TIMBER CONNECTIONS by Dr. Ad Leijten TU-Eindhoven The Netherlands
Transcript of TIMBER CONNECTIONS by Dr. Ad Leijten TU-Eindhoven The Netherlands
Brussels, 18-20 February 2008 – Dissemination of information workshop 1
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
TIMBER CONNECTIONS
by
Dr. Ad Leijten
TU-Eindhoven
The Netherlands
Former PT-member
Brussels, 18-20 February 2008 – Dissemination of information workshop 2
EUROCODESBackground and Applications
We can not escape connections
THE WEAKEST LINK
Brussels, 18-20 February 2008 – Dissemination of information workshop 3
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
What kind of connections do we use?
Brussels, 18-20 February 2008 – Dissemination of information workshop 4
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Carpenter connections (not in Eurocode 5)
National regulations apply
Brussels, 18-20 February 2008 – Dissemination of information workshop 5
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Carpenter connections ���� compression forces
Brussels, 18-20 February 2008 – Dissemination of information workshop 6
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Glued connections (not in Eurocode 5)
Structural Finger joints Glued in steel rods
National regulations apply
Brussels, 18-20 February 2008 – Dissemination of information workshop 7
EUROCODESBackground and Applications
What do we find in Eurocode 5
Section 8: Connections with metal fasteners
Mechanical connections with
Dowel type fasteners- Nails, staples, - punched metal plates, - screws, - dowels and bolts
Connectors- Shear plates- Split-rings
EN1995-1-1: Section 8 - Connections
Brussels, 18-20 February 2008 – Dissemination of information workshop 8
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Nails < 8 mm (EN14592) definition profiled nails Bolts > 8 mm
Dowels > 6 mmScrews
Brussels, 18-20 February 2008 – Dissemination of information workshop 9
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Punched metal plate fasteners
Split-ring connectors64- 104 mm diameter
Bolts M12 to M20
Brussels, 18-20 February 2008 – Dissemination of information workshop 10
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Steel – to – timber
Brussels, 18-20 February 2008 – Dissemination of information workshop 11
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Eurocode 5 allows:
Design by testing:
EN 1075 – tests punched metal plates connections
EN 1380 – tests nails,screws,dowels,bolted conn.
EN 1381 - tests on stapled connections.
EN 26891 – Specimen density selection.
EN 28970 – Test procedure for connection tests.
Design by calculation
- Model provided in EN1995-1-1
Brussels, 18-20 February 2008 – Dissemination of information workshop 12
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Design by calculation - covers
Brussels, 18-20 February 2008 – Dissemination of information workshop 13
EUROCODESBackground and Applications
αα α α
a3,ta3,c
a 4,t
a 4,c
-90° ≤ α ≤ 90° 90° ≤ α ≤ 270° 0° ≤ α ≤ 180° 180° ≤ α ≤ 360°
(1) (2) (3) (4)
a 2a 2
a1
a1
a1
a1
a 2
a 2
a)
b)
12
Fastener spacing requirementsKey:(1) Loaded end (2) Unloaded end (3) Loaded edge (4) Unloaded edge
Brussels, 18-20 February 2008 – Dissemination of information workshop 14
EUROCODESBackground and Applications
Fastener spacing requirements (bolts)
3 d180° � � � 360°a4,c (unloaded edge)
max([2 + 2 sin �) d; 3d)0° � � � 180°a4,t (loaded edge)
max([1 + 6 sin �) d; 4d)4 d
max([1 + 6 sin �) d; 4d)
90°� � < 150 °
150° � � < 210°
210° � � � 270°
a3,c (unloaded end)
max (7 d; 80 mm)-90° � � � 90°a3,t (loaded end)
4 d0° � � � 360°a2 (perpendicular to grain)
(4 + �cos ��) d0° � � � 360°a1 (parallel to grain)
Minimum spacing or distance
AngleSpacing and end/edge distances
(see Figure 8.7)
Brussels, 18-20 February 2008 – Dissemination of information workshop 15
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Spacing requirements determine timber dimensionsa1
a2
Decrease memberwidth ?
