Civil Engineering Reference
In-Depth Information
F
Ed
F
Ed
b
a
h
e
b
FFF
,Ed,1
FFF
,Ed,2
b
/2
b
/2
b
b
/2
b
/2
b
Figure 19.15 Inclined forces acting on a connection (BSI, 2004). Permission to reproduce extracts from BS EN 1995-1-1 is granted by BSI
0
3
5
0
03
w
pl
where w = max
or 1.00 for punched metal plate fasteners
100
or 1.00 for all other fasteners
[8.5]
b
c
d
e
f
w
pl
is the width of the punched metal plate fastener paral-
lel to the grain in mm,
a
ttt
ttt
ttt
and
kF
mo
kF
mo
k
90,k
k
90,k
kF
F
9R
F
9R
0
9R
09R
d
γ
γ
M
M
19.7.2 Dowel type fasteners
The basic theory of dowel type fasteners was developed by
K. W. Johansen and taken further at Brighton University.
The bearing and yield patterns for two and three member
timber-to-timber joints and panel to timber joints are shown in
Figure 19.16
and these are related to the relevant expressions
in
Figure 19.17
.
h
j
k
g
Figure 19.16 Failure modes in 2 and 3 member joints made with
steel plates (BSI, 2004). Permission to reproduce extracts from BS EN
1995-1-1 is granted by BSI
For a thin steel plate in single shear:
Johansen's formulae assume a 'frictionless' dowel that can
slip in the fastener hole under the forces applied to the joint.
Nails (particularly deformed nails such as annular ring shank),
screws and bolts with the prescribed washers are not 'friction-
less' and give an enhancement to the Johansen effect. This
enhancement was proved for bolts at Nottingham University
when the Johansen component alone was found some 30%
lower than the equivalent BS 5268 values!
Note that there is a limit to this enhancement for each type
of fastener, for example, staples 0%, plain round wire nails
15%, other nails 50%, screws 100%, bolts 25% and dowels
0% of Johansen.
Similar failure modes and formulae are given for combin-
ations of steel plates and timber (
Figure 19.17
). Steel plates
are classifi ed as 'thin' if the plate thickness is less than 0.5
fastener diameter and 'thick' if more than one fastener diam-
eter. For plates between 'thin' and 'thick', interpolation of the
formulae is required.
0.
0
.
.
ft
ftd
ftd
d
(
)
a
ft
h,
ft
1
h,
ft
h,
ft
1
F
min
F
=
F
y,R
y,R
k
k
ax,R
F
ax,R
F
11
,
,
11
,
552
52
52
Mf
Mf
d
d
ax,R
ax,Rk
k
(
b
)
+
Mf
y,R
Mf
Mf
y,R
Mf
h,k
Mf
h,k
h,k
Mf
h,k
4
y,R
Mf
y,R
Mf
h,k
Mf
h,k
4
For a thick steel plate in single shear:
f
t d
()
()
c
h,
k
t
t
1
h,
k
+
4
M
F
y,Rk
FF
x,R
k
F
mi
f
t d
2
1
()
d
d
()
=
mi
n
f
f
t
t d
d
2
+
+
−
F
y,R
y,R
k
h,
k
k
t
t
t
1
h,
k
t
t
1
2
4
h,
k
f dt
h
f d
f d
f d
h
f d
1
F
F
a
a
x,R
k
23
,
,
23
,
Mf
Mf
y,
Mf
y,Rkh
M
kh
kh
d
d
a
ax,R
x,Rk
k
(
)
+
e
y,Rkh
kh
M
kh
kh
kh,k
,k
y,R
y,
Mf
y,R
4
y,Rkh,k
4
For a steel plate of any thickness as the central member of a
double shear connection:
