Tata Steel - Slimdek

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Document titleOptional subheadingSlimdek residential pattern bookFor multi-storey residential buildings

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Introduction to Slimdek

The Slimdek construction system 1

Technical aspects of Slimdek Introduction 3

Asymmetric Slimflor Beams (ASB) 3

Deep decking 4

Openings in the slab 5

Edge beams 6

Tie members 8

Connections 8

Columns 9

Discontinuous columns 10

Slimdek in an unbraced structure 10

Fire resistance 11

Acoustic insulation 11

Attachment of cladding to edge beams 13

Service integration 14

The application of Slimdek Chosen building for study 15

Building form 16

Structural grids 17

Plan form and room layouts 18

Floor layout 22

Structural options 22

Material usage 28

Steel balconies and parapets Types of balcony 29

Balcony attachments in Slimdek 30

Parapets and balustrades 32 References 35 36

InTrODuCTIOn TO SlIMDEk

Figure 1.1 6 storey apartment block at Portishead Marina.

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3

Figure 1.2 4 and 6 storey apartment buildings at Penarth Marina, Cardiff.

Steel framed construction has for some years dominated the UK market for multi-storey commercial buildings due to its cost, speed and quality benefits. The proven values of structural steelwork are now being taken advantage of in the fast growing multi-storey residential building market. The Slimdek floor system from Tata Steel offers particular advantages in multi-storey residential buildings. It provides a shallow floor depth and can achieve 60 minutes fire resistance with no added protection. New research has also shown that Slimdek separating floors comfortably meet the acoustic insulation requirements of the new Part E (2003) Building Regulations.

Slimdek floor systemSlimdek is a fully engineered floor solution that has been developed to offer cost-effective shallow-depth floors for multi-storey steel framed buildings with grids of up to 9m x 9m. The system simplifies the planning and servicing of a building resulting in significant cost and speed of construction benefits.

Reductions in floor depth of up to 400mm per storey, compared with conventional construction, can be achieved using Slimdek. This offers the potential for extra floors to be accommodated within a given building height or alternatively a reduction in total building height and consequent savings on envelope costs. Slimdek floors achieve inherent fire resistance of up to 60 minutes with no added fire protection, reducing costs and speeding up programme times. The relative light weight of steel frames also leads to savings on foundation costs.

Slimdek is a shallow depth steel floor system that offers particular advantages in multi-storey residential buildings.

Slimdek plan form and room layouts. Page 17.

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Slimdek residential pattern book Introduction to Slimdek

Figure 1.4 Slimdek installation on site.

Figure 1.5 Typical column-free space achieved using Slimdek.

The key features of the system are:

Figure 1.3 Components of Slimdek

Figure 1.6 Slimdek used in a major renovation project in Covent Garden, London.

A shallow composite slab, which provides excellent load resistance, diaphragm action and robustness.

An Asymmetric Slimflor Beam (ASB), which achieves efficient composite action without the need for shear studs.

An inherent fire resistance of up to 60 minutes with ASB fire-engineered (ASB (FE)) sections.

Lighter, thinner web ASBs, which can be used unprotected in buildings requiring up to 30 minutes fire resistance or in fire-protected applications.

ComFlor 225 deep decking, which can span up to 6.5m without propping (depending on slab weight).

Light weight construction.

Slimdek has been widely employed in the commercial sector, and its advantages are now being realised in residential applications. It has been used in major residential projects in Glasgow, Manchester, Cardiff, Portsmouth, Bristol and London. Recent examples of residential building projects are illustrated in Figures 1.1 and 1.2.

Slimdek can be combined with other components, such as rectangular hollow sections (RHS) for columns and edge beams, light steel infill walls and separating walls that are directly supported by the composite floor, as well as roof-top penthouses and mansard roofs using light steel framing.

This brochure focuses on the practical application of Slimdek in a mixed-use residential and commercial building in an urban area. This building type allows us to examine a variety of design and detailing issues. It is a six-storey building, with car parking below ground and retail outlets at ground-floor level. The same floor grid is used for the car park and apartments, which removes the need for a transfer structure. Two plan forms are illustrated, to show the versatility that exists with Slimdek construction.

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Table 2.2 is defined either by 35mm cover to the ASB or 70mm topping to the decking (this topping depth does not reflect any acoustic requirement). A view through an ASB beam and the composite slab is shown in Figure 1.3.

Slimdek comprises a composite slab, formedon ComFlor 225 deep decking (designatedCF225 for clarity in some diagrams), whichis supported on the bottom flange ofAsymmetric Slimflor Beams (ASB) see Figure1.3. The typical span capabilities of ASB beamsand deep composite slabs in Slimdek are setout in Table 2.1.

Asymmetric Slimflor Beams The Asymmetric Slimflor Beam (ASB) is a hot-rolled section in which the degree of asymmetry between the widths of the top and bottom flanges is approximately 60%. The top flange has a raised rib pattern rolled into it to provide composite action with the concrete encasement, without the aid of a mechanical shear connector.

A range of 10 ASB beams is manufactured with the properties given in Table 2.2. Fire-engineered ASB beams (designated as ASB(FE)) achieve 60 minutes fire resistance

without any additional fire protection, whereas ASB beams achieve 30 minutes fire resistance, increasing to 120 minutes when additional protection is applied to the soffit. For construction the minimum slab depth in

Table 2.1 Typical span capabilities of ASB beams in Slimdek.

300 ASB (FE) 249 249 342 203 313 40 40 340

300 ASB 196 195 342 183 293 20 40 340

300 ASB (FE) 185 185 320 195 305 32 29 325

300 ASB 155 155 326 179 289 16 32 325

300 ASB (FE) 153 153 310 190 300 27 24 320

280 ASB (FE) 136 136 288 190 300 25 22 300

280 ASB 124 124 296 178 288 13 26 300

280 ASB 105 105 288 176 286 11 22 300

280 ASB (FE) 100 100 276 184 294 19 16 295

280 ASB 74 74 272 175 285 10 14 295

Width of Flange Thickness Minimum Designation Mass Depth Slab Top Bottom Web Flange Depth

kg/m mm mm mm mm mm mm

Notes: ASB (FE) are fire engineeed sections

300 ASB (FE) 249 249 342 203 313 40 40 340

300 ASB 196 195 342 183 293 20 40 340

300 ASB (FE) 185 185 320 195 305 32 29 325

300 ASB 155 155 326 179 289 16 32 325

300 ASB (FE) 153 153 310 190 300 27 24 320

280 ASB (FE) 136 136 288 190 300 25 22 300

280 ASB 124 124 296 178 288 13 26 300

280 ASB 105 105 288 176 286 11 22 300

280 ASB (FE) 100 100 276 184 294 19 16 295

280 ASB 74 74 272 175 285 10 14 295

Mass Depth Width of ange Thickness Minimum Slab Top Bottom Web Flange Depth

kg/m mm mm mm mm mm mm

Designation

Notes: ASB (FE) are fire engineeed sections

Table 2.2 Dimensions of ASB beams and minimum slab depths.

280 ASB 74 7.0 6.0

280 ASB 105 7.5 6.0

280 ASB 124 7.5 7.5*

300 ASB 155 9.0 6.0

300 ASB 196 9.0 9.0*

Beam Span Beam spacing (m) (m)

280 ASB (FE) 100 6.0 6.0

280 ASB (FE) 136 7.5 6.0

300 ASB (FE) 153 7.5 7.5*

300 ASB (FE) 185 9.0 6.0

300 ASB (FE) 249 9.0 9.0*

Fire Resistance of 30 mins**

* Propped slab during construction

** Additional fire protection required for R60

Fire Resistance of 60 mins

Beam Designation

Slimdek supported by ASBs.

Technical aspects of Slimdek

Slimdek comprises a composite slab, formed on deep decking, which is supported on the bottom flange of Asymmetric Slimflor Beams.

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Deep decking

Deep steel decking (ComFlor 225) spansbetween the bottom flange of the ASB beamsand supports the wet concrete duringconstruction. The embossments formed in thedecking achieve excellent composite actionwith the concrete, assisted by barreinforcement. Light mesh reinforcement isprovided in the concrete topping for crackcontrol purposes.

A cross section of ComFlor 225 is shown inFigure 2.1. Each decking element is 1.25mmthick and 600mm wide and has specialattachment points for service and ceilinghangers. The ComFlor 225 decking isprovided with end diaphragms and cut-outsto allow placement and retention of theconcrete around the ASB beams, as illustratedin Figure 2.2.

A cross-section through the composite slab inFigure 2.3 shows the positioning of the barreinforcement. A minimum concrete cover of80mm over the decking ensures fire resistanceand acoustic insulation, although it may benecessary to increase this cover depending onthe size of the ASB selected (see Table 2.2). Thetypical slab depth for residential applications is300mm to 330mm, which creates a floor depthof approximately 400mm when combinedwith acoustic insulating layers and asuspended ceiling. The typical spancapabilities of deep composite slabs usingComFlor 225 decking are presented in Table2.3. Temporary propping is not generallyrequired for spans up to 6m. Spans may beincreased to 9m if two lines of temporaryprops are used during construction. Servicescan be passed through openings in the ASBbeams and between the ribs of the slabs.

Slimdek residential pattern book Technical aspects of Slimdek

195

30

30

40

37

30

24030

7

8

33

15 35

600100 400

35

100

Horizontalribs

Verticalembossments

Service hanger(typical detail)

Figure 2.1 Cross-section through ComFlor225 deep decking showing service attachments.

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50 nominal bearing

15

Slabtopping

225

End diaphragm

Deck cut-out50

Coverto top

of beam

Figure 2.2 Detailing of ComFlor 225 decking at ASB beams.

16 16 16 20 20 25 32 N.A.

16 16 20 20 20 25 32 32

16 20 20 20 25 25 32 32

5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0

Bar size (diameter, mm) for Span of slab (m)


No propping Single line props required Double line props required generally

Blue area shows propping requirements for each slab.

N.A. = not generally applicable because natural frequency of slab is less than 5Hz.

Slab depth (mm)

300

320

340

Propping

16 16 16 20 20 25 32 N.A.

16 16 20 20 20 25 32 32

16 20 20 20 25 25 32 32

5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0


No propping Single line props required Double line props required generally

Blue area shows propping requirements for each slab.

N.A. = not generally applicable because natural frequency of slab is less than 5Hz.

Slab depth (mm)

300

320

340

Propping

Table 2.3 Reinforcement requirements (bar diameter) in deep composite slabs for 60 minutes fire resistance.

16, 20, 25 or32 diameter

50

Mesh reinforcement

Main reinforcementAxis

Figure 2.3 Cross-section through composite slab.

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Openings in the slab

Opening may be positioned between the ribs of the decking without affecting the load-bearing capacity of the slab. The maximum width of these openings is 400mm. Wider openings may cut through one or more ribs, in which case it is necessary to reinforce the slab to distribute the forces to the adjacent ribs. A standard edge trim is pre-fixed as a box around the opening.

The maximum recommended size of opening is 1000mm x 2000mm before additional trimmer beams are required. Details of permitted openings and additional reinforcement around the openings are presented in Figure 2.4.

Openings next to columns should be detailed to avoid the ASB and tie members. For these cases, the close proximity of the openings to the ASB does not affect the composite strength to the same degree as when openings occur in the span. As a consequence, some relaxation of the dimensions given in Figure 2.4 is possible. The recommended minimum distance from a grid line to the centre-line of a 150mm opening is 225mm, or 200mm for a smaller opening. It is also possible to accommodate a minor notch in the bottom flange of the ASB near the end connection to provide an opening for a service pipe, but this should be detailed in order to allow for fabrication before delivery to site. A detail showing the provision of a service pipe close to an ASB near a column is presented in Figure 2.5.

ASB

Setting out level

CF225decking

Meshreinforcement

Column (UKC)

A

Service pipe(max. 150 dia.)

Weldedstiffener

Welded stiffener

Servicepipe

225 min.

225 min.

Connectingbolts

Section A - A : Plan view

Tie beam

Tie beam

A

Figure 2.5 Provision of a service pipe close to an ASB in a Slimdek floor near to a column.

ASBbeam

Opening

1000

T12 bar x1500 long

Minimum A142 mesh throughout

400

Centre-lineof ribs

Opening

B

B

AA

Additionalbottomreinforcementto adjacent ribs(by engineer)

beam span/16*500

1000

300

beam span/16for compositebeam design

2000

beam span/16for compositebeam design

Additional topreinforcement

Edge trimfixed as 'box'

Section A - A

Curtailedbar

Transversebar

Temporaryprop

Section B - B

Enddiaphragm

Transversebar

Temporaryprop

Temporaryprop

Temporaryprop

Edge trimfixed as 'box'

ASBbeam

Figure 2.4 Detailing of openings in the slab in Slimdek.

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Edge beams

If the configuration of windows and cladding allow then a downstand beam can be used as an edge beam. However, where this is not possible then two alternative forms of edge beam are recommended ASB or RHS (Rectangular Hollow Sections).

ASB beams may be designed in two alternative configurations:

1. ASB encased in concrete for fire resistance and effective composite action, as illustrated in Figure 2.6. In this case, the edge of the slab is detailed at 200mm from the centre-line of the beam to allow for fixing of the edge trim, and placement of the concrete and L-bar reinforcement.

2. ASB partially encased in concrete, as illustrated in Figure 2.7. In this case, no composite action is developed and the fire resistance is reduced to 30 minutes, unless additional protection is applied. The edge of the slab may be detailed at 100mm from the centre-line of the beam (actual distance is half the flange width or 95mm). To anchor the slab, an L-bar is placed in holes pre-drilled in the ASB. The edge trim allows for a thin concrete topping.

The advantage of the second option is that any eccentricities in the column connection are reduced. However, the disadvantage is that the projecting flange of the ASB has to be cut away (depending on the cladding system), and additional insulation is required to reduce cold bridging.


Figure 2.7 Partially encased ASB details at edge beam.

Figure 2.6 Encased ASB details at edge beam.

150

30

A142 meshEnd diaphragm

Edgetrim

1000

50

200

10 mm dia. additionalL-bars at 300 centres

55

L-bar (10 )at 300 centres A142 mesh

30

20bolt hole

Mineralwoolinfill

ASB cut away by 55 (if necessary)

End diaphragm

150

30

A142 meshEnd diaphragm

Edgetrim

1000

50

200

10 mm dia. additionalL-bars at 300 centres

55

L-bar (10 )at 300 centres A142 mesh

30

20bolt hole

Mineralwoolinfill

ASB cut away by 55 (if necessary)

End diaphragm

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Beam span (m) < 6.0 7.0 8.0 9.0

Non-composite 200 x 150 x 8 200 x 150 12.5 or250 x 150 x 10

300 x 200 x 10 N.A.

Composite 200 x 150 x 8 200 x 150 x 10 200 x 150 x 12.5

Data for 6m span slab onto RHS

200 x 150 x 12.5

Proprietarybattenedraft floor

Separating strip

Acoustic sealant

Deflection head

Resilient barstimber battens,or metal frameceiling

15 min. plasterboardresilient strip

Acoustic sealant

12.5 plasterboardDeep compositemetal deck floor

Rigid insulation inexternal cavity

Light steel stud wallwith 2 layers of gypsum board

External brickworktied to inner stud wall

Trapezoidalprofile

Cavity

Optional additionalinsulation (to reduceU value)

Halfen or similarstainless steelbrickwork support

Cavity barrier tofloor/wall junction

Figure 2.8 Non-composite RHS edge beam supporting brickwork.

