Economic Long Span Concrete Floor Slabs

View Publication •

You have asked to view a publication

•

When you have finished viewing, click on

•

Now choose one of the following options:

view publication chosen

in the toolbar to return to this screen.

return to publications list

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

FOREWORD This publication was commissioned by the Reinforced Concrete Council. The Group was set up in 1988 to promote better knowledge and understanding of reinforced concrete design and building technology. Its members are Co-Steel Sheerness plc and Allied Steel & Wire, representing the major suppliers of reinforcing steel in the UK; and the British Cement Association, representing the major manufacturers of Portland cement in the UK. The authors of this publication are Peter Matthew, partner with consulting engineers Powell, Tolner & Associates and David Bennett, Senior Engineer in the Marketing Division of the British Cement Association.

ACKNOWLEDGEMENTS The authors wish to thank the following organizations for their considerable help in providing the building data for the survey: Anthony Hunt/YRM Partnership Beers Bison Limited Bunyan Meyer & Partners Composite Structures Limited DGI International plc Ferguson & McIlveen Frank Hodgson & Associates James-Carrington and Partners Jan Bobrowski and Partners Ove Arup & Partners Powell, Tolner & Associates Skidmore, Owings & Merrill Waterman Partnership Thanks are also due to Brian Dyer of Tower Associates for drafting the floor plans.

97.311

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

ISBN 0 72101386 4

British Cement Association Telford Avenue, Crowthorne Berks RG45 6YS

First published 1990 Reprinted 1994, 1995

Price Group F

Tel (01344) 762676 Fax (01344) 761214

@ British Cement Association 1990 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.

CONTENTS INTRODUCTION

2

NOTES ON SURVEY

2

DESIGN FEATURES OF SPECIAL INTEREST

3

CHOICE OF FLOOR SLAB DESIGN

4

Solid flat slabs Ribbed slabs Waffle slabs One-way spanning solid slabs and beams Precast slabs Composite precast slabs

CONCLUSION

6

SURVEY DATA

7

Section 1:

Solid flat slabs Reinforced - Buildings 1 to 7 Prestressed - Buildings 8 to 12

Section 2:

Ribbed slabs Reinforced - Buildings 13 to 15 Prestressed - Buildings 16 to 22

Section 3:

Section 4:

Section 5:

15-19

20-22 23-29

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

36-40

Precast slabs Buildings 34 to 36

Section 6:

8-14

41-43

Composite precast slabs Buildings 37 to 40

44-47

INTRODUCTION Traditional concrete designs for office building have been associated with either beam and slab or flat slab floors, typically with 6 to 7.5 m spans. Occasionally, longer-span floors have been designed using ribbed or waffle construction. In recent times, changes in the requirements of end-users and in developers’ specifications have led to more open-plan offices and larger floors. This has increased spans from 6 to 9 m, even to 15 m and more. To verify the competitiveness of concrete long-span floors, a survey has been conducted of concrete-framed office buildings, the majority constructed in recent years. Forty buildings of in situ, precast and composite construction with long spans have been surveyed. In each category, examples were found of floors designed in reinforced and prestressed concrete to carry similar office floor 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, some over 20 m, are reported, with composite in situ slabs acting with precast ribs or other precast members.

(Figure 1) indicates a braced structure where the horizontal forces are transmitted to shear walls by the floors acting as diaphragms. In the case of an unbraced structure [Figure 2), stability is provided from within the frame by the interaction of columns and floors and referred to as ‘frame action’. All tables should be read in conjunction with the corresponding floor plans and section details.

a

Shear walls

NOTES ON SURVEY The survey data are presented in the second part of this publication, beginning on page 7. The information has been arranged according to structural floor types as follows: Section 1 - Solid flat slabs Section 2 - Ribbed slabs Section 3 - Waffle slabs Section 4 - One-way spanning solid slabs and beams Section 5 - Precast slabs Section 6 - Composite precast slabs The structural information and quantities of material for each building surveyed are presented in tabular form and are accompanied by a typical floor plan and floor section. For each building studied, quantities of concrete, reinforcement and prestressing steel are expressed in units/m2 of floor area. All quantities related to vertical components, i.e. columns, walls, etc., have been excluded, thus the effect of storey height and number of storeys is eliminated. The span/depth ratios given in the tables are based on the maximum spans. Notes on the design Code of Practice, concrete grade and method of achieving frame stability have been added to provide useful information on the design of the structure. The column headed ‘Design loads’ gives the floor loadings used in the structural design, i.e. imposed load, finishes, partition and service loads: it does not include the self-weight of the floor. The method of achieving frame stability for each building is indicated in the column headed ‘Stability’ by ‘shear walls’ or ‘frame action’. The term ‘shear walls’ 2

Figure

I:

Lateral stability provided by shear walls.

