DSS

2. 1. Subramanian N., Design of steel structures, Oxford
University Press
2. Design of Steel Structures by B. C. Punmia, 2017
3. Duggal S. K., Limit State Design of Steel Structures
4. S. S. Bhavikatti., Design of Steel Structures by Limit State
Method
References:

3. 1. IS: 800 – 2007, Indian Standard “GENERAL CONSTRUCTION IN
STEEL - CODE OF PRACTICE”( Third Revision)
2. SP-6(1)-1964, Hand Book No.1 for Structural Steel Sections
(Steel Table by Bhavikatti or Ramamrutham)
3. IS: 875 Part 3 – 1987, Indian Standard code of practice for
Design loads (other than Earthquake) for Buildings and
Structures – Wind Loads
IS Standards:

4. SYLLABUS

5. COURSE OUTCOMES

6. Module – I

7. Steel Roof trusses and Columns
Steel Water Tanks

8. Single layer or double layer domes
Truss bridges Plate girder
Roof truss and columns

9. Transmission towers
Chimneys

10.  Roof trusses for factories, cinema halls, auditorium etc.
 Crane girders, columns etc in industrial structures.
 Roof trusses and columns to cover platforms in railway stations and bus
stands.
 Single layer or double layer domes for auditorium, exhibition halls,
indoor stadiums etc.
 Plate girder and truss bridges for railway and roads.
 Transmission towers for microwave and electric power.
 Water tanks.
 Chimneys etc.
COMMON STEEL STRUCTURES

11.  High strength per unit mass - small size, save space and aesthetic view.
 Ductile material - does not fail suddenly.
 Assured quality and high durability - properties do not change with time.
 Structure can be erected easily - fast construction.
 Easy to strengthen and to repair – by welding additional sections.
 Easy to dismantle and transport - if bolted connections.
 If joints are taken care, it is the best water and gas storage structure.
 Steel has highest scrap value amongst all building materials.
 It is also a recyclable material.
Advantages of Steel Structures

12. Disadvantages of Steel Structures
 When placed in exposed conditions → corrosion → require frequent
painting and maintenance
 Strength reduces drastically in ire → Needs fire-proof treatment → Needs
additional Cost
 Excellent heat conductor → may transmit enough heat from a burning
location to adjoining room.
 Fatigue → one of the major drawbacks
 At stress concentration locations → steel may lose its ductility (tearing of
steel)

13. Fatigue Failures

14. Cracks will appear and cracks completely.

15. Physical Properties of Structural steel are:
→ Unit mass of steel () = 7850 kg/m3
→ Modulus of elasticity (E) = 2.0 × 105 N/mm2
→ Shear modulus or Modulus of rigidity (G) = 0.769 × 105 N/mm2
→ Poisson’s ratio (µ) in elastic range = 0.3
in plastic range = 0.5
→ Coefficient of thermal expansion (αt) = 12 × 10-6/oC
STRUCTURAL STEEL
(Refer IS 800-2007, Page 12, clause 2.2)

16. STRESS-STRIN CURVE FOR MILD STEEL

17. STRESS-STRAIN CURVE FOR MILD STEEL

18. Classification of Steel based on Manufacturing Process
(i) Cold Formed Sections,
(ii) Hot rolled Sections
Cold formed sections: produced by steel strips (thickness < 8mm)
→ Light in weight
→ Used for smaller loads where hot rolled becomes un-economical
→ To make light gauge structures
Hot Rolled Sections:
→ Simply called as Rolled Sections
→ More commonly used as structural steel

19. ROLLED STEEL SECTIONS
 Rolled steel I-sections (Beam sections): ISJB, ISLB, ISMB, ISWB, ISHB
 Rolled steel channel sections: ISJC, ISLC, ISMC, ISSC
 Rolled steel Angle sections: ISA (equal and unequal angle)
 Rolled steel T-sections: ISNT, ISHT, ISLT, ISJT
 Rolled steel tube sections
 Rolled steel bars
 Rolled steel flats
 Rolled steel plates
 Rolled steel sheets
 Rolled steel strips
J-Junior
L-Light
M-Medium
W-Wide flange
H-Heavy
SC-Special channel
N-Normal
HT-Heavy flanged T section

20. Rolled Structural shapes and dimensions
Specifications of all the structural steel sections are given in SP: 6 (1) – 1964.
The figures are given in page 19 of IS:800-2007.

21. An I-section is designated by its depth and weight.
ISLB 500 @ 735.8N/m → I-section is 500mm deep and the self weight is
735.8N per meter length.
A channel section is designated by its depth and weight.
ISLC 350 @ 380.6N/m → Channel section is 350mm deep and the self weight
is 380.6N per meter length.
Note:
 All standard I-beams and channels have a slope on the inside face of the
flange of 16.67%.
 ISLB and ISMB are the only I-sections being rolled in India. These are
suitable only for beams because of their sectional properties.
 For columns, ISHB section is most suitable, but since they are not rolled,
ISMB section is used for columns as well.