Minimum Slab Depth (mm)+Designationof RHS

Thickness(mm)

Mass *(kg/m)

Depth(mm) Non-composite Composite

8.0 215 295 295

10.0 215 295 295200 x 150

(240 x 15 plate)12.5 215 295 295

8.0 265 295 335

10.0 265 295 335250 x 150

(240 x 15 plate) 12.5 265 295 335

8.0 315 300 N.A.

10.0 315 300 N.A.300 x 200

(290 x 15 plate) 12.5 315 300 N.A.

* including 15 mm plate

+ Slab depth applies to R60 fire resistance

70

79

91

76

87

100

94

100

126

Table 2.4 Section dimensions of RHS Slimflor edge beams.

Table 2.5 Approximate section sizes of RHS edge beams supporting brickwork.

Rectangular Hollow Sections (RHS) may be used as either composite or non-composite edge beams. Non-composite beams are illustrated in Figure 2.8. RHS edge beams provide an attractive option because of their ease of detailing at the faade line. Furthermore, their high torsional stiffness facilitates eccentric connections, for example, of cantilever balconies. When the edge beam is used only as a cladding support, torsional stiffness is still required because of the eccentric load from the cladding.

For composite construction, shear connectors may be welded to the top flange of the RHS to increase its spanning capabilities by composite action. However, the slab depth needs to be taken as 85mm above the RHS section, which makes the 300mm RHS impractical in composite construction (see Table 2.4). The sizing of the RHS sections generally depends on the orientation of the slab and the cladding load. For scheme design purposes, the RHS sizes given in Table 2.5 may be used.

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At RHS columns, it is often difficult to attach ASBs on adjacent sides. This may be achieved by using alternate extended and flush end plates, as illustrated in Figure 2.12. This approach is only applicable for columns with a minimum width of 200mm. In other cases, welded T-stubs may be used to attach the beams.

flanges to avoid cutting back the ASB section. A typical external UKC column connection with an ASB edge beam is shown in Figure 2.10, and in Figures 3.15 and 3.16.

For RHS columns, connections can be made using Flowdrill or Hollo-bolt connections. Hollo-bolts require the formation of a hole of 1.7 x bolt diameter. As a result of this, the maximum diameter is generally 20mm to allow for edge distances and gaps. A typical external RHS column connection with a RHS Slimflor edge beam is shown in Figure 2.11.

Tie members

Tie members are required to provide robustness by tying columns at each floor. Generally, tie members are in the form of inverted Tees. Smaller UKB or RHS sections with a welded plate are often used where the tie beam supports other local loads. Figure 2.9 illustrates a typical Tee section; this allows for sufficient placement of a Z-section where the deck layout is not in multiples of 600mm. The depth of the Tee is taken as not less than span/40 in order to avoid visible sag. The Tee section does not participate in resisting loads applied to the slab, so reinforcement is placed in the ribs adjacent to the Tee. This does not generally require fire protection, where it is partially encased in the slab. The Tee may be attached by an end plate to the column web or to a stiffener located between the column flanges. This same stiffener may act as a compression stiffener in a moment-resisting connection to the major axis of the column.

Connections

Slimdek has been developed primarily as a flooring system for braced steel-framed buildings. Typically, the beams and slabs are analysed as simply supported elements. Continuity, which is inherent within the system, is only partially used for the serviceability criteria. It is possible to use the ASB beam as part of a sway frame, provided extended end plate connections are used. In this case, columns must be analysed for combined bending and compression.

Beam-to-column connections with ASB or RHS beams should generally be made by full or extended end plates in order to ensure adequate shear and torsional resistance due to out-of-balance loads (primarily during construction). For UKC section columns, beam-to-column connections are generally made to the column flange. Where connections are made to the column web, it may be necessary to weld a plate between the tips of the column

600

Mesh reinforcement

Reinforcementbar

Decking cut to suit setting-out requirement

ASB bottom flange Z section Tee sectioncut from

UKC or UKB

Figure 2.9 Inverted Tee section as a tie member.

ASB end plate

ASB edge beam

Perimeter UKC

ASB edge beam

ASBinternalbeam

Figure 2.10 External UKC section column connection to ASB edge beam.


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Figure 2.12 End plate connections to RHS columns.

50 cavity

Non-loadbearinglight steel stud

Resilient mineral woolseparating RHS andlight steel section

2 x 12.5 plasterboard

Insulation board

RHS column

Vertical channel(to attach wall ties)

Figure 2.13 RHS column incorporated in faade wall (plan section).

Figure 2.11 External RHS column connection to a RHS Slimflor edge beam.

Columns

Universal Column (UKC) sections are recommended for internal columns because of their ease of connection. Rectangular Hollow Section (RHS) columns can be used for fire resistance or for architectural reasons. For example, RHS columns can be contained in the separating or faade walls, as illustrated in Figure 2.13.

A

a) Side view of ASB beam

15 end plate

Flangecut away

A

b) Cross-section A - A

Flowdrill orHollo-bolts

200 RHScolumn

200 RHScolumn

Flowdrill orHollo-bolts

Hollo-boltsPerimeter RHS column (or UKC with plates welded across flange tips for edge beam connections)

RHS Slimfloredge beamwith 15 thickflange plate

Extended end plate

InternalASBbeam

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The moment capacity of typical extended end plate connections is summarised in Table 2.6 (moment capacities for specific ASB weights may be obtained from the Slimdek Manual). These moment capacities are relatively insensitive to the ASB section size, as bending of the end plate controls their design.

The design of wind-moment frames is a special case where the connections are treated as pinned under vertical load and moment-resisting under wind loading. As a simple rule, the maximum number of storeys permitted in a wind-moment frame should not exceed the number of columns in the direction in which the wind forces act (up to a maximum of six storeys). Therefore, for wind acting on the front face of a building with four columns across the width, the maximum height is four storeys.

For a rectangular plan building with wind acting on the short length, there are potentially more columns to resist the wind loads along the building, and the maximum height recommended is increased to six storeys, provided that the columns are orientated so that their stiffer direction is along the building length. In this second orientation, vertical bracing can be eliminated in the faades, leading to large fenestrations and freedom of space planning.

Slimdek in an unbraced structure

Vertical bracing can be eliminated in a structure with Slimdek floors by designing the connections between the ASBs and the columns as moment-resisting. Where UKC columns are used, these connections should be made to the column flanges. Extended end plates increase the effective depth of the connection and increase its moment capacity. A typical extended end plate connection is shown in Figure 2.15. For detailing purposes, dimension A should be taken as 44mm for ASB280 and 62mm for ASB300.

RHS columns may be used, but the moment capacity of beam end connections are generally less effective than for UKC sections, except for the thicker wall sections.

Table 2.6 Moment capacities (kNm) of extended end plate connections

200

d

t f

50

120

300

10

75

75

A

50

40 t f

Figure 2.15 Extended end plate connection to an ASB beam.

Discontinuous columns

Columns can also be designed as storey-high elements and attached to the flanges of the ASB, as illustrated in Figure 2.14. This unusual configuration is possible in medium-rise buildings because the modest compression forces can be transferred through the thick web of the ASB to the concrete encasement. In these cases, moment continuity can be developed in the ASB to optimise its performance. For more heavily loaded columns, vertical stiffeners would be required in the web of the ASB. When adopting this approach, particular care and attention must be paid to the design and detailing, especially to ensure frame stability and resistance to progressive collapse (through horizontal and vertical tying, or by key element design).

