EP1573142B1

EP1573142B1 - Structural metal frames

Info

Publication number: EP1573142B1
Application number: EP03786084A
Authority: EP
Inventors: Shaun Thomas
Original assignee: Framing Solutions PLC
Current assignee: Framing Solutions PLC
Priority date: 2002-11-29
Filing date: 2003-11-28
Publication date: 2006-07-19
Anticipated expiration: 2023-11-28
Also published as: WO2004051014A1; DE60306960D1; AU2003295084A1; EP1573142A1; ATE333542T1; GB0227847D0

Abstract

A structural metal frame comprises an assembly of panels each including inter alia a plurality of elongate frame members (1, 2, 16, 17, 18) each having a central floor (3) and two parallel sides (4) which extend along opposite borders of the floor and which project outwardly from one side of the floor. One or each side of two or more frame members are deformed to produce a generally concave indent (7) on one side and a generally convex protrusion (8) on the other side. The arrangement is such that, on assembly, the indent (7) of one member and the protrusion (8) of another adjoining member cooperate to assist accurate location of the frame members one to the other.

Description

This invention relates to structural metal frames. More especially, but not exclusively, the invention concerns galvanised steel frames for buildings.
Galvanised steel frames are increasingly being employed for buildings, especially houses for residential use. These frames are produced by assembling together a number of suitably dimensioned panels each comprising an assembly of a plurality of elongate frame members. The assembled panels are produced in secure buildings remote from the construction site. The panels are then transported to site and erected on a floor construction. These panels define all internal and external walls of a building, including internal partitions. Once erected by bolting together several panels, the frame is lined internally and externally with suitable materials. Thermal insulating material may be interposed between the frame and these linings if desired and the external lining may be constructed on site around the frame. Typically, external linings comprise rendered brickwork, brickwork, tile hanging and/or timber boarding.
When compared with conventional brick build housing, steel frames provide high strength and stability and the risk of damage in the case of settlement is reduced significantly. Also, internal block work is not required thereby reducing build time and cost. Moreover, the number of skilled tradesmen required on site is reduced and the overall on-site build time is reduced. Furthermore, enhanced quality control is achieved by the use of frame members of uniform dimensions and gauge in the production of the steel frame. Efficient and reproducibility of build are therefore possible.
A steel frame exhibits advantages over a timber frame because of its relative lightness and lack of shrinkage, warping and cracking. Typically, a steel frame is only around one-third of the weight of a corresponding timber frame. Inevitably, timber frames are susceptible to shrinkage over a period of time. Also, a steel frame is not susceptible to problems arising from, for example, dry and wet rot, cracking and insect infestations. Typically, the galvanising of a steel frame has a calculated lifespan of a thousand years. Moreover, a steel frame is significantly less vulnerable to land movements.
GB-A-2146054 discloses a galvanised steel frame which includes a plurality of elongate structural members having a variety of sections. The frame disclosed in this patent has been found to suffer from a number of disadvantages arising from the particular profiles selected for some frame structural members and the lack of any assured way of accurately locating adjoining frame members during the assembly of panels produced from these members.
EP-A-0267337 discloses a galvanised steel frame which includes elongate structural members comprising frusto-conical formations pressed into noggins.
US-B-6279289 discloses a framing system which includes elongate structural members comprising an indentation pressed into a complimentary indentation.
It is an object of the present invention to provide a structural metal frame which overcomes, or at least alleviates, many of these disadvantages.
In one aspect, the invention provides a structural metal frame which comprises an assembly of panels each including inter alia a plurality of elongate frame members each having a central floor and two parallel sides which extend along opposite borders of the floor and which project outwardly from one side of the floor, one or each side of two or more frame members each being deformed to produce a generally curvilinear concave indent on one side and a generally curvilinear convex protrusion on the other side, the arrangement being such that, on assembly, the indent of one member and the protrusion of another adjoining member cooperate to assist accurate location of the frame members one to the other.
One or more indents may be pierced to define one or more apertures for receiving rivets employed to secure adjoining frame members together. Alternatively, self piercing rivets may be employed remote from the indents.
Those parts of frame members which are deformed to include indents and protrusions may also be swaged to a depth substantially equal to the gauge of the frame members. By so doing the exposed surfaces of members which overlap on assembly do not project above the surface of adjoining unswaged lengths of the overlapping members.
Inwardly extending lips may extend along the edges of the side walls of one or more frame members.
The, or a majority of, frame members are preferably produced from light gauge galvanised steel sheet having a gauge preferably in the range 0.8mm to 2.0mm, typically 1.6mm gauge. To produce the required frame member profiles, sheet lengths are normally subjected to a roll forming operation. The indents/protrusions may be formed during the course of this operation. In a preferred embodiment, the profile and indent forming processes are continuous.
The invention will now be described by way of example only, with reference to the accompanying diagrammatic drawings in which:-

Figures 1 to 3 illustrate structural members of a frame in accordance with the invention;
Figures 4 to 7 are side views of panels from which frames of the inventions are produced; and
Figures 8 to 11 are elevational views of frame sections in accordance with the invention.

