[0001] This invention relates to a roof, wall or floor structure comprising at least two
structural members and a purlin extending between the structural members and connected
thereto by cleats, one fixed to each of said two structural members. The structural
members comprise rafters, columns or beams, respectively, depending upon whether the
structure is a roof, wall or floor structure. The purlins usually support an outer
roof or wall cladding such as asbestos or metal sheets or flooring sheets of any conventional
material.
[0002] GB-A-1,487,244 discloses a structure comprising at least two structural members and
a purlin supported by and extending between the structural members and connected thereto
by cleats, one fixed to each of said two structural members, wherein the purlin comprises
a cold rolled section having a pair of spaced side-by-side generally parallel opposed
flanges, each having an inturned lip at one edge and the flanges being interconnected
by a web part at their other edges, the web part comprising a median portion perpendicular
to the flanges and connected by inclined portions to edge portions of the web which
are connected to the flanges to extend perpendicular thereto.
[0003] The purlins used in such structures by virtue of their shape are subject to forces
having a component which extends parallel to the structural members and which tends
to cause the purlins to rotate about a longitudinally extending axis and consequently
such known purlins have to be designed to withstand such forces, and as a result the
cost of a structure has been determined by the need to provide purlins of necessary
dimensions and mass.
[0004] GB-A-1562688 discloses a purlin per se in which the median portion of the web part
is disposed intermediate the one and other edges of the flanges and is offset from
the edge portions of the web part which are disposed at said other edges of the flanges.
[0005] An object of the invention is to provide a structure which is more economical to
produce than that described in GB-A-1,487,244.
[0006] In accordance with the present invention this aim is achieved by virtue that the
median portion of the web part is disposed intermediate the one and other edges of
the flanges and is offset from the edge portions of the web part which are disposed
at said other edges of the flanges, the cleats have a stiffness imparting configuration
and extend between and overlie the edge web portions and the purlin is connected to
the cleats by fasteners engaged with the edge web portions of the purlin.
[0007] The present invention achieves the above stated aim because the purlin, cleat and
fastener configuration according to the invention permits of a purlin comprising a
cold rolled section incorporating less material than has been necessary hitherto to
achieve the necessary strength.
[0008] Moreover, the purlin configuration is, itself, less susceptible to rotation than
many known purlin configurations since the shear centre is within the overall envelope
of the purlin which is to be contrasted with the position of the shear centre in a
conventional channel section purlin and the tendency of a Z-section purlin to rotate
about its longitudinal axis.
[0009] The purlin may be disposed with the web part extending transversely away from the
structural member and the web part may be perpendicular to the adjacent surface of
the structural member.
[0010] The inner flange of the purlin, i.e. that closest to the structural member may be
spaced from the adjacent surface of the structural member to avoid premature failure
by squashing of the purlin between the cleat and structural member.
[0011] The purlin may be provided with a stiffener comprising a member adapted to interfit
with the inner edge web portion, flange and lip to reinforce the inner connection
between the purlin and cleat.
[0012] The cleat may be of the same configuration as the purlin but without flange or may
be the same as the purlin except for the median web portion which may be wider or
narrower than that of the purlin.
[0013] The cleat may be fixed to the structural member by welding.
[0014] Alternatively, the cleat may be generally L-shaped, one limb being connected to the
structural member by fasteners and the other limb being connected to the purlin.
[0015] Longitudinally adjacent purlins may be connected together by a connecting member
of a configuration to conform to at least the web part of the purlins and fastened
to the web parts so as to span between the adjacent purlins.
[0016] The connecting member may be fastened to the edge web parts of the purlins.
[0017] The connecting member may have a flange to conform to and engage below the inner
flanges of the purlins.
[0018] The fasteners may be bolts, both for the cleat to purlin connection and for the cleat
to structural member connection.