Figure 2.14 ASB beams continuous over storey-high RHS columns in medium-rise buildings.

Column size kg/m ASB280 ASB300

203 UKC

x 46 81 85

x 52 86 90

x 60 91 95

x 71 92 97

254 UKC x 73 92 97

x 89 92 97

Data: 15 end plate in S355 steel and M20 bolts


15 endplate

A

A

RHS tie

ASB

150 SHScolumn

a) Side view of ASB beam

b) Cross-section A - A

150 SHScolumn

150 SHScolumn

150 SHScolumn

RHS tie

ASB

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Fire resistance

The fire resistance of the ASBs is achieved by partial encasement in the composite slab. Generally, 60 minutes fire resistance can be achieved by ASB sections, increasing up to 120 minutes if board materials, a suspended ceiling or intumescent coatings, protect them. The fire resistance of the deep composite slab is achieved by bar reinforcement of the minimum sizes shown in Table 2.7. The axis distance defines the distance from the centre-line of the reinforcing bar to the soffit of the decking (see Figure 2.3). Mesh reinforcement is placed in the topping at a minimum top cover of 15mm. The reinforcement detailing requirements are illustrated in Figure 2.3.

Acoustic insulation

Separating floors in Slimdek are easily capable of providing the acoustic insulation (both airborne and impact) required to meet the new Part E (2003) Building Regulations. When combined with the prescribed floor and ceiling treatments the floor has been able to achieve Robust Detail (RD) status (E-FS-1). RD status means that post-completion testing of the floor is not required. A typical cross section through a beam and slab showing the various layers is shown in Figure 2.16. Table 2.8 illustrates the excellent performance in robust detail in-situ tests compared to the requirements given in Part E of the Building Regulations.

Masonry or double-leaf light steel separating walls can be used in conjunction with the Slimdek floor. Doubleleaf walls are generally recommended because of the ease and speed of construction and the elimination of wet trades on site. Typically, this type of wall comprises two leafs of studs (each 50 to 70mm deep) separated by a layer of mineral wool. The outer faces of the studs are fixed to double layers of plasterboard, to give an overall thickness of around 250mm. Care should be taken to ensure an adequate cavity width, and adequate densities for the materials used. Specialist manufacturers have produced a number of proprietary wall and detail solutions.

Table 2.7 Detailing requirements for deep composite slabs.

280 ASB 100

18 thick tongued and grooved chipboard walking surface (or similar)

Proprietary battenwith integral foam strip

Single skin 12.5 thickplasterboard suspended ceiling

Proprietaryresilient bars

Concrete floor slab with ComFlor225 deep decking

Figure 2.16 Cross-section through ASB beam showing acoustic insulating layers.

Parameter Fire resistance (mins)

60 or less 90 120

Min. slab depth 295 mm 305 mm 320 mm

Min. bar diameter 16 mm 20 mm 25 mm

Axis distance to bar 70 mm 90 mm 120 mm

Min mesh size in topping A142 A193 A252

Column size ASB280 ASB300

203 UC x 46 kg/m 81 85

x 52 kg/m 86 90

x 60 kg/m 91 95

x 71 kg/m 92 97

254 UC x 73 kg/m 92 97

x 89 kg/m 92 97

Data: 15 mm end plate in S355 steel and M20 bolts

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Table 2.8 Acoustic performance of Slimdek.

Separating strip

Acoustic sealant

Platform floorProprietarybattenedraft floor

Separating strip

Acoustic sealant

12.5 plasterboard Resilient bars ortimber battens

Deflection head

Acoustic sealant

Deep compositesteel decking

12.5 plasterboardceiling on proprietary

metal frame ceiling

1 layer of 15 plasterboardor other fire-stopping

material laid flat between ASBand light steel channel

Light steel frameseparating wall

Figure 2.18 Acoustic detail of ASB beam and light steel separating wall.

Details of the attachment of a separating wall to an ASB beam are illustrated in Figure 2.18. A deflection head allows for relative movement between the ASB and the separating wall. Note that board present at the top of the wall is needed for fire as well as acoustic purposes.

One of the most crucial features with this typeof wall is the interface between the wall headand the soffit of the slab, particularly when thedeck ribs do not run parallel to the wall. Theattachment of a light steel separating wall tothe soffit of a composite slab with ComFlor225 decking is illustrated in Figure 2.19.Profiled mineral wool inserts are required toprevent both sound and fire passing throughthe voids in the deck. Board beneath theseinserts also serves both fire and acousticpurposes. When this detail is properly achievedthe wall can be expected to passPart E requirement.

More information on expected acoustic performance and typical construction details can be found in the accompanying SCI Publication P336 Acoustic Detailing for Multi-Storey Residential Buildings.

Additional mineral wool inceiling void around junction

Pack withmineral wool

2 layers of 19 mmgypsum board

12.5 mm plasterboardon proprietry metal frame

Deep compositesteel decking

Separating strip

Acoustic sealant

Platform floor Proprietarybattenedraft floor

Separating strip

Acoustic sealant

AcousticsealantLight steel frameseparating wall

Figure 2.19 Acoustic detail of separating wall transverse to composite slab.

Part E 45 62

Robust Detail 47 57

Slimdek Performance (E-FS-1) (Range) 50-64 24-46

(Mean) 56 38

Acoustic Test Data (dB)

Airborne sound reduction Impact sound

DnT,w + Ctr L,nT,w

>_

>_

15

Proprietary battenedraft floor

Separating strip

Acoustic sealant

Deflection head

Resilient bars, timber battens or metal frame ceiling15 min.

plasterboardresilient strip

Acoustic sealant

12.5 plasterboard

Deep compositemetal deck floor

Rigid insulationin external cavity

Light steel stud wall with 2 layers of gypsum board

Externalbrickwork tied to innerstud wall

Halfen or similar stainless steel brickwork support

Cavity

Cavity barrier to floor/wall junction

Optionaladditionalinsulation (to reduceU value)


Cladding sheet

Cladding rail on angle brackets

Sheating board

Breatherpaper

Fixing rail on packers

Sheathing board

Platform floor Slimdek floor

Light steel framenon-loadbearingstud wall

Rigid insulationmaterial

Fire break

Polymer basedrender

15 drainedcavity

Acoustic sealant

12.5 plasterboard

Deep compositemetal deck floor Resilient bars,

timber battensor metal frameceiling

Acoustic sealantSeparating strip

Optional additional insulation

Drained 15cavity

Clay tilecladdingsystem

15 min. plasterboard

Deflection head

Non-loadbearing light steel frame stud wall

Rigid insulationBreatherpaper (with optionalsheathing boardbehind)

Deflection head Resilient bars,



Acoustic sealant

12.5 plasterboard




Separating strip

Acoustic sealant

Deflection head

Resilient bars, timber battens or metal frame ceiling15 min.

plasterboardresilient strip

Acoustic sealant

12.5 plasterboard


Rigid insulationin external cavity

Light steel stud wall with 2 layers of gypsum board

Externalbrickwork tied to innerstud wall

Halfen or similar stainless steel brickwork support

Cavity

Cavity barrier to floor/wall junction

Optionaladditionalinsulation (to reduceU value)


Cladding sheet

Cladding rail on angle brackets

Sheating board

Breatherpaper

Fixing rail on packers

Sheathing board

Platform floor Slimdek floor

Light steel framenon-loadbearingstud wall

Rigid insulationmaterial

Fire break

Polymer basedrender

15 drainedcavity

Acoustic sealant

12.5 plasterboard

Deep compositemetal deck floor Resilient bars,


Acoustic sealantSeparating strip

Optional additional insulation

Drained 15cavity

Clay tilecladdingsystem

15 min. plasterboard

Deflection head

Non-loadbearing light steel frame stud wall

Rigid insulationBreatherpaper (with optionalsheathing boardbehind)

Deflection head Resilient bars,



Acoustic sealant

12.5 plasterboard



Cladding attachments depend on the type of cladding used and the type of edge beam. For encased ASB beams, the centre-line of the ASB is detailed at 200mm from the edge of the slab (see Figure 2.6).

