SMD. Technical Guidance Notes Technical Info. Structural Floor and Roof Solutions SMD.TGN.122. Version Amendments Date

Transcription

1 SMD Structural Floor and Roof Solutions Version Amendments Date V4 All sections reviewed and updated V5 Notes pages added V6 Section 8.4 and 8.15 updated Technical Guidance Notes Technical Info SMD.TGN.122

2 Technical Guidance Notes Contents Page Section Title 04 - Introduction Product certification Specification Fall arrest systems Floor deck material specification Stud welding Roof deck material specification Concrete Health and Safety Management & supervision Documentation Personal Protective Equipment (PPE) Protection of falls from height Trained and competent workforce DO's for associated trades Design - Floor deck Benefits of composite metal deck Sheet lengths Temporary propping Lateral restraint and diaphragm action Bearings / Support Fixings Cantilevers Edge trim Flashings Steps in slab End caps Design - Floor deck Composite stage Reinforcement Saw cuts Fire Moving concentrated loads Long single span propped composite Slabs Forming service holes Page Section Title Design - Floor deck Composite beam design Shear stud LAW (length after weld) Design rules for minimum degree of connection Shear stud reduction factors BS EN Reduction factors for SMD Products BS Section 3.1 Reduction factors for SMD Products Shear stud spacing Transverse reinforcement for composite beams Alternative Shear Connectors Design - Floor deck Considerations Falls and ramps Fixing tool and stud welding gun Restrictions Concrete encased beams Durability Aggressive environments Vibration Acoustics Thermal mass Design - Roof deck Quality Spans Loads Standard end laps Extended end laps Raking supports and cutting Cantilevers Sheet lengths Fire rating Durability Acoustics Airtightness Fixing specification Non-fragility Diaphragm design Protex warranted insulated system Aesthetics 2

3 Page Section Title Supply of materials Delivery and access Pack size and sheet length limits Offloading, hoisting and storage Pack labels / loading-out locations Installation - Fall arrest systems Safety nets Installation - Floor deck and shear studs Cartridge tools Decking around columns Unpainted top flanges Mobile stud welding equipment Static generator or mains supply Testing Scorching of beams Minimising grout loss Page Section Title Product options High Durability floor deck Crushed ends deck sheets VoidSafe Protection System Perimeter toeboard Channel edge trim TAB-Deck Fibre concrete Off-site cutting Service fixings References SMD documentation Industry best practice Design standards Further reading Concrete Site considerations Temporary propping Cleaning the decking Damaged decking Construction joints Reinforcement drawings and bending schedules Concrete mix requirements Placement Surface finish Surface flatness Curing Post-installation characteristics Technical Department SMD.TGN.122.V6 3

4 Technical Guidance Notes Help us to help you! We hope this document provides a useful reference. Every effort has been made in its preparation to ensure the most common queries are comprehensively covered. Should your specific query not be adequately covered, contact our Technical team who will be happy to help. Answering your queries enables us to keep these guidance notes up to date whilst ensuring the most common issues are covered. If necessary, we can also attend your offices to provide a CPD presentation tailored to your learning objectives. References where noted For further reading, reference documents are available online, download or hard copy where the following icons are shown: Most SMD references can be found on our website those not available online, contact our Head Office External source documentation. (Where available, click icon to access the reference docuemnt when viewing online). Visit our website and register your details for CPD requests Refer to XXXX for more information References for SMD guidance notes These guidance notes should be read in conjunction with: Jamie Turner SMD Technical Director BCSA Code of Practice for Metal Decking and Stud Welding MCRMA/SCI Technical Paper No. 13/ SCI P300 REVISED EDITION. Composite slabs and beams using steel decking: Best practice for design and construction Need Further Guidance? Contact us on +44 (0) or our Technical Team on technical@smdltd.co.uk Visit to access all the information in this document on our Technical Info wiki page 4

5 Technical Guidance Notes GUIDANCE NOTES 1.0 Product certification In accordance with legal requirements, all SMD Products are CE Marked to BS EN , audited by The Steel Construction Certification Scheme. The Compliance Documentation for our products is detailed below: Refer to SMD.STD SMD Declaration of Performance for more information 2.0 Specification 2.1 Fall arrest systems All fall arrest systems installed by SMD are supplied, tested and installed in accordance with BS EN : 2014 BS EN : 2014 BS 8411:2007 The contract-specific method statement and risk assessment should detail the preferred method of fall arrest. 2.2 Floor deck material specification SMD floor deck products are typically used as part of a composite floor slab, with the deck acting as both permanent formwork and tensile reinforcement (sagging) in the bottom of the slab, designed in accordance with BS EN BS EN or BS5950: Parts 4 & 6. CE Certificate of 'Factory Production Control' Fig.1.0a Alternatively, the floor deck may be used as permanent formwork only. In this situation, the deck forms the concrete, with reinforcement required to support the specified imposed loads designed by the project structural engineer, ignoring any contribution from the metal deck. SMD floor deck profiles are manufactured from steel strip in compliance with BS EN & BS EN All products are available in minimum yield strengths of 350 (S350) or 450N/mm² (S450) with a minimum coating mass of 275g/m². 2.3 Stud welding Shear studs (Type SD1) are manufactured from low carbon steel with a minimum yield strength of 350 N/mm2 and a minimum ultimate tensile strength of 450 N/mm2 in accordance with BS EN ISO CE mark for SMD products Fig.1.0b Type SD shear connectors as defined in BS EN ISO 13918, are available in 16mm, 19mm, 22mm and 25mm diameter with varying lengths to achieve from 70mm to 170mm length after weld (LAW). Technical Department SMD.TGN.122.V6 5

6 Typical situations where welded shear studs are used include: 1. Thru-deck Stud Welding (on site) for Composite Beams 2. Stud Welding at Works for Composite Beams 3. Plunge Columns 4. Steel Piling 5. Bridge Construction/Refurbishment 6. Refractory Lining and Insulation Connectors 7. Wear Resistant Studs The most common use of welded shear studs (Type SD1) is in the construction of Composite Beams, refer Section 7. For the use of welded shear studs in other situations contact the SMD Operations Team. Surface finish specifications are defined in BS EN 13670: 2009 National Structural Concrete Specification (NSCS) 4th edition Concrete Society Technical Report No. 75 Composite concrete slabs using steel decking For unformed finishes it is important not to over-specify the quality of finish, particularly where it is covered by following finishes. Irrespective of the finish specification, the concrete must always be fully compacted. Concrete surface regularity There are two common concrete surface regularity specifications used when specifying composite floor slabs 2.4 Roof deck material specification The SR TM range of products are manufactured from steel strip in compliance with BS EN and BS EN All products have a minimum yield strength of 320N/mm² (deeper than SR100) or 350N/mm² (up to SR100) and are available in two standard coating options: BS EN 13670: 2009, adopted by NSCS 4th edition BS : A2:2011 Typically, the NSCS Basic or BS SR3 are considered applicable. Galvanised Hot-dip galvanised with minimum coating mass of 275g/m². Polyester White Hot-dip galvanised with a minimum coating mass of 150g/m² with micron bright white polyester to the interior surface. Refer product specific data sheets for more information. 2.5 Concrete Concrete material Concrete should be specified, supplied and assessed in accordance with BS 8500: A1: 2016 Concrete strength class, cement type, minimum cement content, maximum water/cement ratio and aggregate weight / size should always be specified by the party responsible for the overall composite slab design, typically the project structural engineer. Approval of the intended concrete mix design/s must be sought from the relevant party prior to any concrete placement works proceeding. Concrete surface finish 6

7 Technical Guidance Notes GUIDANCE NOTES 3.0 Health and Safety The design, detailing and installation of SMD projects must be planned and carried out ensuring the Health & Safety of operatives undertaking the work, other trades on site, and members of the general public. 3.1 Management & supervision Ensure supervision is experienced in metal decking and that a suitable qualification such as SMSTS is held. Prestart meetings should be arranged to enable agreement of programme, sequence, attendances and co-ordination with other trades. The planning and arrangement of deliveries to allow effective positioning of deck packs onto the steel frame (usually by the erectors) is essential in minimising issues with manual handling. Refer to 'SIG.03 - Loading out and Positioning data sheet' at Robust management of the workforce in relation to Safety, Quality and Production ensures safe and efficient delivery. Handover procedures shall be used to ensure works are complete prior to access being given to following trades. 3.2 Documentation All companies should have a framework of Policies and Procedures relating to the management of Health & Safety. SMD have developed a specific Site Installation Guide to assist operatives with trade-specific guidance notes. Refer to SMD.SDC Site Installation Guide for more information Contract-specific safety documentation, including Method Statements, Risk Assessments and COSHH data sheets are available for all hazards / activities associated with the handling and fixing of metal decking and associated accessories. The communication of this to the workforce, ensures that all operatives understand the risks and preventative measures that have been agreed. An initial toolbox talk on the method statement, followed by further weekly talks ensures procedures on site are appropriate to the ever-changing construction environment. Records of inductions and all toolbox talks should be maintained. Typical hazards associated with metal decking and associated preventative measures are: Falls from Height Handrails, safety nets, temporary cover to voids and suitable access to level Hot Works Exclusion zones, removal of flammable materials, fire blankets, fire watch and fire extinguishers Use of Cartridge Tools Competency, training and PPE Hand Arm Vibration Management procedures to reduce trigger times Noise PPE, management procedures, suitable work equipment and off-site cutting Cuts to Hands Training and PPE Electrical Equipment Maintenance and use of 110v tools Falling Materials from Height Trim / tool tethers and loading out in accordance with best practice Removal of Waste Skips to level, loading bays etc. Adverse Weather Management control Slips, trips and falls Training, management control, PPE and housekeeping measures Manual Handling Design consideration, loading out to drawing and operative training Refer to SMD Risk Assessments for more information Technical Department SMD.TGN.122.V6 7

8 3.3 Personal Protective Equipment (PPE) Task-specific PPE will be detailed in the Project Risk Assessments, however the minimum requirements are: Site PPE - Minimum requirements Hard Hat to BS EN 397 Safety Boots with heavy duty steel toecap and steel mid-sole Hi-Vis clothing to BS EN 471 Class 1 Cut Resistant Gloves to BS EN 388 Cut 1 and Cut 5 rated Ear protection to BS EN Tinted Welding Goggles Eye Protection to BS EN 166 class 1 clear lenses for cutting/ shot-firing, smoked lenses for stud welding Fig.3.3a training matrix of all operatives ensuring all site personnel are kept up-to-date with the latest Health, Safety and Competency training requirements. 3.6 DO's for associated trades Land packs on the frame in the correct position It is essential that the decking packs are loaded out in the position indicated on SMD s decking layout drawings to minimise the manual handling risk! Fix all sheets before leaving area Unfixed decking sheets pose a danger to others on site, ensure that as areas are being laid that they are not left unattended until fixed. At the end of each shift, any unfixed sheets in decking packs must be secured down. Ensure heavy loads are placed over supports Other trades must be made aware of the storage capacity of decking prior to concrete and the appropriate procedures for locating heavy loads on timbers laid above the structural support lines. 3.4 Protection of falls from height In accordance with the Work at Height Regulations 2005 and given that for deck installation avoid work at height and use work equipment to prevent falls is not reasonably practicable, all contracts need to adopt a system of work that minimises the distance and consequence of a fall. Typical methods of fall arrest used are safety netting for steel frame structures or, airbags or similar for other support situations. Where safety netting is provided by SMD, this will be undertaken by FASET (Fall Arrest Safety Equipment Training trade association and training body) trained personnel. The contract-specific method statement and risk assessment will detail the preferred methods for both fall arrest and installation. Passive collective fall protection should always be selected over personal protection, such as harnesses and running lines. 3.5 Trained and competent workforce Ensure that all operatives have received manufacturers training in the use of cartridge tools and general training for abrasive wheels, manual handling, safe use of PPE, working at height, stud welding equipment and fire safety training. They must also have achieved the appropriate level of CSCS qualification. Safety net operatives must be FASET trained and hold IPAF certificates for using Mobile Elevated Working Platforms (MEWP's). Avoid cutting holes in the deck before concreting If additional holes are required to be cut into the decking before concreting, contact SMD Technical Team for guidance. Follow concrete good practice Following concrete trades must be aware of best practice when pouring on upper floor decks, to ensure overloading is avoided and any propping requirements are in place. Check design implications before cutting any sheets to single span Where sheets have been designed and supplied as double-spanning, they must not be cut to single span without checking the safe un-propped single span for the product involved. Cutting a sheet may introduce the need for propping! Contact SMD Technical Team or use SMD Elements Software for guidance. Refer to SMD Elements design software at SMD have a dedicated training manager and detailed 8

9 Technical Guidance Notes GUIDANCE NOTES 4.0 Design - Floor deck 4.1 Benefits of composite metal deck Rapid speed of construction, reducing overall project time Provides the tensile reinforcement requirements of the slab Composite Construction reduces steelwork frame weight Reduced foundation costs, due to reduced loading Integral ceiling and service fixing system The decking acts as permanent shuttering Provides a cover for following trades When fixed, the decking provides a safe working platform Minimal site storage requirements Easily installed into complex designs, with minimal wastage Can achieve up to 4hr fire rating for the slab Construction stage At Construction Stage the decking is designed to support the weight of the wet concrete, reinforcement and an allowance for temporary construction load in accordance with BS5950 Part 4 or BS EN Where this load is likely to be exceeded, SMD Technical Department should be consulted. 3. Materials should be positioned in a workmanlike manner. 4. Materials should be placed onto timbers, pallets or similar, to spread any load. These should be positioned directly over structural support. 5. Timbers or pallets should be positioned with the main support running perpendicular to the ribs of the decking. NOTE: Metal decking is NOT designed to accommodate the storage of materials during its construction stage, therefore until the structural concrete topping is placed, any such storage undertaken is to be carried out with due regard to the above notes Construction stage deflection Floor decks are designed to deflect under the weight of wet concrete as it is placed, in accordance with BS EN & BS EN or BS & 6. Typically, decking is designed for the nominal slab thickness specified with no allowance for any additional load due to excessive concrete thickness as a consequence of deflection of the structural steel frame during construction. The best practice guidance for concrete placement outlined in this manual should be adopted to avoid overloading of the decking. Where necessary to position materials directly on to the metal decking for short periods, the following recommendations should be followed: 1. Any load applied to the metal decking during its temporary construction stage should be restricted to 1.5kN/m². Special attention is required when applying temporary loads where the deck requires propping during construction. Temporary propping must be in place, levelled and suitably braced before any construction traffic is allowed over the deck. 2. Materials should always be positioned directly over suitable structural support. Mid-bay slab deflection Fig.4.1a In accordance with UK National Annex to BS EN and BS5950-4, the deflection of the deck at construction stage is limited to the lesser of Span/180 or 20mm, when the effects of ponding are not considered (deck deflection is less than slab depth/10). This limit is increased to the lesser of Span/130 or 30mm, when Technical Department SMD.TGN.122.V6 9

