Patent Application
20110308197
The present invention relates very broadly to the building and construction industries. More particularly, the invention relates to a structural member for use in the building and construction industries and will herein be described generally in that context. It is to be appreciated, however, that the invention may have broader application.
Reference hereinafter will be generally made in the context of the structural member being in the form of a building pile section and a pile constructed from two or more pile sections. It is to be appreciated that the invention could adopt any other suitable form, including a building column, strut, beam or section thereof.
Structural members in the form of piles and pile sections are used widely in the construction industry both in Australia and overseas to provide deep foundations for supporting buildings, bridges and other structures.
Conventional piles include timber piles, reinforced (or pre-stressed) concrete or steel piles.
Piles are typically driven by means of a hammer piling device into the ground to a depth at which the pile develops enough resistance to support the required load. If the pile is driven into the ground a sufficient distance to rest against hard strata such as rock then it is described as being end-bearing. Often though this is not possible and so load capacity of the pile is achieved by sufficient friction having been generated between the driven pile and the surrounding soil.
It is typical practice in the construction industry to carry out a geotechnical investigation prior to designing a structure. Various investigation techniques are possible, with a common technique being the boring of test holes at the proposed site in order to obtain samples for laboratory analysis. The information gained enables the design of pile parameters including pile type, size and length. Unfortunately, regardless of the number of test holes bored and the level of sophistication in analyzing the samples, the results obtained are at best only a prediction. This is, at least in part because soil and other conditions can vary over the site and so some uncertainty is inherent in such analysis.
Irrespective of the conventional pile type concerned, pile cross-sections are usually constant along the length of the pile, except in the case of timber piles, which generally naturally taper. Round cross-sections are common for timber and concrete piles, but concrete piles may also be of square, hexagonal and octagonal cross-sections. Steel piles most commonly have an H-section, but other shapes are also used, including round steel pipes.
Piles are typically several metres in length. Timber and steel piles are normally available in stock lengths up to 12 or 15 metres, in standard length increments of 1 to 2 metres. Concrete piles are generally made to order, and can be made to any length, but are limited in a practical sense by transport and handling considerations. It is known to the applicant to allow for pile lengths to be slightly greater than anticipated or calculated, as it is far more cost effective to allow an extra metre or so of pile length to reduce the risk of the pile being too short, thus incurring the time and cost of joining together two pile sections in an end-to-end arrangement. In this regard, it is to be appreciated that significant time and cost is involved in aligning and connecting together conventional pile sections.
Piling contractors generally prefer pile lengths of up to 12 metres, as this is the length that can be readily transported, handled and accommodated in existing pile driving rigs. After driving each pile until the specified load capacity is achieved the pile is cut off and the excess length discarded.
Regardless of predictions made by even the most sophisticated methods, piles must actually develop adequate load capacity, verified at the time of driving. For end bearing piles this is straightforward as the pile is driven to “refusal”, at which point it comes to a sudden definite halt against hard strata. For friction piles, pile capacity has traditionally been verified by calculation using a formula relating parameters such as pile mass, and hammer mass, height of fall and penetration per blow of the pile driving rig. Modern sophisticated methods using instrumentation and computers enable more accurate, but still far from perfect, predictions.
Extension of conventional pile lengths is time consuming and costly in terms of material and labour. This is compounded by costs associated with delay to construction activities, with expensive crew on stand-by. For very deep foundations, joining of pile sections is unavoidable and various types of connectors have been developed for both timber and concrete pile sections, but they are relatively expensive. For steel pile sections, butt welding is the normal pile section connection method, but is also expensive, due to the time taken to prepare the pile section ends, involving grinding large bevels and making numerous weld passes. The difficulty and high cost of joining pile sections means that pile driving contractors seek to maximize pile section lengths, which necessitates larger pile driving rigs. As well as being more expensive, large pile driving rigs are more costly to transport and set up on site.
Piles usually develop more load capacity with time (generally known as “set-up”), as the disturbed soil consolidates around the pile and bonds to it, and the lubricating affect of the ground water diminishes. Even if pile driving is interrupted for only a short period of time, as when splicing on an extra pile section length, much greater effort is required when driving restarts. Over the long term the pile capacity usually increases much more because the soil bonds to the pile.