[0019] The purlin may have dimensions in accordance with the following range:
[0020] Where F equals the width of each flange:
[0021] The invention will now be described in more detail by way of example, with reference
to the accompanying drawings, wherein:-
Figure 1 is a cross-sectional view through part of a roof structure embodying the
invention illustrating a purlin to rafter connection;
Figure 2 is an exploded fragmentary perspective view of the part of the roof structure
shown in Figure 1;
Figure 3 is an exploded fragmentary perspective view showing part of another roof
structure embodying the invention and showing a sleeved connection between two purlins;
Figure 4 is a diagrammatic illustration showing the cross-sections of a purlin, cleat
and sleeves used in the roof structure shown in the preceding Figures; and
Figures 5 and 6 are diagrammatic representations of the strength of a purlin to rafter
connection embodying the invention, compared with previously known purlin to rafter
connections.
[0022] Referring now to Figures 1 and 2, a roof structure embodying the invention comprises
a plurality of spaced parallel structural members comprising rafters 10 supported,
in conventional manner, on uprights (not shown). The rafters 10 may be of any desired
appropriate section, but in the example illustrated are of I-section and support their
upper surface 11 a plurality of spaced parallel purlins which extend at right angles
to the rafters 10. One such purlin is illustrated at 12 in Figures 1 and 2.
[0023] Each purlin 12 is connected to its associated rafter 10 by a cleat 13 which, in the
example illustrated, is welded, as indicated at 14 to the upper surface 11 of the
rafter 10.
[0024] The purlins 12 support an outer roof cladding (not shown) of conventional form, for
example, asbestos or metal cladding sheets.
[0025] The purlin 12 is made of cold rolled steel and comprises a pair of spaced side-by-side
parallel opposed flanges 15a, 15b each having an inturned lip 16a, 16b at one edge
which extend perpendicular to their associated flange, and the flanges being interconnected
at their other edges by a web part 17 which comprises a median portion 18 perpendicular
to the flanges and connected by inclined portions 19a, 19b to edge portions 20a, 20b
of the web part which are connected to the flanges to extend perpendicular thereto.
The edge portions 20a, 20b are disposed intermediate the one and other edges of the
flanges 15a, 15b and are offset from the edge portions 20a, 20b which are disposed
at said outer edges of the flanges 15a, 15b.
[0026] The dimensions of the purlin shown in Figures 1 and 2 are set out in the column headed
J in the table below with the metal thickness being 2.7 mm.
[0027] If desired, the purlin may have other dimensions such as those set out in Columns
A-J in the above table and it will be seen that each of the purlins of Columns A to
J may be made in material of any one of a number of specific thicknesses as may be
the purlin illustrated.
[0028] It will also be seen that the dimensions of the inclined web portions, edge web portions
and the angle of inclination of the inclined web portions to the remainder of the
web portions is identical for all of the range of sections. Furthermore, there are
five sections with a flange width of 70 mm, four sections with a flange width of 56
mm and all these have a lip height of 14 mm. There is also a section with a flange
width of 100 mm and lip height of 20 mm.
[0029] All the sections with the same flange and lip dimensions can be made using the same
rolls merely by inserting appropriate roll spacers to produce a median web portion
of the desired width, thereby contributing to the economy of production of the purlin
and hence the resultant roof structure.
[0030] In general terms, the section may have any desired dimensions lying within the following
range of dimensions:
[0031] Where F is equal to the flange width:
[0032] The cleat 13, in the example illustrated, is made of material having the same configuration
as that set out in Column J of the above table but without the flanges and, of course,
inturned lips. Thus the cleat may be made using the same rolling equipment as is used
to make the purlins.
[0033] As mentioned above, the cleat 13 is welded to the rafter 10 and the purlin is secured
to the cleat by four bolts 21 of 12 mm diameter which pass through apertures 26 in
the edge web portions 20a, 20b of the purlin and apertures 27 in the corresponding
portions of the cleat. In order to facilitate assembly of the roof structure, a bolt
check washer is provided as indicated at 22a, 22b. The check washer may be fitted
under either the head of the bolt, as indicated at 22a, or under the nut as indicated
at 22b. In both cases the check washers are of identical configuration having a main
part 23 through which the shank of the bolt extends and a lip 24 extending perpendicular
to the main part 23 to engage a flat on the head or the nut, and an inclined part
25 to engage an inclined portion 19a, 19b of the purlin, or a corresponding inclined
portion of the cleat, depending upon whether the check washer is engaged under the
head or the nut of the bolt.