Brussels, 18-20 February 2008 – Dissemination of information workshop 16
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Spacing requirements determine timber dimensions
a12 2a1 a 2
a 2
0 1( ) ( ) 1 with
0 1
≤ ≤�+ ≥ � ≤ ≤�
kk k
k
ka2a2
ka1a1
ka1a1
k a2a 2
a2
Only for connectors
Split-rings and shear plates
Brussels, 18-20 February 2008 – Dissemination of information workshop 17
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
The strength capacity model for
laterally loaded dowel-type-fasteners
(based on Johansen (1949)
Background:
-Structural Education Timber Program (STEP 1)(1994)
-Timber Engineering; Thelandersson & Larsen (2003) ISBN 0-470-84469-8
Laterally loaded axially loaded
Brussels, 18-20 February 2008 – Dissemination of information workshop 18
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
single shear
fasteners
multiple shear
Brussels, 18-20 February 2008 – Dissemination of information workshop 19
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Double shear
Embedmentstresses
Brussels, 18-20 February 2008 – Dissemination of information workshop 20
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Embedment = femb ffembemb
displacementdisplacement
Starting point for strength model - Embedment strength
Idealised femb= fv
embedment
Brussels, 18-20 February 2008 – Dissemination of information workshop 21
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Determination of embedment strength –EN 383
Eurocode 5 Design clause embedment strength
Nails (not pre-drilled)
Nails pre-drilled
Bolts/dowels
2-0,3h,k k0,082 N/mm f d ρ=
2h,k k0,082 (1- 0,01 ) N/mm d f ρ=
Brussels, 18-20 February 2008 – Dissemination of information workshop 22
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Taken from Sawata and Yasumura (2002).
Background: Whale L. and Smith, I. The derivation of design clauses for nailed and bolted joint in Eurocode5, In Proceedings of paper CIB-W18 paper 19-7-6/ Florenze 1986
Yasumura, M. and Sawata, K., Determination of embedment strength of wood for dowel-type-fasteners. In: Journal of Wood Science, nr. 48, 2002, Japan Wood Research Society, Inst. Of Wood Techn, Akita, Japan
Parallel Perpendicular
Brussels, 18-20 February 2008 – Dissemination of information workshop 23
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Dowels Parallel All wood species
0,0
20,0
40,0
60,0
80,0
100,0
120,0
200 400 600 800 1000 1200
Density
Em
bedm
ent
5mm data
7mm data
8mm data
12mm data
16mm data
20mm data
30mm data
Embedment test - parallel to grain
Background: Leijten, A.J.M. & Köhler, J.& A Jorissen, Review of Probability Data for Timber Connections with Dowel-Type Fasteners; In Proceedings of CIB-W18, paper 37-7-12, Edinburgh, UK, September 2004
Brussels, 18-20 February 2008 – Dissemination of information workshop 24
EUROCODESBackground and Applications
Re-evaluation parallel to grain embedment results
for future consideration in EC5?
