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Slimdek residential pattern book Book · January 2012 DOI: 10.13140/RG.2.2.15763.89124

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Document title Optional subheading Slimdek® residential pattern book

For multi-storey residential buildings

1

Introduction to Slimdek®



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

Figure 1.1 6 storey apartment block at Portishead Marina. 2 2

Types of balcony

29

Balcony attachments in Slimdek ®

30

Parapets and balustrades

32

References

35 36

Slimdek® is a shallow depth steel floor system that offers particular advantages in multi-storey residential buildings. 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 system Slimdek® 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® plan form and room layouts. Page 17.

Figure 1.2 4 and 6 storey apartment buildings at Penarth Marina, Cardiff. 3

Slimdek® residential pattern book Introduction to Slimdek®

Figure 1.3 Components of Slimdek®

The key features of the system are: 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 fireprotected 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.

Figure 1.4 Slimdek® installation on site.

Figure 1.5 Typical column-free space achieved using Slimdek®.

●

4

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.

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

h

Technical aspects of Slimdek® Slimdek® comprises a composite slab, formed on deep decking, which is supported on the bottom flange of Asymmetric Slimflor® Beams. Slimdek® comprises a composite slab, formed on ComFlor® 225 deep decking (designated CF225 for clarity in some diagrams), which is supported on the bottom flange of Asymmetric Slimflor® Beams (ASB) – see Figure 1.3. The typical span capabilities of ASB beams and deep composite slabs in Slimdek® are set out 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.

Slimdek® supported by ASBs.

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.

A range of 10 ASB beams is manufactured with the properties given in Table 2.2. Fireengineered 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

Table 2.2 Dimensions of ASB beams and minimum slab depths.

Width ofASB Flange Thickness Minimum beams in Slimdek®. Top Beam Bottom Web Designation mm mm mm

Slab Flange Depthspacing Beam Span Beam (m) mm mm(m)

Designation

Mass

Depth

Width of flange Top Bottom

kg/m

mm

mm

Thickness Web

Minimum Flange

Slab Depth

mm

mm

mm

mm

of40 60 mins 40 203 Fire Resistance 313 280 ASB (FE) 100 183 293 20 406.0 280 ASB (FE) 136 195 305 32 297.5

340

300 ASB (FE) 249

249

342

203

313

40

40

340

340 6.0

300 ASB 196

195

342

183

293

20

40

340

325 6.0

300 ASB (FE) 185

185

320

195

305

32

29

325

179 300 ASB 289(FE) 153 16 190 300 ASB 300(FE) 185 27

327.5 249.0

325 7.5*

300 ASB 155

155

326

179

289

16

32

325

153

310

190

300

27

24

320

229.0

320 6.0 300 9.0*

300 ASB (FE) 153

190 300 ASB 300(FE) 249 25

280 ASB (FE) 136

136

288

190

300

25

22

300

178 Fire Resistance 288 of13 30 mins**26

300

280 ASB 124

124

296

178

288

13

26

300

176 280 ASB 28674 184 280 ASB 294105

11

300 6.0

105

288

176

286

11

22

300

19

227.0 167.5

280 ASB 105 280 ASB (FE) 100

100

276

184

294

19

16

295

175 280 ASB 285124

10

147.5

295 7.5*

74

272

175

285

10

14

295

295 6.0

300 ASB 155

9.0

6.0

300 ASB 196

9.0

9.0*

280 ASB 74

Notes: ASB (FE) are fire engineeed sections

* Propped slab during construction ** Additional fire protection required for R60

5

Slimdek® residential pattern book Technical aspects of Slimdek®

Deep decking Deep steel decking (ComFlor® 225) spans between the bottom flange of the ASB beams and supports the wet concrete during construction. The embossments formed in the decking achieve excellent composite action with the concrete, assisted by bar reinforcement. Light mesh reinforcement is provided in the concrete topping for crack control purposes. A cross section of ComFlor® 225 is shown in Figure 2.1. Each decking element is 1.25mm thick and 600mm wide and has special attachment points for service and ceiling hangers. The ComFlor® 225 decking is provided with end diaphragms and cut-outs to allow placement and retention of the concrete around the ASB beams, as illustrated in Figure 2.2. A cross-section through the composite slab in Figure 2.3 shows the positioning of the bar reinforcement. A minimum concrete cover of 80mm over the decking ensures fire resistance and acoustic insulation, although it may be necessary to increase this cover depending on the size of the ASB selected (see Table 2.2). The typical slab depth for residential applications is 300mm to 330mm, which creates a floor depth of approximately 400mm when combined with acoustic insulating layers and a suspended ceiling. The typical span capabilities of deep composite slabs using ComFlor® 225 decking are presented in Table 2.3. Temporary propping is not generally required for spans up to 6m. Spans may be increased to 9m if two lines of temporary props are used during construction. Services can be passed through openings in the ASB beams and between the ribs of the slabs.

