MANILA: Room 206, JPD Building, CM Recto Avenue, Manila
CEBU: 4/F J. Martinez Bldg., Osmeña Blvd., Cebu City
Telephone Number: (02) 516-7559 (Manila) E-Mail: buksmarquez1 @yahoo.com
(032) 254-9967 (Cebu)
Review MODULE –
REINFORCED CONCRETE DESIGN (USD SLABS)
SECTION 407- ONE-WAY SLAB (NSCP 2015)
-bending in one direction only
c.
d.
e.
Breadth to length ratio, m
𝑚=
Where:A
S= clear short span
L=clear long span
𝑆
< 0.50
𝐿
Table 407.3.1.1 Minimum Thickness of Solid Non-Prestressed One-Way
Slabs
Support Condition
Minimum h[1]
Simply supported
𝑙/20
One-end continuous
𝑙/24
Both end continuous
𝑙/28
Cantilever
𝑙/10
Expression applicable for normal weight concrete and 𝑓𝑦 = 420 𝑀𝑃𝑎. For other
cases, minimum h shall be modified in accordance with Section 407.3.1.1.3
[1]
Sec.407.3.1.1.1 For 𝑓𝑦 other than 420 MPa , the expressions in Table 407.3.1.1
shall be multiplied by (𝟎. 𝟒 + 𝒇𝒚 /𝟕𝟎𝟎)
Sec.407.3.1.1.2 For non-prestressed slabs made of lightweight concrete having
𝑤𝑐 in the range of 1440 to 1840 kg/m3, the expressions in Table 407.3.1.1 shall
be multiplied by the greater of (a) and (b)
a. 𝟏. 𝟔𝟓 − 𝟎. 𝟎𝟎𝟎𝟑𝒘𝒄
b. 𝟏. 𝟎𝟗
SITUATION 1. The figure shows the plan and cross-section of a solid one-way slab.
L1= 2.0 m
L2= 5.6 m
L3= 4.8 m
S1
S2
S3
L1
L2
L3
h
𝐿 ≤ 3𝐷
There are at least two spans
The longer of two adjacent spans does not exceed the shorter by
more than 20 percent.
Table 406.5.2- Approximate moments for nonprestressed continuous
beams and one-way slabs
Moment
Location Condition
Mu
Discontinuous end integral with
𝑤𝑢 𝑙𝑛2 /14
End span support
Positive
Discontinuous end
𝑤𝑢 𝑙𝑛2 /11
unrestrained
Interior
All
𝑤𝑢 𝑙𝑛2 /16
spans
Interior
Member built integrally with
𝑤𝑢 𝑙𝑛2 /24
face of
supporting spandrel beam
exterior
Member built integrally with
𝑤𝑢 𝑙𝑛2 /16
support
supporting column
Exterior
Two span
𝑤𝑢 𝑙𝑛2 /9
face of
first
More than two spans
𝑤𝑢 𝑙𝑛2 /10
interior
Negative[1] support
Face of
other
All
𝑤𝑢 𝑙𝑛2 /11
supports
Face of
(a) slabs with span not
all
exceeding 3 m
supports
(b) beams where ratio of sum
𝑤𝑢 𝑙𝑛2 /12
satisfying of column stiffness to beam
(a) or
stiffness exceeds 8 at each
(b)
end of span
[1] To calculate negative moments, 𝑙
length.
𝑛 shall be the average of the adjacent clear span
Table 406.5.4- Approximate shears for nonprestressed continuous beams
and one-way slabs
Location
Vu
Exterior face of first interior
1.15𝑤𝑢 𝑙𝑛 /2
support
Face of all other supports
𝑤𝑢 𝑙𝑛 /2
Flexural Reinforcement
Sec.407.6.1.1 A minimum area of flexural reinforcement A s,min shall be provided
in accordance with Table 407.6.1.1
SECTION VIEW
1.
2.
3.