Nails (pre-drilled)
Coniferous
Bolts and dowels
Coniferous
Decideous
EN1995-1-1: Section 8 - Connections
1,07 0,25;0
;90
0,097
?h
h
f d
f
ρ −==
1,35 0,27;0
1,48 0,42;90
0,0104
0,046h
h
f d
f d
ρ
ρ
−
−
=
=
1,09 0,25;0
1,13 0,46;90
0,087
0,106h
h
f d
f d
ρ
ρ
−
−
=
=
Brussels, 18-20 February 2008 – Dissemination of information workshop 25
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Embedment - perpendicular to grain
Brussels, 18-20 February 2008 – Dissemination of information workshop 26
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Embedment – at angle to grain
h,0,kh,�,k
90 sin cosα α2 2
f = f
+ k
h,0,k k0,082 (1- 0,01 ) ρ = d fBolts/dowel:
901,35 0,015 for softwoods0,90 0,015 for hardwoods
dk
d
+�= � +�
Brussels, 18-20 February 2008 – Dissemination of information workshop 27
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Coniferous: Embedment test - perpendicular to grainEmbedding strength, based on average values embedding tests
(European Whitewood (EW), European Redwood (ER), Canadian Spruce Pine Fir (CS))
0
5
10
15
20
25
30
35
40
0 5 10 15 20
Nail or Bolt diameter [mm]
f h;9
0 (E
mbe
ddin
g st
reng
th) [
N/m
m2 ]
Nails ERNails EWNails CSBolts ERBolts EWBolts CSEurocode 5Power (All)Power (Eurocode 5)
BoltsNails
Eurocode 5
Needs adjustment in future EC5
Brussels, 18-20 February 2008 – Dissemination of information workshop 28
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Embedment rules
Nails in:
Plywood
Hardboard
Particleboard & OSB
Taken from DIN 1052
0,3h,k k0,11ρ −=f d
0,3 0,6h,k 30 −=f d t
0,7 0,1h,k 65 −=f d t
Brussels, 18-20 February 2008 – Dissemination of information workshop 29
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Some failure modes of single shear fasteners
Some failure modes of double shear fasteners
Mode I Mode II Mode III
Brussels, 18-20 February 2008 – Dissemination of information workshop 30
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Equations for every failure mode
Fasteners in single shear
h,1,k 1
h,2,k 2
2 2h,1,k 1 2 32 2 2 2
1 1 1 1
y,Rkh,1,k 1 ax,Rkv,Rk
2h,1,k 1
h,1,k 2
(a)
(b)
2 1 1 (c)1
4 (2 )min 1, 05 2 (1 ) (d)2 4
1, 051 2
� �� �� � � � � �� � β + β + + + β − β + � � �� + β � � � � � �� � �
� �β + β= β + β + − β +� + β � � �
+
f t d
f t d
f t d t t t tt t t t
Mf t d FFf d t
f t d y,Rk ax,Rk22
h,1,k 2
ax,Rky,Rk h,1,k
4 (1 2 )2 (1 ) (e)
4
21,15 2 (f)
1 4
�������������� � �β + β� β + β + − β +�
β� � � ��� β +� + β��
M F
f d t
FM f d
Brussels, 18-20 February 2008 – Dissemination of information workshop 31
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Equations for every failure mode
Fasteners in double shear
h,1,k 1
h,2,k 2
y,Rkh,1,k 1 ax,Rkv,Rk 2
h,1,k 1
ax,Rky,Rk h,1,k
(g)
0,5 (h)
4 (2 )min 1,05 2 (1 ) (j)
2 4
21,15 2 (k)
1 4
β ββ β β
β
ββ
���� � �+�= + + − +� � + � � � ��� +� +�
f t d
f t d
Mf t d FF
f d t
FM f d
Brussels, 18-20 February 2008 – Dissemination of information workshop 32
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Some failure modes of single shear fasteners
steel to woodconnections
thick steel plate t > d = fastener diameter
thin steel plate t < 0,5d
Brussels, 18-20 February 2008 – Dissemination of information workshop 33
EUROCODESBackground and Applications
Test results still higher than Johansen equations
Cord effect:
Only valid forMode II and III
Requires knowledge about withdrawalTheory for nails 15% extra
Background: Kuipers, J. Van der Put, T.A.C.M., Betrachtungen zum Bruchmechanismus von Nagel verbindungen, In: Ingenieuholzbau in Forschung und Praxis, J. Ehlebeck and G. Steck, editors, Bruderverlag Karlsruhe 1982
Brussels, 18-20 February 2008 – Dissemination of information workshop 34
EUROCODESBackground and Applications
Test results still higher than Johansen equations
