This document discusses the design of one-way reinforced concrete slabs. It defines one-way slabs as slabs supported on two opposite sides where loads are transferred in the short direction. The strip method is used to analyze one-way slabs by considering a unit strip with a width of one unit and a depth equal to the slab thickness. The document reviews ACI code specifications for one-way slab design including minimum thickness, bar spacing, reinforcement ratios, and moment coefficients. Sample problems are provided to demonstrate the design of one-way slabs using working stress design.

1. Department of Civil and Environmental
Engineering
Course code: CEE 403A
Course Title: Structure V (Reinforced Concrete Design)
Sourav Ray
Assistant Professor
Department of Civil & Environmental Engineering
SUST, Sylhet.
Email: sourav.ceesust@gmail.com
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2. DESIGN OF ONE-WAY SLAB
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3. Book Reference
 Design of Concrete Structures
-by A.H. Nilson (7th edition & 13th/14th edition)
 Structural Concrete: Theory and Design
-by M. Nadim Hassoun
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4. SLAB
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5. TYPES OF SLAB
Supported
by beams
on only
one side
Supported
by beams
on both
sides
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9. In first figure slab is
supported on two opposite
sides only. In this case the
structural action of the slab
is essentially one way.
In second figure there are
beams on all four sides with
a intermediate beam. Now if
length to width ratio is 2 or
greater, slab is one way even
though supports are
provided on all sides.
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10. One way slab is assumed if ratio of side panels is
greater than 2. Loads are assumed to transfer in
the short direction.
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11. LOADING OF ONE WAY SLAB
When slabs are supported
on two opposite sides only
loads being carried by the
slab in the direction
perpendicular to the
supporting beams.
When supports are provided on
all sides most of the load is
carried in the short direction to
the supporting beams and one
way action is obtained.
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12. So finally we can conclude one-way slab as……………..
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13. Strip Method of Analysis for One-way Slabs
• For purpose of analysis and design a
unit strip of such a slab is cut out ,
which may be considered as a
rectangular beam of unit width (say 1ft
or 1m) with a depth ‘h’ equal to the
thickness of the slab and a span ‘la’
equal to the distance between
supported edges.
• The strip can be analyzed by the
methods that were used for
rectangular beams.
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17. ACI code specifications
For design purposes there are some ACI code
specifications.
Such as…..
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18. The ACI code specifies the minimum thickness in the following table
For all slabs of normal weight concrete unless calculation of deflection
proves that lesser thickness may be used without adverse effect.
MINIMUM SLAB THICKNESS
In WSD
Nilson book (7th edition)pp-190
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19. MINIMUM SLAB THICKNESS
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20. SPAN
According to ACI code 8.7.1
If the slab rests freely on its
supports the span length
may be taken equal to the
clear span plus the depth of
the slab but need not exceed
the distance between
centers of supports .
BAR SPACING
The lateral spacing of the
flexural bars should not
exceed 3 times the
thickness h or 18 inch
according to ACI code 7.6.5
The lateral spacing of
temperature and shrinkage
reinforcement should not
be placed farther apart than
5 times the slab thickness
or 18 inch according to ACI
code 7.12.2
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23. MINIMAM REINFORCEMENT RATIO
For temperature and shrinkage reinforcement :
According to ACI Code 7.12.2.1
Slabs with Grade 40 or 50 deformed bars…………. 0.0020
Slabs with Grade 60 deformed bars …………………. 0.0018
Slabs where reinforcement with yield strength
Exceeding 60000 psi …………………………………….....
For flexural reinforcement :
According to ACI Code 10.5.4,
the minimum flexural reinforcement is not to be less than the
shrinkage
reinforcement, or 0.0018
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24. MOMENT COEFFICIENTS
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25. MOMENT COEFFICIENTS
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28. Reinforcement Details in Slab
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29. Reinforcement Details in Slab
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30. Reinforcement Details in Slab
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32. An alternative of this arrangement is shown in the
next slide
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33. Nadim Hossain book pp- 268 33

34. Nilson 7th edition
Considering both way continuous
(see slide #27 for clarification)
**just an assumption here but the real
case can be different.
See the next slide for explanation of
real situation
EXAMPLE PROBLEM-Slab Design by WSD
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Real case: how to select slab thickness
Slab thickness for every individual
span should be calculated and the
maximum of these values will be
taken as the slab thickness

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EXAMPLE PROBLEM-Slab Design by WSD (cont’d)

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formula: As=M/ fs*j*d

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•Selection of reinforcing bars
from amount of reinforcement
is exactly similar to the case of
WSD problem
•Follow the previous problem
and find out size and number of
reinforcing bar. Also find the
amount of extra bars needed
if necessary.

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