Riveted Connections MCQ Quiz in मल्याळम - Objective Question with Answer for Riveted Connections - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Prying forces:

The flexibility of connected parts can lead to deformations that increases the tension applied to the bolts. The additional tension is called prying force.

The prying forces can be kept small  by using a thick plate or by limiting the distance between the bolt and plate edge.

The corresponding prying force can be calculated as follows

\({\rm{Q}} = \frac{{{{\rm{M}}_{\rm{p}}}}}{{\rm{n}}}\)

Where,

n = Number of bolts

M_p = Plastic moment

\({{\rm{M}}_{\rm{p}}} = \frac{{{{\rm{f}}_{\rm{y}}}}}{{1.15}}\frac{{{\rm{W}}{{\rm{t}}^2}}}{4}\)

t = Thickness of end plate 

Concept:

Riveting and Rivet:

• Riveting is one of the methods of making permanent joints of two or more pieces (Metal strips). 
• A Rivet is a short cylindrical rod having a head and a tapered tail. The main body of the rivet is called a shank.

Uses: Rivets are used for joining metal sheets and plates in fabrication work, such as bridges, shipbuilding, games, structural steel work.

Different types of rivet heads are:

• Snap heads: These are used mainly for structural work and machine riveting.
• Countersunk heads: These are employed for shipbuilding.
• Conical heads: These are used where riveting is done by hand hammering.
• Pan heads: These are required where very high strength is needed since they have the maximum strength.
• Mushroom heads: These rivets are used to reduce the height of the rivet head above the metal surface.
• Flatheads: These are most commonly used in sheet metal fabrication where the metal is very thin and the projecting head of the rivet is objectionable. These are also available for heavy fabrication work.

Explanation:

According to IS 2155: 1982, the Diameter of the snap head or pan head is taken as 1.6D, where D is the diameter of a rivet body.

Concept:

\(Efficiency(η ) = \frac{{\min (Ps,Pb,Pt)}}{P}\)

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 = \(b.t.\frac{{{f_y}}}{{1.1}}\)= 180 × 20 × (250/1.1) × 10^-3 = 818.18 kN

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

Explanation:

According to IS 800:2007 Clause 10.2.1, page no. 73,

The diameter of the hole should be the nominal diameter of the bolt plus the clearance as given below: 

Standard Clearance for Fastener Holes (IS 800: 2007, Table no. 19) given below:

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:

Specification for pitch of bolts or rivets

1. Minimum pitch and minimum gauge length

= {2.5 × nominal diameter of the bolt

2. Minimum end and edge distance

\(= \left\{ {\begin{array}{*{20}{c}} {\begin{array}{*{20}{c}} {1.5 \times diameter\;of\;the\;bolt\;hole,for\;machine\;cut\;element}\\ {\;\;\;\;\;\;\;} \end{array}}\\ {1.7 \times diameter\;of\;the\;bolt\;hole,for\;hand\;cut\;element} \end{array}} \right.\)

3. Maximum end and edge distance

\(= \{ 12 \times t \times \epsilon,\)

Where, \(\epsilon = \sqrt {\frac{{250}}{{{f_y}}}}\)

f_y = yield stress

t = thickness of thinner plate

Concept:

In case of double V-butt joint, complete penetration of weld takes place.

Hence, effective throat thickness = Thickness of thinner plate joined = 12 mm

Strength of the weld = Permissible tensile stress of steel × L_eff × effective throat thickness

Calculation:

Effective throat thickness = Thickness of thinner plate joined = 12 mm

Strength of welded joint = 140 × 12 × 160 = 268.8 kN

Concept:

Rivet value: 

• Rivet value is defined as the minimum of shearing strength or (capacity ) and bearing strength of rivet.
• But joint value is minimum of shearing strength of rivet, bearing strength of rivet, and tensile strength of the plate.

Rivet value (Rv) = minimum of (Ps and Pb)

Where Ps = Shear strength of the bolt

Pb = Bearing strength of the bolt

Number of rivets (n) = \(\frac{{Force\;at\;the\;joint}}{{{R_v}}}\)

Calculation:

Given, Force acting at a joint = 90 kN

P_b = 30 kN, P_s = 45 kN

Rivet value (Rv) = minimum of (30 and 45) = 30 kN

Number of rivets (n) = \(\frac{{Force\;at\;the\;joint}}{{{R_v}}}\)

\(n = \frac{{90}}{{30}} = 3\)

Concept:

The number of rivets for eccentric connection is given by(provided rivets in two vertical row)

n = \(\sqrt { 6M \over p (2R_v )}\)

where

M = P × e

p = pitch

R_v = Rivet value

Calculation:

Given:

P = 150 kN

e = 300 mm = 0.3 m

R_v = 40 kN

p = 60 mm

The number of rivets for eccentric connection is

n = \(\sqrt { 6M \over p (2R_v )}\)

n = \(\sqrt {{6 \times 150\times 0.3}\over {40\times 2 \times0.06}}\)   = 7.5

Hence, the number of rivet is 8.

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 \(= \sqrt {\frac{{250}}{{{f_y}}}} \), 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