The applicant has recognized a need for improvement in piles and also an improvement in connecting pile sections together. Numerous designs exist for connecting concrete pile sections, few for timber pile sections, but hardly any for steel pile sections. This may be due to the prevailing view in the industry that, unlike timber and concrete, steel can easily be joined by butt welding. However, aligning and butt welding steel pile sections together is time consuming and expensive, due to the time taken to prepare the pile section ends.
It would therefore be desirable to provide an alternate and potentially improved pile and/or pile section design.
It would also be desirable to provide a pile and/or pile section design that provides a less time consuming and more cost effective arrangement for the connection of pile sections than currently available.
The discussion of acts, materials, devices, articles and the like above is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia before the priority date of each claim of this application.
According to the present invention, there is provided a structural member. The structural member includes a longitudinally extending core and at least two longitudinally extending ribs. Each rib, in profile, extends outwardly from the core to an outer rib edge. The structural member also includes a receiving aperture provided in a first end of the member for receiving an end of an adjacent structural member.
The aperture may be a slot, slit or other suitable form.
In a preferred form, the first end of the structural member includes a first connecting arrangement for connecting the first end to the end of the adjacent structural member.
The connection of structural members is desirable, because the members can be manufactured in standard lengths and be subsequently connected end-to end to provide an overall structure of desired length.
The provision of a receiving aperture and first connecting arrangement is most advantageous because it allows for the first end of the member to nest with the end of the adjacent member. As such, the member and adjacent member may be connected by way of a lap joint, so as to provide a robust and durable connection between the structural member and adjacent member.
The provision of an aperture also facilitates relatively easy alignment of the structural members, in situ, if required. In this regard, the second longitudinal end of the structural member may be driven into the ground by a suitable driving and/or piling device. The height of the structural member extending from the ground may be insufficient for the desired purpose, such that additional height is required. If so, then a second member can relatively easily be aligned and located on top of and then connected to the upper (first) end of the structural member to increase the overall height to that required.
The first connecting arrangement may include one or more fastener receiving apertures provided in at least one rib, such that the overlapping ends of adjacent members may be fastened together using bolts or other suitable fasteners.
It is to be appreciated that the overlapping ends of adjacent members may be welded together, if desired. The use of welding may be in addition to or in place of using fasteners.
The first end of the structural member may include an abutment (or alignment) shoulder for abutment/alignment of the structural member with an adjacent structural member. The abutment shoulder may be provided on one or more of the ribs and/or core.
The structural member may adopt any suitable form. For example, the structural member may include 2, 3 or 4 (or more) longitudinally extending ribs. Further, the core may, in one or more forms, be at least partially hollow.
In one possible form, the profile of each rib tapers from the outer edge to the core. The provision of a taper may provide one way of maximizing the strength to weight ratio of the member, thereby potentially reducing the bending and buckling of the member under axial load. It is to be appreciated however, that each of the ribs may adopt any suitable form, and need not taper. In one alternative form, each rib (in profile) may taper outwardly from the core to the outer edge. In another alternative form, the thickness of each rib may be approximately constant between the core and the outer edge.
The structural member may be of any suitable form, such as a pile section, building column, strut, beam or portion thereof. Indeed, the Applicant considers that the member may be particularly suitable for use as a pile section, in place of a conventional wooden, reinforced concrete or steel pile section.
The profile of each rib may be generally straight, curved, bent or any other suitable profile.
The structural member may include a second connecting arrangement provided at the second longitudinal end thereof for connecting the second end to another adjacent structural member.
One or more ribs may extend outwardly from a location generally aligned with a central axis extending longitudinally through the core. The applicant also contemplates embodiments in which one or more ribs extend outwardly from the core from a location(s) generally not aligned with a central axis extending through the core. Non-limiting examples of both arrangements are illustrated in the accompanying drawings and described in the associated description of drawings.
The core, or at least a central portion thereof, may be solid or hollow. As a further alternative, the core, or at least a central portion thereof, may be solid along a longitudinal portion(s) thereof and hollow along another longitudinal portion(s) thereof.
It will be convenient to hereinafter describe preferred embodiments of the invention with reference to the accompanying drawings. The particularity of the drawings is to be understood as not limiting the preceding broad description of the invention.
