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Under supervision of

Dr . Mohamed Nabil

This report has been prepared by :

Mohamed Mohsen Mohamed Hussein Mohamed Nabil Ali Kamel Mohamed Youssef Mahmoud YoussefAhmed Hamdy Mohamed Hassan

Hollow block & Ribbed slabs


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Outlines

Introduction.

Comparison between different codes.

Solved example by different codes.

One & two way slab solved example.

Effect of cross ribs on deflection.

Modeling.

Case study.

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Introduction

ollow bloc! and "ibbed slabs are formed by placing bloc!s on t#e slab

and concrete ribs.

In case of #ollow bloc! slab voided bloc!s are placed to reduce t#e total

weig#t of t#e slab .

In case of ribbed slab t#e bloc!s are not permanent.

$#e bloc!s are considered as non%structural element as t#ey do not

contribute to strengt# of t#e slab.

loc!s may be made concrete wit# lig#tweig#t aggregate or ot#er material

as polystyrene ' foam (.

$ypes #ollow bloc! slab are one way and two way slabs .

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Introduction

The advantages of Ribbed and Hollow block slabs are as follows:

$#ey provide an economical) versatile lig#tweig#t monolit#ic slab system and

t#is its main advantage reduction of weig#t by removing t#e part of t#e concrete

below t#e neutral axis.

Components are relatively lig#t and no mec#anical #andling is necessary t#ere

is ease of construction.

Economic for spans more t#an *m wit# lig#t or moderate live loads) suc# as

#ospitals) office or residential buildings.

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+CI ,- EC/ 01,

S --1 Euro code 0

Comparison between different codes

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2et distance between ribs 3e3

s#all not exceed 411 mm.

5eb widt# 3b3 s#all not be less

t#an -11 mm or one t#e t#ird of dept# 3t3) w#ic#ever is greater.

Compression slab t#ic!ness 3ts3

s#all not be less t#an *1 mm or

one $ent# -6-1 of distance 3e3)w#ic#ever is greater.


Egptian code !EC" #$%

Limitations of Hollow block slabs :


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$#e minimum value of rib widt# 'b( isn7t less t#an -68 slab t#ic!ness't( or -11 mm w#ic#ever greater) wit# ta!ing into account

re9uirements of concrete cover) distance between bars and fire

re9uirements

Egyptian code 'EC/ 01,(

:istance between ribs axes can be increased up to -.* m .

$#ic!ness of upper slab is determined by a value not less t#an e6-0 or

*1 mm w#ic#ever greater.

Limitations of Ribbed slabs:


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'ritish code !'( )**$


Clear distance between ribs 'e( not more t#an *11 mm ) ;ointed

in cement < sand mortar tsis 0* mm.

Clear distance between ribs 'e( not more t#an *11 mm not

;ointed in cement < sand mortar tsis ,1 mm.

+ll ot#er slabs wit# permanent bloc!s tsis 81 or one%tent#

-6-1 of clear distance between ribs) w#ic#ever is great


Clear distance between ribs not more t#an -.* m tsis *1 mm or one%

tent# of clear distance between ribs) w#ic#ever is greater.

t b

e

b

t

b +t/


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Euro code !En#

$#e rib spacing does not exceed -*11 mm.

$#e dept# of t#e rib below t#e flange does

not exceed 8 times its widt#.

$#e dept# of t#e flange is at least -6-1 of

t#e clear distance between ribs or *1 mm)

w#ic#ever is t#e greater.

$ransverse ribs are provided at a clear

spacing not exceeding -1 times t#e overall

dept# of t#e slab.

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One limitation will c#ange from ribbed slab $#e minimum flange

t#ic!ness of *1 mm may be reduced to 81 mm.


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,merican Concrete Institute !,CI

5#en permanent filling material#aving a unit compressive strengt# at

least e9ual to fc= in t#e ;oists are used ts

s#all be not less t#an -6-0 t#e clear

distance between ribs) nor less t#an 81

mm.

Ot#erwise tsis not to be less t#an -6-0

t#e clear distance between ribs) nor less

t#an *.1 cm

! "ibs are not to be less t#an -1 cmin

widt#) and a dept# of not more t#an ,.*

times t#e minimum web widt#.