Figure 2: Lateral stability provided by frame action.

DESIGN FEATURES

Overall to suit column size c

OF SPECIAL INTEREST

J--r 650

r

Notes on a few of the buildings surveyed are given below to highlight certain construction and design features that provide particular economic advantages for a given floor tY Pe. Building 5 310 mm reinforced solid flat slab, span 9.5 x 7-3 m. Lightweight aggregate concrete with a compressive strength of 30 N/mm2 was used in order to reduce the self-weight of the floor and the cost of the foundations. As the span/depth ratio exceeded the guiding limits in the Code (CPllO), compliance with maximum deflection in the serviceability limit state was proved by calculation. The floor slab was designed as a beam supporting a one-way spanning flat slab, all within the 310 mm depth of construction. The beam, 2.5 m wide, spans longitudinally from the interior column to the lift core. The one-way spanning slab is simply supported at the perimeter and continuous over the beam.

-A-

Plan

Building 7

255 mm reinforced solid flat slab, span 9.2 x 6-0 m. The deflection of the 255 mm flat slab was checked by finite element analysis, taking full account of edge stiffening from the perimeter columns and beams in addition to the internal columns and frame. A lateral stability check was carried out on a three-dimensional computer model of the structure. The inherent stiffness of the perimeter beams and columns plus the internal frame eliminated the need for shear walls.

Section

Figure 3: Detail of steel shearhead.

Building 10 300 mm post-tensioned solid flat slab, span 9.4 x 9.0 m. Steel cross-bracing, in combination with the floor slab acting as a diaphragm, provided the lateral stability. Drop panels were eliminated by forming shearheads within the slab depth (Figure 3). All external columns were connected to steel beams, composite with the slab, to cater for punching shear. Building 13 450 mm reinforced ribbed slab, span 9.0 m. The wide-rib profile, spaced at 1.5 m centres, provides adequate flexibility to accommodate small and large service openings in the floor. The rib profile made it possible to use table forms with integral grp rib moulds to ensure a fast building programme (Figure 4). Building 14

425 mm reinforced ribbed slab, span 9.0 m. The irregular floor plan of the building and the client’s requirement for minimum column sizes resulted in it being inappropriate to provide stability by frame action. Shear walls, with no returns and a minimum of cross walls, were specified to facilitate rapid construction of walls.

Figure 4: Grp rib moulds fixed to table forms. 3

Building 26 500 mm prestressed/reinforcement waffle slab, span 12.0 X 12-O m. The solid beam strips were post-tensioned, with the waffle section reinforced. This allowed the waffle section to be reinforced independently of the beams, thus speeding up construction, whilst maintaining an economical floor depth. Building 31 335 mm one-way spanning prestressed solid slab, span 12.6 m. The frame was designed as a stacked portal, with 160 mm precast perimeter walls supporting a 335 mm post-tensioned solid slab. An important benefit in post-tensioning the slab was that the end moments transferred to the precast walls, due to dead load, were negligible. This in turn led to manageable transfer moments in the wall under ultimate load conditions. The structural solution proved both economic and fast to 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 fixed at the base to provide frame stability. The precast floor beams were simply supported and designed as pin joint connections to the columns. Building 37 560 mm double-T floor units with in situ topping, span 14.5 m. Stability was achieved by a combination of shear walls at the ends of the building and frame action developed from the precast perimeter H frames. The H sections are formed by adjacent perimeter columns and the perimeter edge beam (Figure 5a). The precast column joints are positioned at mid-storey height, i.e. the point of contra-flexure, so a full moment connection to the double-T floor beam was possible (Figure 5b). The precast frame was erected in just under ten weeks.

2400

-II/

(a) Elevation

Figure 5: Detail of precast H frame. 4

4800

CHOICE OF FLOOR SLAB DESIGN In assessing the structural cost of a multi-storey building, it is evident that the bulk of the cost is often for the floor slab construction. Therefore, the overall economy of a structure may depend on the efficiency and economy of the floor slab’ system. While quantities of materials reflect the efficiency of the design and structural layout, the actual cost of the structure may also depend on such factors as s p e e d o f construction, local market conditions, competitive tendering, availability of labour and equipment and cost of construction finance. Consequently a structural design that has proved to be competitive in one region may not always be competitive in another. For a building to meet the needs of major financial occupiers in today’s market, the choice of floor design is often determined by one or more of the following considerations: l

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

0 A maximum floor-to-floor height which allows adequate space for services and ducts, balanced against planning pressure to limit overall building height. 0 An adaptable floor structure which can accommodate future tenant alterations with maximum speed and minimum disruption. The wide range of floor construction in both reinforced and prestressed concrete, highlighted in this survey, demonstrates that concrete floors can be designed economically to meet these requirements. The types of floors and the reasons for choosing them are given opposite.