[0034] If desired, any other suitable fastener may be used instead of bolts 21.
[0035] As will be seen from Figure 1, the inner flange 15b ofthe purlin is spaced from the
rafter 10 by about 10 mm in the example illustrated, so that in the event of any distortion
of the cleat the purlin is not squashed between the cleat and rafter.
[0036] Tests have been performed on the example illustrated in Figures 1 and 2 compared
with other fastening configurations and other purlin shapes and the results of these
tests are indicated in diagrammatic form in Figures 5 and 6 where Test 1 is a test
of a purlin to rafter connection, as illustrated in Figures 1 and 2, and the remaining
tests are of connections having the configurations illustrated in Figures 5 and 6.
It will be seen that the results obtained in Test 1 compared with the other tests
is surprisingly good.
[0037] Referring now to Figure 3, where it is desired to join two purlins 12 together of
the configuration described above, a connecting member having the same configuration
as the purlins, but without flanges, is provided, as illustrated at 30 in Figure 3.
It will be seen that the connecting member 30 is provided with eight apertures for
bolted connections, four of the apertures, indicated at 31, being used to accommodate
bolts corresponding to the bolts 21 illustrated in Figures 1 and 2, and the apertures
32 being provided to accommodate further bolts (not shown) passing through apertures
33 in the edge web portions 20a, 20b of the purlin.
[0038] Figure 4 is a diagrammatic illustration at (a) and (b) respectively of the cross-sections
of the purlin 12 and cleat 13 in Figures 1 to 3 and at (c) the connecting member 30
in Figure 3, as well as at (a) a stiffener 34 which is dimensioned to nest and interengage
with the lower edge web portion, flange and upturned lip and through which the inner
bolts 21 extend.
[0039] The provision of such a stiffener increases the strength of the connection still
further compared with the data given in Test 1.
[0040] An alternative form of connecting member 30a, shown at (d), has a flange 35 which
extends under the inner flange 15b of the purlin 12 to increase stiffness. The stiffener
34 may also be used with the connecting member 30a.
[0041] Normal methods of predicting purlin system load carrying capacity can be expressed
in the form: Where
Z=section modulus in cm3
W=load carried in kN
L=span in cm
K=constant
[0042] The higher the value of K then the lower the section modulus required to carry a
given load.
[0043] Calculations based on classical elastic bending theory give a value K of 182, for
the material quality used in the example illustrated. Tests of roof structures embodying
the invention show that a K value of 240 is to be expected. Furthermore, with regard
to cleat strength, it can be estimated that a conventional laminar cleat bent only
in a direction parallel to the purlin span will need to be 10 mm thick in order to
restrict its deflection to acceptable limits and to provide sufficient stiffness to
prevent premature failure being induced by crushing against the rafter or rolling
of the purlin.
[0044] The cleat of Applicant's invention in the example illustrated is of equivalent strength
to a 12 mm thick plate and has deflection characteristics of an 18 mm thick plate
and so ensures overall stability of the roofing structure without the addition of
external restraints and with considerable economy in material.
[0045] Although the invention has been described above as embodied in a roof structure,
the invention may be embodied in a wall or floor structure. In the case of a wall
structure, components corresponding to the rafters are disposed to provide columns
whilst the purlins act as rails and components corresponding to the roofing sheets
provide wall cladding which is typically vertical, whilst in the case of a floor structure
components corresponding to the rafters are disposed to provide floor beams and whilst
the purlins act as cross beams, components corresponding to the roofing sheets provide
floor sheets.
[0046] For convenience of description, the term "structural member" is used herein to refer
generically to a rafter, a column, or a floor beam and the term "purlin" is used herein
to refer generically to a purlin proper, a wall rail or a floor cross beam.
[0047] The features disclosed in the foregoing description, in the following claims and/or
in the accompanying drawings may, both separately and in any combination thereof,
be material for realising the invention in diverse forms thereof.
