Steel&Timber Structures
Steel&Timber Structures
Evaluation of Embedment Strength Data to
Enable Reliability Analyses of Connections
with dowel type fasteners
Evaluation of Embedment Strength Data to
Enable Reliability Analyses of Connections
with dowel type fasteners
Ad Leijten TU-Delft
Jochen Köhler ETH-Zürich
Results of a STSM
Ad Leijten TU-Delft
Jochen Köhler ETH-Zürich
Results of a STSM
Steel&Timber Structures
Steel&Timber Structures
EC5 Deterministic model
EC5 Deterministic model
−
Double shear fasteners
−
Double shear fasteners
h,1,k 1
h,2,k 2
y,Rk
h,1,k 1
v,Rk
2
h,1,k
1
y,Rk h,1,k
(g)
0,5
(h)
4 (2
)
min 1,05
2 (1
)
(j)
2
2
1,15
2
(k)
1
f t d
f t d
M
f t d
F
f d t
M
f d
β
β
β
β
β
β
β
β
+
=
+
+
−
+
+
Steel&Timber Structures
Steel&Timber Structures
Determination Embedment strength
according to EN383
Determination Embedment strength
according to EN383
Steel&Timber Structures
Steel&Timber Structures
Stress displacement diagrams
Parallel and Perpendicular
Stress displacement diagrams
Parallel and Perpendicular
Steel&Timber Structures
Steel&Timber Structures
Embedment Definition
Embedment Definition
Steel&Timber Structures
Steel&Timber Structures
Data bases
Data bases
Source
Parallel to grain
Perp. To
Total
grain
NAILS (not-drilled)
tension
compr.
compr.
Whale and Smith (1985a,b)
400
120
400
920
DOWELS
Whale and Smith (1985a,b)
360
120
360
840
Ehlbeck and Werner (1992)
79
45
30
154
Sawata and Yasumura (2003)
503
506
1009
Mischler (not published)
80
50
130
Vreeswijk (2003)
62
62
Total Dowels
1249
946
2195
Total Nails + Dowels
1769
1346
3115
Steel&Timber Structures
Steel&Timber Structures
mean
st.d
COV
Sitka Spruce
357
393
39,1
10
Scots Pine
119
458
59
13
European Redwood
358
460
46,6
10
European Whitewood
119
390
41,6
11
Spruce Pine Fir
119
411
36,8
9
Picea jezoerisis (Jap)
1009
398
44,2
11
Spruce
151
446
51,7
12
Coniferous
n
density
Steel&Timber Structures
Steel&Timber Structures
mean
st.d
COV
Keruing
200
707
60,9
9
Greenhart
120
905
35,9
4
Beech
56
717
33,1
5
Teak
5
652
9,7
1
Oak
30
718
36,7
5
Merbau
19
802
36,5
5
Afzelia
20
714
24
3
Bongossi
35
1086
56,3
5
Massaranduba
10
972
27,3
3
Angelim Vermelho
11
1104
40
4
Azobe
10
1072
11,2
1
Cumaru
10
1142
18,7
2
n
density
Deciduous
Steel&Timber Structures
Steel&Timber Structures
Correlations Coniferous wood species
Sitka Spruce n=357 Diameter Emb
Euro Whitew n=119 Diameter Emb
Diameter
1
Diameter
1
Embedment
0,16
1
Embedment
0,57
1
Density
-0,25
0,49 Density
0,36
0,61
Scots Pine n=119
Spr. Pine Fir n=119
Diameter
1
Diameter
1
Embedment
0,07
1
Embedment
0,32
1
Density
0,17
0,76 Density
-0,09
0,41
Euro Redw. n=358
Jap. Pine n=1009
Diameter
1
Diameter
1
Embedment
0,23
1
Embedment
-0,13
1
Density
0,03
0,5 Density
0,11
0,28
Steel&Timber Structures
Steel&Timber Structures
Oak n=30
Diameter Emb
Beech n=56
Diameter Emb
Diameter
1
Diameter
1
Embedment
-0,24
1
