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Research Focus Issue No. 30 AUGUST 1997 PROMOTING THE APPLICATION OF RESEARCH IN BUILDING AND CIVIL ENGINEERING


IN THIS ISSUE Buildings


Building envelope conference Testing for moisture


Construction process Concrete frames studied


Commercial framework Encouraging partnering


Drainage


Help on roof drainage Environment


Okehampton Bypass impact Exports


Exports project seeks input


Ground Engineering Voids under highways


Highways Detecting voids


Okehampton Bypass impact Management


Encouraging partnering Materials


Testing for moisture


Steel demonstration building Safety


Tunnel fires Structures


Bridge detailing guide


Concrete design spreadsheets Steel demonstration building Concrete frames studied


Support to standards Concrete design spreadsheets


Transport LINK transport Research 3–5 8 11 12 9 10 10


6 6


10 11


6 2 11 9 8


8 9


11 12


Research leads to new form of slim floor construction


Research at SCI, sponsored by British Steel, the Department of Trade & Industry and EPSRC under a LINK project, has led to the launch of a new slim floor constructions product, Slimdek.


S


lim floor construction is the generic terminology for a steel beam contained within the depth of the floor slab. The original slim floor beam concept (trademark Slimflor) developed for use in the UK, consists of a Universal Column (UC) section with a plate welded to its bottom flange (see Figure 1). The deep deck sits on the bottom flange plate and spans between the beams. This acts as permanent formwork to the in- situ concrete slab and develops composite action with the concrete to resist the imposed loads.


The cross-section of the Slimflor beam was asymmetric in shape (Figure 1). Under the LINK project, British Steel and the SCI took the next logical step to develop a hot rolled Asymmetric Slimflor Beam (ASB) (see Figure 2). The resulting new product is called Slimdek (a registered trademark) and a British Steel patent defines a range of slim floor methods of construction which use deep deck composite slabs.


Initially, British Steel is producing a range of three ASB sections, two of which are 280 mm deep (with different flange and web thicknesses), and one 300 mm deep. All will be rolled using grade S355 steel. Replacing the Slimflor beam with the ASB section gives the benefit of composite action between the beam and concrete without the use of shear stud connectors at the ultimate limit state. It also reduces steel weight, saves in fabrication costs and eliminates the possibility of plate distortion due to welding. The composite action is enhanced by a raised rib pattern rolled into the top flange of the section. Composite action between the steel beam and concrete has been verified by full scale tests carried out at City University. The Slimdek lightweight shallow floor system generally has 60 minutes’ fire resistance. However, service voids can be included in the Slimflor beam and, where this is done, fire protection is required. The RHS Slimflor edge beam has been developed as an alternative method for edge beam construction. It offers good torsional properties, an aesthetic appearance and is particularly well suited to edge beam applications (see Figure 3).


For use in conjunction with the ASB sections and RHS Slimflor edge beams, a new


Research Focus NO. 30 AUGUST 1997 Fig 1.


Conventional Slimflor construction using deep decking


Fig 2. Asymmetric beam in Slimdek floor


Fig 3. RHS edge beam in Slimdek floor


deep deck profile (designated SD 225) is being supplied by Precision Metal Forming. The new deep deck profile has improved features for construction and service fixings which are illustrated in Figures 2 and 3.


The SCI has prepared two design guides and software in ‘Windows’ format. The guides are available from the Institute Library (01344 872775) and the software via the British Steel Slimdek Team, Teesside (01642 404646).


For further information please contact: Derek Mullett at The Steel Construction Institute (01344 23345; fax: 01344 22944).


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