1. A structure comprising at least two structural members (10) and a purlin (12) supported
by and extending between the structural members (10) and connected thereto by cleats
(13), one fixed to each of said two structural members (10), wherein the purlin (12)
comprises a cold rolled section having a pair of spaced side-by-side generally parallel
opposed flanges (15a, 15b), each having an inturned lip (16a, 16b) at one edge and
the flanges (15a, 15b) being interconnected by a web part (17) at their other edges,
the web part (17) comprising a median portion (18) perpendicular to the flanges (15a,
15b) and connected by inclined portions (19a, 19b) to edge portions (20a, 20b) of
the web (17) which are connected to the flanges (15a, 15b) to extend perpendicular
thereto, characterised in that the median portion (18) of the web part (17) is disposed
intermediate said one and other edges of the flanges (15a, 15b) and is offset from
the edge portions (20a, 20b) of the web part (17) which are disposed at said other
edges of the flanges (15a, 15b), the cleats (13) have a stiffness imparting configuration
and extend between and overlie the edge web portions (20a, 20b) and the purlin (12)
is connected to the cleats (13) by fasteners (21) engaged with the edge web portions
(20a, 20b) of the purlin (12).
2. A structure according to Claim 1 wherein the inner flange (15b) of the purlin (12)
is spaced from the adjacent surface of the structural member (10).
3. A structure according to Claim 1 or Claim 2 wherein the web part (17) is perpendicular
to the adjacent surface of the structural member (10).
4. A structure according to any one of Claims 1 to 3 wherein the purlin (12) is provided
with a stiffener (34) comprising a member adapted to interfit with the inner edge
web portion (20b), flange (15b) and lip (16b) to reinforce the inner connection between
the purlin (12) and cleat (13).
5. A structure according to any one of the preceding claims wherein the cleat (13)
is of the same configuration as the purlin (12) but without a flange.
6. A structure according to any one of the preceding claims wherein the cleat (13)
is of the same configuration as the purlin (12) except for the median web portion
(18) which is wider or narrower than that of the purlin.
7. A structure according to any one of the preceding claims wherein the cleat (13)
is fixed to the structural member (10) by welding.
8. A structure according to any one of Claims 1 to 6 wherein the cleat (13) is generally
L-shaped, one limb being connected to the structural member (10) by fasteners and
the other limb being connected to the purlin (12).
9. A structure according to any one of the preceding claims wherein longitudinally
adjacent purlins (12) are connected together by a connecting member (30) of a configuration
to conform to at least the web part (17) of the purlins (12) and fastened to the web
parts (17) so as to span between the adjacent purlins (12).
10. A structure according to Claim 9 wherein the connecting member (30) is fastened
to the edge web portions of the purlins (12).
11. A structure according to Claim 10 wherein the connecting member (30) has a flange
(35) to conform to and engage below the inner flanges (15b) of the purlins (12).
12. A structure according to any one of the preceding claims wherein the fasteners
are bolts (21).
13. A structure according to any one of the preceding claims wherein the purlin has
dimensions in accordance with the following range:
Where F equals the width of each flange (15a, 15b):
1. Struktur mit wenigstens zwei Strukturelementen (10) und einer Pfette (12), die
von den Strukturelementen (10) gestützt wird und sich zwischen diesen erstreckt und
mit diesen über Rippen (13) verbunden ist, von denen eine mit jeweils einem von zwei
Strukturelementen verbunden ist, und die Pfette (12) einen kalt gewalzten Abschnitt
aufweist mit einem Paar von nebeneinander im wesentlichen einander parallel gegenüberliegenden
Flanschen (15a, 15b), die jeweils eine nach innen weisende Lippe (16a, 16b) an einer
Kante aufweisen und die Flansche (15a, 15b) verbunden sind über einen Stegabschnitt
(17) an den anderen Kanten und wobei der Stegabschnitt (17) einen mittleren Abschnitt
(18) aufweist, der senkrecht zu den Flanschen (15a, 15b) verläuft, und über geneigte
Abschnitte (19a, 19b) mit den Kantenabschnitten (20a, 20b) des Steges (17)-verbunden
ist, die mit den Flanschen (15a, 15b) verbunden sind, um sich senkrecht zu diesen
zu erstrecken, dadurch gekennzeichnet, daß der mittlere Abschnitt (18) des Stegteils
(17) zwischen der einen und der anderen Kante des Flansches (15a, 15b) angeordnet
ist und gegenüber den Kantenabschnitten (20a, 20b) des Stegabschnitts (17) versetzt
ist, die an den anderen Kanten der Flanschen (15a, 15b) angeordnet sind, und wobei
die Rippen (13) eine aussteifende Ausbildung haben und sich zwischen den Kantenstegabschnitten
(20a, 20b) erstrekken und über diesen liegen und die Pfette (12) mit den Rippen (13)
über Befestigungsmittel (21) verbunden sind, die mit den Kantenabschnitten (20a, 20b)
der Pfette 12 verbunden sind.
