Dos PPT 3
Dos PPT 3
Dos PPT 3
CONNECTIONS
INTRODUCTION
The perfect theoretical analysis for stress distribution in riveted connections
cannot be established. Hence a large factor of safety is employed in the design of
riveted connections.
The riveted connections should be as strong as the structural members.
No part in the riveted connections should be so overstressed.
The riveted connections should be so designed that there is neither any
permanent distortion nor any wear.
ASSUMPTIONS FOR THE DESIGN OF
RIVETED JOINT
Procedure for design of a riveted joint is simplified by making the following
assumptions and by keeping in view the safety of the joint.
1.Load is assumed to be uniformly distributed among all the rivets
2.Stress in plate is assumed to be uniform
3.Shear stress is assumed to be uniformly distributed over the gross area of rivets
4.Bearing stress is assumed to be uniform between the contact surfaces of plate
and rivet
5.Bending stress in rivet is neglected
6.Rivet hole is assumed to be completely filled by the rivet
7.Friction between plates is neglected
ARRANGEMENT OF RIVETS
Rivets in a riveted joint are arranged in two forms.
1. Chain riveting 2. Diamond riveting.
Chain Riveting: In chain riveting the rivets are arranged as shown in Fig. In the
figure 1-1, 2-2 and 3-3 shows sections on either side of the joint.
ARRANGEMENT OF RIVETS
Chain Riveting:
Section 1-1 is the critical section, as at other sections, strength of rivets prior to that
section adds the strength of the joint at the section.
Strength of plate in tearing at 1-1 = (b-3D).t.pt
Where b= width of the plate; D=Gross diameter of the rivet and t=Thickness of the
plate.
When safe load carried by the joint (P) is known, width of the plate can be found
as follows;
ARRANGEMENT OF RIVETS
Diamond Riveting: In diamond riveting, rivets are arranged as shown in Fig. All
the rivets are arranged symmetrically about the centre line of the plate. Section 1-1
is the critical section.
ARRANGEMENT OF RIVETS
Diamond Riveting:
Strength of plate in tearing at 1-1 = (b-D).t.pt
When the safe load carried by the joint (P) is known, width of the plate can be
found as follows
• The number of rivets thus obtained is provided on one side of the joint and an
equal number of rivets is provided on the other side of joint also.
• Step 4:
• For the design of joint in a tie member consisting of a flat, width/thickness of the
flat is known. The section is assumed to be reduced by rivet holes depending upon
the arrangements of the rivets to be provided, strength of flat at the weakest
section is equated to the pull transmitted by the joint.
DESIGN PROCEDURE FOR RIVETED JOINT
• Step 4:
• For example, assuming the section to be weakened by one rivet and also assuming
that the thickness of the flat is known we have
The hot driven rivets of 16 mm, 18 mm, 20 mm and 22 mm diameter are used for
the structural steel works. Unwin’s formula gives higher values.
Hence, adopt nominal diameter of rivet = 22 mm;
Gross diameter of rivet = 22 +1.5 = 23.5 mm
PROBLEM 3
Step 2: Rivet value
In double cover butt joint, rivets are in double shear. Assume power driven rivets are
used. As per IS : 800-84,
Shear stress for power driven rivets=100 N/mm2 (MPa).
Bearing stress for power driven rivets=300 N/mm2 (MPa).
Strength of plate in tension = 0.6 fy = 156 N/mm2.
Strength of rivet in double shear = 2 x (π/4) x 23.52 x 100/1000 = 86.75 kN
Strength of rivet in bearing = D x t x pb = 23.5 x 16 x 300/1000 = 112.8 kN
The strength of a rivet in shearing and in bearing is computed and the lesser is
called the rivet value (R). Hence the Rivet value is 86.75 kN.
PROBLEM 3 Thickness of single cover plate = 1.125t
Thickness of double cover plate = 0.625t
Step 3: Pitch of rivets
Let p be the pitch of the rivets. Pt = (p-D) x t x pt
= ((p-23.5) x 16 x 156/100) =2.496 (p-23.5) kN
The pitch of the rivets can be computed by keeping Pt = Ps or Pb whichever is less
Therefore 2.496 (p-23.5) = 86.75
(p-23.5) = (86.75/2.496) = 34.756
p= 34.756 + 23.5 = 58.256 mm
Adopt pitch, p= 55 mm
Adopt thickness of each cover plate t ≈ 0.625 x 16 ≈ 10 mm
Step 4: Efficiency of joint
PROBLEM 4
4. Design a suitable riveted lap joint to connect two steel plates of thickness 10mm
each to carry an axial load of 300kN. Determine the efficiency of the joint designed.
PROBLEM 4
PROBLEM 4
PROBLEM 4
PROBLEM 4
PROBLEM 4
PROBLEM 4
ADVANTAGES OF RIVETED CONNECTIONS
1. Riveted joints can be used for non-ferrous metals like aluminium alloy, copper,
brass or even non-metal like plastic and asbestos.
2. Quality inspection of a riveted joint is very easy and cheap.
3. It is more reliable.
4. At the time of dismantling, the parts joined have less damage as compared to
welded parts.
5. The parts which are joined by riveted joints do not have any damage due to heat
as in the case of welding joints.
DIS ADVANTAGES OF RIVETED CONNECTIONS