I/

I I I I

2400 4,

(b) Section

Solid flat slabs (with or without drops) The principal feature of the dropless floor is its flush soffit which requires only simple formwork and is easy to construct (Figure 6a). The overall depth of this floor is a minimum 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 the column supports and the need to control long-term deflection. The provision of drop panels at the column supports (Figure 6b) avoids the need for shear reinforcement and increases the stiffness of the slab and the economical span range. Alternatively, a structural steel shearhead can be incorporated to maintain a flush soffit to allow for easy construction and efficient use of large forming systems (Figure 6c).

Ribbed slabs Providing ribs to the soffit of the floor slab can reduce the quantity of concrete and reinforcement, and thus the weight of the floor. The deeper, stiffer floor permits longer

spans to be used. Formwork complexity can be minimized by the use of standard modular, re-usable formwork. When flying form panels are used, the ribs should be positioned away from the column lines. Ribbed slab floors are very adaptable for accommodating a range of service openings (Figure 7).

Waffle slabs Waffle slab floors are commonly used when buildings are subjected to heavy imposed loading. They are very efficient in the use of materials and provide very economical long spans, but the additional complexity of formwork can often slow the construction. Where speed of construction is critical, a ribbed slab or a shallow beam solution is often preferred.

One-way spanning solid slabs and beams A wide, shallow beam profile is often preferred in order to reduce the overall depth of the floor, whilst permitting longer spans. The one-way spanning solid slab between the beams facilitates the use of table forms for fast construction (Figure 8).

1-2-1::: 1r-1

I--

“~~-~~-l'-'

'-::-~J--,:-;:-:

:-,r-

Figure 7: Ribbed slab for flexibility to accommodate openings.

(b)

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

Figure 8: Band beam and slab construction using tableforms. 5

Precast slabs

Composite precast slabs

Precast slabs offer the advantage of off-site manufacture, with a reduction in site labour and site formwork. When the slabs are prestressed there are additional benefits of longer spans and higher load capacity. A popular type of precast floor is the hollow core slab (Figure 9). The relatively lightweight units form a flush soffit when placed. A shear key between units ensures load sharing and the construction is commonly capable of developing diaphragm action without the need for a structural topping. The precast units are easy to remove and can accommodate a wide range of floor openings.

Composite precast slabs combine precast floor elements with in situ concrete in an economical way, eliminating traditional formwork for floor construction, and providing long-span floors. Thin precast concrete floor plates can be combined with an in situ topping to form composite one-way spanning floors up to 6 m long, or, in combination with precast beams, to form a composite ribbed slab (Figure lOa). For extremely long spans, double-T precast beams and a composite in situ topping is preferred (Figure 10b).

CONCLUSION The buildings surveyed in this publication demonstrate that reinforced and prestressed concrete floors with spans ranging 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-led design.

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

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 Prestressed - Buildings 8 to 12

Section 2: Ribbed slabs Reinforced -Buildings 13 to 15 Prestressed -Buildings 16 to 22

Section 3: Waffle slabs Reinforced -Buildings 23 to 25 Prestressed - Buildings 26 to 28

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

SECTION 1 SOLID FLAT SLABS

m

2

I

7.2x7.2

mm I

ratio I

300

24

1

m3 1

I

0.30

Jr

kg I

30.0

3600

Ji

1 I

6-O

Solid flat slab -reinforced

’ r ~~~~ ’ Frame

action

3600

1"

GradeC40 Code BS 8110

7200

'i

3600

n

1"

3600

I

I-

300 slab

-

7 J

-

n

7

_I

-

8

n

Solid flat slab -reinforced

No. of floors 10

Materials per m2 Design of floor area load Depth Span/depth Conc;ete Rebar kN/,,$ Slab

Span m

mm

ratio

7.5x6.1 3 0 0

Stability

Notes

Shear walls

Grade C35 Code BS 8110

kg

25

0.30

45.0

6-O

I

I

I

I

8

I

I

I

300 slab I

-

I

I

I

I

I

I

I

Typical floor plan

A

9

Solid flat slab -reinforced

3000

3000

5 i(J 7500

A i

n

8 2

400 slab

400 slab

E

mi

n 1

I

_L

1 /

i

Typical floor plan

10

Solid flat slab -reinforced

No. of floors 7

Materials per m* Design of floor area load Depth Span/depth Conc;ete Rebar kN/,-,-,* mm ratio kg Slab

