Economic Long Span Concrete Floor Slabs

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A survey of 40 office buildingswith long-span concrete floors

P.W. Matthew BE, MSc, MIE(Aust)

and D.F.H. Bennett BSc, MSc, CEng, MICE

FOREWORDThis publication was commissioned by the ReinforcedConcrete Council.

The Group was set up in 1988 to promote betterknowledge and understanding of reinforced concrete designand building technology.

Its members are Co-Steel Sheerness plc and Allied Steel& Wire, representing the major suppliers of reinforcing steelin the UK; and the British Cement Association, representingthe major manufacturers of Portland cement in the UK.

The authors of this publication are Peter Matthew, partnerwith consulting engineers Powell, Tolner & Associates andDavid Bennett, Senior Engineer in the Marketing Divisionof the British Cement Association.

ACKNOWLEDGEMENTSThe authors wish to thank the following organizations fortheir considerable help in providing the building data forthe survey:

Anthony Hunt/YRM PartnershipBeersBison LimitedBunyan Meyer & PartnersComposite Structures LimitedDGI International plcFerguson & McIlveenFrank Hodgson & AssociatesJames-Carrington and PartnersJan Bobrowski and PartnersOve Arup & PartnersPowell, Tolner & AssociatesSkidmore, Owings & MerrillWaterman PartnershipThanks are also due to Brian Dyer of Tower Associatesfor drafting the floor plans.

97.311First published 1990Reprinted 1994, 1995

ISBN 0 72101386 4

Price Group F

@ British Cement Association 1990

Published by the British Cement Association on behalf ofthe industry sponsors of the Reinforced Concrete Council.

British Cement AssociationTelford Avenue, CrowthorneBerks RG45 6YSTel (01344) 762676Fax (01344) 761214

All advice or information from the British Cement Association is intended for those who will evaluate the significance and limitations ofits contents and take responsibility for its use and application. No liability (including that for negligence] for any loss resulting from suchadvice or information is accepted. Readers should note that all BCA publications are subject to revision from time to time and should thereforeensure that they are in possession of the latest version.

CONTENTS

INTRODUCTION 2

NOTES ON SURVEY

DESIGN FEATURES OF SPECIAL INTEREST

CHOICE OF FLOOR SLAB DESIGN

Solid flat slabs

Ribbed slabs

Waffle slabs

One-way spanning solid slabs and beams

Precast slabs

Composite precast slabs

CONCLUSION

SURVEY DATA

Section 1:

Section 2:

Section 3:

Section 4:

Section 5:

Section 6:

Solid flat slabs

Reinforced - Buildings 1 to 7 8-14

Prestressed - Buildings 8 to 12 15-19

Ribbed slabsReinforced - Buildings 13 to 15

Prestressed - Buildings 16 to 22

Waffle slabs

Reinforced -Buildings 23 to 25 30-32

Prestressed - Buildings 26 to 28 33-35

One-way spanning solid slabsand beamsBuildings 29 to 33

Precast slabs

Buildings 34 to 36

Composite precast slabs

Buildings 37 to 40

2

3

4

6

7

20-22

23-29

36-40

41-43

44-47

INTRODUCTIONTraditional concrete designs for office building have beenassociated with either beam and slab or flat slab floors,typically with 6 to 7.5 m spans. Occasionally, longer-spanfloors have been designed using ribbed or waffleconstruction. In recent times, changes in the requirementsof end-users and in developers’ specifications have led tomore open-plan offices and larger floors. This hasincreased spans from 6 to 9 m, even to 15 m and more.

To verify the competitiveness of concrete long-spanfloors, a survey has been conducted of concrete-framedoffice buildings, the majority constructed in recent years.Forty buildings of in situ, precast and compositeconstruction with long spans have been surveyed. In eachcategory, examples were found of floors designed inreinforced and prestressed concrete to carry similar officefloor loadings.

For in situ structures, solid flat slabs and ribbed slabdesigns were common, with spans varying from 6 to 15 m.

A number of precast structures with long spans, someover 20 m, are reported, with composite in situ slabs actingwith precast ribs or other precast members.

NOTES ON SURVEYThe survey data are presented in the second part of thispublication, beginning on page 7. The information hasbeen arrangedfollows:

Section 1 -Section 2 -Section 3 -Section 4 -Section 5 -Section 6 -

according to structural floor types as

Solid flat slabsRibbed slabsWaffle slabsOne-way spanning solid slabs and beamsPrecast slabsComposite precast slabs

The structural information and quantities of materialfor each building surveyed are presented in tabular formand are accompanied by a typical floor plan and floorsection.

For each building studied, quantities of concrete,reinforcement and prestressing steel are expressed inunits/m2 of floor area. All quantities related to verticalcomponents, i.e. columns, walls, etc., have been excluded,thus the effect of storey height and number of storeys iseliminated.

The span/depth ratios given in the tables are based onthe maximum spans.

