ture, and so the floor-to-floor depth is not increased  Fewer components are required (typical ly 30% fewer beam s) leading to reduced construction and installation time  Fire protection costs can be reduced due to the m assivity (weight : exposed profile) of the longer span members  For cellula r beam s, m ultiple c ircular ducts f or services a re cheape r than rectangular ducts  Steelwork costs are not increased significantly, despite the longer spans  Overall building costs are increased by a negligible amount (less than 1%). 4.5.4 Approximate steel quantities For estim ating purposes in the design of office buildings, representative weights of steel m ay be used for build ings of rectangular plan form . These quantities will increase signi ficantly for non rectangular or tall buildings or for buildings with atria or complex façades. The approxim ate quantities are pres ented in Table 4.3, and are express ed in terms of the total floor area of the bu ilding, and do not include steelwork used in the façade, atrium or roof. Table 4.3 Approximate steel quantities for estimating purposes Approximate steel quantities (kg/m 2 floor area) Form of Building Beams Columns Bracing Total 3 or 4-storey building of rectangular form 25–30 8–10 2–3 35–40 6–8-storey building of rectangular form 25–30 12–15 3–5 40–50 8–10-storey building with long spans 35–40 12–15 3–5 50–60 20-storey building with a concrete core 25–30 10–13 1–2 40–50 20-storey building with a braced steel core 25–30 20–25 8–10 55–70 4.6 Factors influencing structural arrangements The construction programme will be a ke y concern in any project, and should be consid ered at the s ame tim e as c onsidering the cost of structu re, th e services, cladding and finishes. The stru ctural scheme has a key influence on programme and cost, and structural so lutions which can be ere cted saf ely, quickly to allow early access for the following trades.