Cord effect:Fax/4 = withdrawal capacity/4 = estimated effect
% are estimatesMaximumNails 15%Grooved nails 50%Screws 100%Bolts 25%Dowels 0%
Brussels, 18-20 February 2008 – Dissemination of information workshop 35
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Fasteners in double shear
h,1,k 1
h,2,k 2
y,Rkh,1,k 1 ax,Rkv,Rk 2
h,1,k 1
ax,Rky,Rk h,1,k
(g)
0,5 (h)
4 (2 )min 1,05 2 (1 ) (j)
2 4
21,15 2 (k)
1 4
β ββ β β
β
ββ
���� � �+�= + + − +� � + � � � ��� +� +�
f t d
f t d
Mf t d FF
f d t
FM f d
Test results still higher than Johansen equations
Brussels, 18-20 February 2008 – Dissemination of information workshop 36
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
theory
kkm
kd FFy
kFF ⋅=⋅=⋅= 69,0
3,19,0modDesign value
Ms = yield bending moment steel fastener
Partial material factor of timber γγγγmapplied to Ms !!Better seperate:
Mode III
schroef,hs dfMF ⋅⋅⋅⋅δ+δ⋅= 12
12
Brussels, 18-20 February 2008 – Dissemination of information workshop 37
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
15,169,079,0 =
⋅⋅=
k
k
FF
factor
Taking both γm - seperately
kd
khschroefked
khschroef
ked
hm
khschroef
sm
ked
FF
fdMF
fd
MF
ky
fd
y
MF
⋅=
⋅⋅⋅+
⋅=
⋅⋅⋅⋅+
=
⋅⋅⋅⋅+
=
79,014
79,0
9,03,11,11
4
14
,1,,
,1,,
mod,
,1,
,
,
δδ
δδ
δδ
For Mode II factor is 1,05
Mode III
Brussels, 18-20 February 2008 – Dissemination of information workshop 38
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Fasteners in double shear
h,1,k 1
h,2,k 2
y,Rkh,1,k 1 ax,Rkv,Rk 2
h,1,k 1
ax,Rky,Rk h,1,k
(g)
0,5 (h)
4 (2 )min 1,05 2 (1 ) (j)
2 4
21,15 2 (k)
1 4
β ββ β β
β
ββ
���� � �+�= + + − +� � + � � � ��� +� +�
f t d
f t d
Mf t d FF
f d t
FM f d
Eurocode 5 equations
Brussels, 18-20 February 2008 – Dissemination of information workshop 39
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Yield moment of dowel type fasteners
Large diameter bolts and dowels
Small rotation at failure ���� No full plastic yielding
0.02.04.06.08.0
10.012.014.016.018.020.0
8 10 12 14 16 18 20 22 24 26 28 30
d
R
diameter
Rotationangle
2,6y,Rk u,k0,3 = f dM
Background: Jorissen, A.J.M. Blass, H.J., the fasteneryield strength in bending, In: Proceedings of CIB-W18 paper 31-7-6, 1998
Brussels, 18-20 February 2008 – Dissemination of information workshop 40
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Failure of multiple of fasteners in a row
Splitting
Shear
Tensile
Brussels, 18-20 February 2008 – Dissemination of information workshop 41
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Failure of multiple of fasteners in a rowCaused by group effect���� Only for load component in grain direction
13d
Cumulatieve stress
Stress ⊥⊥⊥⊥
Brussels, 18-20 February 2008 – Dissemination of information workshop 42
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Failure of multiple of fasteners in one row
Caused by group effect���� effective number
Nails:Empirical (Gehri)
Bolts & dowels:Fracture mechanics
Background:Double shear timber connections with dowel type fasteners, A.J.M. Jorissen, ISBN 90-407-1783-4, DUP Delft, 1998
4 090
13da
nn ,ef =
efef
knn =
a For intermediate spacings, linear interpolation of kef is permitted
0,5-a1 = 4d
0,70,7a1 = 7d
0,850,85a1 = 10d
1,01,0a1 ≥≥≥≥ 14d
PredrilledNot predrilled
kefSpacinga
Brussels, 18-20 February 2008 – Dissemination of information workshop 43
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Be Be carefulcareful withwith cheesecheese connectionsconnections
Brussels, 18-20 February 2008 – Dissemination of information workshop 44
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Steelplate – in – timber
Chees connections
Small dowels
Brussels, 18-20 February 2008 – Dissemination of information workshop 45
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Failure at fastener perimeter (Prof.Racher, Fr.)