In the drawings, the same reference numerals have been used for the same or similar integers.
The structural members illustrated in Figures 1 to 3 are all produced from galvanised steel of the same gauge, typically 1.6mm. In the majority of cases, the cross-sectional dimensions of each species of frame member is the same wherever that member is used in the panels and frame sections illustrated in Figures 4 to 11. The gauge, grade and dimensions of some load bearing members - e.g. lintels - may, however, differ from those of equivalent members used elsewhere.
The structural frame members illustrated in Figure 1 are produced from galvanised steel and comprise a stud member 1 and a head section 2. Head sections are typically employed above window openings. Frame members produced from metals other than steel may be employed and surface treatments other than galvanisation may be used. The stud member 1 is formed from a pair of channel section frame members 1A, 1B each of which comprises a floor 3 bordered by side walls 4 which incorporate lips 5 to enhance strength and stability. Although Figure 1 shows a pair of stud sections, it will be appreciated that stud sections can be used singularly or in pairs to suit the location and structural requirements. In use, the lips 5 of the frame members 1A, 1B abut to produce a hollow section stud member.
The side walls 4 of the stud member 1A are partially swaged to define lengths 6 of reduced thickness (only one of which is shown in Figure 1). The depth of each swaged length 6 is substantially equal to the gauge of the steel from which the frame members are produced. Typical swaged lengths are around 82mm. Within one side of each swaged length 6 is formed a generally curvilinear concave indent 7 which protrudes from the other side of the length 6 to define generally curvilinear convex protrusions 8. Typically, the depth of each curvilinear indent is around 1mm, indent diameters being typically 6mm.
The head section 2 has a floor 9 bordered by side walls 11. The side walls extend beyond the floor to define two arms 12 which, on assembly, embrace the stud member 1A and locate within the swaged lengths 6 on each side of the stud member. The upper and lower extremities of the end of each arm 12 is tapered to assist location of the head section in use. Each arm 12 is formed with a generally curvilinear concave indent 7 which protrudes from the other side of the respective arm to define a generally curvilinear convex protrusion 8. The indents and protrusions of the stud member 1A and the head section 2 are complementary in the sense that their dimensions and profiles are substantially the same. As the arms 12 enter the swaged lengths 6, so the protrusions 8 on the inner sides of the arms engage the complementary indents 7 of the stud member. This process ensures that the stud member and junction channel are correctly and accurately positioned prior to rivetting or screwing.
Whereas single indents and protrusions are shown in Figure 1, two or more spaced curvilinear indents and/or protrusions may be employed. Where two or more indents and/or protrusions are provided, they may be spaced generally vertically from one another.
The arrangement illustrated in Figure 1 is employed for joining various horizontally disposed channel-section frame members to vertically disposed frame members.
The frame members shown in Figure 2 comprise a stud member 1 comprising frame members 1A and 1B, a top channel 16, a lintel 17 and a bracing member 18. In this embodiment, the upper ends of the stud member 1 and bracing member 18 are swaged to define lengths 19, 20 respectively of reduced thickness. These swaged upper ends include curvilinear indents 7. The top channel 17 comprises a floor 21 and downwardly projecting side walls 22 each formed with curvilinear indents 7 and corresponding protrusions which project from the inner surfaces of the side walls. On assembly, the swaged end 19 of the stud member project upwardly between the side walls 22 with the indents 7 and respective protrusions cooperating to locate the stud member within the upper channel in the required position. The swaged end 20 of the bracing member 18 is then introduced into the top channel until its indent 7 locates within the corresponding indent 8 of the top channel. Typically, the frame members of Figure 2 provide bracing within the stud depth.
The lintel 17 includes a floor 24 and side walls 25. Lips 26 are carried by the side walls 25 and one end of the lintel is partially closed by an end plate 27. This end plate is formed with a series of holes 28 which complement holes formed in the adjoining surface of the stud member 1A to enable the lintel to be rivetted or otherwise secured to the stud member. The end plate 27 seats within the swaged end 19 of the stud member 1A.
The arrangement illustrated in Figure 2 is for joining various vertically disposed and inclined frame members to top channel frame members. The same arrangement is employed for joining vertical and inclined frame members to lower channel members or indeed to any horizontally disposed frame members.
Figure 3 illustrates an assembly of a vertical stud member 1 formed with a swaged mid-section 30 and two inclined brace members 31 whose adjoining ends 32 are swaged. The swaged section 30 of the stud member 1 and the swaged ends of the brace members 31 are formed with indents/protrusions as previously discussed.
Two steel fixing plates 33 are provided, each including curvilinear indents/protrusions which complement those of the stud member and the brace members. The fixing plates 33 locate over the swaged sections 30 of the stud member and the swaged ends of the bracing members locate between those lengths of the fixing plates which extend beyond the periphery of the stud member.
The various stages to be employed in producing a steel frame structure system in accordance with the present invention will now be described.
It will be appreciated from the foregoing that the function of the indents and protrusions is to ensure that the various frame members are accurately assembled precisely as required. Also the swaged sections ensure that, once assembled, a continuous and generally flat overall surface is produced with no overlapping flange protruding above the surface of the stud member or other supporting member.
The frame and bracing members described with reference to the drawings comprise the majority of members used in the production of structural steel frames in accordance with the invention.
Frame panels produced from the frame members described with reference to Figures 1 to 3 are illustrated in Figures 4 to 7. The frames are produced and assembled off-site and then delivered to site by transporter. The various frame panels are connected together on site on a suitable foundation base to produce the skeleton frame for a building. The frame is then clad internally and externally. For multi-storey buildings, floor cassettes are provided, these being supported by "Z" brackets or the like connected to or supported from the top channels 16. Assemblies of the panels of Figures 4 to 7 are shown in Figures 8 to 14. These panels include studs 1, head sections 2, bracing members 18, lintels 17 and top channels 16. Fixing plates are provided where required. Window and door openings are referenced 34, 35 respectively.
As will be described below, the profiled frame members are produced by a roll forming operation with the indents and corresponding protrusions being produced during this operation. All frame members are tagged or marked either visually or electronically for ease of assembly.
The system generally provides a light gauge steel frame suitable for single storey structures to structures having six or more storeys. The system provides an inner leaf of external walls and all internal partitions and intermediate floors, including decking, The outer face of the frame assemblies is lined with rigid insulation board. Wall tie channels are fixed through the insulation into steel studs. Wall ties are provided for insertion by a bricklayer into channels at appropriate locations, the outer end of the ties being bedded into the masonry external cladding.
Internally, fire protection is provided with the use of appropriate lining boards.
During the design process of a structure in accordance with the invention, software is employed which includes a three-dimensional parametric modelling package to enable designers to review their designs of the steel frame in three dimensions at any point in the design process.
Architects' and builders' drawings are received for a design either electronically or as hard copy. These designs are converted into two-dimension steel frame component designs using specialist software. Specific elements of the drawing have intelligence to know what the elements represent together with details of size, orientation, material, etc. These computer generated drawings are sent to the client for approval. Approval is important as the steel frame components normally result in an increase in the size of rooms within a dwelling if the overall footprint remains the same. The parameters of the various components are entered into the drawing at this two-dimensional drawing stage.
Once approved, the design is converted from two-dimensional into three-dimensional frame designs. The designer is able at this stage to add further requirements regarding the size of panels to avoid them being too heavy to lift on site, preferred stud centres, size and gauge of studs, locations for bracing, depth of joists, orientation of joist spans, decking orientation and other requirement details.
Once all of the information detailed above has been entered onto the drawings, the software creates an individual panel and floor cassette design for manufacture. The information is displayed in the form of a drawing to enable factory staff to assemble the various components into the panels and cassettes. The design software also produces electronic files for each panel. Features including service hole locations, dimples and the like are included in the files. These files are ultimately sent electronically to a roll-former for an operator to select and instruct the roll-former to manufacture. The operator selects the appropriate components based on the coil steel strip that is loaded onto the mandrel. This is set up so as not to permit accidental selection of a component which is not suited to the coil width or gauge.
The electronic files for the components include coded descriptions of the material required. This file also contains a unique reference number for each component. The roll-former marks this reference onto the component using an ink jet mounted on the roll-former.
The software also produces layout drawings indicating the locations of all the panels of the assembly. The panels' references are included on the drawings which match the reference which the roll-former prints onto the panels. Also, the software produces elevation drawings which indicate the locations, and lengths, of the wall tie channels for the erectors to use.
For manufacture, a roll forming machine is driven by component information generated electronically in the design office. The electronically generated information is transmitted to a computer of the roll forming machine. Each part of the machine instruction is processed by the roll-former to define the component's length, the number of tooling operations required and what to print on the material.
Slit steel coil of up to three tonnes in weight and cut to the appropriate width and gauge is loaded onto a front mandrel of the roll forming machine. The front end of the coil is fed through a leveller unit to remove any shape anomalies that may be present in the material. The material is then passed through a first looping device and into a servo-driven pinch roll. The front end of the strip is then fed through to cropping tools. The first tool defines the front end of the component, and the servo-driven pinch rolls are then reset to zero.
The machine operator will at this point have selected the number of frame files they wish to process from the production schedule. The operator has several options regarding what is to be produced. The operator can select all of the components needed to produce the panels for a house, all of the components appropriate for the coil that is mounted on the mandrel, or a combination of these options. It is, of course, important to maximise the output from the mounted coil.
By selecting the frame files, the control system is able to calculate the total number of material movements and the firing sequence of each tool for the entire production run. The length of material to be processed may be a full three tonne coil, equating to approximately 2000 metres of steel strip.
Finally, the control system is switched to auto and the production run is commenced. The process continues until all the components have been produced or the entire coil of material has been consumed.
The process includes a pre-pierce and dimpling unit which operates at up to two metres per second, or in component terms, approximately one average component per second. Even at such a high speed, the positional accuracy of this process is maintained at plus or minus one quarter of a millimetre. As the components are being processed, locating dimples are pressed into the strip. The positioning of each dimple is determined by the design software and once in place assists the operator to align components quickly within the frame.
The strip is then fed through an accumulator and then into the roll-former.
For studs, the material is driven through a first roll stand where the lip of the component is formed. The part-processed strip then travels through second and third stands to produce a fully formed stud.
There are three different stud sizes: 50, 75 and 100mm, these are available in various gauges depending on the structural requirement of the panels.
The choice of gauge and section size will be dependent on the structural strength required for the panel. This will be influenced by, but not limited to, the floor spans, wind loading and number of storeys. Steel or timber trusses can be fixed to a wall plate secured to the top of the steel frames.
Channels are produced in the same way as studs but they do not require to pass through the first set of rolls, so the appropriate stand is opened up to allow the strip to travel through unhindered.
Once the material is in the second roll stand the roll-former has full control of material movement.
The final piece of tooling is a swaging station. Here, stud sections require to be crushed in a controlled manner so that, when they interact with a channel, a flush fit is achieved.
One of the aims of the present invention is to provide a process which provides flush finish for dry liners to work from.
A further aim of the present invention is to reduce the time taken in frame assembly.
As already described, each component will be uniquely marked by an ink jet printing device with a view to speeding up the assembly process. The printed information received in the design stage provides the details of the contract number, the house type, the plot number and the frame number.
The dimples produced in the studs and channels enable the assemblers to locate the components quickly in their exact locations, thus avoiding the need to manually measure each individual position.
For the frame assembler, the most important piece of information is the component label. Each component is labelled with its own identify number so that at a glance the operator can quickly see where each item fits within the frame.
The fixing system used is referred to as self-pierce riveting and requires no pre-drilling to fit the components together. The fixing process works by driving a hollow galvanised rivet into the two components, the rivet is subjected to around five tonnes of force from a vertically mounted hydraulic cylinder. In order that penetration is successfully achieved, the rivet is made of a material which is slightly harder than the component parts being fixed together. As the rivet is being forced through the components, it draws material into a small button die. As the rivet and the material are forced into the sculptured die the pressure within the hydraulic system starts to increase. Once the system has reached a predefined pressure, the punch will retract leaving a rivet locked in place.
Assembly of a frame structure in accordance with the invention will now be described.
All the components required to build a frame are brought together in the form of a frame kit. The kit is delivered to an assembly station where the operator will fit the parts together and then fix them in place to produce a finished frame.
The line may be configured around a linear flow principle, referred to as a "rolling jig".
Using the self-pierce riveting system explained above, the first operator can fit together all the full height vertical studs into the top and bottom channel thus creating a basic ladder frame.
The drawing and all remaining components from the frame kit are transferred to the second stage of the assembly process. At which point the window and door components are fitted in place, along with any bracing members and support strips.
Finally, the frame is checked and labelled by an inspector then transferred to the relevant transportation stillage ready for despatch.
Floor cassettes may be constructed using a rolled "sigma" joist.
The sigma section is used predominantly for shorter spans or where there is no requirement for complex services runs through the floor zone.
Alternatively, the construction of the floor cassettes may use a fabricated lattice joist. In this cassette, the floor beam is made up of a top and bottom chord which is in the shape of a "T". The T-sections are connected together using angled struts. Two sizes of joist are used in general, these being 225mm and 300mm deep. The former can be used for clear spans of up to 5.3 metres and the latter 6.3 metres. The joist depth is governed by the length of strut used.
The bought-in sections are cut to the required length then riveted together on the two jigs. Such a configuration can produce approximately 200 metres per shift. The joists are then fed down a mechanical conveyor to the next assembly station where the brackets are fitted.
From here, the floor joists feed into the cassette assembly line.
A cassette is produced in two stages. Firstly, a steel skeleton is assembled by attaching the joists to hangers.
The steel skeleton is constructed by positioned the joists as shown on the design drawing. Joists are commonly spaced 400mm apart and are handed to give maximum stability to the cassette. Each joist is produced with a "start end" so that, when correctly placed, clear access is provided for service runs. The joists are attached to the hangers using the same self-pierce riveting system as previously described. When complete, the skeleton is transported by crane to the next part of the process.
Various floor decking materials can be used for the cassettes such as "OSB" and resin impregnated chipboard. Boards are selected and cut to size in the most economic manner in order to minimise waste. PVA wood glue is then applied to the tongue and grooved edges. The first board is fixed to joists using self-drilling, self-tapping countersunk screws. The next board is butted up to the first and screwed on until the decking process is complete.
All joints and exposed edges are taped up to prevent the ingress of moisture. This prevents any swelling of the chipboard through water absorption. Holes are cut out of the decking in order to fit lifting slings which are used both in the factory and on site for transportation purposes and lifting into position.
During erection of a frame structure in accordance with the invention, a builder will firstly normally construct the ground floor. The ground floor frames are delivered to site and craned or fork lifted onto a slab. A dpc is placed around the perimeter of the slab and in the location of any internal partitions. The steel panels are moved manually into position and fixed to the adjacent panels. The positions of the completed walls are checked for accuracy and then secured to the ground floor. When completed the first floor cassettes are delivered to site and craned individually into position on top of the ground floor frames. These are secured to the frames upon which they sit. The process is then repeated with the wall panels and cassettes for the remaining storeys.
The next process is the fixing of the insulation boards to the outside of the frames. The boards are positioned against the outside of the frames. The wall tie channels are positioned on the face of these boards, at the steel stud locations, and fixings for the channels pass through the channel, through the insulation board and into the steel stud behind the boards.
Once this has been completed, the builder can construct the roof and fix the windows and doors in the openings provided in the steel frame. This provides a weather-tight envelope enabling a plumber and electrician to commence their work even prior to bricks being laid above dpc. Bricklaying can progress to suit weather conditions and availability of bricklayers and materials. Normally the bricklaying would be completed before a tradesman can commence internal work. Thus, the speed of construction of the building is greatly enhanced.
It will be appreciated that the foregoing is merely exemplary of structural frames in accordance with the invention and that modifications can readily be made thereto without departing from the true scope of the invention as defined by the appended claims.