Notes on the design Code of Practice, concrete gradeand method of achieving frame stability have been addedto provide useful information on the design of thestructure.

The column headed ‘Design loads’ gives the floorloadings used in the structural design, i.e. imposed load,finishes, partition and service loads: it does not include theself-weight of the floor.

The method of achieving frame stability for eachbuilding is indicated in the column headed ‘Stability’ by‘shear walls’ or ‘frame action’. The term ‘shear walls’

(Figure 1) indicates a braced structure where the horizontalforces are transmitted to shear walls by the floors acting asdiaphragms. In the case of an unbraced structure [Figure 2),stability is provided from within the frame by theinteraction of columns and floors and referred to as ‘frameaction’.

All tables should be read in conjunction with thecorresponding floor plans and section details.

a Shear walls

Figure I: Lateral stability provided by shear walls.

Figure 2: Lateral stability provided by frame action.

2

DESIGN FEATURES

OF SPECIAL

INTERESTNotes on a few of the buildings surveyed are given below tohighlight certain construction and design features thatprovide particular economic advantages for a given floortY Pe.

Building 5310 mm reinforced solid flat slab, span 9.5 x 7-3 m.

Lightweight aggregate concrete with a compressivestrength of 30 N/mm2 was used in order to reduce theself-weight of the floor and the cost of the foundations.

As the span/depth ratio exceeded the guiding limits inthe Code (CPllO), compliance with maximum deflectionin the serviceability limit state was proved by calculation.The floor slab was designed as a beam supporting aone-way spanning flat slab, all within the 310 mm depth ofconstruction. The beam, 2.5 m wide, spans longitudinallyfrom the interior column to the lift core. The one-wayspanning slab is simply supported at the perimeter andcontinuous over the beam.

Building 7255 mm reinforced solid flat slab, span 9.2 x 6-0 m.

The deflection of the 255 mm flat slab was checked byfinite element analysis, taking full account of edgestiffening from the perimeter columns and beams inaddition to the internal columns and frame. A lateralstability check was carried out on a three-dimensionalcomputer model of the structure. The inherent stiffness ofthe perimeter beams and columns plus the internal frameeliminated the need for shear walls.

Building 10300 mm post-tensioned solid flat slab, span 9.4 x 9.0 m.

Steel cross-bracing, in combination with the floor slabacting as a diaphragm, provided the lateral stability. Droppanels were eliminated by forming shearheads within theslab depth (Figure 3). All external columns were connectedto steel beams, composite with the slab, to cater forpunching shear.

Building 13450 mm reinforced ribbed slab, span 9.0 m.

The wide-rib profile, spaced at 1.5 m centres, providesadequate flexibility to accommodate small and largeservice openings in the floor. The rib profile made itpossible to use table forms with integral grp rib moulds toensure a fast building programme (Figure 4).

Building 14425 mm reinforced ribbed slab, span 9.0 m.

The irregular floor plan of the building and the client’srequirement for minimum column sizes resulted in it beinginappropriate to provide stability by frame action. Shearwalls, with no returns and a minimum of cross walls, werespecified to facilitate rapid construction of walls.

Overall to suit column sizec

650J--rr

-A-Plan

Section

Figure 3: Detail of steel shearhead.

Figure 4: Grp rib moulds fixed to table forms.

3

Building 26500 mm prestressed/reinforcement waffle slab,span 12.0 X 12-O m.

The solid beam strips were post-tensioned, with the wafflesection reinforced. This allowed the waffle section to bereinforced independently of the beams, thus speeding upconstruction, whilst maintaining an economical floordepth.

Building 31335 mm one-way spanning prestressed solid slab,span 12.6 m.

The frame was designed as a stacked portal, with 160 mmprecast per imeter wal ls support ing a 335 mmpost-tensioned solid slab. An important benefit inpost-tensioning the slab was that the end momentstransferred to the precast walls, due to dead load, werenegligible. This in turn led to manageable transfermoments in the wall under ultimate load conditions.

The structural solution proved both economic and fastto build, with a maximum net to gross floor area.

Building 36200 mm precast floor slab, span 7.7 m.

The precast columns were designed as vertical cantilevers

CHOICE OF FLOOR

fixed at the base to provide frame stability. The precast l

floor beams were simply supported and designed as pinjoint connections to the columns.

Building 370

560 mm double-T floor units with in situ topping,span 14.5 m. 0Stability was achieved by a combination of shear walls atthe ends of the building and frame action developed fromthe precast perimeter H frames. The H sections are formedby adjacent perimeter columns and the perimeter edgebeam (Figure 5a). The precast column joints are positionedat mid-storey height, i.e. the point of contra-flexure, so afull moment connection to the double-T floor beam waspossible (Figure 5b). The precast frame was erected in just

The need for long spans to provide floor spaceuninterrupted by cores and columns.

A maximum floor-to-floor height which allowsadequate space for services and ducts, balanced againstplanning pressure to limit overall building height.

