2010.05.01 1

Eurocode 3 - Design of jointsDr.Eng. Bjørn Aasen

2

Eurocode 3: Design of steel structures

Part 1-8: Design of joints

1. Introduction

2. Basis of Design

3. Connections made with bolts, rivets or pins

4. Welded connections

5. Analysis, classification and modelling

6. Structural joints connecting H or I sections

7. Hollow section joints

2010.05.01 2

3

EC3 - Part 1-8: Design of joints

1.4.2

connection

Location at which two or more elements meet. …

1.4.4

joint

Zone where two or more members are interconnected. …

A welded connection A beam-to-column joint

4

EC3 - Part 1 - 8: Design of joints

1.1 Scope

This part of EN 1993 gives design methods for the design of joints subject to predominantly static loading using steel grades S235, S275, S355, S420, S450 and S460.

The scope should be also include the design of bolted and welded connections, see Part 1-9 Fatigue:

EN 1993-1-9 gives methods for the assessment of fatigue resistance of members, connections and joints subjected to fatigue loading.

2010.05.01 3

5

However, be careful when fatigue may govern

The requirements given in table 8.7 impose severe restrictions for the use of hollow sections joints when subjected to fatigue:

• t0 and ti ≤ 8mm

• d0 ≤ 300 mm for CHS

• b0 ≤ 200 mm for RHS

6

The new Holmenkollen Ski Jump Hill

2010.05.01 4

7

1st challenge: transport of steel members!

8

2nd challenge: the structures are curved!

2010.05.01 5

9

3rd challenge: the missing link!

Fancy output

Software

Structural analysis

the Missing Link

Handmade

sketches

& calculations

Paperware

Designer

Nice drawings

CAD Software

Drawings

10

The strategy for design of joints

Structural analyses(STAAD)

Manipulation of results(Excel)

Design of joints(Mathcad)

Sketches of joints(SmartSketch)

3D Strutural model

(Tekla)

2010.05.01 6

11

Fabrication of a joint of the wind screen

Design rules for gusset plate connections are not included in Eurocode 3

12

Design of welded a gusset plate connection

2010.05.01 7

13

Strength of welded gusset plate connections

1. Gross section yielding of the hollow section

�EC3 Part 1-1

2. Tensile strength of the hollow section due to shear lag

�CIDECT Design Guide No. 3, 2nd Ed., 2009

3. Tensile strength of the hollow section due to tear-out

� CIDECT Design Guide No. 3, 2nd Ed., 2009

4. Yielding and buckling of the gusset plate

�Design rules proposed by Prof. A. Astaneh-Asl

5. Strength of the welds between gusset plate and chord

�EC3 Part 1-8

14

CIDECT Design Guide No. 3, 2nd Ed., 2009

2010.05.01 8

15

Tensile strength of the hollow section

Two possible failure modes have been identified for gusset plate-to-slotted RHS joints loaded in tension:

• CF: circumferential failure of the RHS and

• TO: tear-out or block shear failure of the RHS

16

Circumferential failure (CF)

Gusset plate-to-slotted RHS joints:

a) longitudinal welds only and

b) longitudinal welds plus a weld return

p

w

7,54,2

w2M

unRd,t

thbw

7,0w

L for

w

L1

11

fA9,0N

−+≈

≥

+

−=γ

2010.05.01 9

17

Tear out failure (TO)

Gusset plate-to-slotted RHS joints:

a) longitudinal welds only (Ant = 0)

b) longitudinal welds plus a weld return

7,0w

L for

f

f1

32

1AA

f9,0N w

0M

2M

u

ygvnt

2M

uRd,t <

++=

γ

γ

γ

18

Gross yielding of the gusset plate

2010.05.01 10

19

Warning!

Failure of truss girder due to gusset plate buckling

H. Schmidt et al:

An uncommon stability problem causes failureDer Stahlbau 77 (2008) No. 12

20

Erection of the first section of wind screen

2010.05.01 11

21

The bottom supports

22

The transition between welded and bolted connections

2010.05.01 12

23

The upper support

24

Connections made with pins

2010.05.01 13

25

Bolted connections

26

The strength of bolted connections

Limits states of fin plate connections

• Shear failure of bolts

• Bearing failure of beam web or plate

• Yielding of gross area of beam web or plate

• Fracture of net area of beam web or plate

• Buckling of gusset plate

• Bending of gusset plate

• Fracture of welds

2010.05.01 14

27

Eurocode 3 - Part 1-1: Net section failure

tp4

sndbA

2

0net

+−= ∑

28

Details of a bolted joint

2010.05.01 15

29

EN 14399-6Washers

8.8 / 8Property classes

EN 14399-3Bolt/nut assembly

EN 14399-2Suitability test

EN 14399-1General requirements

System HR

High-strength structural bolting assemblies

for preloading

30

Erection of the top section

2010.05.01 16

31

Design of simple joints in steel structures

32

Resistance of fin plate connections

Limits states of fin plate connections

• Shear failure of the bolts

• Bearing failure of the beam web or the plate

• Yielding of gross area of beam web or plate

• Fracture of the net area of beam web or

plate

• Buckling of the plate

• Bending of the plate

• Fracture of the welds

2010.05.01 17

33

Concern about bolt design

Some Norwegians question why

bolts should be designed for

the combined effects of a

direct shear and a moment

equal to the shear multiplied

by the eccentricity of the bolt

line from the weld line:

2

1

Rd,bRd,vRd

p)1n(

z61

)F,Fmin(nV

+

⋅+

⋅=

34

Astaneh: Plate hole deformations after tests

The deformations of the plate bolt

holes indicate the direction of

the movement of the bolts

which is expected to be

approximately the direction of

the applied force due to shear

and moment.

2010.05.01 18

35

Astaneh: Recommended design of bolts

It is recommended that bolts be

designed for combined effects

of direct shear and a moment

equal to the shear multiplied

by the eccentricity of the bolt

line from point of inflection

given by

eb = (n-1)(25,4mm)-a

where

n = number of bolts used in the

connection

a = the distance from the bolt

line and the weld line

36

Thank you for your attention!