10 the effects of ponding are considered (deck deflection is greater than slab depth/10). The above must be considered both in specification of the slab surface tolerance (by the designer) and when determining the concrete placement method to be adopted (by the main/concrete contractor) Effect of construction stage deflection on surface and flatness tolerances As recognised in BS , SCI Publication P300 and Concrete Society TR75, it is not possible to construct concrete toppings on upper floor decks to a defined datum level due to deflections in both the deck and steel frame during construction. During concreting on metal deck, the supporting structure (deck, primary and secondary supporting steelwork) will deflect under the load from concrete and site operatives. This can occur for several hours following installation as the structure creeps under the weight of the concrete Refer to Fig 4.1a for indication of how these deflections impact on the surface level/flatness achievable. This is compounded by the differing stiffness and deflections for different elements of the supporting structure due to beam sizes, spans, connections etc. Rolling deflection will also occur during the concreting process (this subsequent Rolling deflection occurs in areas where concrete has already been placed as concrete placement progresses into adjacent deck sheets or structural bays). This is caused as a result of deflection of members connected to the area where concrete has already been placed. It is impractical to return to the initial area concreted to try and level the slab as any additional concrete will result in greater deflections and potential for overloading. guidance, the maximum recommended sheet length is 10 metres - Refer to Table 4.2a. Where longer sheets are required, an appropriate and safe means of installation must be considered, contact SMD Operations Team for further guidance. Profile R51 TR60+ TR80+ Gauge (mm) 4.3 Temporary propping Maximum Length (m) Table 4.2a Decking is usually designed un-propped, however for longer spans, isolated single span locations (i.e. temporary crane void infills) or large overhangs or cantilevers, temporary propping may be required during construction. Where required, temporary propping must be designed to support the wet weight of the concrete and any construction imposed loads. When contracted to carry out detailing, SMD deck general arrangement drawings will indicate areas where temporary propping is required with a chain-dotted line and the notation 'TP'. Due consideration must be given to this aspect by the Project Design Team when considering the effect this may have on following trades/finishes. For example, level to datum specifications are difficult to achieve unless steel beam spacing s are reduced and tight deflection tolerances on supporting steelwork enforced. This design requirement will result in cost implications and therefore subsequent levelling screeds may be more appropriate to attain tight level to datum specifications. Further guidance on recommended pouring methods and surface/flatness tolerance is available in Concrete Society TR75 and SCI AD344: Levelling Techniques for Composite Floors. 4.2 Sheet lengths In accordance with Health and Safety (Manual Handling) Should a project require tighter control of deck deflection at construction stage, the structural engineer may specify temporary propping to spans within the safe load/ span tables to minimise deflections experienced during construction. Where temporary props are required to spans exceeding 4.0m for R51 and TR60+, 5.0m for TR80+, or at any unsupported or large edges (refer to Fig 4.3a), the propping arrangement is to be in position, levelled and adequately braced prior to installation of the deck/edge trim. Consideration should be given to the suitability of fall arrest methods due to the difficulty and logistical issues of installing safety nets in this situation. 10

11 continuous and extend the full width of the bay to ensure zero deflection at propped points. Typically the continuous supporting timbers are propped at maximum 1m centres (refer to Figs 4.3b and 4.3c). GUIDANCE NOTES Temporary propped edge trim detail Fig 4.3a Depending on the design criteria (span, storey height and slab depth) in the location to be propped, props normally consist of either a length of timber and/or steel plate supported by adjustable steel props. In locations where the prop load is excessive, a proprietary shoring system may be more appropriate. The minimum bearing width of the timber and/or plate depends upon the thickness of the slab, these are typically in the range of mm. Temporary propping should not be removed until the concrete has achieved 75% of its design strength. The above information is for guidance only, the design and installation of the temporary propping is the responsibility of others (typically the project structural or temporary works engineer) and should be of adequate strength and construction to sustain the dead weight of the concrete plus any construction live loads. For more extensive guidance on Temporary Propping refer to SCI Publication P300, Concrete Society TR75 or contact SMD Technical Team. MCRMA/SCI Technical Paper No. 13/ SCI P300 REVISED EDITION. Composite slabs and beams using steel decking: Best practice for design and construction Concrete Society TR75: Composite Concrete Slabs on Steel Decking Temporary propped deck at mid-span Fig 4.3b 4.4 Lateral restraint and diaphragm action Metal deck may also be used as lateral restraint to stabilise the beams against lateral torsional buckling during construction (where the deck spans perpendicular to the beam) and, through diaphragm action, to stabilise the building as a whole by transferring wind loads back to the walls or columns (where designed by the structural engineer). Deck is typically fixed to the beam flange using either powder ( shot-fired ) or gas-actuated nails. Where fixings are required to resist lateral forces in accordance with BS EN 1993 or BS5950-1, the more robust Hilti X-ENP19 shot-fired nail (or similar approved) is recommended. The safe working shear resistances (per nail) are indicated in the tables below Note: In some instances the value differs depending on the decking gauge used. Temporary propped deck at mid-span Fig 4.3c The timber/steel bearer and sole plates must be Table 4.4a & 4.4b Safe Working Shear Resistances Figures for each profile are based on maximum fixing spacing over intermediate beams as mentioned in Section 4.6. Technical Department SMD.TGN.122.V6 11

12 b GUIDANCE NOTES Hilti X-U-15 fixings (DAK pin) Deck Gauge Profile (kn) 0.9mm 1.0mm 1.2mm Per nail be given to the height of any continuity reinforcement extending from the core to ensure it does not clash with the troughs of the deck profile. R TR TR Table 4.4a Hilti X-ENP 19 fixings (heavy duty nail) Deck Gauge Profile (kn) 0.9mm 1.0mm 1.2mm Per nail R TR Deck on RSA fixed to concrete core Fig.4.5a TR Table 4.4b Hilti X-P14 G3 MX fixings (gas nail) Deck Gauge Profile (kn) 0.9mm 1.0mm 1.2mm Per nail R TR TR Shelf Angles or bottom flanges To reduce the structural zone it is sometimes necessary to install the decking onto angles fixed to the beam webs or bottom flanges. Where deck ends are supported on shelf angles or bottom flanges between beam webs, the shelf angle or bottom flanges must be designed to extend a minimum of 50mm beyond the toe of the beam top Decking Bearing of Shelf Angle Detail flange. This minimum dimension of 50mm is essential End Caps for TR profiles or Tape (R51) to enable the sheets to be physically positioned between a toes of top flanges and provide access for a cartridge tool to be used to secure the decking into place SMD require(refer sufficient clearance to between Fig the toe of the top flange and the support steel inside the beam flange (a) to enable the deck to be placed inside the beam web and also for access (b) to install the end caps (TR 4.5b). profiles) or tape (R51) to close of the gaps in the end of the troughs. Table 4.4c Example of deck being placed onto shelf angles Slab depth 50 min. Typical 50 min. Typical 50 min. Typical Refer to SCI Publication 093 and SCI Advisory Desk Note AD 175, BS EN 1993 or BS for more information SMD Deck Profile Desired position of deck SMD.DOD.177.V2 Deck placed on angles in beams Fig.4.5b 4.5 Bearings / Support End bearing The minimum bearing requirements for the decking are 50mm on steelwork (this is increased to 60mm where sheets are to receive thru-deck welded shear studs, refer to Composite Beam section of this document) and 70mm on masonry or concrete. Where the deck is to butt up against a concrete core or similar, shelf angles are to be installed by others to provide adequate end bearing for the metal deck (refer to Fig 4.5a). When developing such a detail, consideration must Where the deck spans parallel to the beam web a structural support angle is the recommended detail (refer to Fig 4.5c). It may be possible depending on spacing of secondary beams to utilise a 2.0mm gauge flashing to avoid the requirement for a structural angle, however this will impact on the slab capacity for high concentrated loads locally in the region of the non-structural flashing. Refer to SMD Data sheet SMD.DOD Decking Bearing of Shelf Angle Detail at 12

13 Deck runing in each orientation Fig.4.5c Fixing to steel through deck trough Fig.4.6a 4.6 Fixings Recommended fixing types are as follows: Where steel beams are to receive thru-deck welded shear studs, Hilti X-P14 G3 MX, Hilti X-U 15 (DAK) or similar approved. A = Side laps of decking sheets NOTE: Beams to receive shear studs MUST have the top B = End of deck sheet flanges C = left Intermediate unpainted! supports D = Side stitching Where no shear studs are specified, Hilti X-ENP 19 (No.per sheet width) or Spit SBR 14 shot-fired nails Spacings or similar approved should Product be used. A B C D Endcaps Fixings to masonry should (2) be either (1) R Drill 750 & Hammer X Anchors (Spit P370 or P560, (3) or similar (2) approved) or TR shot-fired fixings (Hilti X-SW or Spit CR9 shot-fired (2) (1) TR nails or similar approved) refer to Fig 4.6e. Fixings to Timber/Glulam Beams, or where shot-fired Spacings fixings are not permitted, should be self-drilling screws Product B D Straps Fixfast DF12 5.5mm, Hilti S-MD55Z 5.5mm, or similar approved. Edge trim <200mm Where high screws are 750 to be used 750 on 750 steel beams Edge trim flanges 201mm thicker - 300mm than 12mm, 750 pre-drilling may be Edge required, trim 301mm contact - 450mm your fixing 750supplier 750for further 250* guidance. *Two sets of restraint straps are necessary (Refer Fig 16.8). At side-stitching of sheets and/or restraint strapping of edge trim, Hilti S-MD01Z 4.8 x 19, Fixfast DF3 HEX 4.8 x 20, or similar approved. Decking must be fixed to supports at 300mm centres at each sheet end and at 600mm centres over intermediate supports, or closest multiples to suit trough centres (for TR mm and 666mm respectively) Refer to Fig. 4.6b. Fixings should be located a minimum of 20mm from the end of the sheet and where more than one fixing per trough is specified, the spacing between fixings in the direction of the deck span is to be 45mm. D A B C D Support A B 1000mm centres Cover Width A Support Mid-span C Support Span Support B Stitching at side laps End of deck sheet Intermediate support Side support Fixings required in various locations Support D Fig.4.6b Side-stitching for R51, TR60+ and TR80+ deck is to be provided at maximum 1.0m centres from mid-span using self-tapping screws. Technical Department SMD.TGN.122.V6 13

14 Where decking is required to provide lateral restraint and no thru-deck welded shear studs are specified, the fixing type should be checked by the engineer, refer to section 4.4. Refer to BS EN 1993 or BS5950 for more information Spacings (No. per sheet width) Profile A B C D End caps R (2) 600 (1) 750 X TR (3) 666 (2) 750 ü the final condition must be designed as fully reinforced considering the mesh reinforcement in the surface of the slab and taking no contribution from the deck and/or trim, to determine whether any additional reinforcement is required to support the final imposed loads. The design and detailing of this reinforcement is the responsibility of others. Where deck spans perpendicular to the edge beam in the direction of the cantilever (refer to Fig 4.7a), a maximum dimension of 450mm is recommended. This is a practical limitation for health and safety reasons, as typically the handrail is located on beam centre line and extending the cantilever further may result in unsafe practice beyond the handrail when stitching trim to the end of the sheet. TR (2) 600 (1) 750 ü Table 4.6a Spacings Edge trim B D Straps <200mm high mm mm * *Two sets of restraint straps are necessary Table 4.6b Deck cantilever perpendicular to beams Fig 4.7a In locations where the above handrail issue does not apply it is possible to cantilever the deck up to 600mm depending on deck profile, gauge and slab depth. For cantilevers greater than 450mm contact SMD Technical Team as temporary propping may be required. Deck fixed to blockwork Fig.4.6e 4.7 Cantilevers Cantilevers or slab edge overhangs are constructed using deck, edge trim or a combination of both. In cantilever locations, the deck and/or edge trim acts as permanent formwork only and does not contribute to the tensile reinforcement for the cantilever. The slab cantilever in Deck and trim parallel to beams Fig 4.7b 14

15 Deck spanning parallel to the edge beam Cantilevers are achieved using edge trim (refer to Fig 4.7b). Decking must not be cantilevered at side locations without additional supports in place (refer to Fig 4.8c). The maximum achievable cantilever from edge of beam depends on the slab depth and edge trim gauge (refer to Table 4.7a for typical situations) up to a maximum of 200mm. For cantilevers or slab depths outside of this table contact SMD Technical Team. Edge trim gauge Slab depth 1.0mm 1.2mm 1.6mm 2.0mm 130mm 105mm 125mm 160mm 200mm 150mm 95mm 115mm 150mm 185mm Refer to National Structural Steelwork Specification (NSSS) 5th Edition for more information In some instances tighter tolerances may be required to suit the cladding contractor. Where this is the case, positions for edge trim should be engineered on site by a site engineer either by advising dimensions from constructed steel position or marking a physical line for theoretical grid position on site to enable the edge trim to be installed accurately from this position and hence reducing the impact of perimeter steel tolerance on slab edge position. However, consideration should be given to the appropriate gauge of edge trim to accommodate this setting out. GUIDANCE NOTES 175mm 90mm 110mm 145mm 175mm 200mm 85mm 100mm 135mm 165mm >250mm Propping required 4.8 Edge trim Propping required Propping required Propping required Table 4.7a Galvanised edge trim is provided where requested around perimeter and void edges. This edge trim acts as permanent formwork only to support the wet weight of concrete during construction. Typically, edge trim is supplied to site in lengths of 3.0m where it is then cut to suit. Edge trims are available in varying gauges; 1.0mm, 1.2mm, 1.6mm and 2.0mm. The material gauge is determined by the depth of the concrete slab and the extent of the slab overhang (refer to Table 4.7c). Edge trim can be either fixed to the end of the decking with self-tapping screws (refer to Fig 4.7a) or to the main supporting structure, using similar fixings as that used to secure the decking (refer to Fig 4.8c). R51 slab edge and flashings Fig.4.8b Extract Clause from NSSS Fig.4.8a Depending on the structure of the design team for the contract, the edge dimensions will typically be provided by either the architect or structural engineer. In accordance with the National Structural Steelwork Specification (NSSS) the tolerance on trim position is +/-10mm from CL of beam, this is in addition to the acceptable tolerance for the perimeter steelwork. The minimum bearings for edge trim are similar to that for the floor deck; 50mm on steelwork or 70mm for masonry or concrete supports. Edge trim should be fixed to supports at both ends and maximum 750mm centres along the length of the piece of edge trim, with restraint straps fixed between the top edge of the vertical leg and the floor deck at 750mm centres (typical), or 500mm centres for slab depths between mm (refer to Fig 4.8b). Where slab depth/edge trim height exceeds 300mm, two levels of restraint straps may be required alternated Technical Department SMD.TGN.122.V6 15

