Web splice

1
Chapter 10

• Web splice

2
Introduction The web of a plate girder consists
generally of several pieces connected together,
since web plate can be obtained according to the
depth in the lengths from 5 to 10 m only. In
welded construction, shop web splice shall be
made with penetration butt welds next Fig ()
3
Field splices in the web shall be designed to
resist the shear and moments at the splice
section. In bolted construction, splice plate
shall be provided on each side as shown in last
Fig. (). If a web is cut at section S S, the
normal stresses and shear stresses at the section
must be transferred from
4
plate A to plate B by splice plates and bolts.
One of the best methods to make a web splice is
to put splice plates on the web 1-Calculation of
splice plate The compression force C1 in the part
of the web (height p1) is transmitted by the two
bolts r1 to the splice plates and from there by
the two bolts to the web plate B.
5
let m No. of bolts in one row depending on
diameter of bolts and pitch. n number of rows
on one side of the splice
6
Horizontal force on one bolt
The shearing force Q is transmitted from the web
plate A by all the bolts in this side to the
splice plate S and from their by all the bolts in
the other side to the web plate B. ? Vertical
force on one bolt
-         The additional forces due the couple
Q?e are usually neglected. - Minimum number
of rows of bolts in the splice plate S is two. ?
Maximum force on remotes bolt
7
-         This maximum force ? (Rsh and
Rb). -         Rsh the shear strength of bolts
(clause 6.4.1, p100). -         Rb the bearing
strength of bolts (clause 6.4.2, p100). qb 0.25
Fub For bolts of grade (4.6, 5.6, 8.8) qb 0.20
Fub For bolts of grade (4.8, 5.8, 6.8, 10.9) Rsh
qb ?As ?n (n No. of shear planes) Rb Fb ?
d ? min? t Fb ? ? Fub
8
Fb ? ? Fub ? depends on end distance (S),
(Table 6.2)
?3d
?2.5d
?2 d
?1.5d
?
9
2-Second Method for web splice The number of
bolts connecting the splice plate to the web is
determined from the condition that the resisting
moment of the web should equal the resisting
moment of the bolts. Let M and Q be the maximum
resistance bending moment and the actual shear
force respectively at the splice section. Mw ?
bending moment takes by the web
The bolts in splice are subjected to vertical
force due to shear force and to horizontal force
to bending moment.
10
Due to moment there will be horizontal force in
each bolt which will be proportional to the
distance of the bolt from the C.G of the bolt
group (all bolts are of the same diameter). Due
to shear, the bolts are subjected to vertical
force and it is assumed that this force is the
same in all bolts. The pitch of bolts provided
should be uniform. This can be proved as shown
below- Let Fmax be the force in the bolt
situated as maximum distance dmax from the C.G of
the bolt group. The force Fi in any bolt at di
distance from C.G of the bolts will be given by
11
I the moment of inertia about the neutral axis
of the bolt group on one side only of the splice
above and below the neutral axis
12

Vertical force due to shear Qbolt
13
Maximum force on remotest bolt least
strength of one bolt (shear or bearing) R
Putting . Number of rows .
3-Thickness of splice plate Two splice
plates, one on each side, are provided the moment
of inertia of the two splice plates must be less
than the moment of inertia of the web.
14
Note hs hw - 2- ?5 cm hs hw - (5 ?10 cm
)