1. IS: 800-2007--- Indian Code of Practice for Construction in Steel
Dr. T. K. Bandyopadhyay
Joint Director general
Institute for Steel Development & Growth

2. TOPICS COVERED INTRODUCTION BRIEF DISCUSSION ON DESIGN METHODOLOGIES
BRIEF OVERVIEW OF IS 800 (2007)
IS 800 (2007) & OTHER INTERNATIONAL CODES
CONCLUSIONS

3. INTRODUCTION
Codes & Standards provides specifications and stipulations for state-of-the-art design to be put into practice.
Codes and Standards pertaining to Steel Design must be
Understandable
Shall be based on good structural theory
Shall deal with elastic instability, dynamic loads and fatigue
IS Basic Code for Design of Steel Structures
The code was revised in the year 2007 and available since Feb’08 i.e. after release of the document.
Earlier version of the code was much outdated compared to the recent developments in steel design all over the world.

4. INTRODUCTION
Earlier IS: 800 was based on Allowable Stress design (ASD) methodology.
Methodology of Design of Steel Structures has undergone major changes during the last two decades due to research all over the world.
Revision of many other steel related codes in India are also dependent on revision of IS 800.
An out-dated code is detrimental to the very purpose of the code of practice itself.
Thus, revision of IS 800 was essential to include design stipulations as are prevalent all over the world and to ensure availability of efficient sections.

5. Table: 1 Countries and their Design Format
INTRODUCTION
Almost all countries are adopting more efficient techniques of design based on various efficient codes.
The current practice all over the world is based on Limit State Method (LSM) or Load and Resistance Factor Design (LRFD) method.
Country wise practice of design procedure is given in Table 1.
Table: 1 Countries and their Design Format
Australia, Canada, China, Europe, U.K., Japan
Limit State Method (LSM)
U. S. A
Load and Resistance factor Design (LRFD) Method & Allowable Stress Design (ASD)
India
Allowable Stress Design (ASD)

6. INTRODUCTION
LSM has become the design philosophy in most of the International design standards.
LSM design ensures
Rationality in Design
Economy of Design
In India it was felt that IS: 800 should be modified to LSM keeping ASD as a transition alternative.
It was also felt that this modification would render steel design novel and will facilitate accuracy of design.
However, it is important that the basic philosophy of both the design methods is understood by all.

7. BRIEF DISCUSSION ON DESIGN METHODOLOGIES
ASD METHODS
Unit stress is not allowed to exceed a pre-defined allowable stress,
factual < fallowable where
The allowable stress is defined by a limiting stress divided by a factor of safety
fallowable = (fy / Fs)
(fy = minimum yield stress and Fs = factor of Safety)
Factor of safety (Fs) is fixed.

8. BRIEF DISCUSSION ON DESIGN METHODOLOGIES
ASD METHODS (Contd.)
No matter how variable the loads are in terms of frequency or magnitude, the factor of safety is always the same.
Advanced knowledge about strength of materials beyond yield point and its plastic plateau led to the development of LSM as an alternative to ASD.
A better way than “Effective length” methods can also be adopted using Merchant – Rankine approach to find the limiting load of the whole structure.
1/Plimit = 1/Pfield + 1/Pcritical
Where, Plimit, Pfield, and Pcritical are the factored limit load of the structure, load at plastic collapse ignoring instability, and the elastic critical load of the structure respectively.

9. BRIEF DISCUSSION ON DESIGN METHODOLOGIES
B. LIMIT STATE METHOD (LSM)
It incorporates Load Factors to take into account of the variability of loading configurations.
A rational but variable factor of safety in different structural performance enables to use steel efficiently and economically in different structural systems to withstand tension, compression etc.
LSM considers the good performance of steel in tension compared to compression and specifies variable factors.