16 between the top edge of the vertical leg and mid-height (refer to Fig.4.8d) Alternative detail for large overhangs or cantilevers Where slab edge overhangs or cantilevers exceed the limits mentioned above, typically temporary propping will be required to the edge prior to installation. This can cause practical or logistical issues on site. Alternatively, additional stub beams can be provided by the steelwork contractor. These large edges can then be formed using a sheet of deck running parallel to the perimeter beam, with trim stitched to the edge of the sheet (refer to Fig 4.8c), the stubs must be located at centres within the maximum un-propped span limits for the deck profile, gauge and slab depth combination. In some instances where this is not practical, it is possible to provide extended height trim to form the outer face of the upstand (refer to Fig 4.8d). The internal face of the upstand will still require traditional formwork by others. There are limitations on overall trim height and gauge, although where trim heights exceed 450mm high, additional bracing/propping to the vertical leg is likely to be required during construction, for further advice contact SMD Technical Department Curved / Faceted edges Where edge trim is required to form a curve, straight lengths are provided to site and the edge trim cut to provide a faceted edge on site to form the desired radius (refer to Fig 4.8e). Alternative edge detail with stub supports Fig 4.8c Faceted trim detail to form radius edge Fig.4.8e Edge trim to form outer face of upstand Typically, it is easier for the outer and inner faces of perimeter upstands to be formed traditionally. The recommended tolerance for edge trim position from the desired radius is +/-25mm, this will be in addition to the perimeter steelwork tolerances at the location in question. During detailing the length of facets and spacing of set-out dimensions must be considered to ensure this tolerance can be achieved. Where tight tolerance control is required, physical dimensions for edge location should be engineered on site by a site engineer. Edge trim to form outside face of upstand Fig.4.8d 4.9 Flashings Where perimeter beams, or intermediate beams that are to receive shear studs, run parallel to the deck span and the deck width either falls short or is positioned such that a trough is not located over the beam flange, galvanised mild steel flashings should be provided to form a closure to the profile (refer to Figs 4.9a and 4.9b). Flashings are available in 1.0mm, 1.2mm, 1.6mm and 2.0mm gauges; supplied to site in standard 3m lengths. The exact geometry and requirement for these flashings will be detailed on SMD decking layout drawings where provided. 16

17 Flashing detail at perimeter beam Fig.4.9b Step in slab formed traditionally Fig.4.10b 4.10 Steps in slab Where a step in the deck/slab level is required, this should be located at supporting beam positions, with angles provided to support the lower level decking. Depending on the difference in level and requirement for slab continuity, the higher level slab may be formed using standard edge trim (refer to Fig 4.10a) or formed traditionally by following trades (refer to Fig 4.10b). When developing the detail to be used, the buildability should be considered as the detail in Fig 4.10b would require a two stage concrete pour, with the lower level poured first End caps Where trapezoidal (TR60+ or TR80+) decking sheets end at the perimeter of the building or at internal voids, the ends of the sheets are sealed with 0.7mm gauge galvanised end caps or polystyrene inserts. These end caps will also be required where you have a change in span direction (refer to Fig 4.11a). Due to the small re-entrant rib size of the R51 profile, sheets are typically sealed using tape or expandable foam. Step in slab formed with edge trim Fig.4.10a End caps Fig.4.11a Technical Department SMD.TGN.122.V6 17

18 Technical Guidance Notes 5.0 Design - Floor deck - Composite stage During the Composite, or Normal Stage, the composite slab must be checked for super-imposed Permanent (Dead) and Variable Imposed (Live) loads as specified by the client / engineer. Composite slabs are usually designed as a series of simply supported slabs in accordance with BS EN or BS Concentrated loads (i.e. line loads from walls) should be checked separately to ensure the specified slab criteria is adequate for the required loadings. Specific checks for concentrated loads can be carried out using SMD Elements design software. span tables for the specified design criteria (deck profile, gauge, slab depth and concrete type/grade). Where designs are outside the scope of the design tables provided, additional bottom reinforcement may be required for fire. For some composite slab designs, reinforcement in addition to that associated with the composite action of the deck and concrete will be required (i.e. cantilevers, void trimming, composite beam transverse reinforcement, building regulation compliance or enhanced crack-control due to sensitive finishes). The design and specification of any additional or increase in reinforcement is the responsibility of others, typically the project structural engineer. During design of the composite slab, consideration should be given to any loadings that may be applied to the slab during the construction phase (i.e. concentrated loads from plant or material storage), as these may be more onerous than the design loadings for the intended building use and impact on the minimum reinforcement required. 5.1 Reinforcement Purpose of reinforcement Normal cover supports (crack control) BS (Clause as noted) 0.1% of gross crosssectional area CI. 6.8 BS EN (Clause as noted) 0.2% of concrete above the ribs (unpropped), 0.4% for propped construction CI (2) Composite slabs require mesh reinforcement in the top of the slab to provide crack control, transverse load distribution and nominal slab continuity in accordance with BS EN clauses 7.4.1(4), 9.4.3(5) & (6) and 9.8.1(2) or BS clauses 6.7, 6.8 and 6.9 the minimum requirements and comparison of the different design codes is shown in table 5.1a. This reinforcement is usually in the form of welded steel fabric (mesh) in accordance with BS4483. Alternatively, in some design cases the steel fibre reinforced TAB-Deck solution, from ArcelorMittal Sheffield, can be used. For Technical information on the TAB- Deck solution and benefits of this form of construction refer Section 13.4 of this document or contact ArcelorMittal Sheffield. Transverse Reinforcement concentrated loads High concentrated loads 0.1% of the concrete above the ribs CI % of the concrete above the ribs for concentrated loads CI % of the concrete above the ribs for concentrated loads up to 7.5kN or 5kN/m CI (5) 20% of the area of principal reinforcement (deck) CI (3) & (2) Refer to SMD.PRO SMD Fibre Reinforced Concrete Slabs Design Guide at Table 5.1a In many cases, the reinforcement provided for the composite stage may be suitable to achieve the required fire resistance. This must be checked against the load/ When specifying reinforcement mesh sizes, it is important to consider the concrete cover over the profile to allow for lapping of sheets of mesh with nesting where appropriate. Typically the concrete cover over the profile can be as 18

19 little as 60mm. Where this is the case, the use of mesh reinforcement with flying ends may be necessary to enable the top cover dimension to the mesh to be achieved. The detailing of all reinforcement within the composite slab is the responsibility of the slab designer. Although cracks do not normally pose a durability or serviceability hazard, there are instances where the composite floor slab is required to provide a wearing surface or receives applied finishes that may be sensitive to cracking. Reinforcement percentages in excess of 0.3% are likely to be required to limit crack widths to an acceptable level. Refer to SMD Elements design software at Fire Refer to BS EN Section 7.3 for more information Refer to Concrete Society TR75: Composite Concrete Slabs on Steel Decking for more information Refer to AD150: Composite Floors Wheel Loads from Forklift Trucks for more information The fire design of a composite slab uses one of two approaches: GUIDANCE NOTES Refer to Eurocode NCCI PN005c-GB or more information Steel Fabric (mesh) and Deck Only: Known and selectable in SMD Elements software as Eurocode NCCI Method for BS EN 1994 design or Simplified Method for BS5950, this method utilises the deck and reinforcement mesh only at the elevated temperatures appropriate for the fire period selected. 5.2 Saw cuts Refer to SCI Publication P-056 (BS5950 Design) or more information Although the formation of saw cuts is a recognised method of controlling cracks on ground slabs, it is not recommended for upper floor slabs on metal deck for a number of reasons, including the danger of severing mesh that is critical for the composite slab fire design. From experience saw cuts do not always perform the intended function of concentrating the cracking in the location expected. To use this method, the composite slab and mesh reinforcement (not necessarily the metal deck) must be continuous over one or more internal supports. Continuity is taken to include all end bay conditions. ü ü The preferred method of controlling cracking in composite slabs is through an increase in reinforcement percentage in the top of the slab. Refer to SCI AD347: Saw Cutting of Composite Slabs to Control Cracking for more information ü X MCRMA/SCI Technical Paper No. 13/ SCI P300 REVISED EDITION. Composite slabs and beams using steel decking: Best practice for design and construction Slab continuity for fire Fig.5.3a This method will usually give the most economic design, but is limited to fire rating periods of 2 hours or less. SMD design tables are based on this approach with the Technical Department SMD.TGN.122.V6 19

20 slab continuous at one end only. It is important to note this when utilising the tables provided. Refer to SMD Elements design software to create calculations Fire engineering method: Known (and selectable in SMD Elements software) as Eurocode Standard Method for BS EN 1994 design or Fire Engineering for BS5950, this method uses additional reinforcement in the troughs of the decking along with top mesh reinforcement (where slab continuity permits) to achieve the required fire rating. Where the composite slab is true single span (i.e. no slab continuity at either end), this method should be used. For minimum mesh lap requirements refer to BS EN or BS8110. Generally, minimum laps should be 300mm for A142 and 400mm for A193, A252 and A393. The mesh must satisfy the elongation requirements of BS4449, for more specific guidance refer to SCI Publication P300 Composite Slabs and Beams using Steel Decking: Best Practice for Design and Construction. In addition to the requirements of Eurocode NCCI PN005-GB, BS EN or BS with regard to structural behaviour under normal design loads, the slab must also meet the minimum insulation requirement specified in BS5950 Part 8, Eurocode NCCI PN005-GB or BS EN Refer SMD Product Data sheets for minimum insulation thicknesses appropriate to each profile Single span slab - fire engineering ü Fig.5.3b Firestop Fillers In some situations, depending on the beam fire design and protection, firestop fillers will be required in the ribs of the deck profile over the beam flanges - Refer SCI Publication P300 Table 5.2. Where required, these are typically installed by following trades. SMD Elements design software enables the user to check designs using any of these methods to suit the design standard chosen. For extensive guidance on the fire design methods mentioned above, refer to Eurocode NCCI PN005c-GB for Eurocode and SCI Publication Publication P-056 for BS5950 design. 5.4 Moving concentrated loads For moving concentrated loads with typical design criteria, the common mode of failure is Horizontal Shear Failure at the deck/concrete interface, it is therefore essential to check the slab for: 1. Worst case bending at fire stage (with load positioned at mid-span) The recommended top cover to the mesh reinforcement is a minimum of 15mm and a maximum of 45mm to ensure the mesh is effective for both the fire and crack-control requirements, refer to Fig.5.3c. Due to the modular size of spacers available and relatively thin concrete depth over the top of the deck rib, in some instances, it may be necessary to position the reinforcement directly on the top of the deck rib. Where this is proposed, it is important that the composite slab design is checked to ensure this does not affect the fire design for the slab design criteria in consideration and that the top cover to reinforcement does not compromise the crack-control provided. Recommended reinforcement cover Fig.5.3c Concentrated load - worst case bending Fig 5.4a 20

21 2. Worst case shear at composite stage (with load positioned adjacent to the support) concrete the opening is boxed out. When the slab has cured, the deck is cut by others using a nonpercussive tool. (Refer Fig 5.6a). GUIDANCE NOTES Options forming voids Fig.5.6a Concentrated load - worst case shear Fig 5.4b When designing for concentrated loads, it is important to consider those that may be applied from plant during construction, as these may be more onerous than the final specified loadings for the building and will impact on the reinforcement required for the slab. 2. Greater than 250mm (for R51) or 300mm (for TR+ profiles), but less than 700mm: Additional reinforcement is required around the opening, generally designed in accordance with BS EN or BS8110. The forming of the hole is as item 1 (Refer Fig 5.6a and 5.6b). 5.5 Long single span propped composite slabs Following research into long single span propped composite slabs (i.e. locations where the slab is not continuous over supports at either end of the span, typically found in light gauge frame construction), design guidance was published by SCI/NHBC in New Steel Construction (October 2011). The guidance introduces more stringent span/depth ratios when long single span slabs require propping. When using SMD Elements software, a guidance note will appear containing a link to the SCI/NHBC guidance where the input design criteria is appropriate. For further guidance contact SMD Technical Team. 5.6 Forming service holes When it is necessary to form service holes in a composite slab the following general rules are recommended. For openings at right angles to the deck span: 1. Up to 250mm (for R51) or 300mm (for TR+ profiles): Openings such as these require no special treatment (i.e. no additional reinforcement). Prior to placing of Trimming reinforcement configuration Fig.5.6b Technical Department SMD.TGN.122.V6 21

22 3. Greater than 700mm: Structural trimming steelwork designed by others and supplied by the steelwork fabricator, is recommended. Items 1 and 2 relate to holes in isolation and not to a series of holes transverse to the direction of span, which should be considered as one large void. In these cases, the metal decking should only be cut after the slab has cured. Typically, for a void to be considered in isolation, the clear dimension between void edges in a direction transverse to the deck span should be no less than the greater of 666mm or 1.5 x void width (A in Fig 5.6b), providing no excessive concentrated loads apply to the unsupported edges. When forming holes in the decking, consideration needs to be given to Health & Safety. Due consideration should be given to protect against falling through holes. If possible, handrails should be erected around the void. Alternatively, SMD can provide: A temporary cover to the opening, by decking over the void (unconcreted), for removal by others at a later date. VoidSafe Protection System - Refer Section 13.2 Refer to VoidSafe Protection System Brochure at These are guidelines only and particular requirements should be checked by the project structural engineer. SMD s responsibility excludes the design of any additional framing or slab reinforcement for holes or openings. MCRMA/SCI Technical Paper No. 13/ SCI P300 REVISED EDITION. Composite slabs and beams using steel decking: Best practice for design and construction Need Further Guidance? Contact us on +44 (0) or our Technical Team on technical@smdltd.co.uk 22

23 Technical Guidance Notes GUIDANCE NOTES 6.0 Design - Floor deck - Composite beam design Thru-deck welded shear studs are commonly used to transfer horizontal shear forces between the steel beam and concrete slab to suit the relevant design standard. These studs are welded to the supporting beams through troughs in the decking. Therefore, it is essential that the decking and beam geometries are considered by the structural engineer when specifying stud quantities, in particular on beams running perpendicular to the decking span. For a beam to be stud welded, the flange thickness must be a minimum of 0.4 x the stud diameter = 7.6mm for the standard 19mm diameter studs used in composite beam design, to avoid damage to the beam flange (known as burn through). Where possible, shear studs should be placed on the centre line of the beam directly over the web to avoid burn through. 6.1 Shear stud LAW (length after weld) When installing shear studs, the length after weld should extend at least 35mm above the top of the main ribs in the deck profile. Therefore, the minimum stud height after weld should be 95mm for TR60+ or R51 and 115mm for TR80+. The recommended minimum concrete cover to the top of the stud is 15mm, this should be increased to 20mm if the shear stud is to be protected against corrosion, as specified in BS Refer to SMD Data sheet 11 at current catch all rules contained in both BS EN and BS Section 3.1:1990 +A The SCI/BCSA research provides the designer with advanced rules that cover wider design criteria than that currently available in the relevant design standards, including: Unpropped construction Partially utilised beams Beams with large web openings Refer to SCI Publication P405: Minimum degree of shear connection rules for UK construction to Eurocode Shear stud reduction factors Methods for determining the resistance of shear studs in solid concrete are outlined in BS EN and BS Section 3.1:1990 +A When used in composite decked slabs, these solid slab stud resistances may need to be reduced due to the decking geometry and/or orientation. 6.4 BS EN Reduction factors for SMD products These figures are calculated in accordance with latest SCI Publication P405 and NCCI document PN001a- GB: Resistance of headed stud shear connectors in transverse sheeting. k mod (modification factor from Table 2.1 of PN001a) is already applied to TR+ values where appropriate. The factors in this table should be applied to the minimum resistance for a stud in a solid slab from equations (6.18) and (6.19) of BS EN Design rules for minimum degree of connection Composite beams with metal decking should be designed in accordance with BS EN or BS Section 3.1:1990 +A However, recent industry research undertaken by SCI and BCSA has resulted in noncontradictory complementary information that provides the designer with advanced rules for design of composite beams removing the conservatism that exists with the R51 TR60+ TR80+ 1 Deck gauge 1.0mm >1.0mm 1.0mm >1.0mm 1.0mm >1.0mm 1 stud (per trough) studs (per trough) Parallel to rib Table 6.4a 1 Figures are based on 95mm LAW shear studs except TR80+ which is based on 120mm LAW. 2 All factors are based on mesh at nominal top cover, except Parallel which is based on below head of stud Technical Department SMD.TGN.122.V6 23