-

Span m 65x45

250

26

0.25

29.0

5 0

Stability

Notes

Shear walls

Grade C35 Code BS 8110

I

17 ccc 45 Typical floor plan

1`

Solid flat slab -reinforced

No. of floors 4

Materials per m* Design of floor area load

Slab Span m

Stability

Depth Span/depth Conc;ete Rebar kNirn2 mm ratio kg

9-5x 7.3 310

30.6

0.31

Typical floor plan

41.5

5.0

Shear walls

Notes (See page 3)

C30 lightweight Code CP 110

Solid flat slab -reinforced

Materials per m2 Design of floor area load Depth Span/depth Co;;ete Rebar kN/r-$ mm ratio kg Slab

No. o f Span floors m 13

5800

8 0x7.2

275

3 irr 7200

275 slab

Typical floor plan

29

0.28

5800

40.7

5-o

Stability

Notes

Shear walls

Grade C35 Code BS 81 10

Solid flat slab -reinforced

Stability I

I

9.2x6.0

7 I

I I

255 II

I

0.26

36

I

I

I

I

I

I

Notes (See page 3)

I

I

II

24.0 II

5.2

-

h

6200

4

5 ((I 6000

255 slab

Typical floor plan

14

Solid flat slab - prestressed

2

(”

Span m

P

x

x

Design load Depth Span/depth Con$ete Rebar Strand kN/r-$ ratio mm kg kg

8.0x8-0 275

29.1

10-2

0,275

,.~- . .

I

Gl

Materials per m2 of floor area

Slab

No. of floors

4

8

10..0

Stability

Notes

Shear walls

Grade C40 Code BS 8110

.‘j----

X i..t

:*

x

x

I”

m

x

x

x x x

0

X

0

Eico

x

Atrium

X

X

m

m

m

m

PI

m

m

P1

J

First-floor plan

Column head detail

I

I

15

Solid flat slab - prestressed

Stability

a

7.2x 7.2 240

30.0

0.240

2.4

4.7

Notes

Shear walls

6.5

* See Concrete Society TechnIcal Reports No 17 and No 25

3 ((I 7200

4800

0 0

cu

P-

n

n

Typical floor plan

c

:i,

950

I / Column head detail

c

475

”

’ 240 $ 50 i 250

Solid flat slab - prestressed

Materials per m’ of floor area

Slab

No. of floors

9

Span m

Depth Span/depth Conx$ete mm ratlo

9 4x9-o 300

31 3

0 300

Design l o a d Rebar Strand kN/mz kg kg

14-l

78

50

Stability

Steel bracing to columns

Notes (See page 3) Grade C40 Code BS 8110 CS TR 17 & 25* Steel c o l u m n s with shearheads

* See Concrete Society TechnIcal Reports No 17 and No 25

45000

P

m

B

a

I

m

I

Typical floor plan

Cross-bracing

17

Solid flat slab - prestressed

No of floors

7

Materials per m* of floor area

Slab Span m

11 5 x 7 5 325

35 4

O-325

11

1

See Concrete Society TechnIcal Reports No 17 and No 25

Typical floor plan

8

Design

load Depth Span/depth Concrete Rebar Strand kN/mz mm ratio m3 kg kg

65

50

Stability

Notes

Frame action

Grade C40 Code BS8110 CSTR 17&25*

Solid flat slab - prestressed

Slab Stability

r

7200

c

3600

*

Typical floor plan

Typical column head detail

7200

2400 *II

7200

+

3600

*

7200

Notes

J

SECTION 2 RIBBED SLABS

Ribbed slab -reinforced

Materials per m* Rib Beam No. Des of floor area ,__ign of wad floors Span Depth Span/depth Span B x D Span/depth Concrc ?te R e b a r kN/m* 10

m

mm

ratio

m

mm

ratio

m3

kg

9.0

450

20.0

8.0

1200 x 450

13.3

0.23

39.5

7.5

Notes

Stability

(See page 3)

Frame action

Grade C35 Code BS 8110

7 ((1 9000

1

I

Typical floor plan

Typidal rib section

20

Typical beam section

Ribbed slab - reinforced

No. of floors 11

Materials per m2 of floor area f$$” Stability

Beam

Rib

Notes (See page 3)

Span Depth Span/depth Span B x D Span/depth ConcJete Rebar kN/m* mm ratio kg m ratio mm m 9.0