Referring to
The pile section 20 includes a receiving aperture in the form of a slot 36 provided in a first end 38 of the pile section 20. The slot 36 is provided for receiving an end 40 of an adjacent pile section 42 (see
In this regard, the first end 38 of the pile section 20 includes a first connecting arrangement for connecting the first end 38 to the end 40 of the adjacent pile section 42. The connecting arrangement includes apertures 44 provided in each of the ribs 24, 26, 28 for receiving a plurality of fasteners. The fasteners may be in the form of screw threaded fasteners (for example, bolts), rivets or the like.
The provision of slot 36 and the first connecting arrangement is most advantageous because it allows for the ends of the pile sections 20, 42 to be nested, so as to be connected by way of a lap joint to provide a robust and durable connection.
The connection of pile sections 20, 42 is desirable, because it allows for the manufacture of pile sections in standard lengths, which can be subsequently connected end-to end to provide an overall pile structure of desired length.
Although not illustrated, it is to be appreciated that the overlapping ends 38, 40 of adjacent members 20, 42 may be welded together, if desired. The use of welding may be in addition to or in place of using fasteners.
Although not illustrated, the pile section 20 may include a second connecting arrangement provided at the second longitudinal end thereof for connecting the second end to another adjacent pile section.
Another pile section 120 according to the present invention is illustrated in
A further pile section 220 is illustrated in
Another pile section 320 according to the present invention is illustrated in
Although not clearly shown, pile sections 1720, 1820 may be substantially identical. Pile section 1620 is manufactured from a pair of angle sections 1650, 1652, and includes ribs 1624, 1626, 1628, 1630, a substantially open core 1622 and at least one (and possibly two) abutment shoulder 1640. The shoulder 1640 illustrated is welded to ribs 1624, 1630. The lower end of pile section 1620 could be driven into the ground to the required depth. Pile sections 1720, 1820 are used to provide an overall pile structure of the required height.
Pile section 1720 can be relatively quickly and easily connected to pile section 1620 when the pile sections are orientated vertically, by inserting the lower end of pile section 1720 into a receiving aperture in the form of a slot or slit (not visible) in the upper end of pile section 1620. The pile section 1720 is lowered in a downwards direction until it abuts the shoulder 1640, at which time fasteners are inserted through aligned holes provided in the ribs of pile sections 1620, 1720 to securely connect the two pile sections 1620, 1720 together.
As similar process is then used to connect the lower end of pile section 1820 to the upper end of the pile section 1720.
More or less pile sections could be connected together in place of the three pile sections 1620, 1720, 1820 illustrated in order to provide an overall pile of a desired height. It is to be appreciated that the specific height of each of the pile sections 1620, 1720 and 1820 may be selected as desired. Also, it is to be appreciated that the profile and type of each pile section may differ from those illustrated in
The connections between pile sections 1620, 1720 and 1720, 1820 are inherently strong. Axial forces are transmitted directly by the abutting surfaces between pile sections, augmented by bolts (and/or welds—not shown). Bending capacity is inherently high because the members overlap. Hence the joint is stronger in both bending and compression than the basic members. It is to be noted that the connections allow for the core of each pile section to be in line, rather than a less desirable arrangement whereby the cores are not in line.
The term ‘core’ as used in this specification is to be interpreted broadly, especially with regard to one or more of the embodiments of the invention as described, defined and illustrated, where a separately identifiable core may not be clearly visible.
The pile sections according to the present invention can also be relatively easily pointed (or otherwise shaped) at one or both ends by trimming the corners of the ribs. This enables accurate location at the start of the piling process and minimises damage to the pile section end from underground obstructions.
The pile sections of the present invention can potentially eliminate at least some of the time, effort and cost associated with geotechnical investigation and predictions potentially need not be so thorough. Project costs can be potentially further reduced because contingency allowances, normally made by contractors in their tenders to cover the cost of extra length of conventional pile sections, can be reduced.
Compared to existing steel structural members such as H-shaped profile pile sections, the X-shaped profile design of the present invention (and possibly also other profile shapes according to the present invention) provide improved axial load. This is potentially at least in part because the X-shaped profile has a reasonably uniform stiffness the entire way around the profile and hence has no identifiable plane of buckling. This is a very desirable characteristic for piles, pile sections, columns, struts and other structural members.
X-shaped profile pile sections according to the present invention can be manufactured from standard hot-rolled steel angles, which are inherently more cost effective to manufacture than the more complex H-shaped pile sections currently used. Additionally, instead of hot rolled steel, the angles used to fabricate the X-shaped profiles can be cold pressed from steel plate, which also minimizes the cost of production.