24 6.5 BS Section 3.1 Reduction factors for SMD products These figures are calculated in accordance with the latest revision of BS Section 3.1:1990 +A The factors in this table should be applied to the minimum resistance for a stud in a solid slab (Q k ) from Table 5 of BS Section 3.1:1990 +A R51 Stud Details Single studs Stud to be placed in the centre of each trough Side lap where two sheets fix together stud (per trough) R51 TR60+ TR C L 102 min flange width 2 studs (per trough) Hatching indicates the ribs of the profile Middle of beam Parallel to rib Table 6.5a 1 Figures are based on 95mm LAW shear studs except TR80+ which is based on 120mm LAW. 2 All factors are based on mesh at nominal top cover, except Parallel which is based on below head of stud R51 Stud Details R51 - Staggered Single row studs studs butt joint Stud to be placed in the centre of each trough Side lap where two sheets fix together Fig.6.6a Refer to SCI Publication PN001a-GB NCCI: Resistance of headed stud shear connectors in transverse sheeting Refer to SCI Publication PN002a-GB NCCI: Modified limitation on partial shear connection in beams for buildings C L 3 O min. single staggered studs (60mm for standard 19mm O studs 30mm min. Hatching indicates the ribs of the profile 95 min. Middle of beam 120 min flange width Refer to SCI AD380: What Height of Shear Stud Should be used in Eurocode 4 R51 Stud Details R51 Studs - Staggered in studs butt joint Stud to be placed in the centre of each trough Side lap where two sheets fix together Fig.6.6b Refer to SCI AD174: Shear connection along composite edge beams 6.6 Shear stud spacing In accordance with BS EN or BS Section 3.1:1990+A1 2010, the dimensions and configurations shown in Figs 6.6a to 6.6f must be followed to ensure the welded shear studs are effective to provide the documented stud resistance values. C L 4 O min. studs in pairs (76mm for standard 19mm O studs Hatching indicates the ribs of the profile Middle of beam 136 min flange width R51 - Studs in pairs Fig.6.6c 24

25 TR+ Shear Stud Layout Details, Single Studs C L Stud to be placed in the centre of each trough Side lap where two sheets fix together 30mm min. 300/ / /333 TR + - Single row of studs TR+ Shear Stud Layout Details, Staggered butt joint Stud to be placed in the centre of each trough Side lap where two sheets fix together 300/ / / min flange width Fig.6.6d 6.7 Transverse reinforcement for composite beams Transverse reinforcement is required in the concrete flange of composite beams to resist splitting forces. This will usually be in the form of mesh and/or additional bars running perpendicular to the beam centre line. In locations where the decking spans perpendicular to the beam centre line, the deck can also be considered, providing it is either continuous across the beam flange or securely anchored with thru-deck welded studs at butt joints. Where the deck is considered as transverse reinforcement at butt joints in the deck sheets, the shear studs should be welded a minimum of 30mm from the end of the sheet and 30mm from the toe of the beam, resulting in a minimum bearing required of 120mm Refer to Fig 6.6e (based on TR+ profiles, but similar detail applies for all floor deck products). GUIDANCE NOTES C L 3 O min. single staggered (60mm for standard 19mm O studs 30mm min. 120 min flange width For beams where the deck spans parallel to the beam centre line, it is recommended to neglect any contribution of deck to the transverse reinforcement requirement as this can introduce impractical limits on sheet lap positions and flashings in deck sheets. Perimeter beams designed as composite may require additional 'U' bars depending on the slab edge dimension, refer BS EN (Clause ) or BS Section 3.1:1990+A (Clause 5.6.5) TR + - Staggered studs TR+ Shear Stud Layout Details, Studs in butt joint Fig.6.6e SMD.DOD.180.V2 MCRMA/SCI Technical Paper No. 13/ SCI P300 REVISED EDITION. Composite slabs and beams using steel decking: Best practice for design and construction Stud to be placed in the centre of each trough Side lap where two sheets fix together 300/ / / Alternative shear connectors C L 4 O min. studs in pairs (76mm for standard 19mm O studs 30mm min. 136 min flange width In some instances, the on-site welding of thru-deck welded shear studs may not be practical (i.e. due to restricted access, fire hazard or galvanised beams). In these cases the beams should be designed as Non- Composite or, where a shear connection is essential, one alternative is the use of Hilti X-HVB Shear Connectors, fixed to the beam with shot-fired fixings using a DX750 or DX76 cartridge tool (refer 6.7a and 6.7b). TR + - Studs in pairs Fig.6.6f SMD.DOD.181.V2 Technical Department SMD.TGN.122.V6 25

26 Hilti X-HVB installation Fig.6.7a Hilti X-HVB Shear Connectors Fig.6.7b It should be noted that these Hilti X-HVB Connectors do not provide the same capacity as welded shear studs and where this alternative connector is specified, the structural steel designer shall advise the quantity and type required for the composite beam design. Refer to Hilti Product Literature on X-HVB Shear Connectors for more information For further information on Hilti X-HVB Shear Connectors contact Hilti (UK) Technical Support Need Further Guidance? Contact us on +44 (0) or our Technical Team on 26

27 Technical Guidance Notes GUIDANCE NOTES 7.0 Design - Floor deck - Considerations 7.1 Falls and ramps Where metal deck is required to be laid to falls or create a ramp, the supports must be similarly laid to falls to enable sheets to be fixed with adequate bearing Refer Fig. 7.1a. It is possible to install metal deck to horizontal flanges where the angle of fall is less than 2.5º, however this will impact on the ability to install thru-deck welded shear studs due to the small gap created between the deck and flange. When considering deck to circular ramps, the orientation of top flanges and beams for both primary and secondary beams must be considered to ensure effective bearings are provided at all edges. Due to the irregular shapes involved in such ramps, the R51 profile is recommended particularly when beams are designed compositely to ensure effective concrete around the studs. As a result, it may be necessary to design the sheets as single span in such scenarios and hence, reducing the beam centres accordingly to avoid temporary propping. Support and deck laid to fall Insufficient bearing. Packer required to maintain 50mm bearing. x Detailing deck on a fall Fig.7.1a Ramped deck on pre studded beams Fig.7.1c Consideration must be given to safe means of installation when designing such slopes. The decking should span along the slope (not up/down the slope) and an area for landing the decking packs during construction must be provided. The concrete design, method of pouring and impact on programme caused by pouring smaller bays/areas to achieve the required slope, must also be considered. Engage SMD in such projects at an early stage to enable the model to be reviewed helping to minimise site buildability and installation issues. 7.2 Fixing tool and stud welding gun restrictions Where deck, edge trim or shear studs are to be installed to beams with obstructions within 570mm of the top of steel level, it may not be possible to achieve the required detail on site. Consideration must be given to sequence of works and possibly the design of non-composite beams in such locations. Deck laid to a steep fall Fig.7.1b Technical Department SMD.TGN.122.V6 27

28 be designed by the structural engineer to sustain the weight of the decking, wet concrete and construction imposed loads to avoid the temporary propping requirement indicated in Fig 7.3a. Decking is then cut back to the line of the shuttering, with temporary propping in place (if required). In this detail, the decking will not contribute to the shear resistance of the finished slab. Hairpin/tie bar reinforcement in the troughs of the decking profile will need to be designed/specified by the engineer. Fixing tool dimensions Fig.7.2a Refer to SMD.DOD Fixing tool access restrictions and guidance at Concrete encased beam Fig.7.3a A similar process to that detailed above can be followed where a building or basement has perimeter concrete walls with continuity reinforcement extending into the floor slab, providing the formwork is designed to support the weight of the decking, wet concrete and construction imposed loads to avoid the need for adjacent temporary propping. Fixing restrictions - stud welding 7.3 Concrete encased beams Fig.7.2b In some instances concrete encased perimeter beams may be specified as part of the fire design. It is recommended that the beam is encased to the top flange level off-site, therefore enabling the decking to be installed to the beam top flange as normal. Where it is not possible to carry out the concrete encasement off-site, the following procedure is possible using R51 profile: Decking installed to top flange of perimeter beam as normal. The shuttering is then provided by others. This must 7.4 Durability All SMD decks are manufactured from galvanised steel coil to BS EN with a standard 275g/m 2 coating which equates to 0.02mm (20μm) per face. Although the galvanising provides a protective coating, it does weather, albeit at approximately one tenth of the rate of bare steel (depending upon the prevailing conditions). Useful references on the life to first maintenance (LTFM) of galvanised steel coil include: Galvanizers Association, The Engineers and Architects Guide: Hot-dip Galvanizing Corus Strip Products UK, Protected with strength - Solutions in Galvatite hot-dip galvanised steel The Steel Construction Institute, P262 - Durability of Light Steel Framing in Residential Building: Second Edition SCI Advisory Desk Note 247: Use of Composite Construction in an Aggressive Environment, New Steel Construction, April

29 In summary, the above references conclude the LTFM for galvanised steel coil with a 20 μm coating as shown in Table 7.4a for the different corrosivity categories. Corrosion category Average Zinc corrosion rate (μm/year) Calculation of LTFM Life o first maintenance C1 <0.1 20/0.1 = 200 yrs C2 C3 0.1 to 20/0.1 = 200 yrs to /0.7 = 28.5 yrs 0.7 to 20/0.7 = 28.5 yrs to /2.0 = 10 yrs Other options that should be considered for extending life to first maintenance are: 1. The addition of a suitable paint finish 2. SMD offer an enhanced galvanised coating (High Durability) option for all floor deck products, R51 HD, TR60 HD and TR80 HD. The HD zinc-based coating incorporates Magnesium and/or Aluminium to offer superior durability, up to 3 times that of the standard 275g/m² galvanised coating - Contact SMD Technical Team for further information. GUIDANCE NOTES C4 2.0 to 20/2.0 = 10 yrs to /4.0 = 5 yrs 4.0 to 20/4.0 = 5 yrs to C /8.0 = 2.5 yrs Table 7.4a From Table 7.4a, it is apparent that identifying the corrosivity category for the design situation is key to obtaining an accurate life to first maintenance. The environment in which the material will be located must be carefully assessed to determine which of these categories is applicable for the location in question. The LTFM figures presented in the table above are similar to those documented by the galvanised steel suppliers for the different locations (shown below): Internal, Dry & Unpolluted: years (Typical for most common applications offices, warehouses, hospitals, airports) Suburban & Rural: 5 10 years Coastal: 2 5 years Industrial and Urban: 2 5 years 7.5 Aggressive environments Where the environment is deemed to be aggressive, additional corrosion protection measures to the metal deck soffit should be considered by the party responsible for the slab and/or overall building design, taking into account aesthetic as well as structural considerations. Steel strip with thicker galvanised coatings of 350g/m² and up to 600g/m² is available, but difficult to obtain, subject to large minimum order quantities and still has limited periods to first maintenance. For profiled steel sheeting used in composite floor construction these non-standard galvanised coatings, although available, do not necessarily provide a practical (as increased coating thickness prevents the use of thru-deck welding for shear studs) or economic way of increasing durability. Refer to SMD High Durability Data Sheet at 3. Utilise the deck as permanent formwork only with the slab designed as an RC slab taking no contribution from the deck. In this situation, any degradation of the metal deck will not affect the structural integrity. However, the metal deck soffit may require an additional coating for aesthetic reasons. For more extensive guidance regarding durability refer to SMD document titled Durability of Steel Decked Composite Floors. Important: When using metal decking in aggressive environments, where water will be located on the slab surface (such as car parks), adequate waterproofing of the slab surface is required to prevent ingress of water through the slab to the upper surface of the deck. Refer to SMD.STD Steel Deck Composite Floors in Car Parks for more information Refer to SMD.STD Durability of Steel Deck Composite Floors for more information Refer to Steel-framed car parks Corus Construction & Industrial for more information Refer to ECCS Publication No. 84 Car Parks for more information Technical Department SMD.TGN.122.V6 29

30 7.6 Vibration The recommended minimum natural frequency for a composite floor plate (consisting of both the composite slab and composite beams) is 5Hz when used in office or domestic type applications. This limit should be increased to 8.4Hz for floors subjected to rhythmic activities such as gyms, dance studios or even plant areas supporting machinery. 7.8 Thermal mass Following a study at Oxford Brookes University; BRE, The Concrete Centre and CIBS all acknowledge that approximately 100mm is the maximum thickness of concrete that can be mobilised within a typical 24-hour cycle of heating and cooling refer graph below. Using SMD Elements software, the dynamic deflection of the composite slab is calculated in accordance with SCI Publication P-354: Design of Floors for Vibration A New Approach. Using the guidance and calculation method contained in P-354, this deflection can then be added to that for the composite beams enabling the Natural Frequency of the floor plate to be determined. Refer SCI Publications P076: Design guide on the vibration of floors and P354: Design of floors for vibration A New Approach 7.7 Acoustics The acoustic performance of a composite slab is a function of both the mass of the slab and the floor and ceiling finishes applied. Robust Standard Details are available to provide performance in accordance with Building Regulations Part E utilising a number of different finishes for both the ceiling and floor. The detailing of such finishes is key to provide the acoustic performance required. Admittance for NWC and LWC Fig.7.8a Composite slabs on R51, TR60+ or TR80+ in the region of 130mm-150mm thickness all provide an effective concrete volume that meets this 100mm optimum thickness. Refer for further information Refer to SCI-P322 Acoustic Performance of Composite Floors for more information Refer to SCI P-336 Acoustic Detailing of Multi Storey Residential Buildings for more information Refer to SCI P-372 Acoustic Detailing for Steel Construction for more information Case Study: St Johns Square, Seaham Part of the SMD contract at St John s Square, Seaham working for Hambleton Steel, utilises the thermal mass of the composite slab by exposing the slab soffit and providing natural ventilation through a series of stacks that penetrate the metal deck and floor slabs. The building housing a Public Library with Offices and a Café, involved the design, supply and installation of 2,700m² of SMD R51 x 1.0mm gauge profile with slab thicknesses of 130mm and 160mm. For guidance relating to the acoustic performance of a bare composite slab, contact SMD Technical Team. It should be noted that for more extensive guidance, an acoustic specialist may be required. The building on completion achieved a BREEAM Very Good Rating. Refer Johns_Square,_Seaham for further information 30

31 St Johns Square, Seaham Fig.7.8.1a St Johns Square, Seaham Fig.7.8.1b Need Further Guidance? Contact us on +44 (0) or our Technical Team on Technical Department SMD.TGN.122.V6 31

32 Technical Guidance Notes 8.0 Design - Roof deck SMD structural roof deck products are typically used as the structural deck (tray) for various insulated roof systems including: Single Ply Membrane Double skin built-up system Standing Seam Green Roofs Asphalt Using the Elements (Roof deck option), full structural calculations can be prepared with a diaphragm design service available upon request. The use of a structural deck in place of a more traditional liner provides benefits from design stage right through to construction: 8.1 Quality Through the robust Factory Control Procedure (FPC) at our state of the art computerised manufacturing facility, all products are CE Marked to BS EN The quality management system closely monitors quality of material and geometry with QA certificates and material certificates available upon request. The SMD structural roof deck installation service also comes quality assured with our ISO 9001 accreditation. Profile SR30+ Gauge mm Grade N/mm 2 Cover width mm Weight kg/m 2 Max. Single Span m Max. Double Span m Cantilever mm In many instances, site operatives can walk directly on the profile without the need for crawl boards The longer span nature of structural roof decks results in less secondary members giving an aesthetic uncluttered soffit whilst also saving time during erection of the frame All SMD deck profiles, ranging from 30mm to 100mm in depth are designed in accordance with BS EN , with all product designs complemented by structural testing carried out at Lucideon. SR35+ SR60+ SR100 SR135 SR153 SR158 SR Table 8.1a 4-point loading test Fig.8.0a NOTE: Numbers shown RED should not be used as sheet lengths exceed recommended maximum for logistic and manual handling reasons. 32