An adaptable floor structure which can accommodatefuture tenant alterations with maximum speed andminimum disruption.

The wide range of floor construction in bothreinforced and prestressed concrete, highlighted in thissurvey, demonstrates that concrete floors can be designedeconomically to meet these requirements.

The types of floors and the reasons for choosing them

SLAB DESIGNIn assessing the structural cost of a multi-storey building, itis evident that the bulk of the cost is often for the floor slabconstruction. Therefore, the overall economy of a structuremay depend on the efficiency and economy of the floorslab’ system. While quantities of materials reflect theefficiency of the design and structural layout, the actualcost of the structure may also depend on such factors asspeed of construction, local market conditions,competitive tendering, availability of labour andequipment and cost of construction finance. Consequentlya structural design that has proved to be competitive in oneregion may not always be competitive in another.

For a building to meet the needs of major financialoccupiers in today’s market, the choice of floor design isoften determined by one or more of the followingconsiderations:

under ten weeks. are given opposite.

2400 4800 2400I/ I/-I I II I4,

(a) Elevation (b) Section

Figure 5: Detail of precast H frame.

4

Solid flat slabs (with or withoutdrops)The principal feature of the dropless floor is its flush soffitwhich requires only simple formwork and is easy toconstruct (Figure 6a). The overall depth of this floor is aminimum and it allows great flexibility for locatinghorizontal services. However, the economical span rangeof a reinforced floor is limited by shear in the vicinity of thecolumn supports and the need to control long-termdeflection.

The provision of drop panels at the column supports(Figure 6b) avoids the need for shear reinforcement andincreases the stiffness of the slab and the economical spanrange. Alternatively, a structural steel shearhead can beincorporated to maintain a flush soffit to allow for easyconstruction and efficient use of large forming systems(Figure 6c).

Ribbed slabsProviding ribs to the soffit of the floor slab can reduce thequantity of concrete and reinforcement, and thus theweight of the floor. The deeper, stiffer floor permits longer

spans to be used. Formwork complexity can be minimizedby the use of standard modular, re-usable formwork. Whenflying form panels are used, the ribs should be positionedaway from the column lines. Ribbed slab floors are veryadaptable for accommodating a range of service openings(Figure 7).

Waffle slabsWaffle slab floors are commonly used when buildings aresubjected to heavy imposed loading. They are veryefficient in the use of materials and provide veryeconomical long spans, but the additional complexity offormwork can often slow the construction. Where speed ofconstruction is critical, a ribbed slab or a shallow beamsolution is often preferred.

One-way spanning solid slabsand beamsA wide, shallow beam profile is often preferred in order toreduce the overall depth of the floor, whilst permittinglonger spans. The one-way spanning solid slab betweenthe beams facilitates the use of table forms for fastconstruction (Figure 8).

(b)

Figure 6: Solid flat slab: (a) without drop panels;(b) with drop panels; (c) with shearhead.

1-2-1:::1r-1 I-- “~~-~~-l'-' '-::-~J--,:-;:-: :-,r-

Figure 7: Ribbed slab for flexibility to accommodate openings.

Figure 8: Band beam and slab construction using tableforms.

5

Precast slabs Composite precast slabsComposite precast slabs combine precast floor elementswith in situ concrete in an economical way, eliminatingtraditional formwork for floor construction, and providinglong-span floors. Thin precast concrete floor plates can becombined with an in situ topping to form compositeone-way spanning floors up to 6 m long, or, in combinationwith precast beams, to form a composite ribbed slab(Figure lOa). For extremely long spans, double-T precastbeams and a composite in situ topping is preferred(Figure 10b).

Precast slabs offer the advantage of off-site manufacture,with a reduction in site labour and site formwork. Whenthe slabs are prestressed there are additional benefits oflonger spans and higher load capacity. A popular type ofprecast floor is the hollow core slab (Figure 9). Therelatively lightweight units form a flush soffit whenplaced. A shear key between units ensures load sharingand the construction is commonly capable of developingdiaphragm action without the need for a structuraltopping. The precast units are easy to remove and canaccommodate a wide range of floor openings.

Figure 9: Precast hollow core planks:flexibility for alterations.

CONCLUSIONThe buildings surveyed in this publication demonstratethat reinforced and prestressed concrete floors with spansranging from 6 to 20 m, are technically feasible andeconomically competitive.

This is a direct consequence of improved design andanalysis techniques, higher strength materials, betterconstruction methods and finally, more construction-leddesign.

Figure IO: Composite floors: (a) precast ribbed floor;(b) double-T beam floor.

