Patent Application
20200256049
See Application Data Sheet.
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This invention relates to an improved building method and in particular to improvements in structural steel beam design and installation in Low Rise and specifically 2 story Residential Buildings. The invention is however not limited to this application.
Structural steel beams or RSJ's (rolled steel joists) are used extensively in the construction industry. They are made in various shapes, commonly called UB (universal beam) or UC (universal column). These commonly available sections are hot rolled and manufactured in a steel mill or in recent times, by welding plate elements together to form what is termed built up beams. The general characteristic of the beams is that the top and bottom flanges are parallel to each other and rectangular in shape, and are connected centrally to each other by a web.
The beams are available in a range of sizes to cater for a range of applications, which are generally defined by span and deflections.
The strength of a beam is defined by cross sectional shape characteristics, namely the depth, flange width and thickness and web thickness. The material strength of the beam is defined by its material/chemical properties, normally designated as yield strength.
In Australia a UB for example is nominated by a depth and kg/metre designation. As the kg/metre increases, the strength of the beam increases in that depth range. In the case of an Australian beam size 250UB37, the beam is nominally 250 mm deep and is 37 Kg/Metre, however its actual dimension is 256 mm, and has a top and bottom flange width of 146 mm and a flange thickness of 10.9 mm.
A 250UB25 on the other hand is nominally 250 mm deep, 25 kg/metre, and is a lower strength capacity than the former beam. The 250UB25 has an actual depth of 248 mm, a flange width of 124 mm and a flange thickness of 8 mm. While the two beams belong to the same nominal 250 class of beams, they differ not only in the kg/metre, but in all other dimensions.
Due to constraints in the hot rolled beam production process, the central rollers are fixed and to increase the beam capacity the external rollers are adjusted to increase the flange thickness, and consequently the overall depth of the beam is increased. This explains why the beams get deeper as the beam capacity of a nominal depth increases.)
The varying depths and flanges widths and thickness in a class of beams make for difficult and challenging detailing and fitment when they are used in conjunction with other construction materials used in house building. For example, timber I joists are commonly used in residential building in conjunction with steel I beams in first floor construction in 2 story homes all over the world.
In Australia, the joists come in a range of sizes—200 mm, 240 mm and 300 mm deep being the more common available sizes. In its preferred form a connection between the timber joist and a steel beam is made by notching the bottom and top flange of the timber joists to suit the steel flange depth so that the bottom surface of the steel I beam is aligned to the bottom surface of the timber I joist, to allow the ceiling linings to be fitted, and the top surface of the beam flange with the top of the joist to allow flooring sheeting to be installed in the same plane.
However, due to the difference in steel beam sizes relative to the timber joist depths, this efficient way of forming connections does not occur. More commonly only the bottom flange is notched when the beam flange thickness allows. In some cases, the steel beam flange thickness exceeds the allowable notch depth in the timber joists, at which time expensive retrofitting of solid timber beams are installed within the flanges and packed to be level with the side of the flange. Expensive brackets/joist hangers are then installed to the retrofitted timber beam and the timber joists are fitted to the brackets.
The exact depth of the beam required does not correspond to the available depth of the timber joists being used in the floor structure. When the design beam depth is larger than the timber I joists, the timber joists are installed with the bottom flange level with the underside of the beam flange and the top flange of the steel beam will extend above the top of the timber joists. This can only occur when the beam is at the edge of the floor, where the external walls cladding may accommodate the height difference. Where the beam is fractionally taller than the timber joists, the timber floor sheeting is then planed to form a recess to fit over the beam flange, resulting in more labour costs and delays.
When the beam depth is less than the timber joists depth, timber packers are installed and sometimes bolted to the top flange of the beam, to carry the timber floor sheeting and load and non-load bearing internal or external wall frames. Additional labour costs and materials is used to accommodate the smaller steel beam fitment into the floor structure.
Generally, timber I joists are supplied to the building site along with the wall frames. The timber joists are supplied in standard pack lengths and the carpenters prepare and cut the floor joists to the desired length to construct the floor. The reason why this occurs is the on-site complication in joist fitment with steel beam differences and tolerances.
This involves notching either top or bottom flanges, installing nogging and packing timbers in steel beams. Where a number of different steel beam sizes are used the flange thickness likely differs from one to the other requiring careful adjustment by the carpenter to cut the exact notch which may be required on each end and may be a different depth on each end because the adjoining steel beams at the connection point on each end may differ in size and flange thickness, adding to the difficulty of site cutting and fitting the joists.