33 All profiles are available in either galvanised or white liner interior finish. 8.2 Spans overlapped by a minimum of 75mm. The typical bearing and standard end lap details are shown in Fig. 8.4a. GUIDANCE NOTES Structural roof decks can be designed for the following span conditions. It is important that sheet weights and manual handling implications are considered when determining span conditions and detailing sheet lengths. End Lap (Purlins / Cold rolled) Lower Roof Deck Upper Roof Deck Span Condition Single Double Multi Description A length of roof deck that only has supports at each end. A length of roof deck that spans across three supports; one at each end and a further support within the length of the sheet. A length of roof deck that spans across 4 or more supports; one at each end and at least a further two within the length of the sheet. Deck sheets overlap (sealant where requested) Lower sheet to be flush with back edge of Purlin Upper sheet to be lapped over as shown above. End Lap (Beams / Hot-rolled) Lower Roof Deck Upper Roof Deck Deck sheets overlap (sealant where requested) SR30+ to SR60+ where beams < 150mm Wide Lower sheet to be flush with back edge of beam Upper sheet to be lapped over as shown above. The span condition impacts the load resistance of the structural roof deck, therefore it is imperative that sheets are installed in accordance with the detailed design. Sheets should not be cut to alter span conditon without written consent from the structural engineer and/or the manufacturer. End laps Roof Deck Fig.8.4a 8.3 Loads The maximum span values in Table 8.1a are based on the following design criteria: Imposed Load of 1.5kN/m² or Line Load of 2kN/m Partial Load Factor of 1.5 (considering all loads as Variable ) Imposed Load Deflection Limit of Span/200 Wind Uplift of 1.5kN/m², subject to appropriate fixings Wind Uplift Deflection Limit of Span/90 Butt joint Butt Joint (Beams / Hot rolled) 8.5 Extended end laps Fig.8.4b Where sheet length restrictions mean a double span sheet is not possible, it is possible to provide extended overlaps at the junction of two single span sheets (> 8% of span either side of support) to create an effective double span; Refer to Fig. 8.5a. For more detailed designs, refer to SMD Elements design software version 2.0 for more information More extensive load tables can be found on the SR product-specific data sheets downloadable at Standard end laps Where the roof is laid to falls, the top flange of the supports must also be laid to falls. At junctions in sheet ends, the roof sheets should be Extended end lap Fig.8.5a Technical Department SMD.TGN.122.V6 33

34 Although this is technically suitable as a detail, it is not recommended for practical reasons (ie. less economical, difficult to install, requires more detailed fixing configuration with additional fixings in webs of sheets). with a suitable flashing fixed to the end of the decking at every rib position to prevent spread of the deck profile; refer to Fig. 8.7a. 8.6 Raking supports and cutting Typically roof deck sheets are supplied to site with square ends, hence where a raking end joint is required these sheets must be cut to suit on site. Cantilever with end stiffener Fig.8.7a Raking butt joint Fig.8.6a At raking joints / verges within the roof deck the sheets are to be butted together as end lapping is not possible due to the trapezoidal profile of the sheets. The support width in these locations must be sized to ensure the minimum end bearing for butted sheets can be achieved. Careful consideration is required for sealing and provision of fillers in raking locations. Consider Off-site cutting? SMD offer an off-site cutting service, with the sheets individually detailed and cut prior to being delivered to site. This service has successfully been in place for the floor deck range for years and has added benefits of: Reduced time working at height Improved site programme Less wastage at height Reduced noise pollution Waste recycled at source This provides an altogether more sustainable and environmentally friendly solution. 8.7 Cantilevers The maximum cantilever figures indicated in this document are based on a point load of 0.9kN positioned at the end of the cantilever. Cantilevers must be stiffened 8.8 Sheet lengths In accordance with Health and Safety (Manual Handling) guidance, the maximum recommended sheet length varies depending on the deck profile and gauge (refer to Section 9.2). Where sheet lengths exceeding the recommended maximum length are required, an appropriate and safe means of installation must be considered, contact SMD Operations Team for further guidance. 8.9 Fire rating Profiled roof deck sheets (non-perforated) generally achieve Class 1 fire rating to BS and Class 0 in accordance with Building Regulations Durability Where roof deck products are to be used externally or in more aggressive environments, an increased coating may be required contact SMD Technical Team for guidance. Any enhanced coating required will be subject to a minimum order quantity and extended lead time Acoustics SMD SR roof products can be provided with the webs partially perforated. When used with a layer of acoustic insulation as part of the site-assembled double skin system this provides sound absorption and reduces reverberation from noise within the internal space. 34

35 Fasteners Use standard washers Perimeter or butt ends in sheets Profiled filler blocks, contact SMD Technical Team for info. GUIDANCE NOTES Around Penetrations, such as pipes Sealant tape and/or flexible flashing With a good standard of workmanship, taking care and attention to detail, a twin skin metal roof structure meeting the air tightness requirements of Approved Document L can be easily achieved. Perforated sheet with typical build-up R Fig.8.11a It should be noted that the roof cladding is only one part of the envelope that contributes to air leakage. In certain situations, junctions at windows, doors, roof lights, smoke vents etc. may be more critical and hence, the attention to detail must apply to all elements of the building envelope. Important Any filler or sealant is only as good as the workmanship installing the detail! Pattern of perforations 60 Fig.8.11b 8.13 Fixing specification The fixing options selected depend on the function they perform and supports to which they are being installed. Hot Rolled Steel Sections: Shot-fired Hilti X-ENP-19 L15 5.5mm carbon steel drill screws, or stainless steel for more aggressive environments The structural properties for perforated profiles are lower than that for the standard products. For load information relating to the perforated profiles, visit or contact SMD Technical Team at Technical@smdltd.co.uk 8.12 Airtightness As recommended by MCRMA, to minimise air leakage through twin skin metal roofing, the liner side of the construction must be sealed as effectively as possible. To provide an effective seal, this will typically involve sealing at the following locations: End Laps Typically using butyl strip with 8/10mm bead as follows: Up to SR60+ 8mm bead SR100 and above 10mm bead Side laps and Perimeter Side Joints Typically with 1mm x 50mm wide butyl tape Cold-formed Steel Purlins: 5.5mm carbon steel drill screws, or stainless steel for more aggressive environments Timber and/or Glulam Beams: 6.5mm stainless steel screws Side stitching of sheets and/or flashings: 4.8mm carbon steel drill screws, or stainless steel for more aggressive environments Note: The above fixing types and centres (from Table 8.14a) will need specific checks for any uplift or diaphragm design required. This may result in a different fixing type or spacing being required to suit the design situation. For all fixing checks carried out, the performance data for the fixings should be tested in accordance with ECCS publication No Fixing Centres and Locations Recommended minimum fixing centres for each profile are detailed in the table below. These may need to be Technical Department SMD.TGN.122.V6 35

36 increased in frequency and/or number where wind uplift load or diaphragm roof design is required contact SMD Technical Team for further information. Primary Fasteners Secondary Fasteners Profile Deck Ends Intermediate Supports Side Laps Side Supports SR30+ Every Trough Alternate Troughs Not Essential* 450mm centres SR35+ Every Trough Alternate Troughs Not Essential* 450mm centres SR60+ Every Trough Every Trough 450mm centres 450mm centres SR100 Every Trough Every Trough 450mm centres 450mm centres SR135 Every Trough Every Trough 450mm centres 450mm centres Fixing locations within the sheet Fig.8.13b SR153 Every Trough Every Trough 450mm centres 450mm centres SR158 Every Trough Every Trough 450mm centres 450mm centres SR200 Every Trough Every Trough 450mm centres 450mm centres Table 8.13a Exposed soffit Where the SR sheets are required to provide an exposed soffit a thicker gauge should be considered, as thinner gauges can be susceptible to marking when subjected to relatively high impact loads during construction Flashing details Due to the fixed trough centres and cover widths of the structural roof deck sheets, there are a number of flashings that must be used to close the profile off at perimeter edges and ridges in the roof. The standard details including flashings are detailed below: Setting out point Underlap / Overlap Fixing configurations Fig.8.13a The below restrictions on fixing position within the sheet are based on fixing types documented above, BS EN recommendations and Hilti literature in relation to cartridge fired pins. Minimum edge/end distance and spacing Fixing to end of sheet (A): 20mm minimum Fixing to edge of support (B): 10mm minimum (based on steel flanges >7mm) Distance between two fixings (C): 20mm minimum Fixing to edge of sheet (D): 10mm minimum Setting out point and typical overlap Fig.8.13c 36

37 No Flashing, sheets lap together Flat plate flashing 'Z' shape flashing <5 slope Side support flashing details Fig.8.13d Deck parallel to shallow ridge (<5 slope) Fig.8.13f Fig.8.14d Flat plate flashing (RED) and 'Z' shaped flashing (GREEN) at Side Supports Flashing to the steel Flashing across the top of the sheets to form the ridge Change in span direction Fig.8.13e >5 slope Deck/flashing parallel to ridge (>5 slope) Fig.8.13g Technical Department SMD.TGN.122.V6 37

38 Flashing to form the ridge Non-fragility test Fig.8.14a Ridge flashing on purlins Fig.8.13h 8.15 Diaphragm design SR structural roof decks provide a clean uncluttered soffit for the roofing system. It is possible to enhance this uncluttered appearance by utilising the structural roof deck as a diaphragm to transfer wind loads from the perimeter walls to internal vertical bracing/walls, therefore reducing, or removing the need for in-plane roof bracing. Valley flashing on purlins 8.14 Non-fragility Flashing to form the valley Fig.8.13i All SMD shallow roof deck profiles (SR30+ to SR100+) have been tested in accordance with ACR(M)001:2005 Test for Non-Fragility of Profiled Sheeted Roof Assemblies [Third Edition] and achieved Class B Non-Fragile Assembly. ACR(M)001:2005 Test for Non-Fragility of Profiled Sheeted Roof Assemblies [Third Edition] To design the deck as a diaphragm, the following must be considered: Implications of deck layout, void sizes/locations and vertical bracing/wall positions. Line loads applied to the diaphragm perimeter Fixings to all perimeter edges of roof deck area Minimum of three vertical bracing/braced wall locations required Note: It is important to note that fixing type and frequency may need to be changed to enable diaphragm design - Refer to Fig.8.13a for recommended standard fixing configurations. For useful guidance on stressed skin diaphragm design, refer to: ECCS Publication No88: European Recommendations for the Application of Metal Sheeting acting as a Diaphragm BS : Structural use of steelwork in building Code of practice for stressed skin design 38

39 SBI Document 174: Stabilisation by stressed skin diaphragm action BS EN : Cold-formed thin gauge members and sheeting, clause Aesthetics The SR+ roof deck products provide aesthetically pleasing trapezoidal appearance, providing clean lines for situations where the soffit is exposed (refer to Fig 8.17a). All profiles are typically available in either galvanised or white liner (polyester white) finish to suit project specifications. For some profiles other colours and soffit finishes are available upon request, but these are subject to extended lead time and minimum order quantity. GUIDANCE NOTES 8.16 Protex warranted insulated system All SMD SR profiles can be used to enhance the structural spanning capability of the Protex Insulated System available. The flexibility of the Protex system provides the end user with different bracket and insulation build-up options depending on the U value required. U values from W/m²k are available subject to insulation depth. Underside of SR35+ deck profile Fig.8.17a Need Further Guidance? Contact us on +44 (0) or our Technical Team on technical@smdltd.co.uk Technical Department SMD.TGN.122.V6 39

40 Technical Guidance Notes 9.0 Supply of materials 9.1 Delivery and access Decking and edge trim are delivered on 25 tonne capacity articulated vehicles with trailers up to 13.50m long. On supply and fix contracts, SMD Construction Manager will contact the client to arrange deliveries to suit minimum product lead times required for delivery of materials. The seven working days stated does not include the day of call off or the day of delivery, this is purely the manufacturing duration. Where site access restrictions apply, deliveries can be arranged on alternative vehicles (i.e. 10 tonne rigid or Hi-Ab); contact SMD Operations Team for further advice. Profile R51 TR60+ TR80+ SR30+ SR35+ SR60+ SR100 Gauge mm Sheet Length (m) kg/m Deck materials being offloaded on site Fig.9.1a SR Upon arrival at site, the driver will allow a maximum two hour offloading period, unless agreed otherwise with the SMD Operations Team. Typically, the offloading is undertaken by the steelwork contractor in conjunction with the erection of the steel frame. SMD do not undertake offloading of delivery vehicles. SR153 SR Pack size and sheet length limits To prevent damage to the sheets during transport and ensure packs are of a weight that is easily offloaded, the maximum and minimum sheet quantities in Table 9.2b apply. SR Table 9.2a RED numbers are not recommended as sheet lengths exceed maximum weight for logistic and manual handling reasons. ORANGE numbers can be used providing pack size and loading-out position consider manual handling distances. 40

41 Profile Minimum Sheets in a Pack Maximum Sheets in a Pack Maximum weight (Tonnes) R TR TR SR SR SR SR SR SR for prolonged periods of time, the packs should be seated on timber bearers to avoid direct contact with the ground. 9.4 Pack labels / loading-out locations Where SMD are detailing the decking layouts, decking bundles are identified on the deck GA drawings. Packs are delivered to site with a unique identification tag (Refer to Fig 9.4a) showing a typical pack label with relevant information). Each floor deck pack has a spray stripe down one side, this indicates the orientation in which they should be loaded onto the steel frame (for aesthetic reasons roof deck packs do not come with this spray paint marking). The spray line corresponds with the overlap side of the sheets and must face towards the setting-out point, as indicated on the relevant SMD deck GA drawing. GUIDANCE NOTES SR SR Table 9.2b Where SMD are detailing as part of the contract, sheet lengths are determined on the SMD layout drawing to suit the support configuration and building footprint. The detailed drawings will be designed to provide the most effective use of the decking by minimising waste, reducing temporary propping requirements and considering Health & Safety concerns related to unloading and manual handling during installation. Where possible, sheet lengths should be restricted to 7.5m for R51, 8.0m for TR60+ and 10.0m for TR80+ due to manual handling restrictions. Deck pack label Fig.9.4a For further guidance refer to industry best practice sheet SIG.04, developed in conjunction with HSE. 9.3 Offloading, hoisting and storage During offloading and hoisting, care should be taken to avoid damage to the decking sheets caused by excessive pressure from slings or chains. Decking bundles should NEVER be dropped (in any way) from delivery vehicles. It is normal for the packs to be loaded directly from the delivery vehicle onto the steel frame. Whilst loading packs onto the steel frame, consideration should be given to pack positions to avoid overloading. Where packs of roof deck are to be installed onto coldrolled pulins, packs should be loaded out directly above the hot-rolled supporting beams. When necessary to store decking packs at ground level To provide a site control measure, the colour of the spray line on the pack indicates the decking gauge: Green 0.9mm gauge Blue 1.0mm gauge Red 1.2mm gauge The loading out positions for deck packs is clearly detailed on SMD deck GA drawings. It is essential that all packs are loaded out in the correct position and orientation to control Health and Safety issues and minimise the manual handling required. Refer to SMD Data sheet 04 for more information For further guidance refer to industry best practice sheet SIG.03, developed in conjunction with HSE. Technical Department SMD.TGN.122.V6 41