6

SURVEY DATA

Section 1: Solid flat slabs

Reinforced - Buildings 1 to 7


Section 2: Ribbed slabsReinforced -Buildings 13 to 15

Prestressed -Buildings 16 to 22

Section 3: Waffle slabsReinforced -Buildings 23 to 25


Section 4: One-way spanning solid slabs and beams

Buildings 29 to 33

Section 5: Precast slabsBuildings 34 to 36

Section 6: Composite precast slabsBuildings 37 to 40

7

SECTION 1SOLID FLAT SLABS

Solid flat slab -reinforced

m m m ratio 1 m3 1 kg 1I I I I I I

2 7.2x7.2 300 24 0.30 30.0 6-O ’ r ~~~~ ’ GradeC40Frameaction Code BS 8110

Jr 3600 Ji 3600 1" 7200 'i 3600 1" 3600 I

7-J

7-_I

-

n

n

300 slab

I-

n

8


No. Slab Materials per m2of floor area Design

of l o a d Notesfloors Span Depth Span/depth Conc;ete Rebar kN/,,$

Stability

m m m ratio kg

10 7.5x6.1 3 0 0 25 0.30 45.0 6-O Shear Grade C35walls Code BS 8110

300 slab

I - I I I I I I

I

I

I

I

8

I

I

I

I

Typical floor plan

A

9


82E

mi1

I

3000A

i

5 i(J 7500 3000

n

400 slab

n

1 / _L

i

400 slab

Typical floor plan

10


No.of -

Spanfloors m

Slab Materials per m*of floor area Design

load NotesStabilityDepth Span/depth Conc;ete Rebar kN/,-,-,*

mm ratio kg

7 6 5 x 4 5 250 26 0.25 29.0 5 0 Shear Grade C35walls Code BS 8110

Typical floor plan

I

17 ccc 45 1̀


No. Slab Materials per m*of floor area Design Notes

of load Stabilityfloors Span

mDepth Span/depth Conc;ete Rebar kNirn2 (See page 3)

m m ratio kg

4 9-5x 7.3 310 30.6 0.31 41.5 5.0 Shear C30 lightweightwalls Code CP 110

Typical floor plan


No. Slab Materials per m2

o fof floor area Design

loadfloors Span

mDepth Span/depth Co;;ete Rebar kN/r-$

Stability Notes

mm ratio kg

13 8 0x7.2 275 29 0.28 40.7 5-o Shear Grade C35walls Code BS 81 10

5800 3 irr 7200 5800

275 slab

Typical floor plan


-

I I I I I II I I I

7 9.2x6.0 255 36I I

0.26I I24.0 5.2

I I I I I I

StabilityNotes

(See page 3)

6200h 4

5 ((I 6000

255 slab

Typical floor plan

14

Solid flat slab - prestressed

No. Slab Materials per m2of floor area Design

of load Notesfloors Span Depth Span/depth Con$ete Rebar Strand kN/r-$

Stability

m mm ratio kg kg

2 8.0x8-0 275 29.1 0,275 10-2 4 8 10..0 Shear Grade C40walls Code BS 8110

Gl P

(”,.~- . .

Ii..tx x :* x x x x

I” m

Atrium

.‘j----

X

x

x

x

X

x

X

X

m m PI m m m m P1 JFirst-floor plan

0

Eico

0

Column head detail I I

15


a 7.2x 7.2 240 30.0 0.240 2.4 4.7 6.5

Stability

Shearwalls

Notes

* See Concrete Society TechnIcal Reports No 17 and No 25

3 ((I 7200 4800

00cuP-

Typical floor plan

950

n

nc :i,

I /’ 240

$ 50i 250

Column head detail c ”475


No.of

floors

SlabMaterials per m’

of floor area Designl o a d Stability Notes

Spanm

Depth Span/depth Conx$ete Rebar Strand kN/mzm m ratlo kg kg

(See page 3)

Grade C40Steel Code BS 8110

9 9 4x9 -o 300 31 3 0 300 14-l 78 50 bracing to CS TR 17 & 25*

columns Steel co lumns with shearheads

* See Concrete Society TechnIcal Reports No 17 and No 25

45000

P m B

I aI m

Typical floor plan Cross-bracing

17


No SlabMaterials per m*

of floor area Designof load

floors Span Depth Span/depth Concrete Rebar Strand kN/mzm m m ratio m3 kg kg

7 11 5 x 7 5 325 35 4 O-325 11 1 6 5 5 0

See Concrete Society TechnIcal Reports No 17 and No 25

Stability Notes

Frame Grade C40

action Code BS8110CSTR 17&25*

Typical floor plan

8

Slab


Stability Notes

7200 3600 7 2 0 0 2 4 0 0 7 2 0 0 3600 7200r c * *- II + * J

Typical floor plan

Typical column head detail

SECTION 2

RIBBED SLABSRibbed slab -reinforced

No. Rib Beam Materials per m*of floor area Des

of,__

floors Span Depth Span/depth Span B x D Span/depth Concrcm mm ratio m mm ratio m3

ignwad Stability

Notes

?te Rebar kN/m* (See page 3)

kg

10 9.0 450 20.0 8.0 1200 13.3 0.23 39.5 7.5 Frame Grade C35x 450 action Code BS 8110