600 400 240 30

100 8 30 Horizontal ribs

7

Service hanger (typical detail)

37 15 35 Vertical embossments

195 30

35 33

30 100

40

Figure 2.1 Cross-section through ComFlor®225 deep decking showing service attachments.

50

Deck cut-out

15

Slab topping

Cover to top of beam

225

End diaphragm 50 nominal bearing

size (diameter, mm) for Span of slab (m) Figure 2.2 Detailing of ComFlor® 225 decking at ASBBar beams. Mesh reinforcementBar size (diameter, mm) for Span of slab (m)

Slab depth (mm) 5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

300

16

16

16

20

20

25

32

N.A.

320

16

16

20

20

20

25

32

32

25

16, 20, 25 or 32 32 diameter32

16

340 Propping

Axis

50

20

20 20 Main reinforcement

No propping generally

25

Single line props required

Double line props required

Figure through composite slab.slab. Blue2.3 areaCross-section shows propping requirements for each N.A. = not generally applicable because natural frequency of slab is less than 5Hz.

Table 2.3 Reinforcement requirements (bar diameter) in deep composite slabs for 60 minutes fire resistance.  Bar size (diameter, mm) for Span of slab (m)

Slab depth (mm) 5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

300

16

16

16

20

20

25

32

N.A.

320

16

16

20

20

20

25

32

32

340

16

20

20

20

25

25

32

32

Propping

No propping generally

Single line props required

Blue area shows propping requirements for each slab. N.A. = not generally applicable because natural frequency of slab is less than 5Hz.

6

Double line props required

ASB beam

Openings in the slab

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.

beam span/ 16*500

Opening

Opening may be positioned between the ribs of the decking without affecting the loadbearing 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.

T12 bar x 1500 long

beam span/16 for composite beam design

300

Minimum A142 mesh throughout

1000

Additional top reinforcement Additional bottom reinforcement to adjacent ribs (by engineer)

1000 B 400 Opening A

A

2000

Centre-line of ribs beam span/16 for composite beam design

B ASB beam Curtailed bar

Transverse bar

Temporary Edge trim Temporary fixed as 'box' prop prop

End diaphragm

Transverse bar

Temporary Edge trim Temporary prop prop fixed as 'box'

Section A - A

Section B - B

Figure 2.4 Detailing of openings in the slab in Slimdek®.

Service pipe (max. 150 dia.)

Column (UKC) Mesh reinforcement

CF225 decking A

A Setting out level ASB Tie beam

Welded stiffener 225 min.

Service pipe

Connecting bolts

225 min.

Welded stiffener

Tie beam

Section A - A : Plan view

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

7

Slimdek® residential pattern book Technical aspects of Slimdek®

10 mm dia. additional 10 mm dia. additional L-bars at 300 centres L-bars at 300 centres 200 55 200 55

150

150

30

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).

1000

1000

30

Edge beams

50

50

ASB beams may be designed in two alternative configurations:

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’.

8

End diaphragm End diaphragm

A142 mesh A142 mesh

Figure 2.6 Encased ASB details at edge beam.

20 L-bar (10 ) 20 L-bar (10 ) bolt hole at 300 centres bolt hole at 300 centres 30

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.

Edge Edge trim trim

30

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.

Mineral Mineral wool wool infill infill

End diaphragm End diaphragm ASB cut away by 55 (if necessary) ASB cut away by 55 (if necessary) Figure 2.7 Partially encased ASB details at edge beam.

A142 mesh A142 mesh

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 façade 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.

Rigid insulation in external cavity

Light steel stud wall with 2 layers of gypsum board

Optional additional insulation (to reduce U value)

Separating strip Proprietary battened raft floor

Acoustic sealant

Cavity

Halfen or similar stainless steel brickwork support Cavity barrier to floor/wall junction

15 min. plasterboard resilient strip

External brickwork tied to inner stud wall

Deep composite metal deck floor Trapezoidal profile

12.5 plasterboard Resilient bars timber battens, or metal frame ceiling

Acoustic sealant Deflection head

Figure 2.8 Non-composite RHS edge beam supporting brickwork.

