Riveted Connections MCQ Quiz - Objective Question with Answer for Riveted Connections - Download Free PDF

Concept:

where, P_s = strength of joint in shear

P_b = strength of joint in bearing

P_t = strength of joint in tearing

P = strength of plate in tearing when no deduction has been made for rivet hole = p.t.f_t

Calculation:

Given,

strength of joint in bolted connection = 620 kN

size of plate = (180 × 20) mm

yield strength of material = 250 MPa

FOS = 1.1

strength of plate = = 180 × 20 × (250/1.1) × 10^-3 = 818.18 kN

efficiency ( η ) = (620/818.18) × 100 = 75.77%

Explanation

Specifications of Pitch of rivet:

• Pitch is the distance between two adjacent rows of rivet parallel to the direction of application of force. The minimum pitch will be 2.5 times the gross diameter.
• The minimum pitch should not be less than 2.5 times the nominal diameter of the rivet.
• As a thumb rule pitch equal to 3 times the nominal diameter of the rivet is adopted.

For Maximum pitch:

The maximum pitch of bolts or rivets or welds in the compression zone 

The maximum pitch of bolts or rivets or welds in the tension zone

Concept:

Specification for the pitch of bolts or rivets

1. Minimum pitch and minimum gauge length

• P = 2.5 × nominal diameter of the bolt

2. Minimum end and edge distance

• emin = 1.5 × diameter of the bolt hole      ....... (for machine cut element)
• emin = 1.7 × diameter of the bolt hole      ....... (for hand-cut element)

Calculation:

Given,

Diameter of bolt = 20 mm, 

as the bolt diameter is in the range of (16 - 24) mm

Hole Dia = Bolt dia + 2 mm = 20 + 2 = 22 mm

Minimum edge Distance for machine flame cut = 1.5 × 22 = 33 mm

Additional Information 

3. Maximum end and edge distance

• emax = 12 × t × ϵ 
• Where, ϵ , fy = yield stress and t = thickness of thinner plate.

4. The maximum pitch of bolts or rivets or welds in the compression zone 

Pmax = minimum { 12 × t or 200 mm }     ....... (For compression zone)

Where, t = thickness of the thinner plate

5. The maximum pitch of bolts or rivets or welds in the tension zone

Pmax = minimum { 16 × t or 200 mm }     ....... (For tension zone)

Where, t = thickness of the thinner plate

Explanation:

(i) As per IS 800:1984 Recommendations, Maximum permissible stress in rivets and bolts

So from the table, it is clear that For field rivets the maximum permissible stresses in rivets and bolts as given in codes are reduced by 10%.

Explanation:

Partial Safety Factor for Bolts

The partial safety factor is a parameter used in design to account for uncertainties in material properties, manufacturing processes, and applied loads. It ensures a margin of safety in the design process. For bolts, the partial safety factor is determined based on codes and standards to ensure their reliability under various conditions.

Analyzing the Given Options

1. "Option 1: 1" (Incorrect)

   • A partial safety factor of 1 would imply no additional safety margin, which is not acceptable in engineering design as it doesn’t account for uncertainties.

2. "Option 2: 1.1" (Incorrect)

   • A value of 1.1 is too low for bolts, considering the uncertainties in material properties and the stress they endure during loading.

3. "Option 3: 1.15" (Incorrect)

   • While 1.15 is a commonly used safety factor for certain materials, it is not the standard for bolts as per codes and standards.

4. "Option 4: 1.25" (Correct)

   • A partial safety factor of 1.25 is widely accepted for bolts in structural design, ensuring adequate safety against uncertainties in material strength and load application.

5. "Option 5: Not provided" (Not Applicable)

   • This option is invalid as it does not specify any value for the partial safety factor.

Concept:

According to clause no. 11.1.4 of IS 800: 2007, when the effect of wind or earthquake load is taken into account, the permissible stress as specified in rivets (or in anchor bolts) may be increased by 25%.

Confusion/Mistake Point:

According to clause no. 11.1.4 of IS 800: 2007, when the effect of wind or earthquake load is taken into account, the permissible stress as specified in structural steel member may be increased by 33.33%.

Concept:

Tensile Stresses in the main plates might result in tearing of the main plate or cover plate across a row of the bolt.

The resistance offered by the plate against tearing is known as the tearing strength or tearing value of the plate.

Tearing efficiency of joints is given by,

Calculation:

Given, Minimum pitch of rivet joint(p) = 2.5d

 =  × 100 = 0.6 × 100 = 60%

Explanation:

Assumptions in the design of riveted joints:

1. The friction among the plates is neglected.
2. Shear stress across a cross-section of a rivet is uniform.
3. The bearing stress distribution on the plate cross-section between rivet holes is uniform.

