aasen ec3 design of joints
TRANSCRIPT
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!