7 ((1 9000

1 I

Typical floor plan

Typidal rib section Typical beam section

20

Ribbed slab - reinforced

Rib BeamMaterials per m2

No. of floor area f$$” Stability Notesof (See page 3)

floors Span Depth Span/depth Span B x D Span/depth ConcJete Rebar kN/m*m m m ratio m m m ratio kg

11 9.0 4 2 5 21 .l 9.0 1800x425

21.1 0.27 38.5 5.0Shear Grade C35walls Code BS 8110

1500_~~ __~125

9000 6750 4 @ 7500 6750 9000i 1

Typical floor plan

5 (u, 9000

L -t

‘T 1425 7I-I Il-l i

1800250

Typical rib section Typical beam section

:425

Ribbed slab - reinforced

No. Rib BeamMaterials per m2

of floor area Dri,n Stability

floors Span Depth Span/depthSpan B x D Span/depth Conc;ete Rc??r kN/mzm mm ratio m mm ratio

5 9.0 3 0 0 30.0 18007-2 x 4 0 0 18.0 0.32 29.0 5.0 Shear

walls

Notes

Grade C35Code BS 8110

6 ((I‘ 7200 9000 7200I i i

1800

Typical rib section Typical beam section

22

Ribbed slab - prestressed

No. Rib Beam Materials per m*Design

ofof floor area

l o a d Notesfloors Span Depth Spacing Span/depth Span B x D Span/depth Type Concrete Rebar Strand kN/&

Stability

m m m m m ratio m m m ratio kg kg

3 9.0 3 2 5 1200 27-71800

6.0 x 3 2 5 18-5 Pt’ 0 194 12 6 3.65 6.0 Frame Grade C35action Code BS 8110

‘Prestressed

Typical floor plan

Typical rib section ki!

100

325

23


I INo.of

floors-I22

*Prestressed

Rib BeamMaterials per m*

of floor area Designload

Span Depth Spacing Span/depth Span B x D Span/depth Type Con;;ete Rebar Strand kN/t-$m m m m m ratio m m m ratio kg kg

9.0 2 5 0 750 36.0 22007.5 x 2 5 0 30.0 Pt’ 0.186 7 . 0 3 5.79 5.0

Stability

Shearwalls

Notes

Grade C40Code CP 110

10 @ 7500i

Typical floor plan

750

125

A - ,

-r - .250 250

2200

I-

s \

175

Typical rib section Column head detail

24


NO. Rib BeamMaterials per m2

of floor area Designof load Stability Notes

floors Span Depth Spacing Span/depth Span B x D Span/depth Type Con;;ete Rebar Strand kN/m*m m m m m ratio m m m ratio kg kg

8 9 . 8 4 0 0 725 24.5 1 9 4 1200 Shear Grade C40x 800 24.2 Pt” 0.354 16.9 9.76 6.0 walls Code CP 110

‘Prestressed

I. I. I. I. I13000 9350 9350 10000

Typical floor plan

725c 725 725P

75

Typical rib section

25


No. Rib Beam Materials per m2Design

o fof floor area

load Notesfloors Span Depth Spacing Span/depth Span B x D Span/depth Type Concrete Rebar Strand kN/r-$

Stability

m m m m m ratio m m m ratio m3 kg kg

5 10.85 450 850 24.1 12.5 1500x 4 5 0

28.0 Pt* 0.280 8.3 6-63 5.0Shear Grade C40wallsL L Code CP 110

‘Prestressed

Typical floor plan

Typical section


No. Rib BeamMaterials per m*

of floor area Designo f load Stability Notes

floor s Span Depth Spacing Span/depth Span B x D Span/depth Type Conc;ete Rebar Strand kN/m*m m m m m ratio m m m ratio kg kg

5 1 3 5 4 7 5 1500 28 4 9 . 0 1500x475

18.9 Pt* 0,285 15.0 4.93 6 0Shear walls Grade C40and frameaction Code BS 8110

l Prestressed

Iririr

I I I I I I I I I I I I I II II II II II II II II II II II II II II I I II I I II I I II II II II I

I II I I II II II I I II II II I I II I I II II I

I I I II II II I I II II II I I II I I II I I II I

L~LJLJL~LJLJLJLJLJLJLJLJLJL.~L.-

w n n Iriririr~r~rlrlr~r~r~r~r~r~r~r~,

/’/ Iu I I I II II II II II II I I I I II II II II I I I I II II II I

I I /I II I I II II I I II II II II II II II II II II II I/ I/

I I II II II II II II II II II II II II 11 II II II I’ II IL~L~L~L~L~L~L~L~L~L~~~~~~~~~~~~~~~~~,~~r-i r iririr~r-lr~r~r~r1rlrlrlr~r~r~r~rlrlI II II I