10. BRIEF DISCUSSION ON DESIGN METHODOLOGIES
B LIMIT STATE METHOD (LSM)
This method renders a structure or part of it unfit for use when it exceeds the limit states.
Beyond this limit states the structure infringes one of the criteria governing its performance.
The two limit states are classified as
Ultimate Limit States It takes care of the structure from strength point of view
Serviceability Limit States ---- It takes care of the structure in terms of safe operation

11. BRIEF DISCUSSION ON DESIGN METHODOLOGIES
B LIMIT STATE METHOD (LSM)
The criteria which defines ultimate limit states are
Strength (Yielding & Buckling)
Stability against Overturning and Sway
Fracture due to Fatigue
Brittle failure
Serviceability limit states takes care of the performance and behavior of the structure during its service period.
The criteria which defines serviceability limit states are
Deflection (including drift)
Vibration
Fatigue checks (including reparable damage due to fatigue)
Corrosion

12. BRIEF DISCUSSION ON DESIGN METHODOLOGIES
B LIMIT STATE METHOD (LSM)
LSM considers the critical local buckling stress of the constituent plate elements of a beam.
Based on slenderness ratio of constituent plate element a section may be classified as
Plastic
Compact
Semi-compact
Slender

13. BRIEF DISCUSSION ON DESIGN METHODOLOGIES
B LIMIT STATE METHOD (LSM)
In LSM, the factored loads, in different combinations, are applied to the structure to determine the load effects.
These are then compared with the design strength of the elements.

14. BRIEF DISCUSSION ON DESIGN METHODOLOGIES
B LIMIT STATE METHOD (LSM)
Mathematical representation of strength check criteria in LSM is
(Function of sy and other geometric variables)
where gL =
partial factor for loads. gf
factor that takes account of inaccuracies in assessment of loads, stress distribution and construction.
gm1 & , gm2
factors that take into account, uncertainty in material strength and quality, and manufacturing tolerances respectively. Qk
specified nominal load. sy
yield strength of the material.

15. BRIEF OVERVIEW OF IS 800 (2007)
A steel member subjected to external system of loading may be subjected to one of the following:
Compression
Tension
Bending
Combined effect of Bending and Tension
Combined effect of Bending and Compression
The basic stresses in a member are either
Compressive
Tensile
Shear
The primary forces are
Compressive forces
Tensile forces
Bending Moments

16. Comparative Study of Design Outputs between ASD and LSM
BRIEF OVERVIEW OF IS 800 (2007)
Comparative Study of Design Outputs between ASD and LSM
The comparisons have been made by designing various sets of members subjected to same tensile, compressive, or flexural Loads.
The charts shown give an account of the percentage of design strength of a member utilised in WSM w. r. t. percentage in LSM.
It may be seen that LSM gives more economy in tension and flexure, whereas in compression WSM gives better results.

17. BRIEF OVERVIEW OF IS 800 (2007) TENSION MEMBERS
Fig 1 Percentage strength utilized in Tension Members

18. BRIEF OVERVIEW OF IS 800 (2007) COMPRESSION MEMBERS
Fig 2 Percentage strength utilized in Compression Members

19. BRIEF OVERVIEW OF IS 800 (2007) COMPRESSION MEMBERS fcd / fy
Slender Ratio 
fcd / fy
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9 1
1.0
1.5
2.0
2.5
3.0
3.5 a b c d
Fig 3 Column Buckling Curves

20. BRIEF OVERVIEW OF IS 800 (2007) Cross Section Limits
Table: 2 Buckling Class of Cross Sections
Cross Section
Limits
Buckling about axis
Buckling Class
Rolled I - Section
h / b > 1.2: tf ≤ 40 mm
40 mm < tf ≤ 100 mm
z - z
y – y
z – z
y - y a b c
h / b ≤ 1.2: tf ≤ 100 mm
tf > 100 mm d
Welded I - Section
tf ≤ 40 mm
tf > 40 mm y d h tw b z tf h y tw tf b z