• All rivets within a riveting group subjected to a direct load passing through their CG share the load equally.
• Rivet shanks and after driving, fill the rivet holes completely.
• The tensile stress is uniform in the section of metal between the rivets.

Concept-

As per IS code-

Rivets under combined stresses must be subjected to a limit as

Where, τ_v and σ_t = The actual shear and tensile stresses in the rivets, respectively.

τ_vf and σ_tf = Allowable shear and tensile stresses in the rivets, respectively.    

As per IS 800:2007 clause no 10.3.6

A bolt required to resist both design shear force (V_sb) and design tensile force (T_b) at the same time shall satisfy:

Where V_sb = factored shear force acting on the bolt

v_db = design shear capacity

T_b = factored tensile force acting on the bolt

T_db = design tension capacity

Concept:

The maximum resultant shear force between F1 ­and F2 is FR given by,

Where,

F1 = shear force in any rivet due to direct load ‘P’

  where n = number of rivets

F2 = shear force in rivet due to twisting moment M

r = radial distance of rivet from C.G of rivet group

The critical rivet is the one for which r is maximum and θ is minimum 

Calculation:

P= 450 kN

n  = 5 

F₁ = 90 kN

F₂ = 120 kN

θ = 0° 

° 

F_R = 210 kN

Concepts:

A rivet has a cylindrical shank with a head at one end. It is used to make permanent joints between two plates. Rivet is inserted into the holes of plates (which are to be joined) and then its protruding part is upset by a hammer.

Advantages of Rivet connection:

1. It is more reliable
2. It can also be used for non ferrous metals
3. Parts assembled by Riveted joint do not have any thermal after effec
4. Its quality inspection is easy and cheap
5. When parts are dismantled riveted parts have less damage compared to welded parts 
6. They have good vibration damping capabilities so where required rivets are used in place of it

Disadvantages of Riveted joints

1. Due to holes plates become weak.
2. Labor cost is more as more and skilled workforce is needed.
3. Overall cost of riveted joints is more.
4. They have more weight than welded joints.
5. Riveting process creates more noise.
6. Stress concentration near holes.

Concept:

Gross diameter is the diameter of rivet when it is fully inserted in the rivet hole or body. This diameter is more than the diameter of shank (when it is cold or before insertion i.e. nominal diameter)

Important points:

Due to the heating effect, the size of rivets gets expanded which upon cooling gets reduced (called shank diameter).

Rivet hole diameter is calculated as:

Calculation:

d = 20 + 1.5 = 21.5 mm

Explanation:

In double cover butt joint, the bolts or rivets can be placed in the following manner:

1. In multiple rows having zero staggered pitch called chain riveting as shown in the following figure:

2. In multiple rows having either non-uniform pitch or having staggered pitch i.e. bolts are placed in a zig-zag pattern as shown below: 

Additional Information

As per IS 800:2007, the tensile strength based on rupture of the net section of the plate is given as:

Where,

fu = Ultimate strength of the plate

Anet = Minimum net area of the section

γ = Factor of safety for plate

To calculate Anet, all possible failure paths (straight as well as zig-zag) are required to be considered and the corresponding net area is to be computed for each possible failure path and the minimum net area is to be selected.

Where,

t is the thickness of the plate joined.

dh­ is the diameter of the hole

s is staggered pitch , g is gauge distance, b is width of plate

Concept:

Strength of rivet in bearing (P_b)

Where σ_b = Permissible bearing stress in rivet.

P_b = Bearing strength of rivet.

d' = Gross diameter of rivet or dia of hole.

25\, mm\)

Calculation:

Given

Bearing stress () = 300 N/mm²

Nominal diameter of rivet (d) = 22 mm

Gross diameter of rivet (d') = 22 + 1.5 = 23.5 mm

Thickness of plate (t) = 12 mm

Bearing strength of rivet (P_b) = 300 × 23.5 × 12 = 84600 N

Bearing strength of rivet (Pb) = 84.6 kN

Explanation:

Gross diameter = Nominal diameter + 1.5 mm, ϕ ≤ 25 mm

Gross diameter = Nominal diameter + 2 mm, ϕ > 25 mm

ϕ = Nominal diameter

Additional Information As per the IS 800 – 2007, the minimum pitch that should be maintained is 2.5 times the nominal diameter of the bolt and

 the minimum end distance that should be maintained is 1.5 times the hole diameter.

The hole diameter is to be calculated based on the following table: