1. Code Comparison between
IS and ACI 318
Presented by
K.Gokulprabhu
&
N.Kumaresan

2. General basic comparison
DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Loading combination
36.4.1
a) 1.5 DL +1.5 LL
b) 1.5 DL l+1.5 WL
c) 1.2 DL+1.2 LL+1.2wl
9.2.1
U= 1.4(D+F)
U= 1.2(D+F+T) (L+H+0.5(Lr or S or R)
U= 1.2D+1.6(Lr or S or R)+(L or 0.8W)
U=1.2D+1.6W+L+0.5(Lr or S or R)
U= 1.2D+E+L+0.2S
U= 0.9D+1.6W+1.6H
U= 0.9D+E+1.6H
Elastic modulus for concrete and steel
Ec=5000 (fck) N/mm2
Es=200xE3 N/mm2
8.5.1
Ec =57000f’c psi
Es =29x10­6 psi
Mu limit
Mu limit = Fck b d2
Mulimit=

3. DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Span to depth ratio in slab
23.2.1
Cantilever
Simply supported - 20
Continuous
One-way slab- 20
Continuous slab-24
Min reinforcement in slab
Plain bar-0.15%
High strength bar-0.12%
200/fy
Nominal cover
Columns
Not less than 40mm
When dimension is 200mm or size of bar is 12mm then cover is 25mm
Footings
Not less than 50mm
Slabs
Not less than 15mm
Beams not less than 20mm
Refer P-47 Table –16A of IS code to get the cover details for fire resistance  
Footing
Resting on mat – 2”
Resting on earth – 3”
Top of piles – 2”
Beams and columns
For dry conditions
Stirrups, spirals, ties – 1.5”
Main reinforcement – 2”
Exposed to earth
Stirrups, spirals, ties – 2”
Main reinforcement – 2.5”
No. 11bars – 0.75”
No. 14 – 18 bars – 1.5”

4. DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
T beams
23.1.1
For T beams
For L beams
8.10.3
Width of slab effective as T beam flange shall not exceed one quarter of the span length of the beam
Effective overhang of flange on either of web shall not exceed
- 8 * slab thickness
- ½ clear dist. Between the web
For slab on one side
- 1/12 of span of beam
- 6 * slab thickness
Minimum area of tension reinforcement a
Ast(min) = 0.85 b d / Fy
For flexural members
Ast(min) = 3fc’ /fy * bw*d
And not less than
200*bw*d / fy
For slabs and foundation
Astmin = 0.14%
Grade steel 0.2%
Grade 60 steel 0.18%

5. DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Minimum horizontal distance between the bars
26.3.2
Greater of this following
1)larger diameter of the bars
2)Size of the aggregate + 5mm
Slabs
Main bars – 3d or 300mm
Distribution bars – 5d or 450mm not greater than the above
Beams
Refer to the IS code P-46 Table-15 it depends on the percentage redistribution
Flexural member
And not greater than
Side face reinforcement
When depth >750mm
Total area of reinforcement = 0.1% area of the web and spacing not exceeding 300mm
10.6.7
When d >36”
Total longitudinal reinforcement not greater than half of the tensile reinforcement
Spacing Ssk not greater than d/6, 12” na and 1000Ab / (d-30)

6. DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Maximum spacing of the tension bars
26.3.3
1) 0% re distribution of the moment 180mm
2) For other percentage of redistribution refer table 15
Compression steel / Tension steel
1) M > Mu li mit compression steel is required
Asc = M - Mu li mit / (352 – fck) * (d - d’)
Ast = (Pt(limit) + Pt2) * b * d / 100
2) if M < Mu li mit compression steel is not required
Ast = Pt * b* d / 100
Span / Effective depth check
(a)
Basic span / Effective depth = 26
Effective span / MF * d  26
MF taken from fig 4&5 using Pt and fs
Fs = 0.58 *fy * (Astreq / Astpro) Or
MF (tension) = 1 / ( * fs – 0.625)  2
MF (compression) = 1.6 * Pc / Pc  1.5

7. c = taken from table 19 using Pt and fck values
DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Shear reinforcement
Asv = 0.46 Sv
0.87 fy
IfV > c
Asv = (v - Cv) b d
0.87fy d
c-refer table 19
 Cmax 2
V = vU / b*d
c = taken from table 19 using Pt and fck values
V < c shear reinforcement is not required
(Asv / Sv)min = (0.4 * b / 0.87 * fy)
c< v < c max / 2
(Asv / Sv) = Vu -c*b*d / 0.87*fy*d
c can be derived from this formula
c = 0.76 (fck*((1+5)^0.5 – 1))^0.5 / 6
 = 0.8*fck / 6.89*Pt
 Vn Vu
where
Vu – factored shear
Vn – nominal shear
Vn = Vc + VS
Vc = 2*fc’ bw*d
For members shear and flexure and for detailed analysis use
Vc = (1.9*fc’ w * Vu *d / Mu ) * bw*d
And not greater than 3.5*fc’ bw*d
Quantity
Vu *d / Mu not greater than 1
For members subj. to axial compression
Vc = 2* (1+Nu / 2000*Ag) * fc’* bw*d
For detailed analysis
Mm = Mu – Nu (4*h – d) / 8
Vc shall not be greater than
Vc = 3.5*fc’* bw*d * (1 + Nu / 500*Ag)