425

9000

21 .l

9.0

1800 x425

6750

21.1

4 @ 7500

5.0

38.5

0.27

i

6750

1

Shear walls

Grade C35 Code BS 8110

9000

5 (u, 9000 Typical floor plan 1500 _~~ __~ 125 L

-t

‘T 1425 I I

l-l

7Ii

425

: 1800

250

Typical rib section

Typical beam section

Ribbed slab - reinforced

floors Span Depth Span/depthSpan m

5

mm

9.0 3 0 0

Materials per m2 of floor area Dri,n Stability

Beam

Rib

No.

ratio

30.0

m

B x D Span/depth

mm

1800 7-2 x 4 0 0

ratio 18.0

0.32

6 ((I‘ 7200

29.0

5.0

Shear walls

I

9000

1800 Typical rib section

22

Notes

Conc;ete Rc??r kN/mz

Typical beam section

Grade C35 Code BS 8110

i

7200

i

Ribbed slab - prestressed

No. of

Rib

Materials per m* of floor area

Beam

Design load

Stability

Notes

Frame action

Grade C35 Code BS 8110

floors Span Depth Spacing Span/depth Span B x D Span/depth Type Concrete Rebar Strand kN/& m mm mm ratio m mm ratio kg kg 3

9.0

3 2 5

1200

27-7

1800

18-5

6.0 x 3 2 5

Pt’

0 194

12 6 3.65

6.0

‘Prestressed

Typical floor plan

100 325

Typical rib section

ki!

23

Ribbed slab - prestressed

I

No.

I

-I of floors

Materials per m* of floor area

Beam

Rib

Stability

Notes

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

22

9.0

mm

mm

250

750

ratio

36.0

m

mm

ratio

2200 7.5 x 2 5 0

30.0

kg

Pt’

0.186

kg

7 . 0 3 5.79

*Prestressed

10 @ 7500

i

Typical floor plan

2200

750 125

,

A -

-r

s

.250

250

I-

\

175 Typical rib section

24

Design load

Column head detail

5.0

Shear walls

Grade C40 Code CP 110

Ribbed slab - prestressed

Materials per m2 Beam Rib NO. Design of floor area of load floors Span Depth Spacing Span/depth Span B x D Span/depth Type Con;;ete Rebar Strand kN/m* mm

mm

ratio

9.8 400

725

24.5

m

8

m

ratio

mm

1 9 4 1200 x 800

24.2

Pt”

0.354

kg

kg

16.9

9.76

6.0

Stability

Shear walls

Notes

Grade C40 Code CP 110 ‘Prestressed

I.

I.

I. 13000

9350

9350

I.

10000

I

Typical floor plan

c

725

75

725

P

725

Typical rib section

25

Ribbed slab - prestressed

Materials per m2 Rib Beam No. Design of floor area o f load floors Span Depth Spacing Span/depth Span B x D Span/depth Type Concrete Rebar Strand kN/r-$ m 5

L

mm

10.85 450

mm 850

ratio

m

mm

ratio

24.1

12.5

1500 x450

28.0

‘Prestressed

Typical floor plan

Typical section

L

Pt*

m3

kg

kg

0.280

8.3

6-63

5.0

Stability

Notes

Shear

Grade C40

walls

Code CP 110

Ribbed slab - prestressed

Materials per m* Beam Rib Design No. of floor area load o f floor s Span Depth Spacing Span/depth Span B x D Span/depth Type Conc;ete Rebar Strand kN/m* m 5

mm

135 475

mm

ratio

1500

28 4

m

mm

ratio

9 . 0 1500 x475

Pt*

18.9

0,285

kg

kg

15.0

4.93

Notes

Stability

Shear walls Grade C40 and frame Code BS 8110 action

60

l Prestressed

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

I

u /’

/

/

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 I I II

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

I I I I

L~LJLJL~LJLJLJLJLJLJLJLJLJL.~L.n n w

I

riririr~r~rlrlr~r~r~r~r~r~r~r~,

ririr

II II II II II I II II I/ I II II II II II II 11 II II II I’ II I II I II II II II II II II II II II II L~L~L~L~L~L~L~L~L~L~~~~~~~~~~~~~~~~~,~~

I I

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

I

r-i r

II

II

I I I I II II II

iririr~r-lr~r~r~r1rlrlrlr~r~r~r~rlrl

II II II II II I I I II II II II II I I I II II II II II I I I L J -JLJLJ LJLJLJL-ILJLJ I I I

n

II II II

I I I

II

II II

n

r -1 -1rir-i r Iririririrl

I

I

II II

I I 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

I I I

I

LJL~ILJLJLJLJLJLJLJ

n

n riririririr

I

I

II II II II II II II II I II II II II II I I LA _ _J L A L A LJLJLJLJLALJ LJLJLJLJLJLJLJLJL.~J II

II

I

8

10

ll~-lrlrl -

I”