! Clear spacing between ribs is not to

exceed 4*.1 cm


Limitations of Hollow block slabs & Ribbed slab:


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Code

Limits

Egyptian codeBritish

code

Euro

code

American

code

Simply sup. -.#$ -.#$

///////////

-.*0

- end cont. -.#1 -.#$2) -.*)21

0 end cont. -.#) ///// -.#*

cantilever -.) -.120 -.)

ts 3 ts 3 ts 3 ts 3

e e + 4$$ mm e + *1$$ mm e + *1$$ mm e + 41$ mm

b b 3 b + t.5 b + t.5 b 3 *$$ mm

Cross ribs

-2- + %

67.m# 8 -s 9

1

-2- 9 %

67.m#

8 -s !5:4

-2- 9

4m2

/////// If - 3 *$ th.b ///////

One ; rib One ; rib % ; ribs

Code

Limits

Egyptian codeBritish

code

Euro

code

American

code

Simply sup. -.#$ -.#$

///////////

-.*0

- end cont. -.#1 -.#$2) -.*)21

0 end cont. -.#) ///// -.#*

cantilever -.) -.120 -.)

e e + 4$$ mm e + *1$$ mm e + *1$$ mm e + 41$ mm

b b + t.5 b + t.5 b 3 *$$ mm

Cross ribs

-2- + %

67.m# 8 -s 9

1

-2- 9 %

67.m#

8 -s !5:4

-2- 9

4m2

/////// If - 3 *$ th.b ///////

One ; rib One ; rib % ; ribs



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( 5 m *

7m )U!"#

EC$

U!"# B

U!"#

EU%&C&'E

U!"#

AC!

( 7m *

7m )A &"EA

&LL&BL&C+LABA ,&A

&LL&BL&C+LAB


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>cu? 0* 26mm0

>y? ,@1 26mm0

>.C? -.* A26m0

B.B? ,.1 A26m0

(olved e


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Code

prop.

Egyptian

codeBritish code Euro code

American

code

th.b -5 mm -5 mm -5 mm /

t 5 mm 5 mm 5 mm 5 mm

h - - - -5

0u

(

+n.m1rib) 23.247 23.247 27.75 -/.5

A -3/./ mm- -55.7- mm- /--.5 mm- --.7 mm-

0ain ribs

dim.2 6 - mm 2 6 - mm 2 6 - mm 2 6 -5 mm

Cross ribs "o cross ribs "o cross ribs &ne cross rib "o cross ribs

oid parthortdir.

ongdir.

hortdir.

ongdir.

hortdir.

ongdir.

hortdir.

ongdir.

./ m. ./ m. ./ m. ./ m..-5

m../ m. ./ m. ./ m.

Conc.

8uantities-.4 m/ -.4 m/ -.3/9 m/ /.7 m/

Solved examples by different codes


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One & two way slab Solved examples

One waslab

Two wa

slab>cu? 0* 26mm0

>y? ,@1 26mm0

>.C? -.* A26m0

B.B? ,.1 A26m0


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LAB ,$E

$%&$.

&ne :ay hoo: boc;s

sab

,:o :ay hoo: boc;s

sab

th.b. /- mm -5 mm

h -5 mm - mm

ts 7 mm 5 mm

0u(+".m1rib) 95.9< dir. = dir.

25.4 25.4

As 5-3.-55 mm-1 rib-/3.4 mm-1 rib. >or < dir.And -52.3 mm-1 rib. ?or =

dir.

%ibs dim. .2- * .-5 m .2 * .- m

"&. o? main ribs 22 2-

"o. o? cross ribs 2 2-

Conc. @uantities 5.459 m/ 5.-/9 m/

%>, 227.73 mm- 1m 342.59 mm-1m

One & two way slab Solved examples

It is obvious t#at t#e ">$ and concrete 9uantities in t#e two way #ollow

bloc! slab is more economic #owever t#e execution of t#e two way #ollow

bloc! slab is #arder t#an t#e one way #ollow bloc! slab.


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Effect of cross ribs on deflection

In $#e previous example t#e effect of cross ribs on deflection will bediscussed on sap program.

+t first one cross rib is put in t#e mid span of t#e slab.

$#en two cross ribs are put at -6, of t#e span from eac# side.

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Case of one cross rib

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