economic long span concrete floors, bca, uk, 1995. 50p

7/27/2019 Economic Long Span Concrete Floors, Bca, Uk, 1995. 50p.

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A survey of 40 office buildings

with long-span concrete floors

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

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


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FOREWORDThis publication was commissioned by the Reinforced

Concrete Council.The Group was set up in 1988 to promote better

knowledge 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 for

the survey:Anthony Hunt/YRM PartnershipBeersBison Limited

Bunyan Meyer & PartnersComposite Structures LimitedDGI International plcFerguson &McIlveenFrank Hodgson & Associates

James-Carrington and PartnersJan Bobrowski and PartnersOve Arup & PartnersPowell, Tolner & AssociatesSkidmore, Owings & MerrillWaterman Partnership

Thanks are also due to Brian Dyer of Tower Associatesfor drafting the floor plans.

97.311

First 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) 762676

Fax (01344) 761214

All advice or information from the British Cement Association is intended for those who will evaluate the significance and limitations of

its contents and take responsibility for its use and application. No liability (including that for negligence] for any loss resulting from such

advice or information is accepted. Readers should note that all BCA publications are subject to revision from time to time and should therefore

ensure that they are in possession of the latest version.


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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 1to 7 8-14

Prestressed -Buildings 8 to 12 15-19

Ribbed slabs

Reinforced - 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 slabs

and beams

Buildings 29 to 33

Precast slabs

Buildings 34 to 36


Buildings 37 to 40

2

3

4

6

7

20-22

23-29

36-40

41-43

44-47


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INTRODUCTION

Traditional 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 waffle

construction. 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 slab

designs 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 SURVEY

The 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 slabs

Ribbed slabs

Waffle slabs

One-way spanning solid slabs and beams

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 byshear 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.

Shear walls

Figure I: Lateral stability provided by shear walls.

Figure 2: Lateral stability provided frame action.


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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 floor

tYPe.

Building 5

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

Lightweight aggregate concrete with a compressivestrength of 30N/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 7

255 mm reinforced solid flat slab, span 9.2 x 6-0m.The deflection of the 255 mm flat slab was checked byfinite element analysis, taking full account of edge

stiffening 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 of

the perimeter beams and columns plus the internal frameeliminated the need for shear walls.

Building 10

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

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 13

450mm 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 14

425 mm reinforced ribbed slab, span 9.0m.

The irregular floor plan of the building and the clientsrequirement for minimum column sizes resulted in it being

Overall to suit column sizec

650J rr

APlan

Section

F i gu re 3 : Detail of steel shearhead.


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Building 26

500mm prestressed/reinforcement waffle slab,span 12.0X12-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 31

335mm one-way spanning prestressed solid slab,span 12.6 m.

The frame was designed as a stacked portal, with 160 mmprecast per imeter walls 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 36

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

Building 37

560 mm double-T floor units with in situ topping,span 14.5m. Stability 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 and

minimum disruption.The wide range of floor construction in both

reinforced 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 DESIGN

In 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, loc al mark et cond iti ons,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 todays market, the choice of floor design isoften determined by one or more of the followingconsiderations:

under ten weeks. are given opposite.

2400 4800 2400 II I I

(a) Elevation (b) Section


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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 locating

horizontal services. However, the economical span range

of 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 slabs

Providing 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 slabs

Waffle 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 permitting

longer spans. The one-way spanning solid slab betweenthe beams facilitates the use of table forms for fastconstruction (Figure 8).

(b)

2 :::r ~~ ~~ l - : : - ~J - - : - ; : - : : - r -F i g u r e Ribbed slab for flexibility to accommodate openings.


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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 can

accommodate a wide range of floor openings.

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

CONCLUSION

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

economically competitive.This is a direct consequence of improved design and

analysis techniques, higher strength materials, better

construction methods and finally, more construction-leddesign.

Figure IO: C it fl ( ) t ibb d fl


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SURVEY DATA

Section 1: Solid flat slabs

Reinforced-

Buildings 1to 7


Section 2: Ribbed slabs

Reinforced -Buildings 13to 15


Section 3: Waffle slabs

Reinforced -Buildings 23 to 25


Section 4: One-way spanning solid slabs and beams

Buildings 29 to 33

Section 5: Precast slabs

Buildings 34 to 36

Section 6: Composite precast slabs

Buildings 37 to 40

7


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SECTION 1

SOLID FLAT SLABSSolid flat slab -reinforced

m m m ratio m3 kgI I I I I I

2 7. 2x7. 2 300 24 0. 30 30. 0 6-O r~~~~ GradeC40rameacti on Code BS 8110

J r 3600 J i 3600 1 7200 i 3600 1 3600

7J

7 _I

n

n

300 sl ab

I-

n

8


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Solid flat slab -reinforced

No. SlabMaterials per m2

of floor area Designof l o a d Notes

floors Span Depth Span/depth Conc;ete Rebar kN/,, Stabilitym 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


