US20140270979A1

US20140270979A1 - Flexible post for use as a pile

Info

Publication number: US20140270979A1
Application number: US14/204,101
Authority: US
Inventors: Paul R. Cusson; Brian M. Flood
Original assignee: Northern States Metals Co
Current assignee: Northern States Metals Co
Priority date: 2013-03-14
Filing date: 2014-03-11
Publication date: 2014-09-18

Abstract

A U-shaped strut is sized and configured to be driven into a substrate as a pile. The strut includes a U-shape cross-section with two open arms. Each arm terminating in an annular 270° configuration with respect to the axis of the arm. Preferably, a plurality of struts used as piles are used to support a two dimensional support rack holding a solar panel array.

Description

PRIORITY DATA

This application claims priority to U.S. Provisional Patent Application No. 61/781,899 filed Mar. 14, 2013.

FIELD OF INVENTION

This invention relates in general to a structure for a pile. In particular, the present invention is related to a flexible post structure that facilitates both driving of the post as a pile and stability of the pile structure.

BACKGROUND

Stable, high-rigidity piling is needed to support overlying structures in a wide variety of different situations. These can include the support of concrete pads with overlaying skyscrapers, or simple vertical struts arranged in a substrate to support a framework, a small building, or a piece of equipment. Depending upon the structure that the piling will support, a wide variety of different piling struts, posts or other structures are in use. Test samples of such conventional structures, along with the present invention, are found in the table of Appendix II.
As with any other arrangement requiring structural elements, a balance must be obtained with regard to strength, weight, costs, difficulty of driving a structure or post used as piling, and the ultimate stability of the piling structure once it has been driven into the ground or substrate.
Appendix II provides test results for only a limited number of examples of some common types of piling structures, as well as the novel structure of the present invention, designated as Solar FlexRack SmartPost. Each of the conventional structures on the Appendix II chart has advantages and disadvantages, as indicated by the stated test results, and other factors.
For example, circular piling structures, as indicated in Appendix II, can be very effective. However, because they have a very low strength-to-weight ratio, they have to be particularly heavy to form stable support pilings. I-beams typically exhibit a high strength-to-weight ratio, but are sometimes difficult to work with since proper alignment is necessary for optimum performance. For instance, when installing an I-beam used to support solar racking (such as that in FIG. 3), the I-beam is typically driven into the ground having an east-west (i.e., cross-sectional) direction so that the flat, facial surfaces of the I-beam are facing east-west to directly bolt a flat surface of a tilt bracket (used to hold the support rack at a southern exposure, i.e., angular tilt). As a result, the strength of the I-beam is greatly diminished. It would be stronger if oriented in a north-south direction. However, if the I-beam was oriented in the north-south direction, the tilt bracket would not be securable to a flat, facial surface of the I-beam and the strength of the connection would be relatively weak. Further, I-beam structures can be very difficult to drive into certain types of substrates due to the rigidity of the I-beam.
There is also a wide variety of various channels and other structures formed of sheet metal. While many of these configurations can be strong, all of the conventional posts or struts are subject to crumpling, bending, or otherwise deforming, when being driven into a hard substrate or encountering rocks in the ground through which the pile is being driven. For example, the C-channel (as described in Appendix II) appears to have a good strength-to-weight ratio. However, it is still susceptible to crumpling at the open ends of the channel. Once this takes place, the piling very often tilts and cannot be driven in a straight, vertical line to effect the desired results expected of a piling structure.
It should be noted that certain rigid piling structures, such as the I-beams, are extremely strong (as shown in Appendix II). However, it is often difficult to drive I-beams into rocky ground when the rigid I-beams tend to twist and change orientation upon hitting an obstruction. As a result, the I-beam may be driven into the substrate at an angle other that the desired 90° (with respect to the surface of the substrate).
On the other hand, more flexible posts or beams can deflect or deform when encountering an obstacle such as a large rock. However, such structures are also very susceptible to crumpling upon reaching an obstruction. This may result in the piling structure not able to be driven into the ground further, or tilting at an unacceptable angle. Eventually, the structure can become entirely useless as a support piling.
A wide variety of different shapes, sizes, and other structural configurations have been used as conventional pilings. However, the appropriate balance between structural stiffness and flexibility has always been elusive in this particular art. Accordingly, an improved piling structure would be configured to have sufficient structural strength to serve as both an appropriate piling, providing a high level of structural support, and a structure sufficiently flexible to be easily driven into any type of substrate.

