U.S. patent application number 10/983741 was filed with the patent office on 2005-04-21 for structural element.
Invention is credited to St. Quinton, David.
Application Number | 20050081477 10/983741 |
Document ID | / |
Family ID | 34525085 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050081477 |
Kind Code |
A1 |
St. Quinton, David |
April 21, 2005 |
Structural element
Abstract
A structural element (1, 20, 30, 40) comprises a web (2)
extending between a pair of flanges (3, 4). The areas of particular
structural importance are the portions (5, 6) of the web and
flanges adjacent to the junction between the web and the flanges.
Material is gathered into these structurally important areas of an
otherwise thin component. This is achieved by providing a plurality
of small ribs (10) to absorb the material in these structurally
important areas (5, 6). The ribs (10) are on a pitch of 2 to 8
times the wall thickness t. The pitch is approximately the same as
a typical self drilling, self tapping fastener to prevent skating
of the fastener, on fixing. The ribs (10) are of a depth of between
1.5t and 3.0t, where t is the metal thickness. These parameters
ensure that in terms of fixing, the ribs allow a fastening screw to
be used and to perform in the same manner as with a flat faced
flange or web.
Inventors: |
St. Quinton, David;
(Scarborough, GB) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W.
SUITE 600
WASHINGTON
DC
20004
US
|
Family ID: |
34525085 |
Appl. No.: |
10/983741 |
Filed: |
November 9, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10983741 |
Nov 9, 2004 |
|
|
|
PCT/IE03/00067 |
May 12, 2003 |
|
|
|
Current U.S.
Class: |
52/846 |
Current CPC
Class: |
E04B 2/7881 20130101;
E04C 3/07 20130101; E04B 2/789 20130101; E04C 2003/0482 20130101;
E04C 2003/0473 20130101 |
Class at
Publication: |
052/720.1 |
International
Class: |
E04C 003/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 10, 2002 |
IE |
2002/0371 |
Claims
1. A structural element comprising a web and at least one flange
extending from the web, the element comprising a plurality of
curved stiffening ribs extending along the longitudinal length of
the element, the ribs being formed in the structural element at
regions of structural importance of the element without
substantially reducing the wall thickness, the pitch of the ribs
being from 2 to 8 times the wall thickness of the structural
element.
2. A structural element as claimed in claim 1 wherein the pitch of
the ribs is from 3 to 7 times the wall thickness of the structural
element.
3. A structural element as claimed in claim 1 wherein the pitch of
the ribs is from 3 mm to 8 mm.
4. A structural element as claimed in claim 1 wherein the pitch of
the ribs is from 3.8 mm to 7.8 mm.
5. A structural element as claimed in claim 1 wherein the depth of
the ribs is from 1.5 to 3 times the wall thickness of the
structural element.
6. A structural element as claimed in claim 1 wherein the bend
radius of the ribs is from 0.5 to 3 times the wall thickness of the
structural element.
7. A structural element as claimed in claim 6 wherein the bend
radius of the ribs is substantially equal to the wall thickness of
the structural element.
8. A structural element as claimed in claim 1 wherein the rib has a
bottom radius which subtends an arc of between 20.degree. and
128.degree..
9. A structural element as claimed in claim 8 wherein the radius
subtends an arc of between 70.degree. and 100.degree..
10. A structural element as claimed in claim 1 wherein the
structural element comprises a pair of flanges and the web extends
between the flanges.
11. A structural element as claimed in claim 1 wherein the ribs are
provided in the or each flange of the structural element.
12. A structural element as claimed in claim 1 wherein the ribs are
provided on the web of the structural element.
13. A structural element as claimed in claim 1 wherein the ribs are
provided adjacent a corner portion between the web and at least one
of the flanges.
14. A structural element as claimed in claim 13 wherein the ribs
are provided adjacent corner portions between the web and the
flanges.
15. A structural element as claimed in claim 1 wherein the flanges
extend from the web in the same direction.
16. A structural element as claimed in claim 1 wherein the flanges
extend from the web in opposite directions.
17. A structural element as claimed in claim 1 wherein the web is
substantially straight.
18. A structural element as claimed in claim 1 wherein the web has
one or more bends therein.
Description
[0001] The invention relates to structural elements of the type
comprising a web extending between a pair of flanges. Such
structural elements are generally of roll formed steel section.