Table 2.4 Section dimensions of RHS Slimflor® edge beams. Designation of RHS 200 x 150 (240 x 15 plate) 250 x 150 (240 x 15 plate) 300 x 200 (290 x 15 plate)

Thickness (mm)

Mass * (kg/m)

Depth (mm)

Minimum Slab

Depth (mm)+

Non-composite

Composite

8.0

70

215

295

295

10.0

79

215

295

295

12.5

91

215

295

295

8.0

76

265

295

335

10.0

87

265

295

335

12.5

100

265

295

335

8.0

94

315

300

N.A.

10.0

100

315

300

N.A.

12.5

126

315

300

N.A.

* including 15 mm plate + Slab depth applies to R60 fire resistance

Table 2.5 Approximate section sizes of RHS edge beams supporting brickwork. Beam span (m)

< 6.0

7.0

8.0

9.0

Non-composite

200 x 150 x 8

200 x 150 12.5 or 250 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

200 x 150 x 12.5

Data for 6m span slab onto RHS

9

Slimdek® residential pattern book Technical aspects of Slimdek®

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.

Decking cut to suit setting-out requirement

Mesh reinforcement

Reinforcement bar 600 ASB bottom flange

Z section

Tee section cut from UKC or UKB

Figure 2.9 Inverted Tee section as a tie member.

ASB end plate Perimeter UKC

ASB internal beam

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, beamto-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

10

ASB edge beam ASB edge beam

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

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.

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.

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

Hollo-bolts

RHS Slimflor® edge beam with 15 thick flange plate

Internal ASB beam

Extended end plate

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

Flowdrill or Hollo-bolts

15 end plate

Flowdrill or Hollo-bolts

A

Flange cut away

A 200 RHS column

a) Side view of ASB beam

200 RHS column

b) Cross-section A - A

Figure 2.12 End plate connections to RHS columns.

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 façade walls, as illustrated in Figure 2.13.

2 x 12.5 plasterboard

Vertical channel (to attach wall ties)

Non-loadbearing light steel stud

RHS column 50 cavity Resilient mineral wool separating RHS and light steel section Insulation board

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

11

Slimdek® residential pattern book Technical aspects of Slimdek®

Discontinuous columns

Slimdek® in an unbraced structure

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).

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.

200 120 50 ASB

15 end plate

40

tf

A 150 SHS column

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 façades, leading to large fenestrations and freedom of space planning.

150 SHS column A

RHS tie

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.

A 75

a) Side view of ASB beam

d 75

RHS tie

150 SHS column

50 10

tf 300

Figure 2.15 Extended end plate connection to an ASB beam.

ASB

150 SHS column

b) Cross-section A - A

Table 2.6 Moment capacities (kNm) of extended end plate connections Column size 203 UKC

Figure 2.14 ASB beams continuous over storey-high RHS columns in medium-rise buildings. 254 UKC

kg/m

ASB280

ASB300

x 46

81

85

x 52

86

90

x 60

91

95

x 71

92

97

x 73

92

97

x 89

92

97

Data: 15 end plate in S355 steel and M20 bolts

12

Fire resistance

Acoustic insulation

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.

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.

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 centreline 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.

Masonry or double-leaf light steel separating walls can be used in conjunction with the Slimdek® floor. Double–leaf 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.

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

Concrete floor slab with ComFlor®225 deep decking

280 ASB 100

Proprietary batten with integral foam strip

Single skin 12.5 thick plasterboard suspended ceiling

Proprietary resilient bars

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

Table 2.7 Detailing requirements for deep composite slabs. 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

A142

A193

A252

Min mesh size in topping

Column size 203 UC

ASB280

ASB300

x 46 kg/m

81

85

x 52 kg/m

86

90

x 60 kg/m 91 95 13 x 71 kg/m 92 97 254 UC

x 73 kg/m

92

97

Slimdek® residential pattern book Technical aspects of Slimdek®

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 type of wall is the interface between the wall head and the soffit of the slab, particularly when the deck ribs do not run parallel to the wall. The attachment of a light steel separating wall to the soffit of a composite slab with ComFlor® 225 decking is illustrated in Figure 2.19. Profiled mineral wool inserts are required to prevent both sound and fire passing through the voids in the deck. Board beneath these inserts also serves both fire and acoustic purposes. When this detail is properly achieved the wall can be expected to pass Part 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.