21. BRIEF OVERVIEW OF IS 800 (2007) Cross Section Limits
Table: 2 Buckling Class of Cross Sections (Contd.)
Cross Section
Limits
Buckling about axis
Buckling Class
Hollow Section
Hot Rolled
Any a
Cold Formed b
Welded Box section
Generally
(Except as bellow)
Thick Welds and
b / tf < 30
h / tw < 30
z – z
y - y c
Channel, Angle, Tee and solid Sections
Built-up Members y tw z b tf h y z y z

22. BRIEF OVERVIEW OF IS 800 (2007) FLEXURE MEMBERS
Fig 4 Percentage strength utilized in Flexure Members

23. Table: 3 Tension Members
PRAMETERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Partial Safety Factor
1.10
1.00
 1.11
1.25
1.20
(In eff. Area)
 1.31 -
0.90
Fabrication Factor
For Punched Hole, dh
dh + 2mm dh
For Drilled Hole, dh
Gross Section Capacity
fy Ag / gmo
f fy Ag
(f = 0.90)

24. Table: 3 Tension Members (Contd.)
PARAMETERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Net Section Capacity
0.9Anfu / gm1
fy Ae
f 0.85 An fu
f. Ae.fu
(f = 0.75)
Plates (Bolted Conn.)
- do -
Plates (Welded Conn.)
Angles
0.9Anc fu / gm1 + b Ago fy / gmo
U An fu / gm1
f 0.85 kt An fu
Single Angle (Bolted)
fy (Ae – 0.5a2 )
kt = 0.85
Double Angle (both side of Gusset) - bolted
fy (Ae – 0.25a2 )
kt = 1.00
Double Angle (Same side of Gusset) - bolted
Single Angle (Welded)
fy (Ae – 0.3a2 )
Double Angle (both side of Gusset) - Welded
fy (Ae – 0.15a2 )
Double Angle (Same side of Gusset) - Welded

25. Table: 3 Tension Members (Contd.)
PARA-
METERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Shear Lag Factor, U
U (General) - kt
Angle (n = 1)
2(e2-0.5do)/An
0.85
0.60
Angle (n = 2)
Angle (n = 3)
Angle (n = 4 or more)
0.80
Unequal angle (short leg conn.)
0.75
Other shapes (n=2)
Other shapes (n=4)

26. Table: 3 Tension Members (Contd.)
PARA-
METERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Block Shear capacity (Case – 1)
Shear Plane capacity
0.6 Avg.fy -
f 0.6 Anv Fy
Tension Plane Capacity
0.9 Atn.fu / gm1
0.6 Ke Atn.fy
f Ubs Agt Fu
Ubs = 1 for uniform tensile stress
Ubs = 0.5 for uniform tensile stress
Block Shear capacity (Case – 2)
f 0.6 Agv Fy
Atg.fy / gmo
f Ubs Ant Fu

27. Table: 3 Tension Members (Contd.)
where n =
Number of bolts
Avn
Net shear plane area d
Diameter of fasteners
Atg
Gross tension plane area dh
Diameter of fastener hole
Atn
Net tension plane area x
Connection eccentricity a2
Area of outstanding leg An
Net area fu
Ultimate tensile stress Ae
Effective area fy
Yield stress
Avg
Gross shear plane area L
Length of connection

28. Table: 4 Compression Members
PARAMETERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Effective Area of Cross Section
Plastic Section
Ae = Ag
Ae =  be.t = Ag
Compact section
Non-compact section
Slender Section
Ae =  beff.t
Ae =  be.t
Capacity of Cross Section
fy.Ag / gmo
fy.Ag
f.kf .fy .An = f.fy .Ag (kf = 1)
fc.fy.Ag
f.kf .fy .An = f.fy .Ae (kf ≠ 1)
kf = Ae / Ag & An = Ag

29. Table: 4 Compression Members (Contd.)
PARAMETERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Eff. Slenderness Ratio, l
Plastic Section
Leff / r
Compact section
Non-compact section
Slender Section
Leff / r (Aeff / Ag )0.5
Section Capacity (Member Buckling)
c.fy.Ag / gmo
f ’y.Ag
f.ac.fy.Ag
fc.Fcr.Ag
c.fy.Ae / gmo
f ’y.Ae
f.ac.fy.Ae
fc.Fcr.Ae
c = f (L/r) ≤1
f ‘y = f (L/r)
ac = f (L/r) ≤1
Fcr = f (L/r) ≤1