L J

nr -1I ILA

II II III II III II I

-JLJLJ

-1rir-iII II I

_ _J L A L A

I II II II II II II II II II II II II II II II II II I

LJLJLJL-ILJLJ

nr IririririrlI II II II II II ILJLJLJLJLALJ

I II II II II II II II II II II II II II II II II II II II II II II II II II II I

LJL~ILJLJLJLJLJLJLJ

n n Iriririririr - ll~-lrlrlI II II II II II II II II ILJLJLJLJLJLJLJLJL.~J

Typical floor plan

1500

125

I108I”

‘r 1500 1

Typical beam section Typical rib section

1, J:425

27


No. Rib Beam Materials per m2of floor area Design

of load Notesfloors Span Depth Spacing Span/depth Span B x D Span/depth Type Concrete Rebar Strand kN/m2

Stability

m m m m m ratio m m m ratio kg kg

5 14.4 650 2400 22.2 12007.2 x 6 5 0 11 .0 R.C.* 0,268 1 4 . 7 4 . 3 3 7.0 Shear Grade C40

walls Code BS 8110

“Reinforced

0B- 8 @ 7200

f 1

:jl n n E n I7 11 r7 fl II11 II II II I i II II II II II II

I II II III II II II

I II II ll II II

I II II iI II II

I II II iI II II

I II : I II II I ;I II II ll II II

H H H H H J u u u I4 M

““““““/- u .-IL Al- u -IL ii- il -IL II_ L L -IL I I - I I AIL u lb

Typical floor plan

2400

Typical section 500

28


No. Rib BeamMaterials per m’

of floor area Designof load Stability Notes

floors Span Depth Spacing Span/depth Span B x D Span/depth Type Concrete Rebar Strand kN/m’m mm mm ratio m m m ratio kg kg

4 16.3 525 850 31 .0 6.3275

X1000 6.3 R.C.* 0.225 9.8 5.66 6.0 Shear Grade C40walls Code CP 110

i7 @ 6300_

t

Typical floor plan

I850 8 5 0 850%

i100

Typical section

‘Reinforced

29

SECTION 3

WAFFLE SLABS Waffle slab - reinforced

No. ColumnMaterials per m*

of floor area Designof spacing Depth Span/depth l o a d Stability Notes

floors m mm ratio Con-v$ete Rebar Strand kN/m2kg kg

5 6.6 X 7.43 350 21.2 0.245 24.0 - 6-O Frame Grade C35action Code BS 8110

5835 7425 3 @ 4950

I ---*

Typical floor plan

Ribs at 900 crs

!125

4;7I

1600

Section at column head

3 0

Waffle slab - reinforced

No. ColumnMaterials per m2

of floor area Designof spacing Depth Span/depth load Stability Notes

floors m mm ratio Con;;ete Rebar Strand kN/m2kg kg

3 7.5x10 5 525 20.0 0.450 67.0 - 6-O Frame Grade C35action Code BS 8110

, 7500 typical ,

Typical floor plan

Typical section

31

Waffle slab - reinforced


Depth Span/depth _ of floor area Designof spacing

ratioload Stability Notes

floors m mm Conc;ete Rebar Strand kN/m2kg kg

3 10.18x10.18 550 18-5 0.396 37.0 - 9.0 Shear Grade C35

walls Code BS 8110

kTypical floor plan

3 @ 10180

Typical section125 14

32

Waffle slab - prestressed

Materials per m2No. Column of floor area Designof spacing Depth Span/depth

ratioload Stability

Notes

floors m mm Compete Rebar Strand kN/m2(See page 4)

kg kg

1 12.0x12.0 500 24.0 0.349 15.9 2.52 6.0Shear Grade C40walls Code BS 6110

4 @ ’ 12000 6000

q CIOOOOOOOrlnnnnnnrin

Typical floor plan

125Typical section

33



Depth Span/depth of floor area Designof spacing

ratioload Stability Notes

floors m mm Cor?$ete Rebar Strand kN/m*kg kg

2 12.7x12.7 500 25.4 0.341 12.2 5.60 6.0 Shear Grade C35walls Code BS 8110

12700*

Typical floor plan

Typical section


Stability Notes

~c~~~Grade C40Code BS 8110CS TR No. 17*

*See Concrete Society Technical Report No 17

5 @ 15000

1 1

,;:j; ji ‘: :’ ‘: ‘_-:::~:: ::p::-::-:,

;.:I. :’ ij :

‘-7..:.::. .I! j: :: :::.:1 :.

: li .::

a :,: .;_;; 1_~1;.1;.1;:1:.:1~1!_.

~.. :.~:.~::~’

. -. ..-.:.::..:..:.::.:: ::..LL: ‘:~::..l‘i‘: .::. ~.i[:lI::~::z..

: :I.. i., .iilii::.!:~:.~I:.::.::.::.:!.:L.:: !

:-:“:.::‘I:.‘,~ . . . . .