Table 2.8 Acoustic performance of Slimdek®. Acoustic Test Data (dB) Airborne sound reduction DnT,w + Ctr

Impact sound , L nT,w

Part E

> _ 45

< _ 62

Robust Detail

> _ 47

< _ 57

(Range)

50-64

24-46

(Mean)

56

38

Slimdek® Performance (E-FS-1)

Platform floor Separating strip Acoustic sealant

Proprietary battened raft floor

Separating strip Acoustic sealant

Deep composite steel decking

12.5 plasterboard Acoustic sealant

1 layer of 15 plasterboard or other fire-stopping material laid flat between ASB and light steel channel 12.5 plasterboard ceiling on proprietary metal frame ceiling

Resilient bars or timber battens

Light steel frame separating wall Deflection head

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

Platform floor

Separating strip

Acoustic sealant

Separating strip Acoustic sealant

Proprietary battened raft floor

Pack with mineral wool

Deep composite steel decking

2 layers of 19 mm gypsum board

12.5 mm plasterboard on proprietry metal frame

Additional mineral wool in ceiling void around junction

Acoustic sealant Light steel frame separating wall

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

14

Attachment of cladding to edge beams 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).

Rigid Rigid insulation insulation in in external external cavity cavity

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.

Light Light steel steel stud stud wall wall with with 2 layers 2 layers of of gypsum gypsum board board

Breather Breather paper paper

Separating Separating strip strip Cavity Cavity

Acoustic Acoustic sealant sealant

Cladding Cladding railrail onon angle angle brackets brackets

Proprietary Proprietary battened battened raftraft floor floor

Halfen Halfen or or similar similar stainless stainless steel steel brickwork brickwork support support

External External brickwork brickwork tied tied to to inner inner stud stud wall wall

Proprietary Proprietarybattened battened raftraft floor floor

Cladding Cladding sheet sheet

Cavity Cavity barrier barrier to to floor/wall floor/wall junction junction

Optional Optional additional additional insulation insulation (to(to reduce reduce U value) U value)

Sheating Sheating board board

Resilient Resilient bars, bars, timber timber battens battens or or metal metal frame frame ceiling ceiling

Deep Deep composite composite metal metal deck deck floor floor 1515 min. min. plasterboard plasterboard resilient resilient strip strip

Deflection Deflection head head

Deep Deep composite composite metal metal deck deck floor floor

Resilient Resilient bars, bars, timber timber battens battens or or metal metal frame frame ceiling ceiling

12.5 12.5 plasterboard plasterboard 1515 min. min. plasterboard plasterboard resilient resilient strip strip

12.5 12.5 plasterboard plasterboard Acoustic Acoustic sealant sealant

Acoustic Acoustic sealant sealant

Deflection Deflection head head

Figure 2.20 Detailing of brickwork support by ASB beams.

Rigid Rigid insulation insulation material material Platform Platform floor floor

Slimdek Slimdek floor floor

Polymer Polymer based based render render

Figure 2.22 Rain-screen cladding attachment in Slimdek®.

Breather Breather paper paper (with (with optional optional sheathing sheathing board board behind) behind)

Rigid Rigid insulation insulation Optional Optional additional additional insulation insulation Separating Separating strip strip Acoustic Acoustic sealant sealant

Proprietary Proprietary battened battened raftraft floor floor

Clay Clay tiletile cladding cladding system system

Fire Fire break break

1515 drained drained cavity cavity

Fixing Fixing railrail onon packers packers

Light Light steel steel frame frame non-loadbearing non-loadbearing stud stud wall wall Sheathing Sheathing board board

Figure 2.21 Insulated render cladding attachment to ASB beams.

Drained Drained 1515 cavity cavity

Deep Deep composite composite Resilient bars, bars, metal metal deck deck floor floor Resilient timber timber battens battens 12.5 12.5 plasterboard plasterboard or or metal metal frame frame Acoustic Acoustic sealant sealant ceiling ceiling 1515 min. min. plasterboard plasterboard Deflection Deflection head head Non-loadbearing Non-loadbearing light light steel steel frame frame stud stud wall wall

Figure 2.23 Brick-tile cladding attachment in Slimdek®.

15

Slimdek® residential pattern book Technical aspects of Slimdek®

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).

300 max. Opening in slab

Horizontal service tray

Mesh 150 max.

T12 bar

50 max.