Typical floor plan

1500 125

‘r

1500

Typical beam section

1, J:

1

425

Typical rib section

27

Ribbed slab - prestressed

Materials per m2 Rib Beam Design No. of floor area of load floors Span Depth Spacing Span/depth Span B x D Span/depth Type Concrete Rebar Strand kN/m2 m

5

mm

14.4 650

mm

m

ratio

22.2

2400

mm

ratio

1200 7.2 x 6 5 0

R.C.*

0,268 1 4 . 7

Notes

Shear walls

Grade C40 Code BS 8110

kg

kg

11 .0

Stability

4.33

7.0

“Reinforced

B0

8 @ 7200 1

f

: I I

II

II II II

II

I I

II

I II I II I II

II II II II II

:I II

jl 11

II

n

ll iI iI II

II II II II

II II II I

ll

II

II

II

n II

E

n Ii

I7 II

11 II

r7 II

fl II

I4 L L

M -IL I I - I I AIL u lb ““““““/

Typical floor plan

2400

28

II II

;

J u u u H H H H H - u .-IL Al- u -IL ii- il -IL II_

Typical section

II

500

Ribbed slab - prestressed

Materials per m’ Rib Beam Design No. of floor area load of floors Span Depth Spacing Span/depth Span B x D Span/depth Type Concrete Rebar Strand kN/m’ m mm mm ratio m mm ratio kg kg 4

16.3 525

31 .0

850

6.3

275 X1000

R.C.*

6.3

0.225

9.8

5.66

Stability

Shear walls

6.0

Notes

Grade C40 Code CP 110 ‘Reinforced

7 @ 6300

_

i

t

Typical floor plan

100

I

850

8

5

0 %

850

i

Typical section

29

SECTION 3 WAFFLE SLABS No. of floors 5

Column spacing m

Waffle slab - reinforced

Materials per m* Design of floor area Depth Span/depth load Stability mm ratio Con-v$ete R e b a r S t r a n d kN/m2 21.2

6.6 X 7.43 350

5835

0.245

kg

kg

24.0

-

7425

I

Frame Grade C35 Code BS 8110 action

6-O

3 @ 4950

---*

Typical floor plan

Ribs at 900 crs

! 125

4;7 I

1600 Section at column head

30

Notes

Waffle slab - reinforced

No. of floors 3

Column spacing m

Materials per m2 Design of floor area Depth Span/depth load mm ratio Con;;ete R e b a r S t r a n d kN/m2

7.5x10 5 5 2 5

, 7500

typical

20.0

0.450

kg

kg

67.0

-

6-O

Stability

Notes

Frame Grade C35 action Code BS 8110

,

Typical floor plan

Typical section

31

Waffle slab - reinforced

No. of floors

Column spacing m

3

10.18 x10.18

Depth Span/depth mm ratio 550

_

Materials per m* of floor area

Design load Stability

18-5

0.396

37.0

-

k

Typical section

9.0

Shear Grade C35 Code BS 8110 walls

3 @ 10180

Typical floor plan

32

Notes

Conc;ete R e b a r S t r a n d kN/m2 kg kg

125 14

Waffle slab - prestressed

No. of floors 1

Materials per m2 of floor area

Design Notes Depth Span/depth load Stability (See page 4) mm ratio Compete Rebar Strand kN/m2 kg kg Shear Grade C40 15.9 2.52 6.0 0.349 24.0 12.0x12.0 500 Code BS 6110 walls Column spacing m

6000

4 @ ’ 12000

q

CIOOOOOOO

rlnnnnnnrin

Typical floor plan

Typical section

125

33

Waffle slab - prestressed

No. of floors 2

Column spacing m

Materials per m* Design of floor area Depth Span/depth load Stability mm ratio Cor?$ete R e b a r S t r a n d kN/m*

12.7x12.7 500

25.4

*

0.341

12700

Typical floor plan

Typical section

kg

kg

12.2

5.60

6.0

Shear walls

Notes

Grade C35 Code BS 8110

Waffle slab - prestressed

Stability

Notes

~c~~~

Grade C40 Code BS 8110 CS TR No. 17*

*See Concrete Society Technical Report No 17

5 @ 15000

1

1 ,;:j; ji

‘: :’ ‘: ‘_-: ::~:: ::p::-::-:,

;.:I.

‘-7.. :.::.

: :: 1

:.

:

li

:’

ij

:

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

: :~::z..

.I! j :::.: .::

a :, : .;_;;

1_~1;.1;.1;:1:.:1~1!_. ~.. :.~:.~::~’

i

.,: :I..

.iilii:

:.!:~:.~I:.::.::.::.:!.:L.::! !L : :-:“:.::‘I:.‘,~ . . . . . .~..~_.