.~..~_. ,..,: ., !L :

Atrium

: :: ::r:: :: :: ‘: :, :__,: ::~:: ::=:: ::-::-::.:,Lo:! !! :, ,, ,! ,I ,I ., ,,

.-..-. . . ..i.:

Typical floor plan

Typical section 225

35

SECTION 4

ONE-WAY SPANNINGSOLID SLABS & BEAMS

One-way spanningsolid slab and beam

No. Slab Beam Materials per m2of floor area Design

of . loadfloors Span Depth Span/depth Type Span B x D Span/depth Type Concrete Rebar Strand kN/+’

Stability Notes

m m m ratio m m m ratio m3 kg kg

4 7 . 4 3 2 0 0 37.2 Pt* 9.0 1 5 0 0x 500 18.0 Pt* 0.261 1 4 . 0 4.11 4.0

Shear Grade C35walls Code BS 8110

‘Prestressed

Typical floor plan

Typical beam section

3 6


No. Slab BeamMaterials per m2

of floor area Designo f load Stability Notes

floors Span Depth Span/depth Type Span BxD Span/depth Type Conc;ete Rebar Strand kN/m*m m m ratio m m m ratlo kg kg

6 10.30 250 41.2 Pt* 15006.0 x 4 5 0 13.3 R.C.+ 0.298 13.9 3.93 6.8 Shear Grade C30

walls Code CP 110t‘Prestressed + ReInforced

250 slab

Typical floor plan

Typical beam section

37


No. Slab Beam Materials per m2of floor area Design

of load StabilityNotes

floors Span Depth Span/depth Type Span BxD Span/depth Type Concrete Rebar Strand kN/m2(See page 4)

m m m ratio m mm ratio m3 kg kg

7 12.6 3 3 5 37.6 Pt* Precast perimeter wall support 0 335 11.8 8.25 6.8 Shear C40 lightweightwalls Code BS 8110

‘Prestressed

335 slab

Typical floor plan

38


No. Slab Beam Materials pe r m2of floor area Design

of load Stability Notesfloors Span Depth Span/dept Tyee Spnn B xD Span/depth Type Conc;et e %??r StFgn d kN/m2

m m m ratio m m m ratio

10 6 75 220 30 7600xR.C.* 10 0 6oo 16.7 R.C.* 0.26 42-O - 5 0 Shear C40 lightweight

walls Code CP 110

*ReInforced

Typical floor plan

Main beam section

E0

39


No. Slab Beam Materials per m2

ofof floor area Design

load Notesfloors Span Depth Span/depth Type Span B x D Span/depth Type Con-$ete Rebar Strand kN/&

Stability

m mm ratio m mm ratio kg kg

5 6.0 175 34.3 1500R.C.* 9.0 x425 21.2 R.C.* 0.25 52.0 - 5.0 Shear Grade C40walls Code BS 8110

‘Reinforced

Typical floor plan

:425

Typical section

40

SECTION 5Precast slab

PRECAST SLABS

SlabMaterials per m2 of floor area

No. Beam Designof

Precast In situload Stability

floors Span Section Span/depth Span B x D Span/depth Conc;ete Rebar Strand Conc;ete Rebar kN/r-$m m m ratio m m m ratio kg kg kg

12 7.0 203 34.5 3006.0 x 6 0 0 10.0 0.145 4.8 40 0,011 0.4 7.0 Shear

walls

Notes

C50, BS 81107% in situHollow coreplanksNo topping

6 @ 6000

. 1

Typical floor plan

Precast “yqFy= :z300

Centre beam section

41

Precast slab

Materials per m’ of floor areaNo. Slab Beam

Precast In situ Designof load

floors Span Section Span/depth Span B xD Span/depth Concrete Rebar Strand Conc$ete Rebar kN/m2m mm ratio m mm ratio m3 kg kg kg

4 7.2 200 36.0 6007.2 x600

12.0 o-193 7.9 3.0 - - 7.0

I I I I I I I I I

Stability

Shear

Notes

Grade C50Code BS 8110Hollow coreplanksNo topping

7200 7200 5400 7200 7200 5400 7200 7200

1 1 1 1 1 1

Typical floor plan

Typical section

42

Precast slab

SlabMaterials per m2 of floor area

No. Beam - Designof

Precast In s i tuload Stability

Notes

floors Span Sectlon Span/depth Span B x D Span/depth Concrete Rebar Strand Con$ete Rebar kN/m* (See page 4)

m m m ratio m m m ratio m3 kg kg kg

Grade C50

3 7 7 200 38.5 7 . 4 3 ,$;o 1 2 . 4 0.157 10.5 2.55 - - 6.5 Frame Code BS 6110

action Hollow coreplanksNo topplng

Typical floor plan

Typical section

43

SECTION 6

COMPOSITEPRECAST SLABS

Composite precast slab

No. Rib Beam Materials per m2 of floor area

of . Precast In situ Designload Stability

Notes

floors Span Depth Span/depth Spanratio

Depth Span/depth Concrete Rebar Strand Concrete Rebar kN/m2 (See page 4)