[0002] A large number of structural elements of this type are known
and used widely, for example in building construction. Various
complex sections have been developed to provide particular
structural performance. Such known sections are however generally
inefficient in terms of the amount of material required to achieve
a desired structural performance because they are derived from a
strip of uniform thickness. Generally the dimensions of the section
are altered to achieve desired properties. For example, the width
of the flanges may be increased to strengthen the section. However,
this has the disadvantage of destabilising the section by moving
the centre of rotation of the section (typically a C or sigma
section) further away from the centroid of the section.
[0003] This increases the need for struts and rotational restraints
or a deeper indent in the web in a sigma or zed section which
thereby loses the advantage of material saving. With zed type
sections, the effect is to change the angle of the neutral axis,
which in most lower pitch applications will move the performance
away from optimum. There is also a threshold at which a long
slender element becomes ineffective and prone to buckling.
[0004] The thickness of the section may be increased to improve
structural properties. However, this results in higher material
costs and the additional cost is not proportional to the
improvement in structural properties.
[0005] It is known to provide a large rib in the flange and/or web
of such a section in an attempt to stiffen the flange by reducing
the effective width. However known sections of this type have the
disadvantage that they reduce the effective width of the flange
which can be screwed into when fastening cladding or the like to
the section. If the rib is hit by a cladding fastener, the fastener
will skate to the bottom of the rib and thereby elongate the hole
into which the fastener is held and the fastening is therefore not
complete. With deep ribs conventional fasteners may not be long
enough to fasten efficiently at the bottom of the rib leading to
potential puncturing of the cladding with an elongate hole. There
is a further problem if the outer part of the web is to be
stiffened by a larger rib since such a large rib may prevent the
use of normal fasteners in the most advantageous fixing
position.
[0006] There is therefore a need for an improve structural element
which will address these problems. In particular, there is a need
for a structural element which can be manufactured from the
thinnest metal without sacrificing structural strength.
STATEMENTS OF INVENTION
[0007] According to the invention there is provided a structural
element comprising a web and at least one flange extending from the
web, the element comprising a plurality of curved stiffening ribs
extending along the longitudinal length of the element, the ribs
being formed in the structural element at regions of structural
importance of the element without substantially reducing the wall
thickness, the pitch of the ribs being from 2 to 8 times the wall
thickness of the structural element.
[0008] In one embodiment the pitch of the ribs is from 3 to 7 times
the wall thickness of the structural element.
[0009] In another embodiment the pitch of the ribs is from 3 mm to
8 mm. Preferably the pitch of the ribs is from 3.8 mm to 7.8
mm.
[0010] In one embodiment the depth of the ribs is from 1.5 to 3
times the wall thickness of the structural element.
[0011] In another embodiment the bend radius of the ribs is from
0.5 to 3 times the wall thickness of the structural element.
Preferably the bend radius of the ribs is substantially equal to
the wall thickness of the structural element.
[0012] In one embodiment the rib has a bottom radius which subtends
an arc of between 20.degree. and 128.degree.. Preferably the radius
subtends an arc of between 70.degree. and 100.degree..
[0013] In one embodiment the structural element comprises a pair of
flanges and the web extends between the flanges.
[0014] In another embodiment the ribs are provided in the or each
flange of the structural element.
[0015] In a further embodiment the ribs are provided on the web of
the structural element.
[0016] In one embodiment the ribs are provided adjacent a corner
portion between the web and at least one of the flanges.
[0017] In another embodiment the ribs are provided adjacent corner
portions between the web and the flanges.
[0018] In one embodiment the flanges extend from the web in the
same direction.
[0019] In another embodiment the flanges extend from the web in
opposite directions.
[0020] In one embodiment the web is substantially straight.
[0021] In another embodiment the web has one or more bends
therein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The invention will be more clearly understood from the
following description thereof given by way of example only with
reference to the accompanying drawings, in which:--
[0023] FIG. 1 is a cross sectional view of a structural element
according to the invention;
[0024] FIG. 1a is an enlarged view of a rib detail of the
structural element;
[0025] FIG. 1b is an enlarged view showing a detail of a single
rib.
[0026] FIG. 2 is a cross sectional view of another structural
element;
[0027] FIG. 3 is a cross sectional view of a further structural
element; and
[0028] FIG. 4 is a cross sectional view of another structural
element according to the invention.