12/50


82Emi

1

I

3000A

i

5 i J 7500 3000

n

400 slab

n

1 / _Li

40 0slab

Typical floor plan

10


13/50


No.of -

Spanfloors m

SlabMaterials per m*

of floor area Designload NotesStability

Depth 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

I17 ccc 45 1


14/50


No. SlabMaterials per m*

of floor area Design Notesof load Stability

floors Spanm

Depth Span/depth Conc;ete Rebar kNirn2 (See page 3)m m rat io kg

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

Typical floor plan


15/50



o fof floor area Design

loadfloors Span

mDepth Span/depth Co;;ete Rebar kN/r- Stability Notes

mm ratio kg13 8 0x7.2 275 29 0.28 40.7 5-o Shear Grade C35

walls Code BS 81 10

5800 3 irr 7200 5800

275 slab

Typical floor plan


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-

I I I I I II I I I7 9.2x6. 0 255 36

I I0.26 I24. 0 5. 2I I I I I

Stability Notes

(See page 3)

6200h 4 5 (( I 6000

255 sl ab

Typical floor plan

14


17/50

Solid flat slab -prestressed


of floor area Designof load Notes

floors Span Depth Span/depth Con$ete Rebar Strand kN/r-$ Stabilitym mm ratio kg kg

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

Gl P

,.~- I tx x : x x x x

I m

Atrium

.j----

X

xx

xX

xX

X

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

0Eico0

Column head detail I


18/50


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

n c :iI

24 0 50i 25 0

Column head detail c 475


19/50


No.of

floors

SlabMaterials per m

of floor area Design

l o a d Stability NotesSpanm

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

(See page 3)

Grade C40

Stee l Code BS 81109 9 4x 9- o 30 0 31 3 0 300 14-l 78 50 bracing t o CS TR 17 &25*

columns Steel col um nswithshearheads

*See Concrete Society TechnIcal Reports No 17 and No 25

45000

P m B

aI m

Typical floor plan Cross-bracing

17


20/50


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 0See Concrete Society TechnIcal Reports No 17 and No 25

Stability Notes

FrameGrade C40

actionCode BS8110CSTR 17&25*

Typical floor plan


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Slab

Solid flat slab - prestressed

Stability Notes

7200 3600 7200 2400 7200 3600 7200r c J

Typical floor plan

Typical column head detail


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SECTION 2

RIBBED SLABSRibbed slab -reinforced

No. Rib BeamMaterials per m*

of floor area Desof

,__floors Span Depth Span/depth Span B x D Span/depth Concrc

m 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 90001 I

Typical floor plan

Typidal rib section Typical beam section

20


23/50

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 1800

x42521.1 0.27 38.5 5.0

Shear Grade C35walls Code BS 8110

1500_~~ __~125

9000 6750 4 @ 7500 6750 9000i 1

Typical floor plan

5 u,9000

L -t 425 Il l i 1800250

Typical rib section Typical beam section

: 42 5


24/50

Ribbed slab -reinforced

No. Rib BeamMaterials per m2

of floor area Dri,n Stabilityfloors Span Depth Span/depthSpan B x D Span/depth Conc;ete Rc??rkN/mz

m mm ratio m mm ratio

5 9.0 3 0 0 30.01800

7-2 x 4 0 018.0 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


25/50

Ribbed slab -prestressed

No. Rib BeamMaterials per m*

Designof

of floor areal o a d Notes

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

3 9.0 3 2 5 1200 27-71800

6.0 x32518-5 Pt 0 194 12 6 3.65 6.0 Frame Grade C35

action Code BS 8110

Prestressed

Typical floor plan

Typical rib section ki

100

325

23


26/50


No.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


27/50


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. 8 400 725 24.5 1 9 4 1200 Shear Grade C40x 800

24.2 Pt 0.354 16.9 9.76 6.0walls Code CP 110

Prestressed

I I I I13000 9350 9350 10000

Typical floor plan

725c 725 725P75Typical rib section

25


28/50


No. Rib BeamMaterials per m2

Designo f

of floor areaload Notes

floors Span Depth Spacing Span/depth Span B x D Span/depth Type Concrete Rebar Strand kN/r-$ Stabilitym 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 5.0 Shear Grade C40wallsL L Code CP 110

Prestressed

Typical floor plan

Typical section


29/50


30/50


31/50


No. Rib BeamMaterials per m


of load Stability Notesfloors 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