42 Technical Guidance Notes 10.0 Installation - Fall arrest systems Since the early 2000 s, SMD and the industry in general has recognised safety nets as the primary form of collective passive fall protection. In accordance with the Work at Height Regulations 2005 and given that for metal deck installation 'avoid work at height' and 'use work equipment to prevent falls' is not reasonably practicable, all contracts need to adopt a system of work that 'minimises the distance and consequence of a fall', this will include handrails, safety nets and suitable access to level. Prior to commencement of works, a suitable system of fall protection and safe access must be in place. There are three principal methods of fall arrest available: Safety Netting Air Bags (also known as Safety Mats or cushions) Running Lines and Harnesses The recommended methods of fall arrest to be used are safety netting for steel frame structures and airbags or similar for all other situations, as these provide Passive and Collective protection. required by the operative. Where this system is proposed, a thorough assessment should be carried out to consider a Passive and Collective method, if possible, in place of the active protection. Refer to BCSA Code of Practice for Metal Decking and Stud Welding for more information In some instances, safety netting will not be suitable, i.e. insufficient storey height (<3m) or inadequate anchor points (blockwork). In these situations, the following fall arrest methods can be considered: Air bags Air bags are another form of collective passive fall protection that can be used for storey heights of 1.9m - 4.5m. hey are predominantly used on blockwork or concrete structures where no suitable anchor points for safety nets are available. To install the system, the Air bags are laid out and connected together in the area where fall protection is required. The Air bags are then inflated as one complete area to form the fall protection. This method of fall protection is slow and requires careful planning to ensure the area to receive Air bags is 100% clear of obstacles with all openings and windows boarded over. Methods of fall arrest available Fig.10.0a Air bags Fig.10.0b The use of running lines and harnesses are not recommended due to the personal nature and action Scaffold platform or crash deck A fully-erected scaffold or system crash deck can 42

43 be erected below the deck level. These are costly, sterilise the area below the floor and have an impact on programme due to the time to erect and dismantle. concrete core or wall. Where deck spans are designed such that pre-propping is required (temporary props in place prior to installation), a different method of fall arrest may be more appropriate due to the logistical issues for net installation and removal caused by the temporary props. GUIDANCE NOTES NOTE: Safety netting must not be fixed to secondary steelwork such as scaffold handrails or cladding rails. Scaffold platform or crash deck Fig.10.0c Early planning Although safety nets are the primary method of fall arrest used, it is important to consider the most suitable method on a project-by-project basis. Involving SMD Operations Team early in the planning stage can avoid use of an inappropriate method and any associated impact on programme or cost Safety nets Control SMD safety net stock, in excess of 50,000m², is managed, repaired, maintained and tested by our fully trained stores teams located at our Logistic Centres in the Midlands (Nottingham) and Scotland (Coatbridge). In addition to a unique visual ID tag attached to the net, all nets carry an RFID tag which is linked to our net management software ensuring net location, test date and required maintenance is logged and maintained in a central system. This ensures these safety critical nets are kept to the highest standard and ready for issue to site as required. Net pole and claw application Fig.10.1a Storey heights Safety nets are usually only suitable for floor heights in excess of 3m. The floor below must be clear of all possible obstructions or protrusions. When planning safety netting, reference should be made to the deflection chart within FASET guidance. As a general rule the storey height in metres should be a minimum of: 2 + (shortest span of the nets in metres) 5 Example: For a net with a shortest span of 6m: 2m + (6m/5) = 3.2m floor minimum storey height Safety net installation When choosing a fall arrest system, the use of nets must be planned; consideration must be given to the following: Fixing Points Safety nets are only suitable as a collective passive form of fall prevention where suitable fixing points with a proven load strength of 6kN are provided. Typically, this takes the form of a primary steel frame or anchored fixings into a Nets installed to area Fig.10.1b Technical Department SMD.TGN.122.V6 43

44 Installation methods There are a number of recognised methods for installing safety nets that are approved by FASET. The preferred method will depend on numerous factors such as storey height, ground condition, site-specific rules etc. The use of a MEWP (mobile elevated working platform) is preferable, however there are instances where this may not be suitable (ie. where use of a MEWP would mean extending the boom through more than one floor of steel work or poor/restricted access for MEWP s). The recommended methods are: Storey heights m Net pole and claw with the occasional use of ladders Rope access is a suitable method for safety net installation where storey heights exceed 4.5m and MEWP access is not possible. It should be noted that the Rope access technique is considerably more time consuming and will therefore impact on both programme and cost. Note: In some circumstances MEWP s may be required when working below 4.5m. Unless MEWP's have been specifically requested the standard Net pole and claw technique should be used. De-rigging nets: Nets can be de-rigged in the same ways in which they are rigged, dependent on the storey heights and the site requirements. Site Operative using net pole Storey height in excess of 4.5m MEWP or rope access technique. Fig.10.1c Nets must not be de-rigged until the decking sheets are 100% fixed into place and stitched together, or on to floors that have had studs welded as this creates multiple snagging points once the nets have been lowered. Safety netting must be de-rigged prior to any welding operations as the weld splatter will burn through and damage nets. Need Further Guidance? Contact us on +44 (0) or our Technical Team on technical@smdltd.co.uk 44

45 Technical Guidance Notes GUIDANCE NOTES 11.0 Installation - Floor Deck and shear studs SMD products should only be installed by those competent and trained to do so. Specific reference should also be given to the BCSA Code of Practice for Metal Decking and Stud Welding and, as a minimum, the following procedure should be followed. Pre-start Prior to commencement of deck installation, a system of fall protection (refer section 10) and safe access must be in place. This should form part of the overall safe system of work agreed by all parties and detailed in the project specific Risk Assessment and Method Statement (RAMS). Weather conditions Decking bundles should only be opened if all the sheets in the bundle can be fixed or left in a safe condition at the end of the shift. Consideration must be given during periods of bad weather to any unfixed sheets as these must be secured at the end of each day by using a temporary strap secured to the frame or decking. Supporting structure Where supports are to receive shear studs, top flanges must be unpainted and free from grease or rust that might adversely affect the weld. Refer to Fixings section (page 24) for guidance on minimum bearings. Access to level Wherever possible, the decking installation should be planned to commence from the corner of a building or phase, so that the number of leading edges are limited. The recommended means of access to and egress from the workface should be either temporary Haki type stair or permanent fixed stair with handrail. Refer to SMD Data sheet 18 at Laying decking sheets Using the access provided, the installer should straddle the first bundle of decking to remove the banding. The first decking sheet will then be pushed out onto the steelwork to be used as a working platform from which to lay the remaining sheets in that bay. Decking sheets should then be lapped, lined up and fixed into place once the adjacent bay has been laid and the troughs of the decking have been lined through. During installation, cumulative measurements of across the bay width should be taken to ensure the effective product cover width is consistently achieved. Cutting / notching Decking sheets are typically delivered to site at the correct square cut length. Where decking ribs sit over beams that are to receive welded shear studs, around columns and other protrusions, notching and/or cutting of the deck will be required. This should be carried out by trained operatives using suitable disc cutters (petrol, cordless, electric or pneumatic) with appropriate blade, plasma cutters or similar approved equipment. For some contracts, cutting will be carried out off-site prior to delivery (refer to section 13.5), in these instances the sheets will be delivered to site at the correct length and shape for installation with only minor notching required around columns and handrails. Deck fixings Fixing of the deck and edge trim to the supporting steelwork or walls will typically be carried out using low velocity powder ( shot-firing ) or gas-actuated cartridge tools. In certain circumstances, the use of self-tapping screws may be necessary. Refer to section 4.6 for recommended fixing types and spacings. Side laps At side laps, the deck sheets must be stitched together using self-tapping screws, installed with suitable screw guns, at maximum 1.0m centres. In addition to stabilising the joint, these help minimise grout loss experienced during concreting. Sealing and finishing off Gaps up to 5mm are acceptable as they are not sufficient to allow concrete aggregate to escape. Note: The decking is not intended to provide a watertight finish and a degree of fines and water seepage (grout loss) is to be expected from the panel ends and joints. In areas where it is essential to reduce grout loss to a minimum, the addition of tape at all butt joints and side Technical Department SMD.TGN.122.V6 45

46 laps may offer an economical solution, it should be noted that this is not standard practice and must be discussed at pre-tender stage. Edge trim Generally supplied in 3.00m standard lengths, each length should be tethered during installation using the holes provided. The edge trim must be fixed to the perimeter supports at maximum 750mm centres, with restraint straps installed to the top of the upstand leg/tick at centres as indicated in the Edge Trim & Flashings section using self-tapping screws Decking around columns Decking around columns is achieved by notching the deck into the web and sealing with tape, foam or flashing to minimise grout loss. Where columns are not framed by incoming beams, angle brackets (provided by the steel contractor) may be required to the relevant column face to support the free end of the decking (refer to Fig 11.2). Forming holes and openings Where trimming steels are provided, the decking sheets may be cut to suit the size of the opening and edge trim installed. Where there is no supporting steelwork, the voids will have to be decked over. The opening should then be formed by the concreting contractor who will box out the opening prior to pouring the concrete. Refer to Section 5.6. MCRMA/SCI Technical Paper No. 13/ SCI P300 REVISED EDITION. Composite slabs and beams using steel decking: Best practice for design and construction It is the Steelwork Contractors responsibility to ensure the supporting structure is in a stable condition, adequately restrained and handed over as 'safe to access' prior to proceeding with the deck installation. Any additional support plates or angles required around columns, penetrations or splices must also be provided by the Steelwork Contractor. Refer to SMD Data sheet 02 at Deck cut around column 11.3 Unpainted top flanges Fig.11.2a Where beams are to receive thru-deck welded shear studs, the top flanges are to be free from any type of paint, grease, loose rust or any other coating, as this prevents effective welding and will subsequently reduce the final weld strength. Important Note: When masking the top flange before painting, the full top flange should be masked. Where a return of paint at the toes of the beam flange is required, this should extend no more than 15mm from the beam toe. Refer to BS EN 1993 or BS5950 in Lateral Restraint section for more information Refer to SMD Data sheet 13 at Cartridge tools Fixing of decking and edge trim is typically carried out using low velocity powder (shot-firing) or gas-actuated cartridge tools. These provide a fast and efficient method of securing the decking sheets. The tools used are generally Hilti DX460 or DX76 (shot-firing), GX 3 (gasactuated) or similar approved. All operators must be fully trained and competent to use these tools and at least 18 years of age. Refer to BCSA Code of Practice for Metal Decking and Stud Welding Publication No. 37/04 for more information 11.4 Mobile stud welding equipment Stud welding is typically undertaken using purpose built mobile stud welding rigs, operating Nelson rectifiers and diesel generators of 250 kva. The rig measuring approximately 7.0m long, 2.5m wide and 4.0m high will 46

47 require access and hardstanding to within 7.5m of the steel frame to enable a suitable and safe earth to be obtained. The distance between the rig and the stud welding tool is restricted to a maximum cable length of 80 metres. Where site logistics prevent access to within 7.5m of the frame, additional steel angle (approx. 50mm x 50mm) may be a possible option to provide a suitable earth. Contact SMD Operations Team for further guidance Static generator or mains supply In many instances, due to the low environmental impact, the preferable option is a 415 volt 3-phase (125 amp per phase, with a HRC fuse or Class D, or above, circuit breaker) mains supply. Refer to SMD Data sheet 05 at For large city centre contracts where mains supply is unavailable and access is restricted for a mobile rig, static generators approximately 3.0m long, 2.0m wide and 2.0m high weighing 6 tonnes can be provided as an alternative. Where a static generator is required, it should be positioned in a well ventilated area and consideration should be given by the Structural Engineer to its location to avoid overloading of the steel frame Testing The testing and recording of welded shear stud tests should be undertaken in accordance with BS EN ISO 14555:2014 and BCSA Code of Practice for Metal Decking and Stud Welding. Pre-start test At the start of every welding shift a Welding Procedure Qualification Record Test (WPQR) must be undertaken. The settings used during this test should fall within the parameters set out in the SMD Welding Procedures Specification (WPS). Refer to SMD WPS Technical Guidance sheet 551 for more information. The WPQR test involves welding 10 no. test studs. These studs shall be bent to an angle of 30 degrees from their original axis by placing a bending bar over the stud and manually bending the stud in the direction of the span of the beam towards the nearest column. Should failure occur, the equipment should be reset and settings adjusted, replacement studs welded and tests repeated to ensure acceptable quality. A record of the WPQR location and settings should be marked on a QA record drawing in line with the requirements of BS EN 14555:2014. Note: The settings for the WPQR will differ for each site due to numerous factors including; atmospheric conditions, weather, parent steel grade, cable distance, ambient temperature etc. Surveillance testing As welding progresses, the ferrules shall be broken away from the base of the stud to enable visual inspection. The broken ferrules are typically left on the deck to be absorbed into the concrete and treated as inert aggregate. All shear studs shall then be ring tested by tapping the head of the shear stud with a hammer, studs that do not give a resonating ring sound should be bend tested. Bend testing must be carried out as described in the Pre- Start (WPQR), but to an inclination of 15 degrees (1 in 4). The bend test shall be carried out to the greater of 5% or at least 2 no. studs per beam. Should a shear stud fail in any location, three studs on either side should also be tested. Any failing studs will need to be replaced. Tested and failed studs shall be noted and marked up on a QA record drawing. When testing shear studs reference should be made to the manufacturer s instructions, BS EN , BS5950: Part 3: Section 3.1, BCSA Code of Practice for Metal Decking and Stud Welding, National Structural Steelwork Specification and BS EN ISO 14555:2014. Refer Nelson Stud Welding Application Information: Removal of Broken Ferrules - WTD (31/01/2006). Stud welding at low temperatures D.J. Laurie Kennedy GUIDANCE NOTES Refer to SMD WPS Technical Guidance sheet 552 for more information. Technical Department SMD.TGN.122.V6 47

48 11.7 Scorching of beams A huge amount of heat is generated by the welding process with temperatures in excess of 1400 C. Paint on underside of flanges <12mm thick will inevitably exhibit scorching to some extent in the area immediately below each stud location Refer image 11.7a Dependent on project specification, touch-up or repair of the area may be required. This should be undertaken by the contractor responsible for the paint coating of the steel frame. Where intumescent paint is applied offsite, this may expand locally below each stud location. It is generally accepted that, provided the surface of the finish remains intact, no remedial action is required subject to the paint manufacturers approval and project specification Minimising grout loss Deck sheets are designed to butt join with the ribs of the profile lined through to avoid gaps and minimise grout loss. Metal deck is not intended to provide a watertight solution, therefore small quantities of grout and water loss are inevitable. Gaps in excess of 5mm should be sealed using either tape or expanding foam. Generally, gaps less than 5mm are acceptable with no special provision as they are too small to allow aggregate to escape, although grout loss will occur. Scorched beams Fig.11.7a For beams >12mm thick, scorching may still be evident although it will be less prolific as beam flange thickness increases. If the soffit and trim is intended to be fully exposed in its final condition, consideration should be give at tender stage to the taping of all joints prior to concreting or alternatively jet-washing the underside of steelwork post concrete pour. The use of needle head vibrating pokers is not recommended as these can encourage greater grout loss. Contact SMD Concrete Team for further information. Need Further Guidance? Contact us on +44 (0) or our Technical Team on technical@smdltd.co.uk 48