Steel beams are rolled in standard lengths by the steel mills. They are supplied to steel merchants in Australia in lengths ranging from 9000 mm to 18000 mm in increments, and steel fabricators choose the size as specified by the engineer or engineering design and beam length to suit the design while minimising wastage. The longer the beam the greater percentage of the beam that can be utilised in the steel fabrication process, hence lowering the production costs.
It is generally too labour cost ineffective to join beam offcuts, and is generally unacceptable to supply fabricated beams with joins in them. The steel mills supply beams to the whole of the steel using industry, which includes commercial, industrial and domestic home buildings. Each industry has its signature range of steel beam sizes and lengths. For example, industrial applications include long span portal structures to 80 metres plus with building heights 6000 mm plus, so beam standard lengths of 12 to 18 metres would be preferred to minimise cutting and plated connections, cutting consistently longer average lengths of steel beams than used in domestic house construction.
In house construction, generally the beams are smaller in section and range from 1200 mm up to 6000 mm, however in some cases longer beams are used. Because the size of the beam used in house building generally falls within a narrowly defined span range, the supply in standard lengths by the wholesalers can cause excessive wastage and the costs are borne by the fabricator. The steel fabricators are generally situated in smaller premises and longer standard lengths beams while helping to minimise wastage, generally are more difficult to move around and unload from delivery trucks.
For example, in a number of houses the same beam span may vary between 4500 mm and 5000 mm spans. In Australia the available practical standard length in the beam size is 9000 and 10500 and in further increments of 1500 mm. A 9000 beam length will enable a 5000 to be cut from it and a 4000 offcut which may have limited re use. Alternatively, the fabricator might order a 10500 beam to cut the longer lengths and deal with extra stock and additional space and handling to store them. A more practical way from the fabricators' perspective would be to buy in 9600 mm long beams, so that on average 4800 beams can be cut from it. When using fully welded beams rather than hot rolled, they can be manufactured at an optimal length to minimise wastage.
Beam connections are made using holed cleats welded to the web of a beam, to which another beam with corresponding holes in its web is bolted to it. Generally, the cleats are welded to the beam web during manufacture in the fabricators factory and commonly involves manual welding. This process slows down production in a medium to small factory where labour resources are minimal in an attempt to maximise profitability.
Holes are also drilled into the mating beams at the desired locations thus requiring two distinct stations to manufacture beams, a hole drilling station, a welding station along with a third, a cut to length station.
The present invention seeks to overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.
It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.
According to a first aspect, the present invention provides a beam and joist assembly comprising:
In a preferred embodiment, a notch is formed in each of the top and bottom surfaces of the joist, wherein the first end of the joist is disposed between the top and bottom flanges of the beam such that the top surfaces of the beam and the joist are level, and the lower surfaces of the beam and the joist are also level.
In another preferred embodiment, the joist is made from timber, and the beam has a minimum beam flange width related to the end bearing length of the timber joist end notch.
In another preferred embodiment, the minimum beam flange width is 100 mm.
In another preferred embodiment, the maximum beam flange width is 225 mm.
In another preferred embodiment, the top and bottom flanges of the beam have a maximum flange thickness related to the maximum depth of the notches to be formed in the top and bottom flanges in the first end of the joist.
In another preferred embodiment, the top and bottom flanges of the beam have a maximum thickness of 16 mm.
In another preferred embodiment, the joist is an I cross-section joist having a top flange and a bottom flange with a web extending therebetween,
In another aspect, the present invention provides a beam and joist assembly comprising:
In another preferred embodiment, the top and bottom flanges of the beam have a maximum thickness of 16 mm.
In another aspect, the present invention provides a set of beams and joists, the set comprising:
In another preferred embodiment, the top and bottom flanges of the steel beam have a maximum thickness of 16 mm.
In another aspect, the present invention provides a set of beams, the set comprising:
In a preferred embodiment, the width of the top and bottom flange of the beams in the set is selected from two predetermined widths.
In a preferred embodiment, the minimum beam flange width is 100 mm.
In another aspect, the present invention provides a steel beam to steel beam connection comprising:
In a preferred embodiment, the second beam comprises another connection plate at a second end thereof.
In another aspect, the present invention provides a I cross-section beam having a top flange and a bottom flange with a web extending therebetween, wherein the top and bottom flanges are notched at first and second ends of the beam, and wherein the beam web comprises a respective connection plate at the first and second ends thereof.