30. Table: 4 Compression Members (Contd.)
PARAMETERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Buckling Curve
Rolled I -Section (z-z) tf ≤ 40 a -
Rolled I -Section (y-y) tf ≤ 40 b
Rolled I -Section (z-z) tf > 40
Rolled I -Section (y-y) tf > 40 c
Rolled H -Section (z-z) tf ≤ 40
b ( tf ≤ 100 )
Rolled H -Section (y-y) tf ≤ 40
c ( tf ≤ 100 )
Rolled H -Section (z-z) tf > 40
d ( tf ≤ 100 )
Rolled H -Section (y-y) tf > 40 d
Welded I -Section (z-z) tf ≤ 40
Welded I -Section (y-y) tf ≤ 40
Welded I -Section (z-z) tf > 40
Welded I -Section (y-y) tf > 40

31. Table: 4 Compression Members (Contd.)
PARAMETERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Buckling Curve (Contd.)
Welded Box-Section (z-z) tf ≤ 40 c b -
Welded Box-Section (y-y) tf ≤ 40
Welded Box-Section (z-z) tf > 40
Welded Box-Section (y-y) tf > 40
Hollow Section (Hot Rolled) a
Hollow Section (Cold Formed)
Channel, angles Tees
Two rolled section (Built-up)
Imperfection Factor ( Curve a )
0.21
 0.21
Imperfection Factor ( Curve b )
0.34
 0.34
Imperfection Factor ( Curve c )
0.49
 0.49
Imperfection Factor ( Curve d )
0.76
 0.76

32. Table: 5 Flexure Members (Compression Flange Laterally Restrained)
PARA-
METERS
IS 800
(2007)
BS 5950
(2000)
Euro
code
(1993)
AS 4100
(1998)
AISC 360
(2005)
Bending Resistance under low shear
[V ≤ 0.6Vd ]
Plastic Section
Zp.fy / gmo
≤ 1.2 Ze.fy / gmo
Zp.fy
f.Zp.fy
≤ 1.5 f. Ze.fy
Mp = f.Zp.fy
Compact Section
Non-compact section
Ze.fy / gmo -
Slender Section
Zeff.fy
Zeff.fy / gmo
f. Ze.fy (lsy – ls)
Zp = Plastic Section Modulus
Ze = Elastic section Modulus
Zeff = Effective Section Modulus
sp = Plastic Limit (Slenderness)
sy = Yield Limit (Slenderness)
s = Section Slenderness Ratio

33. Table: 5 Flexure Members (Compression Flange Laterally Restrained)
PARA-
METERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Bending Resistance (High shear) [V > 0.6Vd ]
Plastic Section
fy / gmo ( Zp - b.Zpv )
≤ 1.2 Ze.fy / gmo
fy ( Zp - b.Zpv ) -
Mp = f.Zp.fy
Compact Section
Non-compact section
Ze.fy / gmo
fy ( Ze - b.Zpv / 1.5)
fy / gmo ( Ze - b.Zpv )
Slender Section
fy ( Zeff - b.Zpv / 1.5)
fy / gmo ( Zeff - b.Zpv )
Zpv (equal Flanges)
Zp - Zf Zv
Zpv (unequal Flanges)
Zf = Plastic modulus of effective section excluding shear area
Zz = Plastic modulus of the shear area b
(2 V / Vd – 1) 2

34. Table: 6 Flexure Members (Compression Flange Laterally Un-restrained)
PARA-
METERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Buckling Resistance Moment
Plastic section
cLT.Zp.fy / gmo
fb.Zp
am.as.f.Zp.fy ≤ 1.5am.as.f.Ze.fy
Lp < Lb ≤ Lr -
Lb > Lr
f.Fcr.Ze
Compact section