Figure 2.20 Detailing of brickwork support by ASB beams.

Figure 2.21 Insulated render cladding attachment to ASB beams.

Figure 2.22 Rain-screen cladding attachment in Slimdek.

Figure 2.23 Brick-tile cladding attachment in Slimdek.

More detail on cladding systems and their attachments is given in Figures 2.20 to 2.23. For details on cladding attachments to RHS edge beams, see Figure 2.8.

Attachment of cladding to edge beams

16

Service integration

Openings in the slab for pipes and service risers.

Openings in the web of the ASB for horizontal service distribution in the floor zone.

Trays embedded in the slab for horizontal distribution of electrics or small diameter pipes in the surface of the slab.

Large openings can be formed between the ribs of the decking and through openings in the ASB beams (subject to effective fire compartmentation). Electrical trays should be positioned to align with the ribs of the decking so that they observe fire resistance and acoustic insulation requirements (see Figure 2.24).

Opening in slab

Horizontalservice tray

150 max.

320 max.

Opening in ASB 160 max.

300 max.

60 min.

50 max.

80 min.

Mesh

T12 bar

ASB bottom flange

Figure 2.24 Service openings and electrical trays in Slimdek.


17

Our example building is a six-storey structure with a roof-top penthouse, illustrated in Figure 3.1. The building design could be extended to ten-storeys without significant modifications to the structure. The interior of the building may be configured with apartments on either side of a central corridor, referred to as the deep plan form, or with apartments configured across the full width of the building around an access core, referred to as the shallow plan form. See Figures 3.5 and 3.6.

The building is be adapted for mixed use, making provision for retail uses at ground floor (by increasing the floor-to-floor height) and for car parking at basement level. The length of the building is not defined, as the plan forms are repeatable.

The flexible use of space provided by Slimdek is illustrated in Figure 3.2.

The building considered has three distinct levels: Below-ground car-parking. Retail or office level at first floor. Residential floors above.

The structural grid adopted is dictated by the car park level, to avoid the use of an expensive transfer structure. This is based on a three-car bay (7.5m wide) along the faade, and columns at 4.8m, 6.7m and 5.0m respectively across the building (deep plan) or 3.9m, 7.2m and 4.8m (shallow plan) to allow for sufficient vehicular access.

The application of Slimdek

Flat Flat

Car Park

Flat Flat

Flat Flat

Flat Flat

CentralCorridor

FlatFlat

Retail

Penthouse

CentralCorridor

CentralCorridor

CentralCorridor

CentralCorridor

Figure 3.1 Deep plan form cross-section through building.

This section examines a typical mixed-use residential building in steel using Slimdek construction.

Figure 3.2 Flexible space using Slimdek.

18

Light steel wallslight steel walls are used for: external walls to create a rapid dry envelope; compartment or separating walls between apartments; internal walls within apartments.

Building form The steel-framed apartment building has the following characteristics:

Prefabricated modulesBathrooms are assumed to be prefabricated modules set into the slab to avoid mis-alignment of the floors.

Minimal foundation costs Foundations are located directly below the columns. The lightweight steel construction minimises foundation costs.

No limit on building heightThe building is six storeys high (plus penthouse and car park levels). The ground floor can be adapted for retail use. There is no limit on building height when using Slimdek, but four to ten storeys is the sensible range for this type of residential construction. Penthouse apartments are located at roof level.

Utility servicingServicing is rationalised by vertical risers in the core and horizontal routes through the floor slab.

Acoustic insulationExcellent acoustic insulation is achieved by the Slimdek floor with its resilient layers.

Slimdek residential pattern book The application of Slimdek

19

7.5m 7.5m

6.7m

5.0 m

4.8m

5.4m

Figure 3.3 Structural grid as dictated by car park level.

Structural grids

Faade materials and finishExternal brickwork cladding with a light steel stud inner skin is assumed for the steelwork designs, although a variety of faade materials may be used. (Ground supported brickwork is not practical above four storeys.)

Minimal floor depthusing Slimdek, the floor depth (including a suspended ceiling and battened floor) is typically 400mm.

Optimum structural grids (i.e. column layout) differ greatly between applications: Car parks grids are normally based on 5m

(two-car spaces) or 7.5m (three-car spaces) as in Figure 3.3.

Residential buildings grids are often based on multiples of 600mm (4.2m being efficient for studios).

Commercial buildings use grids based on multiples of 1500mm (6m, 7.5m and 9m being common column spacings).

From this it is apparent that, for a mixed-use building, the column grids will not align unless either the arrangement of car parking space or residential accommodation is modified. Alternatively, a steel or concrete transfer structure may be designed to transfer loads from the super-structure to the columns of the car park substructure. In this case, it is important that the superstructure is sufficiently light so that the transfer structure is not made deeper increasing foundation costs.

A repeatable floor plan areaA repeatable floor plan area (for either plan form) of approximately 20m x 16m is accessed from a single braced core. Spans of 4.8m to 7.5m achieve a sensible layout of apartments and rooms, which may be reconfigured independently of the beam lines. This allows a range of apartments with floor areas from 60m2 to 120m2 to be created.

20

Deep plan form

The deep plan form has the following features:

Columns are located at 7.5m and 5.4m along the faade.

Columns are located at 5.0m, 6.7m and 4.8m across the plan form of the building.

A 2.1m-wide corridor is provided along the building.

Columns are generally located in the 300mm-wide separating walls between apartments.

An alternative lift location may be introduced (see Figure 3.10).

The ratio of habitable:gross floor area is about 85% per residential floor.

Apartments of approximately 50m2 and 65m2 floor area are provided, which are each suitable for two and four people respectively.

A total of 14 car parking spaces is provided (including two disabled spaces) for the five residential and penthouse levels. The car parking lies fully within the building depth.

The penthouse level is accessed via the stairs and provides two 68m2 apartments, each suitable for four people.

A retail area of 880m2 is provided.

Shallow plan form

The shallow plan form has the following features:

Columns are located at 7.2m and 6.3m along the faade.

Columns are located at 3.9m, 7.2m and 4.8m across the plan form.

Columns are all located in the separating walls between apartments.

Three apartments are accessed directly from each stair/lift area on each residential floor.

The ratio of habitable:gross floor area is about 85% per residential floor.

Apartments of approximately 50 and 75m2 floor area are provided, which are suitable for two and four people respectively.

A total of 13 car parking spaces are provided (including two disabled or wide spaces) for the five residential and penthouse levels. The car parking projects 3.9m to the rear of the building.

A retail area of 640m2 is provided. The penthouse level is accessed via the

stairs and provides two 73m2 apartments, each suitable for four people.

Plan form and room layouts

Two plan forms are considered, which are presented in the following illustrations:

1. A deep plan form with apartments on either side of a central corridor.

2. A shallow plan with apartments across the full depth of the building.

The building is extendable horizontally by repeating the shallow plan form, although with the deep plan form it is possible to serve three units with only two stairs or lift areas (see Figure 3.4).

Figure 3.4 Repeatable floor plan with three units sharing two lift/stair areas.


21

BedroomBedroomKitchen/dining/living

BedroomBedroomBedroomBedroom

1 BED FLAT 1 BED FLAT

2 BED FLAT 2 BED FLAT

Kitchen/dining/living



Figure 3.5 Deep plan form Layout of apartments.