,..,:

.,

: : ::r::

__,:

Lo:!

::~::

!!

.-..-.

:,

,,

:: :

::=:: ,!

,I

‘: :, : ::-::-::.:, ,I

.,

,,

. . ..i.:

Atrium

Typical floor plan

Typical section

225

35

SECTION 4 ONE-WAY SPANNING SOLID SLABS & BEAMS

One-way spanning solid slab and beam

Materials per m2 Slab Beam No. Design of floor area of . load floors Span Depth Span/depth Type Span B x D Span/depth Type Concrete Rebar Strand kN/+’ m 4

mm

ratio

7.43 200

37.2

m Pt*

9.0 1 5 0 0

‘Prestressed

Typical floor plan

Typical beam section

36

mm

x 500

ratio 18.0

m3 Pt*

0.261

kg

Stability

Notes

kg

1 4 . 0 4.11

4.0

Shear

Grade C35

walls

Code BS 8110

One-way spanning solid slab and beam Slab Beam No. o f floors Span Depth Span/depth Type Span BxD Span/depth Type m

6

mm

10.30 2 5 0

ratio

41.2

m

Pt*

mm

1500 6.0 x 4 5 0

ratlo

13.3

R.C.+

Materials per m2 of floor area

Design load

Stability

Notes

Conc;ete Rebar Strand kN/m* kg kg

0.298

13.9

3.93

t

6.8

Shear walls

Grade C30 Code CP 110

‘Prestressed +ReInforced

250 slab

Typical floor plan

Typical beam section

37

One-way spanning solid slab and beam Materials per m2 Beam Slab Design No. of floor area load of floors Span Depth Span/depth Type Span BxD Span/depth Type Concrete Rebar Strand kN/m2 ratio m3 kg kg mm m mm m ratio 7

12.6 3 3 5

37.6

Pt*

Precast perimeter wall support

‘Prestressed

335 slab

Typical floor plan

38

0 335

11.8 8.25

6.8

Stability

Shear walls

Notes (See page 4)

C40 lightweight Code BS 8110

One-way spanning solid slab and beam

Beam Slab No. of floors Span Depth Span/dept Tyee Spnn BxD Span/depth Type m 10

mm

6 75 220

m

ratio

30 7

R.C.* 10

mm

600x 0 6oo

Materials pe r m2 of floor area

Design load

Stability

Notes

Shear walls

C40 lightweight Code CP 110

Conc;et e %??r StFgn d kN/m2

ratio

16.7

R.C.*

0.26

42-O

-

5 0

*ReInforced

E0

Typical floor plan

Main beam section

39

One-way spanning solid slab and beam

No. of floors

Slab

Materials per m2 of floor area

Beam

Design load Span Depth Span/depth Type Span B x D Span/depth Type Con-$ete Rebar Strand kN/& m mm m mm ratio ratio kg kg

5

6.0

175

34.3

R.C.*

9.0

1500 x425

21.2

R.C.*

0.25

52.0

-

‘Reinforced

Typical floor plan

425 :

Typical section

40

5.0

Stability

Notes

Shear walls

Grade C40 Code BS 8110

SECTION 5 PRECAST SLABS

Precast slab

Materials per m2 of floor area Beam Slab Design No. In situ Precast load Stability of floors Span Section Span/depth Span B x D Span/depth Conc;ete Rebar Strand Conc;ete Rebar kN/r-$ m

12

7.0

mm

203

ratio

34.5

m

mm

ratio

300 6.0 x 6 0 0

10.0

kg

0.145

4.8

kg

kg

40

Notes

0,011

0.4

7.0

Shear walls

C50, BS 8110 7% in situ Hollow core planks No topping

6 @ 6000

1

.

Typical floor plan

Precast

“yqFy=

:z

300 Centre beam section

41

Precast slab

m

4

mm

7.2

I

200

I

36.0

Design load B xD Span/depth Concrete Rebar Strand Conc$ete Rebar kN/m2

m

mm

7.2

600 x600

ratio

I

I

m3

ratio

12.0

1

Typical floor plan

Typical section

kg

o-193

I

7200

5400

1

1

kg

Stability

Notes

Shear

Grade C50 Code BS 8110 Hollow core

kg

3.0

7.9

I

7200

7200

42

Materials per m’ of floor area In situ Precast

Beam

Slab No. of floors Span Section Span/depth Span

-

I

-

I

7200

planks No topping

I

7200

5400

1

7.0

1

7200

1

Precast slab

Materials per m2 of floor area Slab Beam No. - Design In situ Precast load of floors Span Sectlon Span/depth Span B x D Span/depth Concrete Rebar Strand Con$ete Rebar kN/m* m