2. Struktur nach Anspruch 1, wobei der innere Flansch (15b) der Pfette (12) mit Abstand
von der benachbarten Fläche des Strukturelements (10) angeordnet ist.
3. Struktur nach Anspruch 1 oder Anspruch 2, wobei der Stegteil (17) rechtwinklig
zu der benachbarten Fläche des Strukturelements (10) angeordnet ist.
4. Struktur nach einem der Ansprüche 1 bis 3, wobei die Pfette (12) mit einem Versteifungselement
(34) versehen ist, das ein zur Passing mit dem inneren Kantenstegabschnitt (20b),
dem Flansch (15b) und der Lippe (16b) eingerichtetes Element aufweist zur Verstärkung
der inneren Verbindung zwischen der Pfette (12) und der Rippe (13).
5. Struktur nach einem der vorangehenden Ansprüche, wobei die Rippe (13) wie die Pfette
(12), aber ohne Flansch, ausgebildet ist.
6. Struktur nach einem der vorangehenden Ansprüche, wobei die Rippe (13) wie die Pfette
(12) ausgebildet ist mit der Ausnahme, daß der mittlere Stegabschnitt (18) breiter
oder enger ist als derjenige der Pfette (12).
7. Struktur nach einem der vorangehenden Ansprüche, wobei die Rippe (13) mit dem Strukturelement
(10) verschweißt ist.
8. Struktur nach einem der Ansprüche 1 bis 6, wobei die Rippe (13) im wesentlichen
L-förmig ist, wobei ein Schenkel mit dem Strukturelement (10) über Befestigungsmittel
und der andere Schenkel mit der Pfette (12) verbunden ist.
9. Struktur nach einem der vorangehenden Ansprüche, wobei in Längsrichtung benachbarte
Pfetten (12) miteinander durch ein Verbindungselement (30) verbunden ist, das wenigstens
dem Stegteil (17) der Pfette (12) entsprechend ausgebildet und an dem Stegteil (17)
so befestigt ist, daß es sich zwischen den benachbarten Pfetten (12) erstreckt.
10. Struktur nach Anspruch 9, wobei das Verbindungselement (30) an den Kantenstegabschnitten
der Pfette (12) befestigt ist.
11. Struktur nach Anspruch 10, wobei das Verbindungselement (30) einen Flansch (35)
aufweist, um den inneren Flanschen (15b) der Pfetten (12) zu entsprechen und unterhalb
dieser einzugreifen.
12. Struktur nach einem der vorangehenden Ansprüche, wobei die Befestigungselemente
Bolzen (21) sind.
13. Struktur nach einem der vorangehenden Ansprüche, wobei die Pfette eine Ausdehnung
entsprechend dem folgenden Bereich hat:
wobei F der Breite jedes der Flansche entspricht.