Embedment
-0,65
1
Density
-0,01
0,57 Density
0,18
0,17
Bongossi n=35
Merbau n=19
Diameter
1
Diameter
1
Embedment
-0,85
1
Embedment
-0,79
1
Density
0,85
-0,7 Density
0,5
-0,13
Correlations Deciduous wood species
Steel&Timber Structures
Steel&Timber Structures
Data analyses
Assumption:
-Density and Diameter are
Independent variables
Steel&Timber Structures
Steel&Timber Structures
Identified combinations
for multi-linear regression
analyses
with
NAILS
DOWELS
Coniferous parallel
parallel
perpendicular perpendicular
Deciduous parallel
parallel
perpendicular perpendicular
Steel&Timber Structures
Steel&Timber Structures
for multi-linear regression analyses
With:
femb
is the embedment strength
A,B and C model parameters
is the density
d
is the fastener diameter
B C
h
f A d
ρ
=
ρ
ρ
*
*
*
*
h
f A B
Cd
ρ
ε
=
+
+
+
Steel&Timber Structures
Steel&Timber Structures
Nails
Nails
n=397
n=319
n=120
n=80
Parallel
Perpend Parallel
Perpend
Coniferous Coniferous Deciduous Deciduous
µa0
-4,562785 -3,085869 -5,533446 -7,904825
σa0
0,439676 0,390547 0,513015 0,533076
µa1
1,345241 1,148261 1,506924 1,886664
σa1
0,071756 0,064172 0,076790 0,079256
µa2
-0,272704 -0,419665 -0,181376 -0,418183
σa2
0,029885 0,026845 0,037282 0,038645
µsigeps
0,174512 0,140670 0,119008 0,100721
σsigeps
0,004379 0,003938 0,005432 0,005630
cov(a0;a1)
-0,995002 -0,994941 -0,993812 -0,993843
cov(a2;a1)
0,084639 0,039359 0,005608 0,004097
cov(a2;a0)
-0,181708 -0,137500 -0,114606 -0,112836
cov(a2;sigeps) 0,000030 -0,000033 0,000034 0,000258
cov(a0;sigeps) 0,000047 0,000580 0,000823 0,000177
cov(sigeps;a1) -0,000054 -0,000584 -0,000833 -0,000208
Regression parameters
Steel&Timber Structures
Steel&Timber Structures
Regression results
Nails Parallel All Coniferous Species
10,0
15,0
20,0
25,0
30,0
35,0
40,0
45,0
50,0
300
400
500
600
Density [kg/m3]
Embedment [N/mm2]
2,65mm top
6mm bottom
2.65mm data
6mm data
Steel&Timber Structures
Steel&Timber Structures
Regression results
Nails Parallel All Coniferous Species
10,0
15,0
20,0
25,0
30,0
35,0
40,0
45,0
50,0
300
400
500
600
Density [kg/m3]
Embe
dme
n
t [N/mm2
]
3,35mm top
5mm bottom
3.35mm data
5mm data
Steel&Timber Structures
Steel&Timber Structures
Regression results
Nails Perpendicular All Coniferous Species
10,0
15,0
20,0
25,0
30,0
35,0
40,0
45,0
50,0
300
400
500
600
Density [kg/m3]
Embedment [N/mm2]
2,65mm top
6mm bottom
2.65mm data
6mm data
Steel&Timber Structures
Steel&Timber Structures
Regression results
Nails Perpendicular All Deciduous
0,0
20,0
40,0
60,0
80,0
100,0
120,0
500
600
700
800
900
1000 1100
Density [kg/m3]
Embedment [N/mm2]
3,35mm top
6mm bottom
3.35mm data
6mm data
Steel&Timber Structures
Steel&Timber Structures
Regression results
Dowels Parallel Japanese Pine
10,0
15,0
20,0
25,0
30,0
35,0
40,0
45,0
50,0
300
350
400
450
500
550
600
density
embedment
8mm top
12mm
16mm
20mm bottom
8mm data