80 min. 60 min.

Opening in ASB

160 max.

320 max.

Figure 2.24 Service openings and electrical trays in Slimdek®.

16

ASB bottom flange

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

Penthouse

Flat

Central Corridor

Flat

Flat

Central Corridor

Flat

Flat

Central Corridor

Flat

Flat

Central Corridor

Flat

Flat

Central Corridor

Flat

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.

Retail

Figure 3.2 Flexible space using Slimdek®. Car Park

Figure 3.1 Deep plan form – cross-section through building.

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 threecar bay (7.5m wide) along the façade, 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.

17

Slimdek® residential pattern book The application of Slimdek®

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

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

No limit on building height The 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.

Acoustic insulation

Utility servicing

Prefabricated modules

Excellent acoustic insulation is achieved by the Slimdek® floor with its resilient layers.

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

Bathrooms 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.

18

A repeatable floor plan area A 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.

Structural grids 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. 7.5m

5.4m

7.5m

4.8m

6.7m

Minimal floor depth

Façade materials and finish

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

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

5.0 m

Figure 3.3 Structural grid as dictated by car park level.

19

Slimdek® residential pattern book The application of Slimdek®

Plan form and room layouts

Deep plan form

Shallow plan form

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

The deep plan form has the following features:

The shallow plan form has the following features:

Columns are located at 7.5m and 5.4m along the façade. ● 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. ●

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.

20

Columns are located at 7.2m and 6.3m along the façade. ● 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. ●

1 BED FLAT

1 BED FLAT Kitchen/ dining/living

Bedroom

Bedroom

Bedroom

Bedroom

Kitchen/ dining/living

Kitchen/ dining/living

Kitchen/ dining/living

Bedroom

2 BED FLAT

Bedroom 2 BED FLAT

Figure 3.5 Deep plan form – Layout of apartments.

2 BED FLAT Bedroom

Kitchen/ dining/living

2 BED FLAT Bedroom

Bedroom

Kitchen/ dining/living

Bedroom

Bedroom

Kitchen/ dining/living

1 BED FLAT

Figure 3.6 Shallow plan form – Layout of apartments.

21

Slimdek® residential pattern book The application of Slimdek®

Figure 3.7 Deep plan form – car parking level.

Retail Unit

Figure 3.8 Deep plan form – layout of retail level.

22

Retail Unit

Bedroom

Bedroom

Kitchen/ Dining/Living

Kitchen/ Dining/Living

Bedroom

2 BED FLAT

Bedroom

2 BED FLAT

Figure 3.9 Deep plan form – penthouse level.

2 BED FLAT

1 BED FLAT

Bedroom

Bedroom

Kitchen/ dining/living

Bedroom

Kitchen/ dining/living

Bedroom

Bedroom

Kitchen/ dining/living

Kitchen/ dining/living 1 BED FLAT

2 BED FLAT

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

23

Slimdek® residential pattern book The application of Slimdek®

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 façade, depending on fenestration positions and sizes. Bracing locations can be difficult to design in highly glazed façades. 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 façade, 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 bracedframe design. Moment continuity is achieved by using extended end plates welded to the ASB or RHS beams.

24

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.