Bedroom

1 BED FLAT

2 BED FLAT




Bedroom Bedroom Bedroom

2 BED FLAT

Bedroom

Figure 3.6 Shallow plan form Layout of apartments.

22

Retail UnitRetail Unit

Figure 3.7 Deep plan form car parking level.

Figure 3.8 Deep plan form layout of retail level.


23

1 BED FLAT

BedroomBedroom Kitchen/dining/living

Bedroom

2 BED FLAT

BedroomBedroom




1 BED FLAT2 BED FLAT

Figure 3.10 Deep plan form layout of apartments for alternative lift location.

2 BED FLAT2 BED FLAT

Bedroom BedroomBedroomKitchen/Dining/Living

Bedroom Kitchen/Dining/Living

Figure 3.9 Deep plan form penthouse level.

24

Floor layout The structural layout of the floor in both plan forms comprises 280 ASB beams spanning up to 7.5m, and a deep composite slab spanning up to 7.5m between the beams (spans in excess of 6m require temporary propping in normal-weight concrete). The slab depth is nominally 300mm. Shallow decking may be supported off the bottom flanges to create a shallow slab in the core area, providing an additional zone for servicing within the floor.

Structural options The various structural layouts of the building are presented in Figures 3.11 to 3.15. In a braced frame, longitudinal bracing is provided at suitable locations in the faade, depending on fenestration positions and sizes. Bracing locations can be difficult to design in highly glazed faades. The advantage of a wind-moment frame design is that vertical bracing can be omitted in the longitudinal direction of the building, which allows full-height glazing to be used throughout. Alternatively, vertical bracing has to be located between columns in separating walls, in the faade, or around the core. The disadvantage of the wind-moment frame option is that it is not generally appropriate for buildings of more than six storeys, and columns are often heavier than in a braced-frame design. Moment continuity is achieved by using extended end plates welded to the ASB or RHS beams.

Tie members (generally in the form of Tees) are provided parallel to the decking, in the absence of the ASB beams. At the perimeter of the buildings, ASB beams or RHS sections with a welded plate may be used. The centre-line of the ASB beams is offset by 200mm from the edge of the slab to allow for access of the edge trim (see Figure 2.6). The connection is detailed as in Figure 3.16. Alternative details not requiring this eccentricity, but requiring additional fire protection to the exposed ASB, are presented in Figures 2.7 and 3.17. The equivalent detail of an RHS edge beam to a RHS column is not eccentric, as shown in Figure 3.18. For this reason, RHS edge beams are preferred.

At internal columns using smaller RHS sections, the ASB will project outside the column, in which case bolted connections may be made to plates welded to the RHS, as shown in Figure 3.19.

The columns are detailed to be located within a 300mm separating wall, which consists of two 100mm C-sections with a 40mm gap, and two layers of fire-resisting plasterboard. The maximum column width is therefore 200mm (i.e. 203 UKC or 200 x 200 RHS or 300 x 200 RHS). If the column size is increased to 254 UKC, an intumescent coating should be used to provide adequate fire resistance. Where columns align with partitions, exposed RHS columns may be used, which are fire protected by intumescent coating or filled with concrete. An example of the use of RHS columns located in a light steel separating wall is illustrated in Figure 3.20.


25

Figure 3.11 Structural layout for deep plan building ASB edge beams and UKC columns.

Figure 3.12 Structural layout for deep plan building ASB edge beams and UKC columns - propped.

165

x 15

2T@

20 k

g/m

S27

5

165

x 15

2T

@20

kg/

m S

275

280 ASB 100

280

ASB

74

or20

3 U

KC 4

6 +

pla

te

165

x 15

2T@

20 k

g/m

S27

5

280 ASB 100or 254 UKC 89 + plate

203 UKC 46S355

5000

280

ASB

74

254

x 14

6 U

KB31

S275

152x

89 I

5400

280 ASB 100

300 deepNWC slabon CF225decking

2200

280 ASB 100

4800

254 x 146 UKB31S275

280 ASB 74

280

ASB

74

280

ASB

74

280

ASB

74

CF225

CF51

Stair Lift

Void

CF51

CF51

152x89 I

280

ASB

74

or20

3 U

KC 4

6 +

pla

te

280

ASB

74

with

anc

hore

d re

-bar

sor

203

UKC

52

+ p

late

165

x 15

2T@

20 k

g/m

S27

516

5 x

152T

@20 kg/m S275

7500 7500 7500

6700

203 UKC 86S355

203 UKC 86S355

203 UKC 46S355

203 UKC 46S355203 UKC 46

S355

203 UKC 46S355

203 UKC 52S355

203 UKC 52S355

203 UKC 46S355

203 UKC 46S355

203 UKC 71S355

203 UKC 71

S355

203 UKC 71S355

203 UKC 71S355

203 UKC 46S355 280 ASB 100or 254 UKC 89 + plate

280 ASB 74280 ASB 100


280 ASB 74or 204 UKC 52 + plate280 ASB 100

or 254 UKC 89 + plate


P P

P = Decking propped at construction stage

5400

4800

280

ASB

74

280

ASB

100

280

ASB

74

CF225P

165 x 152 T@20 kg/m S275

165 x 152 T@20 kg/m S275

280

ASB

100

165 x 152 T@20 kg/m S275

280

ASB

74

280

ASB

100

7500

280

ASB

74

or 2

54 U

KC89

+ p

late

280

ASB

100

or 2

54 U

KC10

7 +

pla

te

7500


280 ASB 74 with anchored re-barsor 203 UKC 46 + plate

254

x 14

6 U

KB31

S275

152x

89 I

Void

StairLift

CF51

CF51 CF51

2200

4800

280

ASB

74


165 x 152 T@20 kg/m S275

280 ASB 74

254 x 146 UKB31S275

280

ASB

74

165 x 152 T@20 kg/m S275

280 ASB 74with anchored re-barsor 203 UKC 46 + plate

280

ASB

74

280

ASB

74

or 2

54 U

KC89

+ p

late

6700

= Decking propped at construction stage

P

P

P P

P

P

203 UKC 46S355

203 UKC 46S355

203 UKC 71S355203 UKC 71

S355

203 UKC 71

S355

203 UKC 71S355

203 UKC 46S355

203 UKC 46S355

203 UKC 46S355

203 UKC 52S355

203 UKC 52S355

203 UKC 46S355

203 UKC 46S355

203 UKC 86S355

203 UKC 86S355

203 UKC 46S355

280 ASB 74 with anchored re-barsor 203 UKC 46 + plate

7500


280 ASB 74 or203 UKC 46 + plate

26

165

x 15

2T@

20 k

g/m

S27

5

165

x 15

2T@

20 k

g/m

S27

5

5400

280 ASB 100 280 ASB 74

165

x 15

2T@

20 k

g/m

S27

5

7500

250

x 15

0 x

6.3

RHS

+pl

ate

S355

7500 7500

300 x 200 x 8.0 RHS+ plate S355

300 x 200 x 8.0 RHS+ plate S355

250 x 150 x 8.0 RHS+ plate S355

5000

280

ASB

74

254

x 14

6 U

KB31

S275

280

ASB

74


Void

Stair Lift

CF51

CF51

CF51

300 x 200 x 8.0 RHS+ plate S355

280 ASB 74

300 x 200 x 8.0 RHS+ plate S355

280

ASB

74

280

ASB

74

CF22

5

150 x 9

0 I

150 x 90 I

152 x 89 I

250 x 150 x 8.0 RHS+ plate S355

165

x 15

2T@

20 k

g/m

S27

516

5 x

152T

@20

kg/

m S

275

250

x 15

0 x

6.3

RHS

+pl

ate

S355

250

x 15

0 x

6.3

RHS

+pl

ate

S355

2200

4800

6700

300 x 200 x 10.0 RHSS355


300 x 200 x 10.0 RHSS355

300 x 200 x 10.0 RHSS355

250 x 150 x 8.0 RHSS355

250 x 150 x 8.0 RHSS355

250 x 150 x 8.0 RHSS355

250 x 150 x 8.0 RHS

S355

200 x 200 x 10.0 RHSS355

200 x 200 x 10.0 RHSS355

200 x 200 x 10.0 RHSS355

280 ASB 100

280 ASB 100280 ASB 100 280 ASB 74300 x 200 x 10.0 RHS

S355

250 x 150 x 8.0 RHSS355

200 x 200 x 12.5 RHSS355

200 x 200 x 12.5 RHSS355

250 x 150 x 8.0 RHSS355

200 x 200 x 10.0 RHSS355

P P

Figure 3.13 Structural layout for deep plan building RHS edge beams and RHS columns as a wind moment frame option.


27

280

ASB

74

280 ASB 74

280

ASB

74

280 ASB 74 280 ASB 74

280

ASB

74

300

x 20

0 x

6.3

RHS

+ p

late

250 x 150 x 10.0 RHS+ plate

280 ASB 74

Stair

280

ASB

100

Riser

Lift

280

ASB

100

2700 2100

250 x 150 x 10.0 RHS+ plate

250 x 150 x 10.0 RHS+ plate


280 ASB 74

254

x 14

6 U

KB31

S275

254

x 14

6 U

KB31

S275

254 x 146 UKB31S275

203

x 13

3 U

KB25

S275

203

x 13

3 U

KB25

S275

280

ASB

136

300

x 20

0 x

12.5

RH

S+

pla

te

4800

1900

1000

2300

2000

3900

7200

1200 4800 1200

7200 6300 6300

150 x 150 x 6.3 RHSS355

250 x 150 x 8.0 RHSS355

250 x 150 x 10.0 RHSS355

200 x 200 x 12.5 RHSS355

250 x 150 x 8.0 RHSS355

250 x 150 x 8.0 RHSS355

300 x 200 x 12.5 RHSS355

250 x 150 x 10.0 RHS+ plate

250 x 150 x 8.0 RHSS355 250 x 150 x 10.0 RHS+ plate

300 x 200 x 12.5 RHS

S355

P

PP

250 x 150 x 8.0 RHS

S355

150 x 150 x 6.3 RHS

S355200 x 200 x 10.0 RHSS355

200 x 200 x 10.0 RHSS355

200 x 200 x 10.0 RHSS355


280

ASB

74

280 ASB 74

280

ASB

74

165 x 152T@20 kg/m S275

165 x 152T@20 kg/m S275

280

ASB

74

280

ASB

74

or25

4 U

KC73

+ p

late

1200 4800 1200

7200 6300 6300

4800

280 ASB 74

Stair

280

ASB

100

Riser

280

ASB

100

2700 2100

Lift

300 deepslab onCF225

decking280 ASB 74

254

x 14

6 U

KB31

S275

254 x 146 UKB31S275

254

x 14

6 U

KB31

S275

203x

133

UKB

25S2

7520

3x13

3 U

KB25

S275


280

ASB

136

203 UKC 86S355

280

ASB

100

or 2

54 U

KC +

pla

tew

ith a

ncho

red

re-b

ars

3900

1900

1000

2300

2000

7200


PP

203 UKC 46S355

203 UKC 86S355

203 UKC 86S355

203 UKC 46S355

203 UKC 46S355

203 UKC 86S355

203 UKC 46S355

203 UKC 46S355

203 UKC 52S355

203 UKC 46S355

203 UKC 46

S355

152 UKC 30

S355

152 UKC 30S355





P

Figure 3.15 Structural layout for shallow plan building RHS edge beams and RHS columns acting as wind moment frame.

Figure 3.14 Structural layout for shallow plan building ASB edge beams and UKC columns.

28

203 UKC 86Column

4 No. M 20bolts

300 x 300x 15 thk plate

4 No. M20g8.8 bolts

300 x 200 x 12 thkASB end plate

280 ASB 74edge beam

280 ASB 136

80 120

120

200

120

80

120

320 x 180 x 12thk plate

Figure 3.16 ASB connection to edge column (showing eccentric detail).

120

31.5

80

4 No. M20g8.8 bolts

300 x 200 x 12 thkASB end plate

280 ASB 74edge beam

120

203 UKC 86Column

280 ASB 136320 x 200

x 12thk plate

4 No. M 20bolts

80 120

140

Figure 3.17 ASB connection to edge column (no eccentricity).


29

320 x 200x 12thk plate

250 x 150 x 10 thkRHS column

4 No. M 20Hollo-bolts

280 ASB 136

170 x 430x 12 thk plate

M20 Hollo-boltsin 33 O/ holes

280 ASB 136

250 x 150 x 6.3 thkRHS Slimflor beamand 15 mm thk plate

80 120

120

70

50

10010

40

(min.)

Figure 3.18 RHS edge beam connection to RHS column.

100

ASB

Tie beamcut from457 x 191 UKB

ASB

Tie beamcut from457 x 191 UKB

Facade line Facade line


(a) Column on centre-line of edge beam

(c) Plan on column in (a) (d) Plan on column in (b)

(c) Column along facade line

20050

200

100

50

50 50 100

50

200

360

300

20 mmdia. bolt

150

80

300

SHS column

Flowdrillbolt holes(20 mm dia.)

12

12

200

300

Seating platewelded betweenend plates

Seating platewelded betweenend plates

50

Figure 3.19 ASB bolted connections to RHS column.

30

Table 3.1 Summary of steel weights kg/m2 for various structural options.

A typical detail of a light steel separating wall at a RHS column is illustrated in Figure 3.20. The wall thickness is 300mm when using a 200 x 200 RHS column. The wall thickness will increase if larger columns are used.

Material usage

The typical steel usage for a six-storey building (relative to the gross floor area) is:

Beams 32-38kg/m2

Columns 7-10kg/m2 Bracing, secondary beams 1-3kg/m2

The precise values for the various structural options are presented in Table 3.1. A steel weight of 40-45kg/m2 may be used for scheme design using Slimdek, increasing to 50kg/m2 for more complex building shapes.

The structural arrangement can be adapted to any sensible plan form.

It is apparent that the weight increase in the steel structure is negligible for this six-storey building when designing using the wind moment principle. However, the connections may be more complex.

The self-weight of the 300mm-deep composite slab is 350kg/m2 in normal weight concrete, which requires propping during construction for spans in excess of 6m. However, the self-weight is reduced to 280kg/m2 when lightweight concrete is used, which does not require propping for spans of up to 6.3m.

19 mm plank

12 mm fireresisting board

Mineral wool insulation

30 mm thickdense mineralwool board

200 x 200SHS column

100

100

38 300

Figure 3.20 Detail of separating wall at RHS column.


Beams Edge Columns Bracing Beams

ASB ASB UKC Braced 33 7 1 41

WindASB RHS RHS moment 35 8 43 frame

Braced -ASB ASB UKC slab span 33 8 1 42 longitudunal

Braced -ASB ASB UKC slab span 39 8 1 48 transverse

WindASB ASB UKC moment 39 8 - 47 frame

WindASB RHS RHS moment 38 9 - 47 frame

Structural weights (kg/m2)

Beams Columns Bracing

BuildingOptions

ShallowPlanForm

DeepPlanForm

Total

kg/m2

31

In the first case, no vertical load is transferred to the structure or faade of the building, but the modules are attached to the structure for horizontal restraint. In the second case, the size of the balcony is limited in order to reduce the moments that are transferred to the internal structure. In the third case, the ties can be relatively unobtrusive but vertical ties will require a projecting structure such as a roof truss, to carry the loads on all the balconies.

In conventional concrete construction, the slab is continued outside the building envelope to form a balcony or other projection. However, this is no longer the preferred solution because of the need to prevent cold bridging through the slab, to meet the new Part L Building Regulations. It is now necessary to provide a thermal break in the slab, or to insulate it externally.

Types of balcony Modern balconies are usually prefabricated steel units, which are attached to the internal structure by brackets or through posts, so that thermal bridging effects can be minimised.

The three generic balcony systems are detailed below:

1. Stacked ground-supported modules, which may be installed as a group by lifting into place. The columns extend to ground level.

2. Cantilever balconies, achieved by either: - Moment connections to brackets attached

to torsionally stiff edge beams. - Moment connections to wind-posts

connected between adjacent floors.

3. Tied balconies achieved by either:- Ties back to wind-posts or to the floor

above. - Vertical ties to a supporting structure

located at roof level.

Figure 4.1 Steel balconies attached to curved edge beam in Slimdek at Harlequin Court, London (Goddard Manton Architects).

Steel balconies and parapets

Balconies and terraces are important additions to modern urban living, which often require interesting architectural solutions.

32

Balcony attachments in Slimdek

In Slimdek, RHS edge beams are torsionally very stiff and are recommended for cantilever attachments of balconies, where brackets are welded to them. To minimise cold bridging, a single bracket at each side of the balcony should be used.

Wind-posts may be bolted to the top and bottom of ASB edge beams or to fin plates welded to RHS edge beams. They are designed to resist moments developed by the cantilever balcony and can be relatively large. Again, RHS sections may be preferred. The attachment of balconies to a curved faade in Slimdek is illustrated in Figure 4.1.

50 200

Facade line

Slab level

Cut inedge trim

Bolted connection

a) Bracket connection to ASB b) Longitudinal view of bracket

Figure 4.2 Bracket attachment to ASB edge beam.


a) Pre-welded cantilevers b) Bracket or fin attachment

Figure 4.3 Cantilever or fin attachments to RHS edge beams.

Details of various forms of attachment of balconies to RHS and ASB edge beams are illustrated in Figure 4.2 and Figure 4.3. They are designed to minimise cold bridging.

The support of a tied steel balcony to ASB edge beams is illustrated in Figure 4.4. The fin plate welded to the ASB provides a direct attachment both for the balcony and for the tie to the balcony below, and minimises cold bridging. Torsional effects are resisted by the continuity effect of the slab, when the deck ribs are orientated as in this figure. When the deck ribs are orientated parallel to the ASB, and it is merely acting as a cladding support, torsional effects should be taken into consideration in the design of the beam.

The same principles may be followed for other types of balconies, such as where RHS posts are introduced to which the balconies are attached. In this case, fins are welded to the post rather than to the beams to minimise cold bridging. A cantilever attachment may be made using steel ferrules to the sides of RHS edge beams, as in Figure 4.5.

Slimdek residential pattern book Steel balconies and parapets

33

Figure 4.4 Detail of attachment of tied balcony in Slimdek. Figure 4.5 Cantilever balcony attachment in Slimdek.

34

Figure 4.6 Detail of balustrade attachment in Slimdek. Figure 4.7 Detail of parapet wall attachment in Slimdek.

Slimdek residential pattern book Steel balconies and parapets

Insulation

Single ply membrane bonded to metal flashing

Walkway tile

Steel channel section exposed visually

Aluminium flashing

Galvanised steel balustrade

Screed laid to falls

Steel fin plate welded to beam to providesupport to channel section (max. 2 m centres)

Insulation (passing both sides of fin plate)

Facing brick/masonry external leaf

2 layers plasterboard on light steel framing

Single ply membrane (or simply roofing membrane) on insulation on screed to falls

Steel posts @ 1200 centres

Colourcoat steel coping

Angle at top of posts

18 mm ply or blu-clad or similar board faced with vapour permeable membrane

Colourcoat cladding to external face of parapet

Insulation

Angle attached to top of beam by pre-fixed bolts

Figure 4.6 shows a steel balustrade directly connected to a steel channel section, which is attached by a welded fin plate to a fin plate connected to the ASB. This detail ensures continuity of the insulation in the warm roof and in the cladding. Because of the relatively weak torsional stiffness of the channel section, it is recommended that the fin plates are spaced at not more than 2m along the beam.

Figure 4.7 shows a parapet wall directly connected by a steel angle or channel to the top flange of the ASB. Bolts can be pre-attached to the top flange to receive stub columns (normally RHS) at, say, 1200 mm centres. Light steel infills may be used between these stub columns. The external brickwork is held in place by wall ties, and the top bricks by an exposed angle.

4.3 Parapets and balustrades

Parapets and balustrades often pose particular technical issues because of the need to resist lateral forces and hence torsional effects on the edge beam, and also to avoid cold bridging through the slab. Two examples are illustrated.

35

References

Sources of informationBuilding Regulations 2003 Approved Document E: Resistance to the passage of sound.

The Stationery Office, 2003.

Slimdek Manual. www.tatasteelconstruction.com

Steel in multi-storey residential buildings (P332). The Steel Construction Institute, 2004.

Acoustic Detailing for Multi-Storey Residential Buildings. (P336). The Steel Construction Institute, 2004

Design of Asymmetric Slimflor Beams using Deep Composite Decking (P175). The Steel Construction Institute,1997.

Design of RHS Slimflor Edge Beams (P169). The Steel Construction Institute, 1997.

Case studies on residential buildings using steel (P328). The Steel Construction Institute, 2003.

List of contributors Peter Lusby-Taylor - HTA Architects Prof. Mark Lawson - The Steel Construction Institute Prof. Ray Ogden - Oxford Brookes University Dr. Stephen Hicks - The Steel Construction Institute Dr. Jim Rackham - The Steel Construction Institute

Guidance on the design and use of structural sections and plates Tata Steel provides free advice to the construction industry covering all aspects of the design, specification and use of its range of construction products.

Tata Steel manufactures structural sections and plates for building and civil engineering applications. Advice is provided by our team of qualified engineers with extensive experience in the design and construction of buildings and bridges.

Specialist advice in fire engineering, durability and sustainability is also available. Our regional network of engineers covers the whole of the UK and Ireland and is supported by a dedicated design team based at our manufacturing centre in Scunthorpe.

General Enquiries on other products and systems manufactured by Tata Steel will be routed to our Construction Centre who will direct you to the appropriate source of market and product expertise.

Tata Steel

Construction Services & Development

PO Box 1Brigg RoadScunthorpeNorth Lincolnshire DN16 1BP

Construction hotline +44 (0) 1724 405060Email: [email protected]: www.tatasteelconstruction.com

Support for the construction industry from Tata Steel

36

While care has been taken to ensure that the information contained in this brochure is accurate, neither Tata Steel Europe Limited nor its subsidiaries accept responsibility or liability for errors or information which is found to be misleading.

Copyright 2012Tata Steel Europe Limited

References to British Standards are in respect of the current versions and extracts are quoted by permission of the British Standards Institute from whom copies of the full standard may be obtained.

www.tatasteeleurope.com

Tata Steel Construction Services & DevelopmentPO Box 1Brigg RoadScunthorpeNorth LincolnshireDN16 1BPConstruction hotline +44 (0) 1724 405060E: [email protected]

Tata Steel Europe is registered in England under number 05957565 with registered office at 30 Millbank, London SW1P 4WYEnglish Language version

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