1. By: Prof Dr. Akhtar Naeem Khan chairciv@nwfpuet.edu.pk
Lecture 04: Bolted Connections
By: Prof Dr. Akhtar Naeem Khan

2. Topics to be Addressed Types of connectors Tightening procedures
Behavior of Bolted & Riveted connections
Types of Bolted connections
Types of connection failures
Code Requirements
Design Examples

3. Types of Connectors
Components which make up the complete structure are fastened together by means of:
RIVETS (older version)
BOLTS (newer version)
WELDS

4. Types of Connectors Rivets:
They are made from rivet bar stock in a machine which forms one head and shears the rivet to desired length.
Steel rivets are always heated before driving
Most rivets are driven by pressure-type riveters which complete riveting in one stroke.
Typical Round Head Rivet

5. Types of Connectors Rivets:
Rivets are generally made from steel conforming to ASTM A502 and comes in 2 grades:
Grade 1(carbon steel)
Grade 2 (carbon-manganese steel)

6. Types of Connectors
Rivets:
Round Head Rivet
Countersunk Rivet

7. Types of Connectors
Rivets:

8. Types of Connectors Rivets: Riveting processes Rivet Heating Oven
Rivet Heater

9. Types of Connectors Rivets: Riveting processes Earlier Riveting Gun
Modern Riveting Gun

10. Types of Connectors Rivets: Characteristics of riveted connections
In riveted connections magnitude of clamping is function of length of rivet and magnitude of shrinkage after the head is formed.
Magnitude of slip depends on the extent to which rivet fills the hole.

11. Types of Connectors Rivets: Causes of rivet obsolescence
Riveting required a crew of 4 to 5 experienced riveters
Bolt installation is less labor intensive
Riveting is time consuming operation requiring preheating, driving and finishing

12. Types of Connectors Rivets: Causes of rivet obsolescence
Rivet strength is low compared to high strength bolts
High strength bolts are now economical
Riveting is still used in some industries and applications such as aircraft industry

13. Types of Connectors Bolts: Two common types of bolts are:
Unfinished (A307)
A307 is known by names unfinished, rough, common, ordinary and machine.
They are made of low carbon steel having tensile strength of 60Ksi.

14. Types of Connections Bolts: Two common types of bolts are:
High strength bolt (A325,A449,A490).
A325 is made of medium carbon steel whose tensile strength decreases with increase in dia.
High strength bolts can be tightened to large tensions.

15. Types of Connections
Bolts:
Typical High Strength Bolt

16. Tightening procedures
Research Council on Structural Connections (RCSC) prescribes four tightening procedures.
Turn of the nut method
Calibrated-wrench tightening
Installation of alternate design bolts
Direct-tension-indicator tightening

17. Tightening procedures
Torque Wrench

18. Tightening procedures
Positive Tension Shear Bolt
Bolt Installation Procedure

19. Tightening procedures
Direct Tension Indicating Washers

20. Behavior of Bolted & Riveted connections
T = Tensile Force on
Connection
∆ = Joint Displacement

21. Behavior of Bolted & Riveted connections
In riveted connections magnitude of clamping is function of length of rivet and magnitude of shrinkage after the head is formed.
Magnitude of slip depends on the extent to which rivet fills the hole.

22. Types of Bolted connection
Slip-Critical connections
Connection transmits the force by friction produced between the faying surfaces by the clamping action of the bolts.
Slip-critical connections are recommended for joints subjected to stress reversal, severe stress fluctuation, impact, vibration or where slip is objectionable

23. Types of Bolted connection
Slip-Critical connections
The clamping force applied to the bolt brings the two members close
enough so that appreciable friction is produced between them which
is then responsible for resisting the load. The more the clamping
force the more is the friction and strong is the connection but the
clamping force need not to be greater than tensile strength of the
bolt.
Slip critical connection becomes bearing type connection after the
slip occurs so every slip critical connection is essentially a bearing
type connection also.

24. Types of Bolted connection
Bearing type connections
Load is transferred by shearing and bearing on the bolt.
Capacity in shear depends on whether shear plane intersects the body of bolt or threaded portion.

25. Types of Bolted connection
Bearing type connections
Bearing type connection is the most widely used general type
connection in which the load is resisted by the bolt body without
any friction between faying surfaces.

26. Type of connection Failures
Shearing Failure of Bolts.
Bearing Failure of plate.
Tearing failure at edge of plate.

27. Type of connection Failures
Shearing failure of bolts

28. Type of connection Failures
Shearing failure of bolts

29. Type of connection Failures
Bearing Failure of Plate

30. Type of connection Failures
Shear & Bearing Area

31. Type of connection Failures
Tearing Failure at edge of Plate
Shearing Failure edge of plate
Transverse Tension Failure

32. Type of connection Failures
Tearing Failure at edge of Plate
Tests showed, failure by tearing through free edge of material will not occur if Le measured parallel to line of applied force is not less diameter of bolt multiplied by ratio of bearing stress to tensile strength of connected part.

33. Type of connection Failures
Tearing Failure at edge of Plate
Force transmitted by the bolt
P = fp D t (A)
Force to cause failure along two shear planes
P = 2(Le – D / 2 ) t u
u = 0.7 Fu
P = 1.4DtFu(Le/D –1/2) -----(B)
Equating (A) & (B)

34. Type of connection Failures
Tearing Failure at edge of Plate
(C)
Eqn (C) can be approximated as
So Eqn becomes

35. Type of connection Failures
Tearing Failure at edge of Plate
LRFD
ASD
Tearing length or Edge distance
 = 0.75
With FOS= 2

36. Type of connection Failures
Tearing Failure at edge of Plate
LRFD
ASD
Spacing between holes

37. Eccentricity of Applied Force
Type of connection Failures
Eccentricity of Applied Force
Plates of lap joint tends to bend.
Bending produces non uniform bearing of the fastener on the plates

38. Code Requirements Topic Ref. Text Book Ref. LRFD Code
Minimum edge Distance
Table 2-8
Table J3.4
Allowable Working Stress on Fasteners or Connected Material
Table 2-9
Allowable Load for Slip-Critical Connections
Table 2-10
Table J3.6
Allowable Stresses A502 Rivets
Table 2-12
Design Strength of Fasteners
Table 2-13
Table J3.2

39. Code Requirements
AISC Minimum Edge Distance

40. Code Requirements
Minimum installation tension

41. Code Requirements
Allowable Stresses

42. Code Requirements
Properties of structural bolts

43. Code Requirements
Allowable load for Slip critical connection

44. Code Requirements
Design strength of fasteners

45. Design Example No.1 (ASD Method)

46. Design Example No.1 (ASD Method)

47. Design Example No.1 (ASD Method)

48. Design Example No.1 (ASD Method)

49. Design Example No.1 (LRFD Method)

50. Design Example No.1 (LRFD Method)

51. Design Example No.1 (LRFD Method)

52. Design Example No.1 (LRFD Method)

53. Design Example No.2 (LRFD Method)
W = 10 in
t = .25in

54. Design Example No.2 (LRFD Method)

55. Design Example No.2 (LRFD Method)
Fub

56. Design Example No.2 (LRFD Method)2” 6” 3”
P = 77 Kips

57. Thanks