8. For members subjected to axial tension
DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Shear reinforcement
For members subjected to axial tension
Vc = 2*(1 + Nu / 500*Ag) *fc’* bw*d but not less than zero
Where Nu is negative for tension
Nominal shear strength provided by concrete when diagonal cracking results results from the combined shear and moment
Shear strength
Vci = 0.6*fc’* bw*d + Vd + Vi * Mcr / Mmax and not less than 1.7 *fc’* bw*d
Mcr = I / t * (6*fc’ + fpe – fd)

9. DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Spacing of shear reinforcement
Not greater than d/2
When V­s exceeds 4*fc’* bw*d the above spacing is reduced to 1/2
Minimum shear reinforcement
If Vu > ½ * Vc
Av = 0.75*fc’* bw*s / fy
Not less than 500* bw*s / fy
Spacing of the shear reinforcement
Vu >  * Vc
Vs = Vu -  * Vc / 
For straight bars
Vs = Av*fy*d / s
Inclined stirrups
Vs = Av*fy (sin + cos)*d / s
Group of bars all bent up
Vs = Av*fy*sin not greater than 3* fc’* bw*d
Spacing are calculation for straight bars
Av / s = Vu - *Vc / *fy­*d

10. DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Torsion
41.4.2
The longitudinal reinforcement shall be designed to resist an equivalent BM
Me1 = Mu + Mt
Mt = Tu (1+D/b / 1.7)
If Mt > Mu
Then longitudinal reinforcement shall be provided on flexural compression member to withstand the moment Me2
11.6.1
  11.6.3   
Torsion can be neglected when
For non prestressed members
Tu < f*fc’*(A2 cp / Pcp)
For non prestressed members subjected to axial tensile or compressive force
If it exceeds the condition as per
Calculate the factored torsional moment
For solid sections
For hollow sections

11. DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Transverse reinforcement
41.4.3
Total transverse reinforcement not less than 
Longitudinal reinforcement
Additional longitudinal reinforcement shall be not less than
Minimum torsion reinforcement
11.6.5
When Tu > values of
Not less than
Minimum total area of longitudinal torsional reinforcement
At least one longitudinal bar in each tie. When c/s exceeds 450mm additional reinforcement to be provided
At/ s shall not be less than

12. DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Spacing of the torsion reinforcement
Rectangular closed stirrups. Spacing shall not exceed x1, x1+y1 / 4 , 300mm
11.6.6
Spacing shall not exceed
 12” or PA/8
Column reinforcement
 39.4.1
0.8 to 6% of gross c/s area
4 – rectangular bars
6- circular bars
Minimum dia. 12mm
Spacing of bars not greater than 300mm
SPIRAL REINFORCEMENT
Ratio of volume of helical reinforcement to volume of core shall not be less than
10.9
Minimum longitudinal reinforcement
0.01% to 0.08% gross cross sectional area
Minimum bars
3 – triangular bars
6- enclosed spirals
Minimum diameter 3/8” no.3 bar
LATERAL TIES
Diameter not less than 0.02 times greater dimension of the member
No.3 to No. 5 bar
Vertical spacing of bar
Not greater than
-16 times dia. Longitudinal bar
- 48 times dia. Of tie bar

13. DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Column reinforcement d
Maximum pitch not greater than 75mm
LATERAL TIES
Pitch of the transverse reinforcement shall not be more than the least of the following
- least lateral dimension
- 16* dia. Longitudinal bar
- 300mm
dia. Of the lateral ties not less than ¼ of the largest longitudinal bar
Minimum diameter 3/8” no.3 bar
Diameter not less than 0.02 times greater dimension of the member
No.3 to No. 5 bar
Vertical spacing of bar
Not greater than
-16 times dia. Longitudinal bar
- 48 times dia. Of tie bar
- 0.5 times least lateral dimension
Foundations
Footing thickness
34.1.2
Thickness at the
Edge
Footing on soil not less than 150mm
Piles – 300mm
15.7
Depth of the footing above the bottom reiforcement should not be less than
- Footing on soil 6”
- footing on piles 12” 

14. DESCRIPTION
IS 456 – 2000
ACI
CLAUSE
Contents
Footing - Critical section for shear
D / 2 distance alround the face of the column
15.5.4
dp / 2, alround the face of the column
Minimum reinforcement in footings
34.5.2
Nominal reinforcement for concrete thickness greater than 1m shall be 360mm2.this provision does not supercede the requirement of the min. tensile reinforcement based on depth calculation
 Longitudinal reinforcement atleast 0.5% of the c/s area of the supported column
Astmin = bh
Grade steel 0.2%
Grade 60 steel 0.18%
Development length of bars
is taken from the table
12.2.1
For deformed bars
Not greater than 2.5
Ld not less than 12”

15. Slender Columns with biaxial bending
Isolated footing with Moment Click