Find the minimum thickness of slab S1.
Find the minimum thickness of slab S2.
Find the minimum thickness of slab S3.
SITUATION 2. Given the concrete section of the solid one-way slab shown in
Situation 1 has unit weight of 1800 kg/m3. The reinforcing steel bars used has
strength of fy= 345 MPa.
4. Calculate the thickness of slabs S1, S2 and S3.
SITUATION 3. A one –way slab having a thickness of 160 mm is reinforced with 12
mm ø bars spaced at 150 mm center to center. Assuming the steel cover of 25 mm
and fc’= 21 MPa and fy= 276 MPa
5. Compute the effective depth of the slab.
6. Compute the steel ratio of the slab
7. Compute the ultimate moment capacity of the slab.
Simplified Method of Analysis for Non-Prestressed Continuous Beams
and One-way Slabs
Sec.406.5.1 It shall be permitted to calculate Mu and Vu due to gravity loads in
accordance with this section for continuous beams and one-way slabs satisfying
(a) through (e)
a. Members are prismatic
b. Loads are uniformly distributed
Table 407.6.1.1 Asmin for Non-prestressed One-way Slabs
Reinforcement
fy, MPa
As,min
Type
Deformed bars
<420
0.0020Ag
0.0018𝑥420
Deformed bars
Ag
𝑓𝑦
or welded wire
> 420
Greater of
0.0014Ag
reinforcement
Sec.407.7.2.3 Maximum spacing s of deformed reinforcement shall be the
lesser of 3h and 450 mm.
Sec.425.2.1 For parallel non-prestressed reinforcement in a horizontal layer,
clear spacing shall be at least the greatest of 50 mm, d b, and (4/3)dagg.
MANILA: Room 206, JPD Building, CM Recto Avenue, Manila
CEBU: 4/F J. Martinez Bldg., Osmeña Blvd., Cebu City
Telephone Number: (02) 516-7559 (Manila) E-Mail: buksmarquez1 @yahoo.com
(032) 254-9967 (Cebu)
Review MODULE –
REINFORCED CONCRETE DESIGN (USD SLABS)
Shrinkage and Temperature Reinforcement
Sec.424.4.3.2 The ratio of deformed shrinkage and temperature reinforcement
area to gross concrete area shall satisfy the limits in Table 424.4.3.2
Table 424.4.3.2 Minimum Ratios of Deformed Shrinkage and Temperature
Reinforcement Area to Gross Concrete Area
Reinforcement
fy, MPa
Minimum reinforcement ratio
Type
Deformed bars
<420
0.0020
0.0018𝑥420
Deformed bars
or welded wire
> 420
Greater of
𝑓𝑦
reinforcement
0.0014
Sec.424.4.3.3 The spacing of deformed shrinkage and temperature
reinforcement shall not exceed the lesser of 5h and 450 mm
SITUATION 5. From the given floor plan, the following data are given:
𝐷 = 4.5 𝑘𝑃𝑎 (Weight of slab included)
𝐿 = 3.0 𝑘𝑃𝑎
𝑈 = 1.2𝐷 + 1.6𝐿
Beam dimensions, 𝑏𝑥ℎ = 300𝑥400 𝑚𝑚
Slab thickness= 100 𝑚𝑚
Slab reinforcement= 10 𝑚𝑚ø
Clear concrete cover to slab reinforcement= 20 𝑚𝑚
𝑆 = 2.6 𝑚
𝐿 = 6.0 𝑚
L
A
L
B
C
L
D
S
H
G
A
A
I
J
E
F
A
S
K
L
A
S
P
O
M
N
t=100
h=400
mm
b= 300
mm
SECTION A-A
8.
Determine the ultimate negative moment on the slab at the span
bounded by FGJK.
9. Determine the ultimate positive moment on the slab at the span bounded
by FGJK.
10. Determine the maximum spacing of the 10 mm ø bars as prescribed by
design codes.