In a preferred embodiment, the connection plate extends perpendicularly to the web.
In a preferred embodiment, the connection plate comprises four holes which are symmetrical around both the vertical and horizontal axes of the beam
In another aspect, the present invention provides a method of construction, the method comprising:
In a preferred embodiment, the method further comprises forming a notch in each of the top and bottom flanges in a first end of the joist, and inserting the first end of the joist between the top and bottom flanges of the beam such that the top surfaces of the beam and joist top flanges are level, and the lower surfaces of the beam and joist bottom flanges are also level.
In another aspect, the present invention provides a method of construction, the method comprising
In a preferred embodiment, the top and bottom flanges of the beam have a maximum thickness of 16 mm.
In another aspect, the present invention provides a method of construction, the method comprising:
In a preferred embodiment, the width of the top and bottom flange of the beams is selected from two predetermined widths.
In another preferred embodiment, the minimum beam width is 100 mm.
In another aspect, the present invention provides a method of construction, the method comprising:
In another aspect, the present invention provides a beam and joist set comprising:
Preferably, a notch is formed in each of the top and bottom surfaces in a second end of the joist, the notches having a depth substantially equal to a thickness of the top and bottom flanges of the mating steel beam,
Preferably, the timber joist is an I cross-section joist having a top flange and a bottom flange with a web extending therebetween, wherein the notches are formed in the top and bottom flanges.
The present invention also provides a method of construction using the beam and joist set of paragraph 52, the method comprising:
The present invention also provides a method of construction using the beam and joist set of paragraph 53, the method comprising:
Other aspects of the invention are also disclosed.
Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings.
It should be noted in the following description that like or the same reference numerals in different embodiments denote the same or similar features.
The web has a web thickness 14 and the flanges both have a flange thickness 15. The beam 10 has a depth (height) 16 and flanges have a width 17.
As shown in
The beam depth 16 is equal to the height 26 of the joist 20. The flange thickness 15 is less than the maximum notching height of the flanges 22 and 23 of the joist 20. This maximum notching height is 12 mm to suit timber joists (currently in use in Australia however the flange thickness is adjusted to suit any timber joist which has a maximum notch depth). The beam flange width 17 is the minimum width to support the notched timber I joist 20 in the spaces 19 on each side of the beam 10.
The single sided timber joist 20 connection to the steel beam 10 shows notches 31 in the top and bottom flanges 22 and 23 of the joist 20 of a height for fitment into the space 19 of beam 10. The top surfaces 34 of the beam and joist top flanges 12 and 22 are level, and the lower surfaces 35 of the beam and joist bottom flanges 13 and 23 are also level.
The present invention comprises an I beam with an overall depth corresponding to the overall depth of timber I joists which are used in the construction of timber floors.
The depth sizes of the I joists used in Australia are 200 mm, 240 mm, 255 mm, 300 mm, 360 mm and 400 mm depth. The most commonly used I joists, being the 240 mm and 300 mm depths, come in a number of different timber flange sizes (widths) enabling larger spanning capacities.
The timber joists 20 are fitted to a structural steel beam 10 by notching 31 its bottom flange 23 to a depth of the steel beam bottom flange 13, but no greater than the allowable design notch depth (12 mm) to maintain structural capacity of the joists 20. The length of the notch 31 can be no shorter than the minimum that will maintain structural adequacy of the joist.
The timber joists 20 are manufactured off site and provided in predetermined depths and lengths, they are pre-notched in the top and bottom flanges 22 and 23 at each end or on one end only of the timber I joists, transported to the site in cut to length and ready to use to construct the floor structure.
The steel beam 10 in the invention incorporates a flange thickness 15 which is common to the beams in a beam group of the same depth 16. For example, the beam flange width 17 for the 240 mm depth beams can be 125 mm and 200 mm wide. In the 300 mm depth beams, the flange widths are 125 and 200 mm. The standardisation of flange width in a beam group means that carpenters can visually size the beam width and cut their joists to length.
In the prior art, the flange thickness can differ between beam groups of different steel beam depths due to maximising steel beam material efficiencies, however in the preferred form of the invention, the flange thickness is the same for all steel beam depths.
The flange thickness is the same for all beam depths, and the flange thickness is equal to or less than the maximum notch depth of the timber joists. The beam capacity in each group comprising the same depth is increased by widening the top and bottom flange width 17.