35. Table: 6 Flexure Members (Compression Flange Laterally Un-restrained)
PARA-
METER
IS 800 (2007)
BS 5950 (2000)
Euro
(1993)
AS 4100
(1998)
AISC 360
(2005)
Buckling Resist. Moment
Non-compact Section
(cLT.Ze)fy /gmo
fb.Ze
cLT.Ze. fy /gmo
Lp< Lb ≤ Lr -
Lb > Lr
f.Fcr.Ze ≤ 0.9E kc.Ze / l2
Slender Section
fb.Zeff
cLT.Zeff. fy /gmo
Same as Non-compact Section
- Do -
cLt & fb = Depends on equivalent slenderness
am = Moment Modification Factor
as = Slenderness Reduction Factor

36. Table: 6 Flexure Members (Compression Flange Laterally Un-restrained)
PARAMETERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Equivalent Slenderness Ratio -
Imperfection factor (Rolled Section)
0.21
 0.21
Imperfection factor (Welded Section)
0.49
 0.49
Effective Length
Normal
Destab.
Warping restraint
0.70L
0.85L
Both Flanges fully Restrained
0.75L
0.90L
Comp. Flange fully restrained
0.80L
0.95L
Both Flanges partly Restrained
1.00L
Comp. Flange partly restrained
1.20L
Warping not restrained in both direction
Compression Flange laterally restrained against torsion

37. Table: 6 Flexure Members (Compression Flange Laterally Un-restrained)
PARAMETER
IS 800
(2007)
BS 5950
(2000)
Euro
(1993)
AS 4100
(1998)
AISC 360
(2005)
Effective length (Contd.)
Norm
Destab -
Partially restrained by bottom flange support connection
1.0L+ 2D
1.2L+ 2D
Partially restrained by bottom flange bearing support
1.4L+ 2D
Compression flange laterally restrained against torsion
Permissible Shear Vd
Av.fy / (3.gmo)
0.6 fy.Av
0.6 f fy.AwCv
dw / tw ≤ 82 / (fy / 250) 0.5
f 0.6 fy.Av
dw / tw > 82 / (fy / 250) 0.5
av.f 0.6 fy.Av
 = 0.9 to 1.0
Cv ≤ 1.0

38. Table: 6 Flexure Members (Compression Flange Laterally Un-restrained)
PARAMETERS
IS 800
(2007)
BS 5950
(2000)
Eurocode
(1993)
AS 4100
(1998)
AISC 360
(2005)
Shear Area
Hot Rolled I & H Section
(Major Axis Bending)
h.tw
A – 2b.tf + (tw + 2r).tf
Rolled Channel Section
A – 2b.tf + (tw + r).tf
Welded I, H & Box Section
 (d.tw)
Rolled & Welded I, H & Box Section
(Minor Axis Bending)
2 b.tf
1.8 b.tf
A -  (d.tw)
RHS Loaded parallel to depth ( h )
A h / (b + h)
0.9A h / (b + h) -
RHS Loaded parallel to width ( b )
A b / (b + h)
0.9A b / (b + h)
CHS
2 A / 
0.6 A
Plates and Solid Bars A
0.9 A _

39. CONCLUSIONS
It is evident from the comparative charts shown above, with load factors and partial safety factors being proposed keeping Indian conditions in consideration.
The code has been mainly modeled in line with the Eurocodes which are generally referred for design in the European Countries.
Additional references have been taken from the existing British Codes also.

40. CONCLUSIONS Contd.
An important aspect of this latest code is that this code does not totally exclude the existing Allowable Stress Design (ASD) method of analysis.
One chapter in this code has been totally dedicated to design concepts based on the ASD method, with certain modification from the Indian Standard (IS ) Code.
In American code, both ASD and LRFD method of design is equally prescribed.
In case of IS 800, ASD method with minor modification has been included to help in making a smooth and proper transition of design practice in India from ASD philosophy to LSM philosophy.

41. Institute for Steel Development & Growth
Thank You
Institute for Steel Development & Growth