Claims

A structural metal frame which comprises an assembly of panels each including inter alia a plurality of elongate frame members (1A, 1B, 2, 16, 17, 18, 31) each being formed as a channelled section, having a central floor (3, 9, 21, 24) and two parallel sides (4, 11, 22, 25) which extend along opposite borders of the floor and which project outwardly from one side of the floor, the sides of two or more frame members (1A, 1B, 18, 31) being partially swaged to define a length (6, 19, 20, 30, 32) of reduced thickness, one or each side of two or more frame members (1A, 1B, 2, 16, 18, 31) each being deformed to produce a generally curvilinear concave indent (7) on the swaged portion on one side and a generally curvilinear convex protrusion (8) on the swaged portion on the other side, the arrangement being such that, on assembly, the indent (7) of one member and the protrusion (8) of another adjoining member cooperate to assist accurate location within the channels of the frame members one to the other.
A frame as claimed in claim 1 wherein one or more indents (7) are pierced to define one or more apertures (28) for receiving rivets employed to secure adjoining frame members together.
A frame as claimed in claim 1 wherein self piercing rivets are employed remote from the indents.
A frame as claimed In any one of the preceding claims wherein those parts of frame members which are deformed to include indents (7) and protrusions (8) are also swaged to a depth substantially equal to the gauge of the frame members.
A frame as claimed in any one of the preceding claims wherein inwardly extending lips (5, 26) extend along the edges of the side walls of one or more frame members.
A frame as claimed in any one of the preceding claims wherein the, or a majority of, frame members are produced from light gauge galvanised steel sheet having a gauge in the range 0.8mm to 2.0mm.
A frame as claimed in claim 6 wherein the steel sheet has a gauge of 1.6mm.