X10006.3 R.C.* 0.225 9.8 5.66 6.0 Shear Grade C40

walls Code CP 110

i7 @ 6300_ t

Typical floor plan

I 850 8 5 0 850 i100Typical section

Reinforced

29


32/50

SECTION 3

WAFFLE SLABSWaffle slab -reinforced

No. ColumnMaterials per m*


of spacing Depth Span/depth l o a d Stability Notesfloors m mm ratio Con-v$ete Rebar Strand kN/m2

kg 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


33/50

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 kg3 7.5x10 5 525 20.0 0.450 67.0 - 6-O Frame Grade C35

action Code BS 8110

, 7500 typical ,

Typical floor plan

Typical section

31


34/50

Waffle slab re i n f o rced


Depth Span/depth _ of floor area Designof spacingratio

load Stability Notesfloors m mm Conc;ete Rebar Strand kN/m2

kg kg

310.18

x10.18550 18-5 0.396 37.0 - 9.0


kTypical floor plan

3 @10180

Typical section125 14

32


35/50

Waffle slab -prestr essed

Materials per m2No. Column of floor area Design

of spacing Depth Span/depthratio

load StabilityNotes

floors m mm Compete Rebar Strand kN/m2 (See page 4)kg kg1 12.0x12.0 500 24.0 0.349 15.9 2.52 6.0


4 @ 12000 6000

q CIOOOOOOOrlnnnnnnrin

Typical floor plan

125Typical section

33


36/50

Waffle slab -prestressed


Depth Span/depthof floor area Design

of spacingratio

load Stability Notesfloors m mm Cor?$ete Rebar Strand kN/m*

kg kg

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

12700

Typical floor plan

Typical section


37/50


38/50

SECTION 4

ONE-WAY SPANNING

SOLID SLABS&BEAMS

One-way spanning

solid slab and beam

No. Slab BeamMaterials per m2

of floor area Designof . load

floors Span Depth Span/depth Type Span B x D Span/depth Type Concrete Rebar Strand kN/+ Stability Notesm m m ratio m m m ratio m3 kg kg

4 7. 43 20 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


39/50

One-way spanning

solid slab and beam


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*1500

6.0 x 4 5 013.3 R.C.+ 0.298 13.9 3.93 6.8

Shear Grade C30walls Code CP 110t

Prestressed +ReInforced

250 slab

Typical floor plan

Typical beam section

37


40/50

One-way spanningsolid slab and beam



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 kg7 12.6 3 3 5 37.6 Pt* Precast perimeter wall support 0 335 11 .8 8.25 6.8 Shear C40 lightweight

walls Code BS 8110

Prestressed

335 slab

Typical floor plan

38


41/50

One-way spanning

solid slab and beam

No. Slab BeamMaterials pe rm2


of load Stability Notesfloors Span Depth Span/dept Tyee Spnn BxD Span/depth Type Conc;et e %??r StFgndkN/m2

m m m ratio m m m ratio

10 6 75 220 30 7600x

R.C.* 10 0 6oo 16.7 R.C.* 0.26 42-O - 5 0 Shear C40 lightweightwalls Code CP 110

*ReInforced

Typical floor plan

Main beam section

E0

39


42/50

One-way spanning

solid slab and beam


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 34.31500

R.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


43/50

SECTION 5Precast slab

PRECAST SLABS

SlabMaterials per m2of floor area

No. Beam Design

ofPrecast In situ

load Stabilityfloors 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 x600

10.0 0.145 4.8 40 0,011 0.4 7.0Shearwalls

Notes

C50, BS 8110

7% in situHollow coreplanksNo topping

6 @ 6000

.

Typical floor plan

PrecastyqFy=300

Centre beam section

41


44/50

Precast slab

Materials per mof floor areaNo. Slab Beam Precast In situ

Design

of loadfloors Span Section Span/depth Span BxD Span/depth Concrete Rebar Strand Conc$ete Rebar kN/m2

m mm ratio m mm ratio m3 kg kg kg

4 7.2 200 36.0600

7.2 x60012.0 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 54007200 7200

1 1 1 1 1

Typical floor plan

Typical section

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Precast slab

SlabMaterials per m2of floor area

No. Beam - Designof

Precast In situload 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 6110action Hollow core

planksNo topplng

Typical floor plan

Typical section

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SECTION 6

COMPOSITE

PRECAST SLABS

Composite precast slab

No. Rib BeamMaterials per m2of floor area

of . Precast In situ Designload Stability Notesfloors Span Depth Span/depth Span

ratioDepth Span/depth Concrete Rebar Strand Concrete Rebar kN/m2

(See page 4)

m mm m mm ratio m3 kg kg m3 kg

500x FrameGrade 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$$arDouble Tees, wrthwalls

In situ toppingPrecast H frame

4800 typical

14500. I

Typical floor plan

I47600

1200i , I n s i t u t opp n

- /

Typical section Precast double-T beams

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Composite precast slab

No. Rib BeamMaterials per m2of 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

750x

6 / 12.0 1 610 / 19.7 j 9.0 ,in;FU, 14.8 0.134 (13,751 - 0.111 110 721 5.7

Stability Notes

In situ C35Frame Precast C45action Code BS 8110

55% In situ

I II II II I

r iririr i r i r i r irir ir iririr irwirlir irII 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

I 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

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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

UDC

624.073.012.4.003.1

economic long span concrete floors, bca, uk, 1995. 50p

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