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General
- RC design
Topics:
Section
properties of reinforcing bars
|
Bar
|
Nominal
diameter
|
Cross
Section
|
Perimeter
|
Normal
weight
|
|
No.
|
in
|
mm
|
in
|
mm
|
in
|
mm
|
in
|
mm
|
|
3
|
0.375
|
9.52
|
0.11
|
71
|
1.178
|
29.9
|
0.376
|
0.56
|
|
4
|
0.5
|
12.7
|
0.2
|
129
|
1.571
|
39.9
|
0.668
|
0.994
|
|
5
|
0.625
|
15.88
|
0.31
|
200
|
1.963
|
49.9
|
1.043
|
1.552
|
|
6
|
0.75
|
19.05
|
0.44
|
284
|
2.356
|
59.8
|
1.502
|
2.235
|
|
7
|
0.875
|
22.22
|
0.6
|
387
|
2.749
|
69.8
|
2.044
|
3.042
|
|
8
|
1.000
|
25.4
|
0.79
|
510
|
3.142
|
79.8
|
2.67
|
3.973
|
|
9
|
1.128
|
28.65
|
1.00
|
645
|
3.544
|
90.0
|
3.4
|
5.06
|
|
10
|
1.27
|
32.26
|
1.27
|
819
|
3.990
|
101.4
|
4.303
|
6.404
|
|
11
|
1.541
|
35.81
|
1.56
|
1006
|
4.43
|
112.5
|
5.313
|
7.907
|
|
14
|
1.693
|
43.00
|
2.25
|
1452
|
5.32
|
135.1
|
7.65
|
11.38
|
|
18
|
2.257
|
57.33
|
4.00
|
2581
|
7.09
|
180.1
|
13.6
|
20.24
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Type
of cements
|
Type
|
Name
|
Description
|
|
I
|
Normal
|
General purpose
|
|
II
|
Moderate
|
Moderate sulfate and heat resistance
|
|
III
|
High early strength
|
Fast strength development
|
|
IV
|
Low-heat
|
Generate low-heat during hydration
|
|
V
|
Sulfate-resisting
|
High sulfate resistance
|
Elastic
modulus of concrete
The elastic modulus of concrete, Ec
(lb/in2) is (ACI 318-05 Sec 8.5)
Ec
= wc1.5 (33) Öfc’
lb/in2
Ec = wc1.5
(0.043) Öfc’
MPa
where wc
is unit weight of concrete between 90 to 155 lb/ft3. fc’ is compression strength of concrete in
lb/in2.
For normal weight
concrete
Ec
= 57000 Öfc’
Modulus
of rapture
fr
= 7.5 Ö
fc’ lb/in2.
fr
= 0.62 Ö
fc’ MPa
|
Concrete
strength
|
Elastic
modulus
|
Modulus
or rapture
|
|
psi
|
MPa
|
ksi
|
MPa
|
psi
|
MPa
|
|
3000
|
20.7
|
3156
|
21759
|
411
|
2.8
|
|
3500
|
24.1
|
3409
|
23503
|
444
|
3.1
|
|
4000
|
27.6
|
3644
|
25126
|
474
|
3.3
|
|
4500
|
31.0
|
3865
|
26650
|
503
|
3.5
|
|
5000
|
34.5
|
4074
|
28091
|
530
|
3.7
|
|
5500
|
37.9
|
4273
|
29462
|
556
|
3.8
|
|
6000
|
41.4
|
4463
|
30772
|
581
|
4.0
|
|
6500
|
44.8
|
4645
|
32029
|
605
|
4.2
|
|
7000
|
48.3
|
4821
|
33238
|
627
|
4.3
|
|
7500
|
51.7
|
4990
|
34405
|
650
|
4.5
|
|
8000
|
55.2
|
5154
|
35533
|
671
|
4.6
|
Design
load combinations from ASCE 7-98
Load combination
or strength design (ASCE 7-98, sec, 2.3.2)
1. 1.4(D+H)
2.
1.2(D+F+T)+1.6(L+H)+0.5(Lr or S or R)
3. 1.2D+1.6(Lr or S
or R)+(0.5L or 0.8W)
4.
1.2D+1.6W+0.5L+0.5(Lr or S or R)
5.
1.2D+1.0E+0.5L+0.5(Lr or S or R)
6. 0.9D+1.6W+1.6H
7. 0.9D+1.0E+1.6H
Load combination for allowable stress design (ASCE 7-98, Sec. 2.4.1)
1. D
2. D+L+F+H+T+(Lr or
S or R)
3. D+(W or 0.7E)+L+(Lr
or S or R)
4. 0.6D+W+H
5. 0.6D+0.7E+H
Where D is dead
load, L is live load, Lr is roof live load, W is wind load, E is earthquake
load, F is fluid pressure, R is rain load, S is snow load, T is temperature
force.
Note: A 75% load
reduction is allowed on two or more loads plus dead load for allowable stress
design on load combination 2 to 5. For
example, load combination can be D+0.75(W+L).
Design
load combinations from ACI 318-05
Load combination
or strength design (Sec 9-2)
1.
1.4(D+F)
(9-1)
2.
1.2(D+F+T)+1.6(L+H)+0.5(Lr or S or R)
(9-2)
3. 1.2D+1.6(Lr or S
or R)+(1.0L* or 0.8W)
(9-3)
4. 1.2D+1.6W**+1.0L*+0.5(Lr or S or R)
(9-4)
5. 1.2D+1.0E***+1.0L*+0.2S
(9-5)
6. 0.9D+1.6W**+1.6H
(9-6)
7. 0.9D+1.0E***+1.6H
(9-7)
*1.0L can be reduced
to 0.5L except garages, public assembly and area that has 100 lb/ft2
of live load.
**1.6W can be
reduced to 1.3W when wind load W is not reduced by directional factor (See ASCE
7-02 wind calculation)
*** Where seismic
load, E is calculated based on service load, 1.4E shall be used instead of 1.0E.
Strength
reduction factor, f,
ACI 318-05
1.
Tension-controlled sections, 0.9 (Sec. 9.3.2.1)
2.
Compression-controlled sections (Sec. 9.3.2.2)
(a) Column with
spiral reinforcement, 0.7
(b) Tie columns,
0.65.
3. f
is permitted to vary from 0.65 to 0.9 when the net tensile strain in
extreme tension steel at nominal strength varies from compressive control strain
to 0.005.
4. Shear and
torsion, 0.75 (Sec. 9.3.2.3)
5. Bearing on
concrete, 0.65 (Sec. 9.3.2.4)
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