POUTRE A AME PLEINE

PLATE WEB GIRDER

Abrégé anglais

ABSTRACT
A plate web girder comprising two flanges spaced by
a web of which the web comprises a metal sheet which is
"rippled", that is corrugated with small amplitude small
wave length corrugations or ripples and then corrugated
with large amplitude large wave length corrugations;
both the ripples and the corrugations extending in the
same direction from flange to flange.

Revendications

CLAIMS
1. A girder comprising a corrugated web having
curvilinear corrugations, said web being fixedly
interposed between two flanges, wherein said web is
rippled, the ripples extending in a direction
substantially parallel to the direction of extension of
the corrugations and wherein the wave length "b" of the
ripples is in the range
3t ? b ? 6t
wherein "t" is the thickness of the web material and the
apmplitude "a" of the ripples is in the range
2t ? a ? 6t.
2. A girder according to claim 1 wherein the wave length
"L" of the corrugations is in the range
2A ? L ? 4A
where "A" is the amplitude of the corrugations.
3. A girder according to claim 1 fabricated from metal.
4. A girder according to claim 2 fabricated from metal.
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Description

The present invention relates to plate web girders
which conventionally comprise a pair of elongate parallel
spaced apart flanges and an elongate web extending
therebetween.
It is well established that, when a bending moment is
imposed upon such plate web girders a large proportion of
the resultant bending stress is carriecl by the flanges and
that the web must be sufficiently stiff to hold the
flanges in spaced apart parallel relationship. That is to
say, the integrity of the girder depends inter alia, on
the web not buckling.
It is known to corrugate the web to increase its
stiffness to thereby provide a girder with an improved
increased strength to weight ratio. However, it has been
found that large corrugated webs are none the less prone
to buckling because due to the size of the corrugations,
the web acts locally like a plane web and as a result
local buckling may occur.
It is an object of the present invention to provide
an improved girder.
Accordingly, the present invention consists in a
girder co~prising a corrugated web as defined herein,
fixedly interposed between two flanges, characterised in
that said web is rippled, the ripples extending in a
direction substantially parallel to thè direction of
extension of the corrugations.
A preferred embodiment of the present invention will
now be described by way of example only, with reference
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to the accompanying drawings in which;
Figure 1 is a sectional plan view of a girder
according to the invention; and
Figure 2 is an enlarged sectional plan view showing
an encircled portion of the girder in figure 1.
Referring to the drawings, a girder 1 is shown which
comprises a corrugated web 2 fixedly interposed between
two flanges 3, only the lower one of which is shown for
clarity.
As is best shown in figure 2 the corrugated web 2 is
rippled.
Preferably, the thickness "t" of the web material
is in the range,
2t~ a~ 6t
where "a" is the amplitude of the ripples.
Additionally, the wave length "b" of the ripples
should be in the range
3t~ b ~6t
It has been found that a suitable way of producing
the rippled corrugated plate is to firstly pass a flat
plate through a press which stamps the ripples, a few at
a time, into the plate using a pair of dies fashioned in
the manner of a pair of intermeshing racks. The rippled
un-corrugated sheet is then passed betwèen a pair of
parallel rollers, each having axially extending, radially
projecting, intermeshing protruberances which effect the
bending of the rippled plate into its final corrugated
form. The rippled corrugated web is then welded to the
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flanges in conventiorlal manner.
Preferably, the wave lenght "L" of the corrugations
is in the range,
~ A ~ L ~ 4A
where "A" is the amplitude of the corrugations.
In the preferred embodiment the corrugations are
defined by a serles of substantially semi-circular,
opposed curve portions. However, a corrugated web is
d~flned herein to comprise a web being corrugated in any
manner so as to have crests and troughs and is not
restricted to include only webs having sinusoidal
corrugations.
Similarly the ripples may have any of the
abovementioned forms.
For preference the gi~ders are fabricated rom steel
however, they may be fabricated from any metal or from
any suitable plastic.
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Dessin représentatif