1. Structure comprenant au moins deux éléments de construction ou éléments porteurs
(10) et une panne (12) supportée par et s'étendant entre les éléments porteurs (10)
et reliée à ceux-ci par des goussets (13), un gousset étant fixé sur chacun des deux
éléments porteurs (10), structure dans laquelle la panne (12) comprend un profilé
laminé à froid comportant une paire d'ailes (15a, 15b) espacées côte à côte, de façon
générale parallèles et en opposition entre elles, chacune présentant un rebord replié
vers l'intérieur (16a, 16b) sur une rive et les ailes (15a, 15b) étant reliées entre
elles par une partie d'âme (17) sur leurs autres rives, la partie d'âme (17) comprenant
une portion médiane (18) perpendiculaire aux ailes (15a, 15b) et reliée par des portions
inclinées (19a, 19b) à des portions de rive (20a, 20b) de l'âme (17) qui sont reliées
aux ailes (15a, 15b) pour s'étendre perpendiculairement par rapport à celles-ci, caractérisée
en ce que la portion médiane (18) de la partie d'âme (17) est disposée de façon intermédiaire
entre l'une et les autres rives de l'aile (15a, 15b) et en ce qu'elle est décalée
par rapport aux portions de rive (20a, 20b) de la partie d'âme (17) qui sont disposées
au niveau des autres rives des ailes (15a, 15b), les goussets (13) présentent une
configuration leur conférant une rigidité et s'étendent entre et recouvrent les portions
d'âme de rive (20a, 20b) et la panne (12) est reliée aux goussets (13) par des moyens
d'assemblage ou fixations (21) s'engageant dans les portions d'âme de rive (20a, 20b)
de la panne (12).
2. Structure selon la revendication 1, caractérisée en ce que l'aile intérieure (15b)
de la panne (12) est espacée de la surface contiguë de l'élément porteur (10).
3. Structure selon la revendication 1 ou la revendication 2, caractérisée en ce que
la partie d'âme (17) est perpendiculaire à la surface contiguë de l'élément porteur
(10).
4. Structure selon l'une quelconque des revendications 1 à 3, caractérisée en ce que
la panne (12) est munie d'un raidisseur (34) comprenant un élément apte à s'emboîter
dans la portion (20b) d'àme de rive intérieure, dans l'aile (15b) et dans le rebord
(16b) pour renforcer l'assemblage intérieur entre la panne (12) et le gousset (13).
5. Structure selon l'une quelconque des revendications précédentes, caractérisée en
ce que le gousset (13) présente la même configuration que la panne (12) mais sans
aile.
6. Structure selon l'une quelconque des revendications précédentes, caractérisée en
ce que le gousset (13) est de la même configuration que la panne (12) sauf en ce qui
concerne la portion d'âme médiane (18) qui est plus large ou plus étroite que celle
de la panne.
7. Structure selon l'une quelconque des revendications précédentes, caractérisée en
ce que le gousset (13) est fixé sur l'élément porteur (10) par soudage.
8. Structure selon l'une quelconque des revendications 1 à 6, caractérisée en ce que
le gousset (13) est généralement en forme de L, une branche étant reliée à l'élément
porteur (10) par des fixations et l'autre branche étant reliée à la panne (12).
9. Structure selon l'une quelconque des revendications précédentes, caractérisée en
ce que des pannes contiguës longitudinalement (12) sont reliées entre elles par un
élément d'assemblage (13) d'une configuration épousant au moins la partie d'âme (17)
des pannes (12) et fixée sur les parties d'âme (17) de façon à couvrir la portée entre
les pannes contiguës (12).
10. Structure selon la revendication 9, caractérisée en ce que l'élément d'assemblage
(30) est fixé sur les portions d'âme de rive des pannes (12).
11. Structure selon la revendication 10, caractérisée en ce que l'élément d'assemblage
(30) comporte une aile (35) épousant la configuration et s'engageant sous les ailes
intérieures (15b) des pannes (12).
12. Structure selon l'une quelconque des revendications précédentes, caractérisée
en ce que les fixations sont des boulons (21).
13. Structure selon l'une quelconque des revendications précédentes, caractérisée
en ce que la panne comporte des dimensions à l'intérieur de la plage suivante:
dans laquelle F est égal à la largeur de chaque aile (15a, 15b):