3

77

mm

200

ratio

38.5

m

mm

m3

ratio

7 . 4 3 ,$;o 1 2 . 4

0.157

kg

10.5

kg

Stability

Notes (See page 4)

kg

2.55

- -

6.5

Frame action

Grade C50 Code BS 6110 Hollow core

planks No topplng

Typical floor plan

Typical section

43

SECTION 6 COMPOSITE PRECAST SLABS Rib No. of . floors Span Depth Span/depth Span mm m m ratio

9

14.5

560

25.9

4.8

Composite precast slab

Materials per m2 of floor area In situ Precast

Beam

Design load Depth Span/depth Concrete Rebar Strand Concrete Rebar kN/m2 mm ratio m3 kg kg m3 kg 500x 1000 (Perimeter)

Stability

Grade C60 Code CP 110 any$$ar Double Tees, wrth In situ topping walls Precast H frame Frame

4.8

0.150

5.75

0.080

6.3

14500

.

2.2

5.0

I

4800 typical

I

47600 Typical floor plan

1200

, In s i t u t o p p i n g

i

-/

Typical section

44

Precast double-T beams

Notes (See page 4)

Composite precast slab

f10 2 Span

m

4

16.7

22.0

4.9

600x 900 (Perimeter)

1.54

Frame action

5.0

9 @ 4877

?

~f?~+kPl-rr~P~~~n’n-n

i

‘II II II ‘I I II ‘II II ‘II II Ii ‘II Il l II II ‘I I II I ‘II II II ‘II II II ‘II II II - + tit c- b !,

z co

0,075

0,133 5 - 4 8 7 . 7 9

5.4

2438 ‘i *

111 1) 1

I

In situ

Notes

load Stability Depth Span/depth Con;;ete Rebar Strand Conc;ete Rebar kN/m’ mm ratio kg kg kg

Depth Span/depth Span mm ratio m

785

Materials per m” o Precast

Beam

Rib

No.

II II I I

II

II

II

II

II

II

II

II

II

2438

8

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 I I II III Ill II lib II III II III II III II II IIP II II III I I II III

I I I I I I

I I

I I I I I I I I 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 II III L km c hL c Lu,u--u-uLu~ u-u~u-u,u-u-uLu, u u4 Ad 4 u Am11 4 4 44 -IF

Typical floor plan

1200

/’

In situ topping

1 j-=-f

Precast double-T beams Typical section

J

n~n’n~n~n-n’n~~n~~n~nLr~~n111141ild 1’1111Vfb II

I

75 (average)

Grade C60 Code CP 110 Double Tees, with in situ topping Precast H frame

;710

I

Composite precast slab

Rib No. of floors Span Depth Span/depth Span m

6

mm

/ 12.0 1

m

ratio

610

/

Design

. load

Stability

Notes

Depth Span/depth Concrete Rebar Strand Concrete Rebar kN/m* ratio mm m3 kg kg m3 kg

750x j 9.0 1 ,in”;FU, 1

19.7

Materials per m2 of floor area Precast In situ

Beam

14.8

1 0.134 (13,751 - 1 0.111 110 721

5.7

Frame action

In situ C35 Precast C45 Code BS 8110 55% In situ

I

r ir’ir’ir i r ’ i r ’ i r I I

II II II

ir’ir

II

II

II

II

II

II II

II

II

II

I

ir ir’ir’ir irwirlir ir

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 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 plank Precast rib Typical rib section

46

Typical in situ beam section

Composite precast slab

3

Materials per m2 of floor area Precast In situ

Beam

No. o f floors Span

Design load

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

m

mm

ratio

m3

kg

kg

m3

kg

21.2

750 Precast

28.3

0,123

4.9

7.6

0.060

2-28

5.0

Stability

Shear walls

Notes

Grade C62 Codes CP 115, CP 116 40% In situ

72000

1

c

,

8 cv i;

_ ~n-=-rt-~n-“-~-un~~~~nn~~~“~h~~n~n~n~~~~~nnnunu~~~=-n~~n~~~~ ,, ,, II Ii II I II II II II I I I II 1 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,

II

11

II

II

‘II

II

II ‘I ~:I~_:~ ”

11, AlI !I, ‘I, JIl

II II II I! II

II II

II llr :! Id II lli:

I’

II ‘I Nt ~ ‘I ” I’ I’ I

II II II

~~11R# II- 11~;

II II II

II II

II v ,I Ii

;~

II t

II II! II IIL IlL

I

II IIL II II II IIL II 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 @

Precast soffit planks

Precast beam Typical section

1500 crs.

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