49 Technical Guidance Notes GUIDANCE NOTES 12.0 Concrete 12.1 Site Considerations Building envelope To enable an acceptable surface finish to be achieved, where possible, concrete pours should be carried out in an enclosed environment to provide adequate protection of the works from prevailing weather conditions (including wind, surface water, frost, driving rain and excess heat from the sun). Ambient temperatures must be suitable for concrete placing and finishing operations. In some instances this may require provision of heaters and/or insulation material to the top and underside of the slab. It is appreciated that this is not always feasible due to site programme and logistics etc. A Project Team must also understand that the lack of a weatherproof building envelope could have a detrimental effect (dependent on severity of the conditions) on the final surface finish achievable and this is beyond the control of a flooring contractor. Wash-out facility Adequate wash-out facilities for the disposal of surplus concrete material from both the pump and trucks should be provided, i.e. designated area in the ground and/ or polythene lined skips, including a water supply for cleaning of plant and equipment. Loading platforms Where loading out plant and materials directly to the working area is not possible, loading platform/s should be provided. These should be safe and adequately sized to permit the storage of plant, materials and enable site personnel to access from all sides. Ground conditions Suitable hard standing areas are required to accommodate all construction traffic loads associated with the concrete works, including concrete pump and trucks. Access / egress facilities Safe means of access and egress must be provided, positioned to suit the start and finish locations of each pour area. Specific consideration should be given to this item when powerfloat operations are to be carried out. Site protection Adequate protection from on-site activities must be provided to all adjoining properties/premises, including items contained within its boundaries. This is not specific to the concrete works and should typically be considered by a Main Contractor at planning stage. Where there are completed works in close proximity to the concrete pour area, adequate protection must also be provided to avoid damage. Pump hopper discharge Fig.12.1a Site protection screening Fig.12.1b Lifting to level A means (crane/telehandler) for lifting plant and materials to level is required to enable works to commence. Other trades Adequate protection and/or segregation areas must be provided for other trades working in the vicinity of the concrete works. Technical Department SMD.TGN.122.V6 49

50 Refer to SMD Data sheet 15 at Refer to Nelson Stud Welding Application Information: Removal of Broken Ferrules - WTD (31/01/2006) for more information Refer to SMD Data sheet 19 at Temporary propping Where SMD are contracted to carry out the decking, temporary propping will be identified on SMD drawings, where required. It is the responsibility of a Main Contractor to obtain a temporary works design approval for any propping that is required and ensure the props are installed prior to concreting Damaged decking Care should be taken when utilising the decking as a working platform, or storing materials for following trades, as any damage resulting from these activities will require a site inspection with any damaged sheets likely to require replacement. Important: For areas exhibiting damage, the concrete pour must not progress until an appropriate inspection has been carried out and any remedial action implemented. Temporary propping should not be removed until the concrete has achieved 75% of its design strength. The design and installation of the temporary propping is the responsibility of others (not SMD) and should be of adequate strength and construction to sustain the dead weight of the concrete plus any construction live loads. For guidance on propping loads to be resisted contact SMD Technical Team Construction joints With composite floor slabs, it is possible to achieve continuous concrete pours in excess of 1,000m 2. Where construction joints are required, these should always be formed as close as possible to the deck support at the butt joint in the deck sheets. The distance from the centre of the end support to the stop end should never exceed one-third of the span between the supports (Refer to Fig 12.5a). Propping Fig.12.2a 12.3 Cleaning the decking Prior to the concrete being placed, the decking should be cleared by others of any debris, grease and/or dirt which could adversely affect the bond between the concrete and the decking. Typically, ceramic ferrules from the shear stud thru-deck welding process can be left distributed over the decking surface and lost within the concrete pour. Final clarification should be sought from the project structural engineer Construction joints Fig.12.5a Construction joints should be formed using either timber or one of the proprietary joint systems available for use on composite floor deck profiles. Where a day joint is required, adequate continuity reinforcement must be provided either by extending a sheet of mesh or additional bars through the joint location to provide slab continuity between pours. 50

51 12.6 Reinforcement drawings and bending schedules Mesh fabric, loose bar (i.e. U bars or straight bars in troughs or over beams) and steel fibre reinforcement should be detailed by the slab designer (typically the project structural engineer). These drawings, including corresponding bar bending schedules, must be available in sufficient time to allow for procurement, delivery and installation to meet the project programme. Where SMD are contracted to carry out the concrete works, a reinforcement detailing service including preparation of drawings and associated bending schedules is available, contact the Concrete or Technical Team for further information. possible collapse Avoid additional cost for over consumption of concrete Ensure design slab thickness is maintained for precambered beams Where the concrete contractor proposes to pour the concrete to a defined datum (i.e. using a laser level), this must be checked with the project structural engineer and metal deck manufacturer to assess whether the additional concrete weight for ponding (as a result of deflection of the steel frame) has been considered in design. GUIDANCE NOTES 12.7 Concrete mix requirements The concrete mix design must be suitable for the intended method of installation (e.g. pumpable) and finishing. Concrete with a minimum consistence class of S3 should be utilised, in accordance with BS The mix design should be prepared in accordance with the strength class, maximum water/cement ratio and minimum cement content specified the engineer. The concrete contractors proposed mix design must be approved by the engineer prior to commencement of concrete placement works. Concrete placement Fig.12.7a 12.8 Placement BS : A1:2012: Concrete. Complementary British Standard to BS EN Method of specifying and guidance for the specifier. Refer to 'Concrete Society Technical Report No.75 - Composite slabs using steel decking' for more information MCRMA/SCI Technical Paper No. 13/ SCI P300 REVISED EDITION. Composite slabs and beams using steel decking: Best practice for design and construction As detailed in section of SCI P300 Composite Slabs & Beams Using Steel Decking: Best Practice for Design & Construction, concrete on metal deck should be placed to achieve a constant thickness rather than a defined datum level to: Eliminate the risk of overloading the deck and Refer section entitled Effect of Construction Stage Deflection on Surface Level and Flatness Tolerances. The recommended means of pouring concrete onto metal deck is by pumping. Where the concrete is transferred into position using barrows or by lines of pipe for pumping, boards should be used to provide a loadspreading platform across the deck, thus reducing the risk of accidental damage to the profile. The wet concrete must not be heaped, or dropped from a height exceeding 1.0m in any area during the laying sequence. When poured in the same direction as the decking span, concrete should be poured evenly over two spans starting at beam positions. When concrete is poured in a direction at right angles to the span it should be placed first at the edge where a decking sheet is supported by the underlap of an adjacent sheet. This helps to ensure that the longitudinal side laps between sheets remain closed and hence minimises grout loss. The concrete should be well compacted using either a vibrating beam or plate vibrator, particularly locally Technical Department SMD.TGN.122.V6 51

52 around shear studs. Needle head vibrating pokers are not recommended as these can result in greater grout loss. Refer to SCI AD 344: Levelling techniques for composite floors for more information Refer to 'Concrete Society Technical Report No.75 - Composite slabs using steel decking' for more information MCRMA/SCI Technical Paper No. 13/ SCI P300 REVISED EDITION. Composite slabs and beams using steel decking: Best practice for design and construction Skip/Easy float finish Fig.12.9b 12.9 Surface finish The concrete finish should be specified taking into consideration the proposed use of the floor slab and any surface finishes being applied. The slab finish may require additional surface preparation to facilitate the installation of some floor/roof finishes, advice should be sought from the finishes supplier. Where curing membranes are applied this must also be checked for compatibility with the subsequent applied finishes. Skip/Easy float finish Normally a trowel finish is applied to suspended upper floor concrete using a skip/easy float (defined as Basic in 4th edition of the National Structural Concrete Specification for building construction). It should be noted that this type of surface finish is likely to leave localised ridges, reinforcement ripple, surface laitance and a mottled effect in the final surface appearance. These areas may require some minor remedial attention prior to receiving subsequent floor finishes. Pan finish Fig.12.9c Pan finish Fig.12.9d Skip/Easy float finish Fig.12.9a Pan or Powerfloat finish These can be provided (respectively defined as Ordinary or Plain in 4th edition of the National Structural Concrete Specification for building construction), although it must be specified in the context of the previous deflection 52

53 section i.e. powerfloating will make the surface appear smoother and flatter, but not level to datum. Restrictions on working hours, particularly in built-up areas, may prevent the option of these types of finishes being provided. GUIDANCE NOTES Straight Edge Fig.12.10a Surface flatness designations (surface regularity) achievable with this type of construction are detailed in Table 12.10a. Polished finish Fig.12.9e BS 8204 Flatness Designation Maximum gap (mm) below a 2m straight edge laid on the surface Comments SR1 3 (1 in 667) Not achievable on suspended floors of any construction SR2 5 (1 in 400) May be achievable on parts of a composite floor, but will not be achieved over all of a floor, owing to deflections. This is a tight flatness tolerance and high levels of workmanship are required to achieve SR2 on any type of suspended floor. SR3 10 (1 in 200) May be achievable over most of a floor, depending on the deflections of the supporting beams. Table 12.10a Polished finish Fig.12.9f Refer to 'Concrete Society Technical Report No.75 - Composite slabs using steel decking' for more information Surface flatness Surface flatness is the measurement of surface regularity over short distances to a defined plane when placed directly in contact with the slab (i.e. a 2m straightedge as documented in BS8204-2). This should not be confused with surface level relative to a fixed datum point, refer to Fig 12.9c. Surface regularity should be measured in accordance with methodology outlined in BS and SCI P300 using a 2m long straightedge placed in direct contact with the concrete surface under its own weight. Deviations of the floor surface are then measured from the underside of the straightedge, between two points of contact with the floor surface, by means of a slip gauge / graduated wedge. Refer to SMD Data sheet 14 at Where SMD are contracted to carry out the concrete works, surface flatness survey measurements will be taken at predetermined grid spacing s to suit the slab area and steel configurations for the contract. In areas Technical Department SMD.TGN.122.V6 53

54 receiving a skip/easy float surface finish, the positioning of the straightedge will be adjusted, if necessary, to avoid being situated over any localised ridging caused by this method of finishing. The greatest deviation measured is then recorded in a table format to correspond with a drawing identifying the straightedge locations and positions. On completion of works, a formal copy of the surface regularity survey will be issued in accordance with the above as evidence of compliance. be observed on a completed floor. Wherever practical, specifications should give specific criteria to be achieved, but it is recognised that some floor characteristics are not easily defined and their descriptions can be open to interpretation. Requirements relating to surface regularity and deflection are discussed separately in Section Curing Refer to BS : A2:2011: Screeds, bases and in situ floorings. Concrete wearing surfaces. Code of practice for more information Curing should take place in line with good concrete practice, failure to provide adequate curing measures is likely to result in increased shrinkage cracking. Where possible, curing should be applied immediately after pouring/finishing. Where pouring large areas with a skip/easy float finish, it may not be possible to apply a curing membrane immediately after installation due to access. In this scenario curing should be carried out the following day, once the slab is accessible, without causing surface damage. The use of spray applied curing agents are generally the most practical option (refer to Fig 12.11a), however compatibility of such products should be checked against any subsequent floor finishes being applied. Refer to 'Concrete Society Technical Report No.75 - Composite slabs using steel decking' for more information Cracking There is a high risk of cracking in composite floor slabs, both when the concrete is in its plastic and hardened state. Plastic shrinkage The main cause of plastic shrinkage cracks is rapid drying of the exposed concrete surface. If the rate of evaporation from the surface exceeds the rate at which bleed water rises to the surface, net shrinkage will occur. As the concrete has little or no intrinsic tensile strength, plastic cracking may occur. The cracks tend to be 1-2 mm wide, mm long and mm deep, though in some circumstances they may extend through the full depth of a member. The pattern of plastic shrinkage cracks is usually random but may be influenced by the direction in which finishing operations have been carried out. Materials and mix design normally have a limited influence but highly cohesive concretes with very low bleed characteristics are particularly susceptible. Concretes with low water/cement ratios or containing fine additions such as limestone powder or silica fume may also be at a higher risk. If possible to apply, re-vibration or powerfloating of the concrete may help close the cracks. Loss of moisture from the surface can be reduced by protecting the surface from drying air flows, particularly in warm weather. Protection from wind and sun is important but this is impractical when working at height with no enclosure. There are also practical difficulties in applying curing measures early enough to prevent plastic shrinkage cracking. Applying curing agent Fig.12.11a Post-installation characteristics This section is intended to help provide an understanding of what can be expected of floor surfaces and to evaluate the significance of particular features that may Plastic settlement Settlement cracks can form at an early age while the concrete is still plastic i.e. no intrinsic tensile strength. As water moves upward, the denser constituents settle which can be obstructed by the top layer of reinforcement or by the decking profile. Arching over the obstruction brings the surface into tension causing cracks to develop at 54

55 regular spacing usually following the line of the uppermost bars. There may also be shorter cracks at right angles over the bars running in the opposite direction. High consistency concretes are more susceptible to settlement although as composite floor slabs are relatively thin, the downward movement is minimized. Re-vibration or power- floating of the concrete may help close the cracks. Drying shrinkage and movement Cracking in the hardened concrete is associated with the restraint to drying shrinkage, flexure over supports and deflection. Generally, cracks developed have no structural significance, providing the minimum levels of reinforcement have been detailed and placed. consists of a series of parallel troughs in line with the upper bars in the top mat in the slab but in the worst cases the slab takes on a quilted effect as troughs are formed over the top mat bars in both directions. Reinforcement ripple is considered an aesthetic issue, not a structural or durability problem. There appears to be no way of preventing this when the method of finishing the concrete is by a skip/easy float or similar methods. The only known way of overcoming the problem of reinforcement ripple is to carry out further finishing operations on the slab such as powerfloating or powertrowelling, both of which prolong the finishing operation. GUIDANCE NOTES Generally, most composite floor slabs are covered by flooring, e.g. raised access computer floors, so any cracking is of minimal consequence. This risk of cracking needs to be considered if bonded brittle finishes are to be applied, e.g. terrazzo tiles, coatings etc. due to the possibility of reflective cracking occurring in these types of applied finishes. Where the composite floor slab is intended to be left exposed, e.g. power-trowelled finishes, cracking can be an issue. Reinforcement ripple Fig.12.12b Surface laitance Surface laitance is the development of a fine, powdery material comprising of water, cement and fine particles, that easily rubs away from the surface of hardened concrete. Drying shrinkage cracking Fig.12.12a The frequency and appearance of cracks can be exacerbated by temporary early age loading. If cracking is a potential problem for the serviceability of the floor, the control of cracking should be considered early in the design stage by the project engineers Reinforcement ripple Reinforcement ripple is the name given to a surface irregularity that sometimes occurs on the surface of large areas of flat concrete slabs. It takes the form of shallow troughs over the line of the reinforcement after the concrete has been finished. In some cases this just Fresh concrete is a fairly cohesive mass, with the aggregates, cement, and water uniformly distributed throughout. A certain amount of time must elapse before the cement and water react sufficiently to develop hardened concrete. During this period, the cement and aggregate particles are partly suspended in the water. Because the cement and aggregates are heavier than water, they tend to sink. As they move downward, the displaced water moves upward and appears at the surface as bleed water, resulting in more water near and at the surface than in the lower portion of the concrete. Thus, the weakest, most permeable, and least wearresistant concrete is at the top surface. Where subsequent finishes are to be applied to concrete surfaces, consideration as to the effects of surface laitance on their installation should be given, mainly when a skip/easy float surface finish is specified. Surface laitance is more prevalent in concrete surfaces finished by Technical Department SMD.TGN.122.V6 55