The flange 12/13 with can be widened to suit a design capacity required for a beam in any group with the same depth. In the preferred form, the flange widths 17 are the same for each beam grouping.
In another embodiment of the preferred form of the invention, the minimum beam flange width 17 is twice the minimum bearing length for the notch 31 in the timber joists 20 plus twice the root radius between the flange 12/13 and the web 11 and the beam web thickness 14 and 2×8 mm clearance. Using Australian joists and the preferred beam design, this equates to 2×45 mm (minimum bearing length) plus 2×6 mm (radius 6 mm on the join between the web and the flange each side) plus 7 mm (web thickness) and 2×10 mm (clearance) which sums to 124 mm. Hence the minimum flange width 17 in the beams 10 of this preferred embodiment is nominally 125 mm.
The maximum flange width is designed to support the external brick veneer, nominally 110 mm thick and the internal (normally) load bearing timber wall which is nominally and usually 90 mm thick. The brick cladding is allowed to overhang the steel beam by 25 mm, and given a brick veneer cladding and internal wall with cavity between them is nominally 250 mm thick, the generally accepted flange width to support the wall is 200 mm.
As shown in
Generally, one end of a beam 10b is fixed to another beam 10 using a cleat and bolt connection. So instead of welding a cleat to a beam to form a connection during manufacturing, a standard sized plate 30 with at least four holes 32 equi-spaced top and bottom is welded to each end 33 of the stock length supplied beam, perpendicular to the web 11.
The four holes 32 in the connection plate 30 are symmetrical around both the vertical and horizontal axes of the beam, which means the beam is not handed in regard to the connection plate.
Generally only 2 bolts are required in most beam to beam connections. So in this connection, to maintain the connection loading directly into the beam web 11 attached to the bracket plate 30, bolts have to be installed across the diagonal. So only two diagonally opposite holes need to be drilled in the mating beam web, this saves time labor and obviously two bolts and labor on site.
The benefit of this bolting arrangement is that the loading through the connection is co-linear with the webs 11, and the mating beam diagonal holes do not make the beam handed, they are equi-spaced about the centerline of the connection, and regardless in which direction the holes are made across the diagonal, there will always be a pair of diagonally opposed holes in the 4 holes connection plate 30 to complete the connection. This is far superior to a plate and web connection because the web of the mating beam can be connected to the plate either side of the plate, making the beam location either correct or incorrect. So it requires management to make sure connections that are not formed on beam centerlines are joined in the correct way.
When the beam 10b is cut to length the beam is complete except for painting if required. The connection is completed by drilling four corresponding holes in the mating beam, thus voiding a welding process during manufacturing. If the beam 10b is not connected to another beam at the other end, than the connection plate 30 is simply cut from the end of the beam 10b.
The embodiment thus supplies pre-primed standard length beams to a fabricator with prefixed connection plates fixed to each end. The pre-fixed cleats 30 to each end, in its preferred form centrally located on the beam axis, makes the fabricators manufacturing material efficient and speeds up production by reducing the need for welding cleats for connections in the production line.
The preferred embodiment provides an improved design for a range of structural steel beams, that will have a number of beams, whereby each beam depth matches the corresponding depth of each timber floor joist.
The preferred embodiment provides having a flange thickness common to all beam sizes and less than or equal to the maximum allowable notch depth in the timber joists.
The preferred embodiment provides having beam capacity within a beam nominal depth is increased or decreased by varying the width of the top and bottom flange together.
The preferred embodiment provides standardisation of the notching requirement of the range of timber joists so that it will remain the same for all beams.
The preferred embodiment provides a beam which uses beam flange thickness less than the allowable notch depth in the timber I joists
The preferred embodiment provides the standardisation of the beam depths and standardising joists notching sizing.
The preferred embodiment provides common thickness flanged beams enabling standard notching and cut to length joist supply to site by a manufacturer, or as a minimum supplying the standard packs to site with one or both ends of each timber joist notched top and bottom during manufacture so that at least one end is available to fit a standard beam, reducing labour costs on site.
The framing companies cannot at this time supply joists cut to length and pre notched to site mainly due to the complications caused by the beam differences. The above embodiment will make a real difference in the site labour costs reductions if they were cut to length and pre-notched. The invention allows this to be done now because of the standardised flange widths and the flange thickness.
