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Bolts

Spacings

Following values are given in the standard as minimum and maximum spacings for bolts in shear:

Spacing

Where is:

t

  • The minimum material thickness

d0

  • The hole diameter

e1, e2, p1, p2

  • The distance given in the figure above

Following values are recommended:

Bolts

Recommended spacing (mm)

p; p2

e

e

M12

44

30

25

M16

55

40

30

M20

70

50

40

M24

80

60

50

M27

90

70

55

M30

100

75

60

M36

120

90

70

Shear resistance

The design value of shear resistance of n bolts in unthreaded portion is given by the expression:

The resistance in threaded portion is calculated for bolt materials 4.6, 5.6, 8.8 using expression

and for material 4.8, 5.8, 10.9 with the help of this formula:

Where is:

Fv.Rd

  • The shear resistance

fub

  • The ultimate tensile strength

As

  • The tensile stress area of bolt

The program calculates only the shear resistance in threaded portion of the bolt. The shear resistance of the unthreaded portion is not considered in the analysis

Bearing resistance

The bearing resistance in vertical direction is calculated for the minimum of coefficient α

and for minimum value of k1

For the horizontal direction, the minimum value of α is selected from these formulas

the minimum value of k1 is selected from following expressions for horizontal direction

The resistance is given by the formula

Where is:

Fb.Rd

  • The design value of bearing resistance

d0

  • The hole diameter

e1, e2, p1, p2

  • The spacing according to the figure above

d

  • The bolt diameter

t

  • The material thickness

Slip resistance

The preloading force is calculated using the expression (3.7):

The design value of slip resistance is given by the formula (3.6)

The connections may be preloaded only in serviceability limit state. In that cases, shear and bearing resistance of bolts are verified for ultimate limit state. The software considers the preloading in the ultimate limit state. In such cases, only bearing resistance is checked.

Following values of slip factor μ are used in the software (based on the table 3.7):

Class

Description

μ

A

Blasted with shot or grit

0.5

B

Blasted with shot or grit (spray-metallised with aluminium or zinc based product or with alkali-zinc silicate paint with a given thickness)

0.4

C

Cleaned by wire brush or flame cleaning

0.3

D

Without any treatment

0.2

Long joints

The shear resistance Fv.Rd in long joints, where the distance between the centres of the end fasteners is more than 15d, is reduced with the help of the coefficient

Where Lj is the distance between the centres of the end fasteners.

The resistance reduction for long joints

The design resistance of single lap joint with only one bolt row is limited according the chapter 3.6.1(10) using expression

Single lap joint with only one bolt row

Angles connected by one leg

The resistance of single angle in tension, that is connected by a row of bolts in one leg, is calculated in accordance with the chapter 3.10.3 using the following expressions

joints with one bolt

joints with 2 bolts

joints with 3 or more bolts

Where is:

γM2

  • The partial safety factor of net section

Anet

  • The net area of angle

β2, β3

  • The reduction factors according to the chapter 3.10.3

The values of reduction factors β2, β3 are based on the table 3.8 of EN 1993-1-8:

Pitch

≤2,5d0

≥2,5d0

Two bolts

0,4

0,7

Three bolts and more

0,5

0,7

The resistance reduction of unsymmetrical angle

All angles in the software are analysed as unsymmetrical.

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