280 ASB 74

20

280 ASB 100 or 254 UKC 89 + plate

4800

46 KC 355 3U S

280 ASB 74 or 203 UKC 60 + plate

5000

165 x 152T

@20 kg/m S275

52 KC 355 3U S

280 ASB 100

46 KC 355 3U S

46 KC 355 3U S

46 KC 355 3U S

165 x 152T @20 kg/m S275

2200

20

280 ASB 74

20

20

20

165 x 152T @20 kg/m S275

P

71 KC 355 3U S

71 KC 355 3U S

86 KC 355 3U S

280 ASB 100 or 254 UKC 89 + plate

CF225 20

20

20

280 ASB 100

280 ASB 74

280 ASB 74 P

6700

280 ASB 74 with anchored re-bars or 203 UKC 52 + plate

CF51

280 ASB 74 or 203 UKC 46 + plate

254 x 146 UKB31 S275

280 ASB 74

280 ASB 74

280 ASB 100

52 KC 355 3U S

152x89 I

20

254 x 146 UKB31 S275

71

165 x 152T @20 kg/m S275

46

CF51

KC 3U 20 355 S

Void

300 deep NWC slab on CF225 decking

Lift

152x89 I CF51

280 ASB 100 or 254 UKC 89 + plate

KC 3U 20 355 S

280 ASB 100

71 KC 355 3U S

86 KC 355 3U S

20

20

165 x 152T @20 kg/m S275

280 ASB 74 or 204 UKC 52 + plate Stair

46 KC 355 3U S

46 KC 355 3U S

46 KC 355 3U S

20

280 ASB 100 or 254 UKC 89 + plate

7500

280 ASB 74 or 203 UKC 46 + plate

5400

20

7500

20

7500

P = Decking propped at construction stage

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

4800

280 ASB 74

280 ASB 74 or 254 UKC89 + plate 2200

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

280 ASB 100 or 254 UKC107 + plate

6700 4800

254 x 146 UKB31 S275 152x89 I

CF51

280 ASB 100

280 ASB 100

280 ASB 74

280 ASB 100

280 ASB 74

280 ASB 74

P

46 KC 355 3U S 20

280 ASB 74

71

280 ASB 74

165 x 152 T @20 kg/m S275

52 KC 355 3U S 20

165 x 152 T @20 kg/m S275

280 ASB 74 or 203 UKC 46 + plate

52 KC 355 3U S 20

CF225

46 KC 355 3U S 20

165 x 152 T @20 kg/m S275

P

46 KC 355 3U S 20

46 KC 355 3U S 20

46 KC 355 3U S 20

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

280 ASB 74

KC 3U 20 355 S

P

71 KC 355 3U S 20

86 KC 355 3U S 20

165 x 152 T @20 kg/m S275

254 x 146 UKB31 S275

71

P

Void

P

CF51

CF51

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

Lift

KC 3U 20 355 S

300 deep NWC slab on CF225 decking

280 ASB 74 or 203 UKC 46 + plate Stair

71 KC 355 3U S 20

86 KC 355 3U S 20

165 x 152 T @20 kg/m S275

7500 46 KC 355 3U S 20

P

46 KC 355 3U S 20

46 KC 355 3U S 20

P

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

5400

280 ASB 74 or 254 UKC89 + plate

7500

7500

= Decking propped at construction stage

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

25

Slimdek® residential pattern book The application of Slimdek®

7500

5400

7500 20 0x

250 x 150 x 6.3 RHS +plate S355

4800 6700

2200

165 x 152T @20 kg/m S275

0x

20

300 x 200 x 8.0 RHS + plate S355

S RH 5 .0 S35

S RH 55 8.0 S3

10

165 x 152T @20 kg/m S275

0x

20

0x

15

S RH 55 8.0 S3

S RH 55 8.0 S3

= Decking propped at construction stage

S RH 5 .0 S35

10

280 ASB 100

5000

CF51

280 ASB 74

CF51

280 ASB 74 280 ASB 74

0x

20

CF225

0x

20

280 ASB 74

280 ASB 74

S

S RH 5 .0 S35

0x

25

0x

15

0x

15

250 x 150 x 8.0 RHS + plate S355

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

26

P

10

S RH 5 .0 S35

10 0x

25

0x

25

300 x 200 x 8.0 RHS + plate S355

280 ASB 74

250 x 150 x 6.3 RHS +plate S355

254 x 146 UKB31 S275 150 x 90 I

CF51

RH

165 x 152T @20 kg/m S275

0.0

0x

S RH 5 .5 S35

12

0x

20

20

0x

280 ASB 100

S RH 5 .0 S35

10

x1

0x

30

0x

30

20

165 x 152T @20 kg/m S275

0x

20

280 ASB 100 0 20 0x 30 355 S

P

0x

280 ASB 74

S

S RH 5 .0 S35

10

152 x 89 I

20

RH

0x

20

S RH 5 .5 S35

12 0x

20

P

8.0

150 x 90 I

Void