The beams are manufactured off site and provided in predetermined depths and lengths, they are pre-notched in the top and bottom flanges at each end or on one end only of the timber I joists, transported to the site in cut to length and ready to use to construct the floor structure.
Conventional floors squeak if the ends of the joist are in contact with the web of the steel beam, which is a common problem in the industry. The standard length notching of the above embodiment will overcome that problem as well.
The preferred embodiment allows to manufacture beams to standard lengths that suit their application maximising efficiency of manufacturing and minimising offcut wastage within the domestic building industry.
The preferred embodiment provides a range of simple and optimised structural beam cross sectional shapes that will standardise and significantly reduce the installation costs of labour and material in floor structures built on site.
Although a preferred embodiment of the present invention has been described, it will be apparent to skilled persons that modifications can be made to the embodiment shown.
The beam flange thickness is an avenue for optimization of the process, whereby the joists allowable maximum notch depth is not exceeded by the flange thickness. The optimal flange thickness suits the beam capacity and material efficiency to suit the span range of a depth of beam in the most efficient way.
The flange thickness may not be the same in each depth grouping of the beams, however it is preferred that they are the same for all the different beam depths. In the preferred embodiment, the flange thickness is 10 mm which works for both the 240 mm and 300 mm deep beams.
The reason why the larger flange beam of nominal 200 mm depth is that in many cases, the beams are used to support the external brick wall as well as the timber floor joists and timber wall. The wider flange allows the brick wall to be supported on one side of the beam flange, and the joists and timber walls on the other side of the top flange.
The brickwork can overhang the beam flange max 25 mm, the timber wall frame cannot overhang more than 10 mm. However, when the flooring is sandwiched between it obviously can be more, hence 250 mm overall wall thickness including 90 mm timber wall, 50 mm cavity and 110 brickwork with 25 mm overhang, has the 90 mm wall frame hang over the internal half of the top flange by 25 mm,
In another embodiment of the beam, it now can be made to a 240 mm or 300, deep, whereas they are currently 250 mm (pfc—parallel flange channel) plus a 10 mm plate or 260 mm, or 230 mm pfc with 10 mm plate making it 240 mm with a very thick bottom flange, or a 300 pfc with a 10 mm plate or 310 mm overall and not useful.
The invention in one embodiment provides having the beam overall depth being equal to the timber joist depth.
The connection end plate is centrally located at mid height of the beam and is symmetrical about the web, so the vertical centre line of the connection plate is to the centre of the beam web.
The joist in the example is a timber I-beam but can alternatively be solid timber, steel I beam, steel trussed joist, timber trussed joist, or purlin joists.
The maximum flange thickness can be up to 16 mm rather than the example 12 mm described. This allows an opportunity to optimise to suit any joist system and any future joist system allowing a deeper notch depth, since the beams flanges in this depth range are around 16 mm maximum.
The optimal (preferred) form of the beam connection to suit the current timber I joists is 12 mm flange thickness, a smaller beam flange width of 125 mm and larger beam flange width of 200 mm.
The present invention provides a beam and joist set comprising an I cross-section steel beam and a timber joist, wherein the beam depth and the joist height are the same. A notch is pre-formed/pre-cut to the top and bottom surfaces in a first end of the joist, and preferably in both ends of the joist. The notches have a depth substantially equal to a thickness of the top and bottom flanges or just slightly deeper.
In use, the first end of the joist is disposed between the top and bottom flanges of the beam such that the top surfaces of the beam and the joist are level, and the lower surfaces of the beam and the joist bottom flanges are also level.
If the second end of the joist is pre-notched, the second end can also be inserted into a second steel beam.
The joist is preferably cut to length prior to delivery to site.
The timber joist is preferably an I cross-section joist having a top flange and a bottom flange with a web extending therebetween, wherein the notches are formed in the top and bottom flanges.
The present invention also provides a method of construction using the beam and joist set of the above including supplying the timber joist to site with the notches at the first end pre-cut prior to delivery to site; and disposing the first end of the joist between the top and bottom flanges of the beam.
The present invention also provides a method of construction using the beam and joist set of the above including supplying the timber joist to site with the notches at the first and second ends pre-cut prior to delivery to site, disposing the first end of the joist between the top and bottom flanges of a first beam, and disposing the second end of the joist between the top and bottom flanges of a second beam.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019900396 | Feb 2019 | AU | national |
| 2019903713 | Oct 2019 | AU | national |