22. A T-section is designated by its depth and weight.
ISNT 150 @ 223.7N/m → the T-section is 150mm deep and the self weight is
223.7N per meter length.
An angle section is designated by its leg lengths and thickness.
ISA 40×25×6mm → the section is an unequal angle with legs of 40mm and
25mm length and the thickness of the legs is 6mm.
Steel plates are designated by length, width and thickness.
ISPL 2000×1000×8mm → the plate is 2000mm long 1000mm wide and 6mm
thick.

23. Properties of some typical structural steels which conform IS: 2062
(Refer IS 800-2007, Page-14, Table 1)

24. Comparison b/w Physical Properties of Major Structural Materials
Properties Mild Steel Concrete (M20)
Unit mass (kg/m3) 7850 2400
Maximum Stress (MPa)
Compression 250 20
Tension 250 3.13
Shear 144 2.8
Young’s Modulus (MPa) 2×105 22,360
Coefficient of linear expansion (oC) 12×10-6 10 –14×10-6
Poisson’s ratio 0.3 0.2

25. DESIGN PHILOSOPHIES
1. Working Stress Method (WSM)
2. Ultimate Load Design (ULD)
3. Limit State Design (LSD)
LOAD AND LOAD COMBINATION
Refer IS 800-2007, Page-15, Clause 3.2 to 3.5
Refer IS 800-2007, Page-28,
Clause 5.2

26. Design Criteria in Limit State Design
 Design Action  Design Strength
i.e. Load factor × characteristic Load
< characteristic strength / material factor
26
Limit State: the states beyond which the structure no longer
satisfies the performance requirements specified.

27. LIMIT STATE DESIGN
27
1. Limit State of Strength
2. Limit State of Serviceability
a. Loss of equilibrium of structure
b. Loss of stability of structure
c. Failure by excessive deformation
d. Fracture due to Fatigue
e. Brittle fracture
a. Deformations/deflections
b. Vibrations
c. Repairable damage due to fatigue
d. Corrosion and durability
e. Fire
Refer IS 800-2007,
Page-28, Clause 5.2

28. SECTION 5 LIMIT STATE DESIGN
 5.1 Basis for Design (page 27)
 5.2 Limit State Design
 5.3 Actions or Loads
 5.4 Strength
 5.5 Factors Governing the Ultimate Strength
 5.5.1 Stability
 5.5.2 Fatigue
 5.5.3 Plastic Collapse
 5.6 Limit State of Serviceability
 5.6.1 Deflection
 5.6.2 Vibration
28
and Table 6 → Deflection Limits (page 31)
and Table 4 → PSF for load (page 29)
and Table 5 → PSF for Material strength (page 30)
5.6.3 Durability
5.6.4 Fire Resistance
IS: 800 – 2007

29. 29
CONNECTIONS
 Riveted Connections
 Bolted Connections
 Welded Connections

30. 30
Riveted Connections
Riveting is a method of joining together pieces of metal by inserting ductile
metal pins called rivets into holes of pieces to be connected and forming a
head at the end of the rivet to prevent each metal piece from coming out.

31. 31
Disadvantages of Riveted Connections
 It is associated with high level of noise pollution.
 It needs heating the rivet to red hot.
 Inspection of connection is a skilled work.
 Removing poorly installed rivets is costly.
 Labour cost is high.

32. 32
Bolted Connections
A bolt is a metal pin with a head formed at one end and a shank threaded at the
other end in order to receive a nut. Bolts are used for joining together pieces of
metals by inserting them through holes in the metal and tightening the nut at
the threaded ends.

33. 33
Types of Bolts
(1) Unfinished Bolts; (ordinary or common or rough or black bolts)
(2) High Strength friction bolts
(1) Unfinished Bolts; (Refer Table 1, pg-13, IS:800-2007)

34. 34
(2) High Strength friction bolts
Commonly used grades of bolts are 8.8S, 10.9S (written at cap of bolt)
 8.8S (diameter < 16 mm) ult. Stress 800 Mpa yield stress 640 MPa
8.8S (diameter > 16 mm) ult. Stress 830 Mpa yield stress 660 MPa
10.9S ult. Stress 1040 Mpa yield stress 940 MPa

35. 35
Advantages and Disadvantages of Bolted Connection

36. 36
Concentric Connections Eccentric Connections
Types of Bolted Connections
1. Classification based on type of resultant force to be transferred
a) Concentric → when load passes through CG of connection
→ in case of axial loads
a) Eccentric → load is away from CG of connection
→ such as bracket connection, seat connection, beam-column
connection in framed structures

37. 37
Concentric Connections
Eccentric Connections

38. 38
2. Classification based on type of force experienced by the bolts
a) Shear connection → Shear force in bolt
→ lap joint, butt joint
Shear Connections
Single
shear
Double
shear

39. 39
b) Tension connections → Tension on bolts
→ hanger connections
Tension Connection