The present invention thus potentially obviates the high investment cost associated with rolling mills, as at least the X-shaped profile can be relatively easily manufactured from stock angle sections in ordinary workshops using straightforward techniques, using simple jigs to provide manufacturing accuracy.
Joining (or splicing) of pile sections according to the present invention is also a relatively straightforward process when compared to that required for existing pile sections. Pile sections according to the present intention are inherently self-aligning so that another pile section simply slots into place and is immediately self-supporting. Then it can be simply a matter of inserting and tightening the bolts to provide a sound, secure lapped joint connection, considered generally stronger than the parent material.
It should be appreciated that pile sections according to the present invention would typically (but not essentially) include a substantially identical slot, slit or other suitable aperture and associated connecting arrangement at each end of the pile section, allowing either end of the pile section to be connected to the end of an adjacent pile section or, as illustrated in
Unlike existing pile sections, there is no need for a pile comprising two or more pile sections according to the present invention to have a constant profile along the entire length of the pile. Instead, it may be that the lowermost pile section is larger because that is where the load capacity on the assembly is likely to be greatest. The remaining (upper) pile sections of the structure may have a smaller profile, thereby reducing the total mass of the assembled pile by up to 25% (or more). Alternatively, the uppermost or middle portions may be larger so as to provide greater resistance to buckling. The reduced mass provides a way of reducing the overall cost of pile. This is possible, because the present invention allows different pile section thicknesses and sizes to be connected together relatively easily.
Pile sections driven through fill can experience additional loading due to down-drag arising from settlement of the fill. With the smaller upper section as described above this effect may be reduced.
Overhead restrictions such as power lines, trees, or inside buildings can sometimes cause problems for pile driving. Short pile sections and a small driving rig is often the only practical solution, with the latter connection of pile sections to create an overall pile being necessary. The present invention provides a means of relatively quickly and easily connecting (or splicing) pile sections together.
The ease of connecting pile sections together according to the present invention results in pile section off-cuts being relatively easily re-used, possibly for use in a neighboring pile assembly. Thus, off-cut wastage can be significantly reduced when compared to existing pile arrangements. This has a further benefit, in that there is a potentially greatly reduced need for off-cuts to be removed from the construction site. Further, piling contractors are potentially far less likely to err on the high side when selecting lengths of pile section, which is currently a common practice that can typically result in 10 to 20% pile wastage. Another advantage is that choice of length is not critical which means steel mills, merchants, and piling contractors do not need to produce or stock a large range of length increments, thereby reducing inventory costs.
A comparison of a pile having an X-shaped profile according to the present invention can be made with a conventional H-shaped pile having similarly sized profile dimensions and a similar linear mass, such as provided below.
The X-shaped profile is considered by the applicant to be inherently superior. This is because the stiffness of the X-shaped profile is fairly uniform in all directions, whereas the H-shaped pile is significantly weaker about one of its two profile axes.
The pile having an X-shaped profile is also less susceptible to local damage than a conventional pile having an H-shaped profile, as the X-shaped pile ribs are thicker. Sturdy edges ensure greater resistance to damage during transport and handling and, more importantly, when striking boulders or other buried objects during the pile driving process. Another advantage of the thicker ribs is corrosion resistance, ie. thick ribs suffer comparatively less weakening for a given amount of metal loss due to corrosion than thin ribs.
The applicant also considers that piles and pile sections having an X-shaped profile will be cheaper to produce than conventional steel piles and pile sections having an H-shaped profile. Ease and low cost of joining steel pile sections means that pile driving contractors no longer need to seek to maximize pile lengths. Accordingly, smaller pile driving rigs can be used, thereby saving capital outlay, and lower transport and setting up costs.
One or more of the above referred advantages of piles/pile sections having an X-shaped profile may also be inherent in the other profile shapes of the piles/pile sections and other structural members discussed, illustrated and contemplated in the present application.
Again, it is to be appreciated that the structural member of the present invention may be of any suitable form, including a pile section, pile, building column, strut, beam or portion thereof.
Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the construction and arrangement of the parts previously described without departing from the spirit or ambit of this invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009900559 | Feb 2009 | AU | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AU2010/000126 | 2/8/2010 | WO | 00 | 9/8/2011 |