300 deep NWC slab on CF225 decking

Lift

0x

0x

0x

20

280 ASB 100

300 x 200 x 8.0 RHS + plate S355

15 0x 25 355 S

Stair

30

0x

20

165 x 152T @20 kg/m S275

250 x 150 x 8.0 RHS + plate S355

S RH 5 .0 S35

S RH 55 8.0 S3

S RH 55 8.0 S3

10

0x

0x

15

15

20

0x

0x

0x

25

25

300 x 200 x 8.0 RHS + plate S355

250 x 150 x 6.3 RHS +plate S355

7500

2000

254 x 146 UKB31 S275

203x133 UKB25 S275 4800

3900 1900 7200

280 ASB 100

4800

280 ASB 74 or 254 UKC73 + plate

280 ASB 74

280 ASB 74

1000

203x133 UKB25 S275

254 x 146 UKB31 S275

280 ASB 100

280 ASB 136 280 ASB 74

46 KC 355 3U S 20

46 KC 355 3U S 20

46 KC 355 3U S 20

46 KC 355 3U S 20

280 ASB 74 with anchored re-bars or 203 UKC 52 + plate 1200

165 x 152T @20 kg/m S275

52 KC 355 3U S 20

86 KC 355 3U S 20

P

6300

46 KC 355 3U S 20

46

P

280 ASB 74

280 ASB 74 with anchored re-bars or 203 UKC 52 + plate

P

30

280 ASB 74

86 KC 355 3U S 20

86 KC 355 3U S 20

165 x 152T @20 kg/m S275

KC 3U 20 355 S

P

280 ASB 74 with anchored re-bars or 203 UKC 71 + plate

280 ASB 74

Riser 300 deep slab on CF225 decking

KC 2U 15 355 S

254 x 146 UKB31 S275 Lift

Stair

46 KC 355 3U S 20

86 KC 355 3U S 20

280 ASB 74 with anchored re-bars or 203 UKC 71 + plate

2100

280 ASB 100 or 254 UKC + plate with anchored re-bars 2300

30 KC 355 2U S 15

2700

280 ASB 74 with anchored re-bars or 203 UKC 52 + plate

1200

7200

6300

= Decking propped at construction stage

Figure 3.14 Structural layout for shallow plan building – ASB edge beams and UKC columns. 15 0x 15

2700

2100

0x 0x 20 10 0x

S

20 0x 10

S RH 5 .0 S35

250 x 150 x 10.0 RHS + plate

4800

20

RH

280 ASB 74

.5

S RH 55 8.0 S3

4800

12

0x

1200

280 ASB 74

0x

15

S RH 55 8.0 S3

S RH 55 8.0 S3

250 x 150 x 10.0 RHS + plate

300 x 200 x 6.3 RHS + plate

S RH 5 .0 S35

20 0x 30 355 S

0x

0x

0x

15

15

280 ASB 74

3900

0x

280 ASB 74

P

6300

P

1900 1000

20

280 ASB 74

25

0x

0x

25

25

250 x 150 x 10.0 RHS + plate

7200

280 ASB 100

S

S RH 5 .5 S35

S RH 5 .5 S35

12

12

0x

0x

280 ASB 74

2300

RH

P

20

20

300 x 200 x 12.5 RHS + plate

S275

2000

254 x 146 UKB31 S275

203 x 133 UKB25 S275

S RH 5 .0 S35

203 x 133 UKB25 S275

10

.0

280 ASB 100

0x

x8

280 ASB 74

0x

0x

30

20

280 ASB 136

S

20

RH

0x

.3

20

x6

0 15 0x 25 355 S

P

250 x 150 x 10.0 RHS + plate

280 ASB 74

Riser

300 deep NWC slab on CF225 decking

0 15 0x 15 355 S

S RH 55 8.0 S3

S RH 5 .0 S35

254 x 146 UKB31

S RH 55 6.3 S3

10

0x

0x

15

15

0x

0x

25

25

250 x 150 x 10.0 RHS + plate

254 x 146 UKB31 S275 Lift

Stair

1200

7200

6300

= Decking propped at construction stage

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

27

Slimdek® residential pattern book The application of Slimdek®

280 ASB 136 320 x 180 x 12thk plate

203 UKC 86 Column 120

80

120 4 No. M 20 bolts

200 300 x 200 x 12 thk ASB end plate

4 No. M20 g8.8 bolts 80

120

300 x 300 x 15 thk plate 280 ASB 74 edge beam 120

Figure 3.16

ASB connection to edge column (showing eccentric detail).

280 ASB 136

320 x 200 x 12thk plate

203 UKC 86 Column

140

80

120 4 No. M 20 bolts

300 x 200 x 12 thk ASB end plate

4 No. M20 g8.8 bolts 80

120

280 ASB 74 edge beam 31.5

Figure 3.17

28

120

ASB connection to edge column (no eccentricity).

320 x 200 x 12thk plate

280 ASB 136

250 x 150 x 10 thk RHS column

120

80

120 4 No. M 20 Hollo-bolts

M20 Hollo-bolts in 33 O / holes

50 40

280 ASB 136 250 x 150 x 6.3 thk RHS Slimflor® beam and 15 mm thk plate

170 x 430 x 12 thk plate

10

70

100 (min.)