DETAILED DESCRIPTION
[0029] Referring to the drawings there are illustrated profiles of
various structural elements according to the invention. These
profiles are indicative only and the invention may be applied to a
wide variety of sections of this type.
[0030] In FIG. 1 the structural element 1 has a generally C-profile
comprising a web 2 extending between a pair of flanges 3, 4 which
in this case extend generally at right angles to the web 2 from the
same side of the web. The areas of particular structural importance
are the portions 5, 6 of the web and flanges adjacent to the
junction between the web and the flanges. According to the
invention material is gathered into these structurally important
areas of an otherwise thin component. This is achieved by forming a
plurality of small ribs 10 to absorb the material in these
structurally important areas 5, 6. The ribs 10 are on a pitch which
is approximately the same as a typical self drilling, self tapping
fastener to prevent skating of the fastener, on fixing. The pitch p
of the ribs is from 2 to 8 times, most preferably from 3 to 7 times
the wall thickness (t) of the structural element. The ribs 10 are
of a depth x of between 1.5t and 3.0t. The bend radius r of the
ribs is from 0.5 to 3 times the wall thickness t, most preferably
approximately equal to the wall thickness.
[0031] The typical size of fixings used for cladding is between 4.8
mm and 6.5 mm. The pitch p of the ribs should preferably be between
0.8d and 1.2d, where d is the fastener diameter. Thus, the pitch p
should be from about 3 to about 8 mm, preferably from 3.8 mm to 7.8
mm. These parameters ensure that in terms of fixing the ribs allow
a fastening screw to be used and to perform in the same manner as
with a flat faced flange or web. A large portion of the flange is
subject to plastic deformation in the manufacturing process,
thereby increasing the yield strength of a large part of the
flange.
[0032] Referring in particular to FIG. 1(b) each rib is symmetrical
about a longitudinal axis and has lead-in portions defined by arcs
and a bottom with a radius which subtends an arc .alpha. of between
20.degree. and 128.degree., most preferably 70.degree. to
100.degree..
[0033] Small ribs of this type (ratio of pitch to bolt to be less
than 0.75 of the diameter) may be used in the locality of fixing
bolts with a benefit to the bearing capacity of the connection by
virtue of the increased area of metal contact with the bolt. Such
localities comprise the web of the structural element, the bolts
being used to fix the web to a cleat.
[0034] The following properties of structural elements of the
invention are improved:
[0035] 1. Section modulus Z.sub.xx
[0036] 2. Section moment of inertia I.sub.xx
[0037] 3. Local yield strength Y.sub.a
[0038] 4. Specific tortional stiffness (compared to weight and
thickness of parent material)
[0039] 5. Screw pull out capacity
[0040] 6. Screw spin out capacity
[0041] 7. Material distribution in section.
[0042] The following properties of structural elements of the
invention are not adversely affected:
[0043] 1. Angle of section neutral axis
[0044] 2. The freedom to position section fastening bolts in the
web
[0045] 3. The freedom to position fasteners in the flange.
[0046] In the invention, the material which would produce a wide
flange with the attendant problems described above is condensed
into a narrower flange using a plurality of small ribs formed in
the flange. A similar effect is achieved in the web.
[0047] Referring to FIG. 2 there is illustrated another structural
element 20 which is similar to that described with reference to
FIG. 1 and like parts are assigned the same reference numerals. In
this case the web has an indent 21 and the section is of sigma
shape.
[0048] Referring to FIG. 3 another structural element 30 of zed
section is illustrated in which the flanges extend on opposite
sides of the web.
[0049] Another structural element 40 similar to the element of FIG.
3 is illustrated in FIG. 4. The web in this case has an indent
41.
[0050] The material of the structural elements is generally
galvanised steel.
[0051] The sections may be of a range of different shapes and
sizes. For example, small ribs could be provided in structurally
significant regions of any suitable thin gauge components. For
example, the invention may be applied to profiled metal sheet
decking of the type described in WO 00/04250A. Such ribs could be
applied to the flanges of such decking to enhance the deflecting
and bending capacity of the decking.
[0052] The invention is not limited to the embodiments hereinbefore
described which may be varied in detail.
* * * * *