m mm m mm ratio m3 kg kg m3 kg

500x Frame Grade C60Code CP 110

9 14.5 560 25.9 4.8 1000 4.8 0.150 5.75 6.3 0.080 2.2 5.0(Perimeter)

any$$ar Double Tees, wrth

wallsIn situ toppingPrecast H frame

4800 typical

14500. I

Typical floor plan

I

47600

1200i , In situ t o p ping

-/

Typical section Precast double-T beams

44


Rib BeamMaterials per m” o

No. Precast In situ

f10 2 Span

load Stability NotesDepth Span/depth Span

m mm ratio mDepth Span/depth Con;;ete Rebar Strand Conc;ete Rebar kN/m’

mm ratio kg kg kg

Grade C60600x Code CP 110

4 16.7 785 22.0 4.9 900 5.4 0,133 5 - 4 8 7 . 7 9 0,075 1.54 5.0 Frame Double Tees, with(Perimeter) action in situ topping

Precast H frame

2438 9 @ 4877 2438‘i * 8 J

? ~f?~+kPl-rr~P~~~n’n-n n~n’n~n~n-n’n~~n~~n~nLr~~n111141ild 1’1111Vfb111 1) 11 II II I I II II II II II II II II II II II I I I I II II II II I I II II I I I I I I I I II II II II II II II I I I I III

‘II II III I II III

‘I I II IIII II IllII II lib

‘II II IIz ‘II II Ii

II II III

co ‘II II II II I I III

Il l II IIII II III

‘I I II IIII II IIP

‘II II IIII II III

‘II II III I II III

‘II II II II II II II II II II II II II II II I I I I II I I II II I I II II II I I II I I I I II I I II II II II II II I I II III

i - + tit - c b !, L km c hL c Lu,u--u-uLu~ u -u~u-u,u-u-uLu, u u 4 Ad 4 u Am11 4 4 44 -IF

Typical floor plan

1200

/’In situ topping

75 (average) 1

j-=-f ;710

Precast double-T beams

Typical section


No. Rib Beam Materials per m2 of floor area

ofPrecast In situ Design

floors Span Depth Span/depth Span. load

m mm ratioDepth Span/depth Concrete Rebar Strand Concrete Rebar kN/m*

m mm ratio m3 kg kg m3 kg

750x6 / 12.0 1 610 / 19.7 j 9.0 1 ,in”;FU, 1 14.8 1 0.134 (13,751 - 1 0.111 110 721 5.7

Stability Notes

In situ C35Frame Precast C45action Code BS 8110

55% In situ

I II II II II II I

r ir’ir’ir i r ’ i r ’ i r ir’ir ir ir’ir’ir irwirlir irII II II II II II II II II II II II II II II II II

I II II II II II II II II II II II II II II II II II

I II II II II II Ii II II II II II II II II II II II II II II II II II II II II II II II II II II II’

Typical floor plan

55 precast soffit plankPrecast rib

Typical rib section Typical in situ beam section

46


No. Beam Materials per m2 of floor area

o fPrecast In situ Design

load Notesfloors Span Depth Span/depth Concrete Aebar Strand Concrete Rebar kN/m’

Stability

m m m ratio m3 kg kg m3 kg

Grade C62

3 21.2 750Precast 28.3 0,123 4.9 7.6 0.060 2-28 5 .0 Shear Codes CP 115,

walls CP 11640% In situ

72000

c 1

, _~n-=-rt-~n-“-~-un~~~~nn~~~“~h~~n~n~n~~~~~nnnunu~~~=-n~~n~~~~,, ,, II Ii II I I I II II I I I I I II 11 II II II II il II II II II I I’ II II II ‘I II II II II II II ‘I II II II II I, II II II II II ,, ,,

‘1, I I 11 I I tII II

‘II IIII llr

11, IIII ‘I ~:I~_:~ ” I’ II II ‘I Nt ~~ ‘I ” I’ I’ II :! Id

8 II II I I II II lli:cv AlI II

!I, III I II I I II

i;II II!

‘I, I! R#~~11 II- 11~;I I

v ;~I I IIL

JIl IIII ,I Ii II IlL

II IILII II II IILII II II II II II II 1: 1: I’ II I’ I! I’ II II II II II II II II II II II II II II II II II !I II II II II II II II II II II II II II II II II

vYv-Y~~Y~4_yu~~~L-L_-v~y~.~_yu_u_y-y-y _ y--y-y4~-y~y-&icy~~ 4 y u y~y-y~y--y~yy-yy

Typical floor plan

Beams @ 1500 crs.

Precast soffit planks

Precast beam

Typical section

Economic long-span concrete floors

P.W. Matthew and D.F.H. Bennett

BRITISH CEMENT ASSOCIATION PUBLICATION 9 7.3 11

CI/SfB

I (13) I q4 I (Y6)

U D C

624.073.012.4.003.1

Documents

Economic Long Span Concrete Floor Slabs