Block shear:Full penetration
Plug shearPartial penetration
Tensile or shear failure, which happens first?Literature: Johnson, H, Stehn, L, A Linear Fracture Mecanics Evaluation of Plug Shear Failure,In Proc of 8th
world conf on Timber Engineering WCTE 2004, Finland
Brussels, 18-20 February 2008 – Dissemination of information workshop 46
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
�t,1
�t,2
�v,1 �v,2 �v,3 �v,4
�v,5 �v,6 �v,7 �v,8
1
2
net,t t,o,kbs,Rk
net,v v,k
1,5max
0,7
��= ���
A fF
A f
t ef
Fasteners keep straight
Not correct in EC5
see previoussheet
Tensile failure
Shear fracture
Correlationparameters
Brussels, 18-20 February 2008 – Dissemination of information workshop 47
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Amendment A1:Contains:
New design rules for: compressive strength perpendiculer to grainPresent rules unsafe
13
l
lef
Brussels, 18-20 February 2008 – Dissemination of information workshop 48
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Amendment A1
AdditionAxially loaded screws
Traditional screwsDiameter thread=smooth shankNot very effective
not hardenedlow bending moment>8mm requires predrilled holes
Brussels, 18-20 February 2008 – Dissemination of information workshop 49
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Amendment A1
AdditionAxially loaded screws
Very effectivehardenedself tappinghigh axial stiffness
Background: Blaß, HJ; Bejtka, I: Self-tapping screws as reinforcements in connections with dowel-type fasteners. In:Proceedings. CIB-W18 Meeting, Karlsruhe, Germany 2005. Paper 38-7-4Blass H.J. Joints with dowel-type-fasteners, In: Timber Engineering Thelanderson and Larsen, editors, Wiley & Sons (2003):
Brussels, 18-20 February 2008 – Dissemination of information workshop 50
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Brussels, 18-20 February 2008 – Dissemination of information workshop 51
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Some examples
Leg or coach screw
Brussels, 18-20 February 2008 – Dissemination of information workshop 52
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Some examples
Spax-S
Heco Topix/Fix
Rapid Komprex
Brussels, 18-20 February 2008 – Dissemination of information workshop 53
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Tecfi Woodpecker
BMF Torx
SFS WT
Brussels, 18-20 February 2008 – Dissemination of information workshop 54
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Check:- Withdrawal failure
- Tear-off failure of the head
- Pull through of the head
- Tensile failure of the screw
- Torsional capacity
- Group effect (neff number of effective fasteners)
Brussels, 18-20 February 2008 – Dissemination of information workshop 55
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
-Withdrawal: Code proposals in EU countries
( )aa
ldR kefkaax 22
5,138,0
,, cos5,1sin106,3
⋅+⋅×⋅⋅⋅=
− ρπ
efk
kax ldaa
R ⋅⋅⋅+⋅×=
−
2342
26
; cossin1060 ρ
( ) ( ) ρ⋅−⋅⋅+= nomhecnomkax dldR 6,05,1,
Eurocode 5 = (1)
( )aa
ldR kefkax 22
38,0
1, cos5,1sin100,3
7,1⋅+⋅×⋅⋅⋅⋅=
− ρπ
(1)
(2)
(3)
(4)
Brussels, 18-20 February 2008 – Dissemination of information workshop 56
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Model uncertainty – evaluation of test results
0
5
10
15
20
25
-1 -0,8 -0,6 -0,4 -0,2 0 0,2 0,4 0,6 0,8 1
ln(model/meetpunt)
Freq
uent
ie..