SUMMARY OF THE INVENTION

Accordingly, it is a principle object of the present invention to overcome the limitations of conventional piling structures.
It is an additional object of the present invention to provide a piling structure that can be easily driven into the ground or other substrate.
It is a further object of the present invention to provide a piling structure that is sufficiently stiff to provide structural support for a foundation.
It is another object of the present invention to provide a piling structure that can be deformed to move around obstructions in the ground.
It is still a further object of the present invention to provide a piling structure with greater holding capacity and pullout strength than conventional structures of a similar size.
It is yet an additional object of the present invention to provide a piling structure with a superior strength-to-weight ratio when compared to conventional structures.
It is again another object of the present invention to provide a piling structure with a balance of strength and flexibility to more easily be driven into the ground or other substrate.
It is yet a further object of the present invention to provide a piling structure that can be used in a wide range of different applications, encompassing a wide range of different piling sizes while remaining effective as a support for a wide variety of different structures.
It is still an additional object of the present invention to provide a piling structure that has a lower cost for the equivalent structural strength found in a conventional piling structure.
It is yet another object of the present invention to provide a piling structure that facilitates easy external connections, and is configured so as to provide multiple surfaces for connections to external structures.
It is again an additional object of the present invention to provide piling structures that are configured to be easy to store and transport.
These and other goals and objects of the present invention are achieved by a U-shaped strut having arms with annular structural end pieces formed in a 270° configuration with respect to the axis of the arms.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a top view of the post constituting the present invention;