Figure 3.18

RHS edge beam connection to RHS column.

200

50 50

Facade line

50

300

200

Flowdrill bolt holes (20 mm dia.)

150

360 200

300 200

(a) Column on centre-line of edge beam

ASB

Facade line

100

80

20 mm dia. bolt

300

50

(c) Column along facade line

Facade line

Facade line

ASB

12

Tie beam cut from 457 x 191 UKB

12 50 100

Seating plate welded between end plates

SHS column

50 100

Seating plate welded between end plates

(c) Plan on column in (a)

Figure 3.19

Tie beam cut from 457 x 191 UKB

(d) Plan on column in (b)

ASB bolted connections to RHS column.

29

Slimdek® residential pattern book The application of Slimdek®

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:

Mineral wool insulation 12 mm fire resisting board 19 mm plank

30 mm thick dense mineral wool board

100

200 x 200 SHS column

38

Beams 32-38kg/m2 ● Columns 7-10kg/m2 ● Bracing, secondary beams 1-3kg/m2

300

●

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.

30

100

Figure 3.20 Detail of separating wall at RHS column.

Table 3.1 Summary of steel weights kg/m2 for various structural options. Building Options Shallow Plan Form

Deep Plan Form

Beams

ASB

Edge Beams

Columns

ASB

UKC

Bracing

Structural weights (kg/m2) Bracing

Total kg/m2

Beams

Columns

Braced

33

7

1

41

35

8

–

43

ASB

RHS

RHS

Wind moment frame

ASB

ASB

UKC

Braced slab span longitudunal

33

8

1

42

ASB

ASB

UKC

Braced slab span transverse

39

8

1

48

ASB

ASB

UKC

Wind moment frame

39

8

-

47

ASB

RHS

RHS

Wind moment frame

38

9

-

47

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

In the first case, no vertical load is transferred to the structure or façade 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.

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).

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Slimdek® residential pattern book Steel balconies and parapets

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 façade in Slimdek® is illustrated in Figure 4.1.

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.

Facade line 50

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.

Cut in edge trim

200 Slab level

Bolted connection

a) Bracket connection to ASB

b) Longitudinal view of bracket

Figure 4.2 Bracket attachment to ASB edge beam.

Facade line

a) Pre-welded cantilevers

Figure 4.3 Cantilever or fin attachments to RHS edge beams.

32

Facade line

b) Bracket or fin attachment

Figure 4.4 Detail of attachment of tied balcony in Slimdek®.

Figure 4.5 Cantilever balcony attachment in Slimdek®.

33

Slimdek® residential pattern book Steel balconies and parapets

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.

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.

Colourcoat steel coping Galvanised steel balustrade

Angle at top of posts

Single ply membrane bonded to metal flashing

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

Walkway tile

Steel posts @ 1200 centres

Insulation Screed laid to falls

Insulation

Aluminium flashing

Angle attached to top of beam by pre-fixed bolts

Steel channel section exposed visually

Facing brick/ masonry external leaf

Colourcoat cladding to external face of parapet

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

Steel fin plate welded to beam to provide support to channel section (max. 2 m centres) Insulation (passing both sides of fin plate) 2 layers plasterboard on light steel framing

Figure 4.6 Detail of balustrade attachment in Slimdek®. 

34

Figure 4.7 Detail of parapet wall attachment in Slimdek®. 

References

Support for the construction industry from Tata Steel

Sources of information

Guidance on the design and use of structural sections and plates

Building 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 Prof. Mark Lawson Prof. Ray Ogden Dr. Stephen Hicks Dr. Jim Rackham

- HTA Architects - The Steel Construction Institute - Oxford Brookes University - The Steel Construction Institute - The Steel Construction Institute

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 1 Brigg Road Scunthorpe North Lincolnshire DN16 1BP Construction hotline +44 (0) 1724 405060 Email: [email protected] Website: www.tatasteelconstruction.com

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www.tatasteeleurope.com 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 2012 Tata 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.

Tata Steel Construction Services & Development PO Box 1 Brigg Road Scunthorpe North Lincolnshire DN16 1BP Construction hotline +44 (0) 1724 405060 E: [email protected] www.tatasteelconstruction.com Tata Steel Europe is registered in England under number 05957565 with registered office at 30 Millbank, London SW1P 4WY English Language version 36 View publication stats