Eurocode 5
Current EC5 design rule unsafe
(1) (4) (2) (3)
Brussels, 18-20 February 2008 – Dissemination of information workshop 57
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
New proposal in Amendment A1:
RequirementScrews as defined in EN 14592
6 mm ≤≤≤≤ d ≤≤≤≤ 12 mm
All other screws:
Parameters determined by tests EN 14592 (EN 1382)
80
22 21
,
a
kefaxefk,a,ax acos,asin
l.d.fnR ��
��
�
ρρ
⋅+=
acos,asin
l.d,nR
,k
,ef
efk,a,ax 22
8090
21
520
⋅+ρ⋅
=
Brussels, 18-20 February 2008 – Dissemination of information workshop 58
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
- Head tear off- Axial screw strength:
Determine by tests:EN 14592
- Torsional capacityEN 14592
axax fAR ⋅=
Brussels, 18-20 February 2008 – Dissemination of information workshop 59
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Head pull throughEN 14592Test standard EN 1383
axax fAR ⋅=
( ) ( )( ) kcskk fddR ,90,2
212
21 0,3- ⋅⋅⋅⋅⋅= π
Eurocode 5:
20,16 kk dN ⋅=
Zulassung Germany 9.1-235:
In the absents of information Clause 8.5.2. bolt washers
Brussels, 18-20 February 2008 – Dissemination of information workshop 60
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
•short elastisch behaviour•Large non-elastic traject
Brussels, 18-20 February 2008 – Dissemination of information workshop 61
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Model uncertainty design rule 9.1-235andn Eurocode 5 for screws with washers
0
1
2
3
4
5
6
7
8
9
-1 -0,5 0 0,5 1 1,5
ln (model/meetwaarde)
Freq
uent
ie
Eurocode 5Zulassung
Brussels, 18-20 February 2008 – Dissemination of information workshop 62
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
- Group (tear out) effect:Due to a lack of background informationBased on test by Gehri (empirical):
0,9ef =n n
Brussels, 18-20 February 2008 – Dissemination of information workshop 63
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Splitting by perpendicular to grain forces
FEd
Fv,Ed,1 Fv,Ed,2
he h
bα
bb/2b/2
a) b)
Background: Leijten A.J.M. & Vander Put T.A.C.M, Evaluation of Perpendicular to Grain Failure of Beams caused by Concentrated Loads of Joints, In: Proceedings of CIB-W18, paper 33-7-7, Delft, 2000.
Design clause 8.1.4 (3) is formulated as a maximum shear force criterion on either side of the connection
Brussels, 18-20 February 2008 – Dissemination of information workshop 64
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Splitting by perpendicular to grain forces
0,35pl
max for punched metalplate fasteners100
1
1 for all other fasteners
w
w
� �� �� � �
�� � = � �� ���
e90,Rk
e
14
1
=� �
− ��
hF b w
h
h
Fracture mechanics background
14 is calibration parameter
w = (political factor)
Design clause 8.1.4 (3) is formulated as a maximum shearforce criterion on either side of the connection
Brussels, 18-20 February 2008 – Dissemination of information workshop 65
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Splitting by perpendicular to grain forces
Some empirical models consider
Fastener spacing
�=
��
��
�=
��
��
�
+=
��
��
�+=
n
i i
r
s
.
hh
nk
ha.
.maxk
f)ht(ha
.kkF
1
2
1
kt,90,80
ef2
2
rsk90,
4170
1
1856
Brussels, 18-20 February 2008 – Dissemination of information workshop 66
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Splitting by perpendicular to grain forces
Fracture mechanicalmodel
Consider energybalance after crack appearance
Brussels, 18-20 February 2008 – Dissemination of information workshop 67
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Splitting by perpendicular to grain forces
UK-Test results versus design proposals
05000
100001500020000250003000035000400004500050000
0 0,2 0,4 0,6 0,8 1
he/h
Str
engt
h [N
]
Test Results Eurocode 5 design
Punched metal plate fasteners
Brussels, 18-20 February 2008 – Dissemination of information workshop 68
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Comparison between models
Eurocode 5
Brussels, 18-20 February 2008 – Dissemination of information workshop 69
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Splitting by perpendicular to grain forces
Assumed governing failure mechanism is shearNot by tensile stresses perpendicular to grain
For loaded edges>0,7 h ���� no splitting
Simply supported����max F
Cantilever beam���� max F/2
F
F/2
hh
hh
he
he
Brussels, 18-20 February 2008 – Dissemination of information workshop 70
EUROCODESBackground and Applications EN1995-1-1: Section 8 - Connections
Frequently heard:
Not found in Eurocode
We don’t know everything
Research in progressFuture changes and additions are
expected