FIG. 2 is a perspective view of the post shown in FIG. 1; and,

FIG. 3 shows an installed solar rack 10 supported by a plurality of posts as depicted in FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention admits to a wide variety of different applications, from pilings that support building foundations, to relatively lightweight vertical supports to which a wide variety of structures can be attached. FIG. 3 depicts one example of a preferred use of an embodiment of the present invention, supports for a solar panel array 10.
Appendix I includes a series of 9 photographs depicting the various stages of pile driving the post 1 of the present invention. This conventional process is already well-known, and it is only the configuration of the flexible strut or post 1, which constitutes the piles, that is novel. Appendix II includes a chart comparing strength characteristics of a wide variety of different structures or struts used as pilings, including the flexible post 1 of the present invention. This Appendix is used for comparative purposes, and can be referred to as proof of the relative strength of the present invention.
The post of the present invention, as depicted in FIGS. 1 and 2, is used as a vertical support for a solar panel support array. The posts or piling structures 1 (as depicted in FIGS. 1 and 2) have been sized and driven into the ground to accommodate the particular panel support array 10 being used in the example shown in FIG. 3.
It should be understood that a wide array of different sizes and applications are also feasible, and expected when using the flexible post or piling structure 1, as depicted in FIGS. 1 and 2. It should also be noted that the characteristics of post 1, as a piling structure, are particularly appropriate for the application depicted in FIG. 3. In particular, it is necessary to have a proper vertical support structure as provided by post 1, upon which to mount the support rack for a solar panel array 10, as depicted in FIG. 3.
FIG. 1 depicts a top view of a representative flexible strut or post 1 which can be used as a pile structure in accordance with the present invention. Preferably, post 1 is made of rolled steel between 0.15 inch and 0.2 inch. Post 1 is in the shape of a U, having a base or back portion 2 and two arms 3A, 3B. Each of the arms 3A, 3B is connected to base portion 2 at curved joints or radius parts 5A, 5B, and terminates in annular structural ends 4A, 4B, respectively. The annular structures 4A, 4B are configured so that the curve is approximately 270° with respect to each of the respective arms 3A, 3B.
The base 2 in the FIG. 1 depiction is approximately 6½ inches long. The two arms 3A, 3B are between 3.2 inches and 5.2 inches in length. The annular structural ends 4A, 4B of the two arms are approximately 1.5 inches in circumference, with approximately 4 inches between the inside curves of both of the annular structures 4A, 4B. It should be understood that while these measurements are appropriate for one preferred embodiment of the present invention, the size of the present invention can be varied in accordance with the type of support desired from the installed piling structure.
The exact measurements of post 1 are determined by considering the parameters of the type of ground, the depth which the pile is to be driven and the type of machinery being used to drive the piles. Likewise, while the example in FIG. 1 is an ASTM A653 grade 55 steel (galvanized to a thickness to be G90) with standard roll tolerances, other types of steel, or even other types of metal, can be used within the concept of the present invention.
It should be understood that the configuration of the post 1 is the key inventive feature. In particular, for the amount of steel involved, the present invention is generally lighter and less massive than a similar sized I-beam, which is commonly used as a pile structure. Further, the present invention provides far greater surface area (to hold the pile structure steady in the ground by means of surface tension) than is found with an equivalent sized conventional structure, such as an I-beam, for example. The annular structures 4A, 4B also provide additional surface area to enhance surface tension cohesion and greater stability.
The present invention, embodied by post 1, is a configuration that is sufficiently robust to be driven into a wide variety of different substrates by a piledriver, while still being sufficiently flexible to slightly deform around obstructions in the ground, or substrate. As a result, flexible post 1 can be used as a pile structure without tilting or compromising the structural integrity of the final pile configuration.
The open U-shaped configuration allows the two arms 3A, 3B to flex in and out, thereby permitting post 1 to slide past rocks or other obstructions in the ground, without losing structural integrity. The strength of the ends of arms 3A, 3B is maintained by annular structures 4A, 4B, respectively. These structures keep the ends of arms 3A, 3B from crumpling because of the additional strength provided by the 270° curvature of the annular structures 4A, 4B. Without annular structures 4A, 4B, the U-shaped post 1 might crumple when the end of one of the arms 3A, 3B is driven into an obstruction, such as a rock.
With the annular structures 4A, 4B, arms 3A, 3B flex upon encountering an obstruction in the ground, and will deform sufficiently to get around the obstruction. Normally, this is accomplished by the arms 3A, 3B flexing at the curved radius parts 5A, 5B (0.375 inch in the FIG. 1 embodiment) connecting arms 3A, 3B to back or base 2. This is the natural operation of this type of structure, and the integrity of the ends of the arms 3A, 3B is maintained by the annular structures 4A, 4B, respectively.
However, the mid-portions of the lower edges of arms 3A, 3B can also deform when the bottom edges encounter obstructions and are forced outwards with respect to the rest of the respective arms 3A, 3B. This deformation generally is limited to areas near the bottom edges of the two arms 3A, 3B, and will tend to force the arms 3A, 3B edges either inwards or outwards with respect to the plane of the respective arm.
When this type of deformation of arms (3A, 3B) of post 1 takes place within the ground as post 1 is being driven in as a pile structure, a stronger structural relationship between the pile 1 and the substrate is established due to the aforementioned deformations. The overall surface tension is greater as different surface orientations provide greater surface tensions with the substrate. Also, deformation of the bottom edges (of arms 3A, 3B) will turn out and slightly upwards. This phenomenon makes the pile far more difficult to remove, and provides a greater level of structural stability than would otherwise exist if this outward deformation did not take place.