56 skip/easy float methods where rapid drying of the surface can take place (particularly when concrete placement occurs in exposed environments subject to prevailing weather conditions i.e. rainfall, cross winds, sunlight etc.) as curing is generally applied the following day after placement, due to access restrictions. Surface laitance can be removed by grinding off the thin/weak friable layer to expose the solid concrete underneath. Another method for consideration would be to apply a surface hardener to improve its wearing ability and reduce dusting of the surface. Several factors affect the occurrence of delamination including differential setting of the surface (the slab construction has no walls and the surface is unprotected from drying wind and solar gain), air content, bleed characteristics of the concrete and the application of a dry-shake topping. Delamination is generally only an issue when the concrete is to be the wearing surface. The surface can be reinstated using thin bonded repair mortars Delamination Delamination is the process whereby a thin (typically 2 4mm) layer becomes detached from the concrete surface. It is primarily caused by the entrapment of air and/or bleed water beneath the surface of the concrete during finishing operations. It is believed that there is a strong link between bleed water and air within the concrete, as the air uses the fine bleed channels to escape. If closing of the surface prevents bleed water from escaping, the air can accumulate causing a weak plane and, potentially, delamination. Delamination Fig.12.12c Need Further Guidance? Contact us on +44 (0) or our Technical Team on technical@smdltd.co.uk 56

57 Technical Guidance Notes GUIDANCE NOTES 13.0 Product options 13.1 High Durability floor deck What is HIGH DURABILITY HD? Our HD products provide the same structural capacity as our standard floor deck range but come with an enhanced metallic coating with a unique composition of Zinc, Aluminium and Magnesium. Benefits: Improved corrosion resistance with similar coating thickness Suitable for aggressive environments (e.g. chloride and highly alkaline) Excellent cut-edge protection (self healing effect) The difference in coating The dense and compact nature of the enhanced metallic coating used on the HD products (refer Fig 13.1a (left image)) provides superior corrosion resistance compared to the more porous structure provided by our standard Hot Dip Galvanised Z275 coating (refer Fig 13.1a (right image)). HD (Left) and Standard (Right) coating Fig.13.1b Coating performance in salt spray test Fig.13.1c Where could HD deck be used? External locations Car Parks Areas identified as aggressive environments (i.e. category C2-C3 or above) HD (Left) and Standard (Right) coating Fig.13.1a Corrosion behaviour - Salt spray test The samples in Fig 13.1b and graph (refer Fig 13.1c) show comparison between the two coating options under salt spray test (highly chloride environment) carried out in the lab. Time scales for samples shown in Fig 13.1b are: HD after 34 weeks Standard Zinc after 6 weeks HD Product Specification Coating weight 310 g/m2 (total for both sides) Coating thickness 25μm per side Structural steel grade S350 (350 N/mm2) Composite beams Thru-deck stud welding with HD Suitability of stud welding tested in accordance with BS EN ISO Technical Department SMD.TGN.122.V6 57

58 Weld settings (WPS) for welding current, time, protrusion and lift available. Un-painted top flanges still required (as always). Un-painted top flanges not suitable for the environment? Consider pre-studded beams (painted) with single span, crushed ends, deck sheets (refer to Section 13.2). 50mm bearing 13.2 Crushed ends deck sheets Where required, floor deck sheets can be provided with crushed ends. This is the process of closing the end of the sheet ribs by crushing the rib to form a slope to the end of the trapezoidal rib (refer to Fig.13.2a). Crushed ends option is only available with the TR80+ profile. Crushed ends deck sheets Benefits Where might it be used? Crushed ends offer a number of benefits specific to certain types of construction or detail: Fig.13.2a Quicker to install in single span situations as avoids need for end caps Provides a greater concrete section locally to the shear stud, improving stud performance Enables solid concrete strip over centre of support avoiding need for acoustic and/or fire profile fillers Reduces grout loss on pre-studded projects where deck sheets have to be single span (refer to Fig.13.2b) Popular in light gauge frame construction As with all product options, crushed ends are not suitable in all situations as there are implications on sheet bundling and layout configurations. Contact SMD Technical or Operations teams for further guidance. Pre-studded beam Crushed ends to pre-studded beam Crushed ended deck sheet 13.3 VoidSafe Protection System Fig.13.2b VoidSafe is a moulded non-slip composite Glass Reinforced Plastic (GRP) floor grating system, it is designed, supplied and installed by SMD along with the metal deck operations. The installation of VoidSafe eliminates the requirement for void handrail protection systems and temporary void protection during construction, providing a final void riser protection product which minimises floor obstructions during the process. Material specification Two main components produce composite GRP: Polyester, resin and glass fibres. Isopthalic polyester resin is used to manufacture VoidSafe mesh due to its flexibility and cost. Properties Product Load/Span Table Nominal Thickness mm Mesh Open Size (mm) Panel Weight (kg/m 2 ) x Span (mm) / Load (UDL in kg/m) Table 13.3a Product ,740 6,281 3,225 1, Table 13.3b Fire resistance Standard Iso Resin - BS 476 Part 7 Class 2 Typical edge detail The minimum bearing required for VoidSafe is 50mm. Around the void perimeter, the VoidSafe is supported on specially engineered trim manufactured from 2.0mm gauge material with a 40mm recess to provide the VoidSafe at the same level as the adjacent slab. Ref Fig 13.3a and 13.3b. 58

59 Service penetrations Where service penetrations are required in the VoidSafe Protection System, additional trimming support may be required. Should voids be required, a detailed void layout must be submitted to enable any additional support requirments to be specified. GUIDANCE NOTES This information should be made available at design stage, to avoid the need for support to be installed retrospectively. 2D edge section of VoidSafe on trim Fig.13.3a X = 114mm minimum, this will need increasing for shallow slab depths (<150mm). Service penetrations with support Fig.13.3d 3D edge section of VoidSafe on trim Fig.13.3b Fixings Fixings must be in each corner, be at a minimum of 1000mm centres and there should be a minimum of 4 fixings in each sheet Perimeter toeboard It is recommended and typical for the perimeter toeboard to be provided as part of the edge protection system. However, there are instances where it may be necessary for the perimeter toeboard to be provided as an addition to the perimeter edge trim. Where required, the recommended detail utilises a C shaped edge trim with the toeboard as a secondary trim fixed to the top of the C shaped edge trim. This has limitations due to the access required to fix the edge trim to supporting steelwork, but is easier to remove upon completion. Fixing washer options Fig.13.3c Perimeter toeboard Fig.13.4a Technical Department SMD.TGN.122.V6 59

60 13.5 Channel edge trim Where a brickwork or cladding support system is to be integrated into the slab edge, specially manufactured channel pourstop can be provided. SMD do not design or manufacture this product but can detail and install as part of the contract Refer detail 13.5a. There are a number of different manufacturers available, each with slightly different design rules. The structural designer should contact the specific product supplier for design guidance relating to channel size and specification. Concrete Design The specific mix design will always depend on the local materials available but should follow these basic guidelines: Cement minimum 350kg/m 3 of CEM I or CEM IIIA Aggregates maximum 20mm Fines Content minimum 450kg/m 3 of smaller than 200μ including cementitious content Water/Cement Ratio 0.50 Minimum Slump 70mm (before the addition of steel fibres and super-plasticizer) ArcelorMittal Sheffield Ltd can provide advice on individual mix designs and check suitability for specific projects. Mixing The best method for integrating the HE 1/50 steel fibre into the fresh concrete is by blast machines, available on request from ArcelorMittal Wire Solutions. This is a self-sufficient operation where the steel fibres are blown into the preloaded ready mix truck allowing easy homogenisation of the steel fibres into the concrete mix. Alternatively, the steel fibres may be loaded via mobile conveyor belts or placed on the aggregate belt at the ready mix plant. Channel edge trim 13.6 TAB-Deck TM Fibre concrete Fig.13.5a Developed in partnership with ArcelorMittal Sheffield Ltd, TAB-Deck fibre reinforced concrete should be installed, cured and finished in exactly the same way as nonfibre reinforced concrete. The only fibre that has been extensively tested for use in TAB-Deck projects is Arcelor Mittal Sheffield Ltd HE 1/50 steel fibre (refer to Fig 13.6a) at a dosage of 30kg/m 3. TAB-Deck fibre by ArcelorMittal Fig.13.6a HE 1/50 Technical Specification Wire dimension 1.0mm (+/- 0.04mm) Fibre Length 50mm (+/- 3mm) Number of Fibres per kg 3100 No Total fibre length per 10kg 1575m Tensile strength of drawn wire 1100 N/mm 2 Rod wire C4D or C7D according to EN Finishing Where a power float finish is specified when using steel fibres, consideration should be given by the Project Team for an application of a fibre suppressant dry shake topping which would significantly reduce the likelihood of exposed/protruding fibres becoming apparent in the final surface finish. For further information and design guidance contact ArcelorMittal Sheffield Ltd or SMD for a copy of the TAB- Deck design manual Off-Site Cutting What is it? Typically metal deck sheets are delivered to site in packs with square cut ends, to be cut to suit on site. The SMD Off-Site Cut service involves cutting the sheets to exact shape and size required at the factory prior to delivery to site. Any small notches or alterations are then undertaken on-site using a bespoke plasma cutting tool developed for metal deck construction. The service was developed originally to meet the environmentally sensitive requirement to Reduce Noise for deck installation in London. The extent of cutting required depends on the complexity of the project, but the benefits the service offers (detailed below) have now seen the service adopted on a number of large city centre contracts. 60

61 Benefits Reduce noise pollution on site - <70dB at source compared to 110dB when using petrol driven disc cutters Reduction in site wastage and difficulty in scrap removal Cutting undertaken in a controlled factory environment Wastage recycled at source Reduction in time working at height Less wastage = Reduction in delivery vehicles standard projects; set-out points must consider column sizes and utilise flashings to minimise the requirement for site notching, further limiting any site wastage. The detailing and drawings are modelled in a 3D environment using Tekla; using the fabrication model for this service is a must to ensure sheet sizes provided reflect the exact frame being erected. Therefore, sharing of models and utilising BIM principles is an essential part of this service (refer to Fig 13.7b). GUIDANCE NOTES Involve SMD early in the project alongside the Steel Fabricator and Principal Contractor. This enables details to be developed to minimise the impact and cost of the off-site cutting requirement. When should it be adopted? The Off-Site service may not be necessary for many contracts, but can be essential in certain locations where: The site is located in a particularly environmentally sensitive area Where noise pollution could create a nuisance to adjacent buildings Projects with large volumes of decking and where a high degree of splayed (or raking) cutting is required, to reduce the on-site programme. Cutting Process With direct control over the manufacturing facility, a designated cutting area (Refer Fig 13.7c), specifically trained labour, detailing cut part drawings and a detailed QA procedure at our factory, the quality of our off-site cutting service is assured. Tekla model of cut sheets Fig.13.7b Deck design with flashings and SOP Fig.13.7a Off-Site Design It is important to involve SMD early in the process for Off- Site contracts as there may be design implications or the potential to develop a more enhanced Off-Site option. The design process for off-site cutting differs from Off-site cutting Fig.13.7c Installation - decking by numbers Packs are delivered to site with the sheets already cut to suit the required size and splay. Packed in a safe manner to minimise risk during offloading (refer to Fig.13.7d). Technical Department SMD.TGN.122.V6 61

62 the 3-Phase 415v Bespoke Plasma Cutting Unit. Take Off-Site further. For some projects there may be solutions to take the Off- Site construction ethos further to suit specific building requirements and details. One case study of this was at London Bridge Place, London. For this contract bespoke sheet widths were produced, Off-Site cut and then delivered to the steelwork contractor for installation into pre-detailed and designed perimeter modules. These modules were then delivered to site and erected with the majority of the perimeter section of deck sheets already in place (refer to Fig 13.7g). Pre-cut decking delivered to site Fig.13.7d Pre-cut deck on perimeter modules Fig.13.7g Drawing identifying pre-cut sheets Fig.13.7e With each cut sheet given a unique identity number (shown on the drawing), the installation on site becomes a decking by numbers process (refer to Fig 13.7e). This bespoke Off-Site design offered yet more site benefits by: Further reducing work at height Minimal time working at the building perimeter Minimising the risk on high-rise buildings Engaging SMD early in the design process is essential to ensure the benefits of Off-Site construction of metal decking are maximised and realised! 13.8 Service Fixings Specification All SMD floor deck profiles offer the opportunity of utilising soffit fixings for suspending ceilings and services. Soffit fixings, also known as wedge nuts, are available to suit drop rod thread sizes of 6mm, 8mm and 10mm and can support safe working loads of up to 2.0kN (depending on the profile and drop rod size). Plasma cutting where required on site Fig.13.7f Any small notches or alterations required around handrail pots or unforeseen details are then accommodated using To avoid potential localised overloading of the slab, fixings should not be locally grouped; as a general guide, it is recommended that fixings be on a nominal minimum 600mm grid. Design advice for closer groupings should 62

63 be sought from SMD Technical Team as this will depend on slab depth, profile and other design criteria for the slab. Note: Soffit fixings are only to be installed/loaded after the concrete slab has gained specified design strength. GUIDANCE NOTES TR+ 'Wedge nut' detail Fig.13.8d R51 'V nut' fixing Fig.13.8a Installation of Service Fixing 1. Ensure you have selected the correct wedge nut. 2. Thread wedge onto the required rod. 3. Insert wedge into the dovetail rib from below and rotate through 90 degrees so that the sloped face of the wedge bears on the decking rib. 4. The rod should then be tightened by hand up to the roof of the dovetail and a washer/locking plate set against the soffit of the decking. 5. Use mechanical tightening to finish to the torque force in the fixing manufacturers recommendations, refer to Fig. 13.8b and 13.8d. Availability Wedge nuts for all our floor deck products are available from Lindapter International Ltd. The wedge nut product names for our profiles are as follows: R51 Profile V Nut TR60+ and TR80+ TR60 Nut R51 'V nut' detail TR+ 'Wedge nut' fixing Fig.13.8b Fig.13.8c Other Options for Suspended Loads Other fixings and proprietary anchors are also available. These should be used in accordance with fixing manufacturers guidance. The approval of such fixings should be sought from the project structural engineer. Where the load to be suspended exceeds the wedge fixing recommendation, ensure the load does not exceed the slab design capacity before considering any alternative options. Where bolting through the slab is proposed: Ensure the use of non-percussive methods to minimise disturbance of the bond between deck and concrete. Position any bolt position through the trough section of the slab with an appropriate spreader plate size to suit the load applied. The exact load and position should be checked using SMD Elements design software. For any queries relating to a specific soffit type fixing, or load, contact the SMD Technical Team. Technical Department SMD.TGN.122.V6 63