12mm data
16mm data
20mm data
Steel&Timber Structures
Steel&Timber Structures
Regression results
Dowels Perpendicular Japanese Pine
10,0
15,0
20,0
25,0
30,0
35,0
40,0
45,0
50,0
300
350
400
450
500
550
600
density
embedment
8mm top
12mm
16mm
20mm bottom
8 mm data
12 mm data
16 mm data
20 mm data
Steel&Timber Structures
Steel&Timber Structures
Regression results
Dowels Parallel Coniferous excl. Japanese data
10,0
15,0
20,0
25,0
30,0
35,0
40,0
45,0
50,0
55,0
60,0
300
350
400
450
500
550
600
density
embedment
5mm top
8mm
12mm
16mm
20mm bottom
5mm data
7mm data
8mm data
12mm data
16mm data
20mm data
Steel&Timber Structures
Steel&Timber Structures
Principal of lower 5%-Fractile prediction
EC5
Steel&Timber Structures
Steel&Timber Structures
Prediction of 5%-Fractile for Nails
Nails d = 3.35 mm (n=140) Parallel All Coniferous Species
0
5
10
15
20
25
30
35
40
45
50
300
350
400
450
500
550
600
Density [kg/m^3]
embeding strength [MPa]
5%-Frac
Mean regression
3.5mm data
EC5
Steel&Timber Structures
Steel&Timber Structures
Prediction of 5%-Fractile for Nails
Nails Perpendicular (n=100) All Coniferous Species
0
10
20
30
40
50
60
300
350
400
450
500
550
600
Density [kg/m^3] (5%-Frac)
embeding strength [MPa] (5%-
Frac)
5%-Frac
Mean
3.35mm data
EC5
Steel&Timber Structures
Steel&Timber Structures
Prediction of 5%-Fractile for Dowels
Dowels Parallel (n=140) Coniferous excl. Japanese Pine
0
10
20
30
40
50
60
300
350
400
450
500
550
600
Density [kg/m^3]
Embeding strength [MPa
]
5%-Frac
Mean 12 mm
12 mm Data
EC5
Steel&Timber Structures
Steel&Timber Structures
Prediction of 5%-Fractile for Dowels
Dowels (n = 116) Parallel Japanese Pine
0
10
20
30
40
50
60
300
350
400
450
500
550
600
Density [kg/m^3]
Em
beding strength [M
Pa]
5%-Frac
Mean
20 mm Data
20 mm EC5
Steel&Timber Structures
Steel&Timber Structures
Prediction of 5%-Fractile for Dowels
Dowels Perpendicular (n=118) Japanese Pine
0
5
10
15
20
25
30
300
350
400
450
500
550
600
Density [kg/m^3]
embeding strength [MPa]
5%-Frac
20mm Mean
20 mm Data
20mm EC5
Steel&Timber Structures
Steel&Timber Structures
Prediction of 5%-Fractile for Dowels
Dowels Parallel (n=65) Deciduous Species
0
20
40
60
80
100
120
140
500
600
700
800
900
1000
1100
1200
Density [kg/m^3]
e
m
be
ding s
tre
ngth [MPa
]
5%-Frac
8 mm Mean
8 mm Data
8 mm EC5
Steel&Timber Structures
Steel&Timber Structures
Prediction of 5%-Fractile for Dowels
Dowels Parallel (n=91) Deciduous Species
0
20
40
60
80
100
120
500
600
700
800
900
1000
1100
1200
Density [kg/m^3]
embeding strength [MPa
]
5%-Frac
16 mm Mean
16 mm Data
16 mm EC5
Steel&Timber Structures
Steel&Timber Structures
Conclusions:
- Reliability evaluation results in
considerable lower 5% embedment
strength compared to Eurocode 5.
-Assumed cov of density (10%) and
embedment strength (20%) does not
affect 5% embedment as much as
uncertainty in regression