In the example provided by FIG. 3, the posts 1 are used as vertical substrate supports for a solar panel rack 10. In this case, the plurality of posts 1 are driven into the ground to a preferred depth of between 6-15 feet. To better facilitate this use, post 1 is configured so that easy attachment can be made between the post and external devices, such as the panel support array 10. The open, U-shape of post 1 allows installers to place their hands to hold bolts to facilitate easy connection to other, external structures. The three flat surfaces constituting the base 2 and the arms 3A, 3B also facilitate easy connection to external devices. As a result, connection to external devices is much easier and less expensive. Plus, the flexibility of post 1 that makes it an adaptable pile structure also makes it an excellent vertical support for attachment to structures (such as support array 10) that require stable support.
Notably, load testing was conducted on the flexible post 1 versus an I-beam (i.e., best identified in the trade as a “Section W—6×15 I-beam”). The testing was conducted at three separate proposed solar array sites to study different soil types and conditions. The field testing was performed in general accordance with ASTM International Standard ASTM D3689-07—Test Methods Static Axial Tensile Load Testing. The post 1 and I-beam embedment depths varied from 8 to 10 feet below the ground surface. Further, static axial loads of 2.5 kips, 5 kips and 7.5 kips were induced incrementally and maintained for four (4) minute intervals at each load range, measured with linear potentiometers and recorded electronically via a data acquisition system. A total of twelve (12) flexible posts 1 and four (4) I-beams were load tested at the subject three sites.
The axial load testing results indicate that fifty percent (50%) of the flexible posts 1 tested in the vertical direction exhibited lower deflection values (i.e., stronger uplift resistance) to the induced vertical loading when compared to the test results for the I-beams. Although the skin friction at the interface between the exterior surface of the post 1 piling and I-beam (i.e., surrounding soil matrix) is the primary component providing vertical resistance, in the case of the post 1, a secondary and important component supplementing the skin friction value was discovered when the post 1 piles were extracted from the ground. Moreover, in ninety percent (90%) of the cases, deformation of the post's cross-section occurred. At the toe or bottom of the pile post 1, there was an outward deflection of the curled annular structures 4A, 4B and arms 3A, 3B which occurred during the installation of the posts 1. This deflection or flaring of the post 1 bottom created a “belled” condition similar to a “belled” caisson installation and was measured to be approximately 2-inches laterally. The final test results are summarized in Appendix II.
This unique flaring dynamic adds value to the post's resistance to vertical uplift loading. Caused by the permanent metallurgical deformation, the interior cross-sectional space of the post 1 is occupied with soil dynamically compacted into the interior space as the post is driven into the ground. The dynamically compacted soil maintains the flared deformation of the post end and impedes compression of the post 1 to its original cross-section upon extraction.
Further describing the invention, the nature of the overall construction of the flexible post 1 makes it easily scalable so that post size and strength can be selected for the type of pile or vertical support that is needed. Accordingly, the dimensions provided for the FIG. 1 example can be increased or decreased to obtain the desired pile structure or vertical support structure. Because flexible post 1 is relatively light compared to equivalent I-beams, it is far more easily handled, and thus is more easily set up for being driven into the substrate.
The present flexible post 1 is far less expensive than an equivalent I-beam since the post 1 is preferably made of rolled steel as previously specified. The tooling needed to make a wide variety of different sizes and weights of the flexible post 1 is less costly than that needed to fabricate a steel I-beam. Little or no additional expense is incurred, for example, to include connecting holes in the fabrication of the flexible post 1. The holes are simply punched in the roll forming process. On the other hand, when fabricating I-beams, the connecting holes would have to be drilled in a separate operation. Further, steel I-beams come only in a limited number of sizes and weights due to the expense of manufacturing them. On the other hand, precise sizes and weights are not an issue when using the flexible post 1 of the present invention. This means that it is not necessary to pay for extra size and weight with the present invention as it might be for a steel I-beam.
Besides the size and weight, I-beams can often be difficult to work with. For example, if an I-beam has to be oriented in a certain direction to achieve its maximum preferred strength-to-weight ratio, there will be difficulties in trying to connect additional structures to the I-beam. More specifically, special straps or U-bolts are used for connection around the I-beam similar to the connections used to connect to round, tubular beams. No such difficulties are found with the flexible post 1 of the present invention, which provides three flat sides that are easily punched (during the fabrication process as discussed above) for a wide variety of different connecting apertures.
While one preferred embodiment has been described, with precise dimensions by way of example, the present invention is not limited thereby. The post constituting pile 1 can be made much larger or somewhat smaller than the depiction in FIG. 1. Further, while the material described for the first preferred embodiment is a particular type of steel commonly used for piles, a wide range of materials can be used within the concept of the present invention. Further, the present invention should be understood to include any and all modifications, variations, permutations, derivations, adaptations and embodiments that would occur to one skilled in this art having possession of the teachings of the present invention. Accordingly, the present invention should be construed as being limited only by the following claims.

Claims

What is claimed is:

1. A U-shaped strut configured to be driven into a substrate as a pile, said strut comprising a U-shape cross-section with two open arms, each said arm terminating in an annular 270° configuration with respect to a major axis of each said arm.

2. The strut of claim 1, wherein said structure comprises three flat surfaces configured for connection to external structures.

3. The strut of claim 2, wherein said two open arms are configured to deform when said strut is driven into said substrate as a pile.

4. The strut of claim 3, wherein said two open arms are configured to deform outwardly at a non-vertical angle to an upper surface of said substrate.

5. The strut of claim 4, wherein said strut comprises rolled steel.

6. The strut of claim 5, wherein said two open arms are attached to a center piece by structures having a radius.

7. The strut of claim 6, wherein at least one surface of said strut comprises an aperture to facilitate connection to external structures.

8. The strut of claim 7, wherein a plurality of said struts are driven as piles into a substrate to support a solar panel support array in a stable state.