40. 40
c) Combined shear and tension connection
→ inclined member connected to a bracket
→ bracing connections
Combined Tension plus Shear Connection

41. 41
3. Classification based on Load transfer mechanism in the Bolts
a) Bearing type (Unfinished or Ordinary Bolts)
b) Friction grip type (High Strength friction bolts)
Bearing type
M5 to M36.
M16, M20, M24 and
M30 are common
Friction grip type
M16 to M36.
M16, M20, M24 and
M30 are common

42. 42
Force Transfer Mechanism In
Bearing Type Bolted Connection
Force Transfer Mechanism In
HSFG Type Bolted Connection

43. 43
Force Transfer Mechanism In Bearing Type Bolted Connection
Force Transfer Mechanism In HSFG Type Bolted Connection

44. 44
 Lap Joints
 Butt Joint
Types of bolted joints based on the method of connection:
 Shear strength of double cover butt joint = 2 × Shear strength of Lap joint
 In double cover butt joint → no bending

45. 45
Types of Failure in Bolted Joints
Source: Design of steel structures by Subramanian N

46. 46
Block Shear
Source: Design of steel structures by Subramanian N

47. 47
Terminology in Bolted Connection
IS:800-2007 Specifications for Spacing and Edge Distances
of Fasteners
(Refer clause 10.2.2 to 10.2.5, pg-73, IS:800-2007)

48. 48
(Refer clause 10.2.2 to 10.2.5, pg-73, IS:800-2007)

49. 49
(Table 19, pg 73 – IS: 800)

50. 50
Strength of Bearing type Bolted Connection
Strength of a bolt or Bolt value = Minimum of
1) Strength of bolt in shear
2) Strength of bolt in bearing, and
3) Strength of bolt in tension
Strength of joint = Minimum of
a) strength of bolt or bolt group, and
b) net tensile Strength of plate

51. 51
1. DETERMINATION OF SHEARING STRENGTH OF BOLT:
where
fub or fu =Ult. tensile strength of bolt (Table 1, pg 13)
nn = No. of shear planes with threads
ns = No. of shear planes without threads (shanks)
Asb = Nominal area of shank
Anb = Net c/s area of bolt  0.78 d2/4
Design shear capacity of bolt, Vdsb = Vnsb / γmb
where mb = partial safety factor of material of bolt = 1.25
Nominal Shear capacity of bolt,
(Refer 10.3.3, pg 75 – IS: 800)
(Refer Table 5, pg 30 – IS: 800)

52. 52
(Refer 10.3.3, pg 75 – IS: 800)

53. 53

54. 54
(Table 1, pg 13 – IS: 800)
(Table 5, pg 30 – IS: 800)

55. 55
(a) Reduction factor in shear for Long Joints
If the length of joint > 15d → Long Section
If the section is long → Stress in outer bolts > inner bolts
→ Need to apply Reduction factor (βij)
βij accounts for overloading of the end bolts
Where, lj = length of joint
= distance between first and last row of bolts measured in
direction of load

56. 56
(Refer 10.3.3.1)

57. 57
(b) Reduction factor in shear for Large grip length
(i.e. due to more thickness of plates)
More thickness of plates → more grip length of bolt
→ More Bending Moment in Section
For the safe design → Need to apply a reduction factor for large grip
length (βlg)
If total thickness of the connected plates > 5 x nominal dia of the bolt
→ more grip length → Use βlg

58. 58
(Refer 10.3.3.2)

59. 59
(c) Reduction factor for packing Plates
If packing plate thickness > 6 mm,
→ bending is developed in shank
→ Need to apply a reduction factor in shear capacity (βpk)
where tpk = thickness of packing plate
The nominal shear strength of the bolt

60. 60
(Refer 10.3.3.3)

61. 61
2. DETERMINATION OF BEARING STRENGTH (CAPACITY) OF BOLT
Nominal bearing strength of bolt
= projected bearing area × ultimate Tensile stress
The design bearing strength of a bolt on any plate,
(Refer 10.3.4, pg 75 – IS: 800)

62. 62
(Refer 10.3.4)

63. 63
3. DETERMINATION OF TENSILE STRENGTH OF BOLT
Nominal tensile capacity of bolt is given by
(Refer 10.3.5, pg 76 – IS: 800)
Ex: Hanger connections

64. 64
(Refer 10.3.5)

65. 65

66. 66
4. DETERMINATION OF TENSILE STRENGTH OF PLATE
The design strength of a plate in tension, Tdn
Where,
fu = ultimate stress in MPa
An = net effective area in mm2
m1 = partial safety factor = 1.25
(Refer 6.3.1, pg 32 – IS: 800)

67. 67
(Refer 6.3.1, pg 32 – IS: 800)

68. 68
STRENGTH AND EFFICIENCY OF JOINT
Example Problems on Bearing type
Bolted connections
 = Strength of bolted joint/gauge x 100
Strength of solid plate/gauge