WO1995026444A1

WO1995026444A1 - Multiple pier foundation and method of constructing same

Info

Publication number: WO1995026444A1
Application number: PCT/US1995/003764
Authority: WO
Inventors: Thomas H. Gentry
Original assignee: Blue Ribbon Products, Ltd.
Priority date: 1994-03-25
Filing date: 1995-03-24
Publication date: 1995-10-05
Also published as: AU2195995A

Abstract

A method for constructing a multi-pier foundation in which concrete piers are formed at the construction site. Multiple holes (14) are formed in the ground at spaced intervals. A spike (4) having a support surface (20) is positioned in each hole such that the support surfaces of the spikes so positioned are substantially at the same elevation. Concrete (3) is then poured in the holes to fix the spikes in that position and complete the formation of the piers.

Description

MULTIPLE PIER FOUNDATION AND METHOD OF CONSTRUCTING SAME

BACKGROUND OF THE INVENTION This invention relates to building foundations generally, and more specifically to a multiple pier foundation and method for its construction.

Generally, there are several types of foundations used in the building industry. These include slab on grade, placed pier and grade beam, poured-in-place pier, and precast pile type foundations. Typically a slab foundation is constructed by pouring concrete into a perimeter form system. Frequently certain sections within this perimeter are excavated to form a trench that yields a below ground footing for load bearing walls. Within the concrete is placed reinforcing steel (mesh, bars, rods, and/or cables) . Among the drawbacks of slab foundations are that they require a large amount of concrete as compared to discrete spaced piers, involve many steps to fabricate, as evident from the foregoing description, and require a variety of workman skills including forming, steel bending and cutting to form the reinforcement structure, concrete pouring, leveling and finishing.

The pier or pile foundations generally comprise a number of discrete, spaced concrete footings. The placed pier, which optionally can include a grade beam, is the simplest of these types of foundations. To construct one of these foundations, multiple prefabricated concrete footings or blocks are placed directly on ground or in shallow trenches. Upon these piers, poles are erected to support the floor. With this foundation, however, it is generally necessary to subsequently level the floor with the use of shims. Some local building codes further require that a grade beam, which is a solid perimeter foundation, be added. The grade beam is either formed and poured, like a slab, or is made of several large precast pieces. As evident from the foregoing, grade beams significantly add to the labor, material and material transportation costs of the foundation. Even in the case where grade beams are used, placed pier foundations are generally unsuitable where the foundation must withstand lateral (shear) or uplift (tension) loads. These loads are often experienced during seismic or severe weather conditions such as high winds or hurricanes.

Poured-in-place pier foundations comprise a number of discrete, spaced concrete piers on top of which are connected leveling devices. Each footing is fabricated by creating a hole, building forms for the above ground concrete portion and then filling with concrete. During the finishing process of the top of each concrete pier, a leveling device is attached. After all the piers are completed, the building floor is fabricated on top of the leveling devices. Once the completed floor is leveled, each leveling device must be revisited to permanently fix its position. The process of attaching leveling devices to each pier, adjusting the devices to level the floor placed thereon and then fixing the position of the leveling devices to construct a level poured-in-place pier foundation involves a significant amount of labor and 9S/26444

3 material and, thus, constitutes a drawback of this type of foundation. In addition, while poured-in-place piers are suitable for use in areas with expansive soil, they generally perform poorly under shear and tensile forces. Pile foundations comprise a number of discrete, spaced prefabricated concrete or steel piles which are driven into the ground by successive pounding until a desired compressive resistance is met or a predetermined penetration is achieved. To withstand this pounding, each concrete pile is extensively reinforced with steel rods, for example. The reinforcement also is provided to facilitate handling of the piles. In addition to increasing fabrication costs, the additional weight of the reinforcement increases shipping and handling costs. Leveling the piles also is a problem. Since the piles are pounded into the ground, it is generally impossible to level the top of each pile with the others during installation. In order to level the top surface of each pile, it is generally industry practice to cut the tops of the piles to the appropriate height after insertion is complete. If the pile is expected to withstand shear or tensile forces, then the concrete is broken away from a portion of the top of the pier so as to expose sufficient reinforcing steel to make a structural connection to the building floor. In the alternative, a cap is secured to the pile to form the connection with the building floor. Due to the extremely high labor, equipment and material costs, and the difficulty in establishing a connection between the building floor and the pile steel reinforcement discussed above, pile foundations have been generally limited to high- rise buildings, bridges and highways.

SUMMARY OF THE INVENTION The present invention is directed to a multiple pier foundation and a method of its construction that avoids the problems and disadvantages of the prior art. According to the present invention, multiple holes are formed in the ground. Then a spike, having a support surface, is positioned in each one of the holes such that the support surfaces of the spikes so positioned are substantially at the same elevation. A fluid capable of solidifying into a solid mass, such as concrete, is poured into the holes to anchor the spikes therein and complete the foundation. An important advantage of this method is that the concrete can be added after the spikes have been leveled. This eliminates the need for conventional leveling jacks and other costly methods customarily needed to level a building such as a house after the foundation has been placed. That is, the spike system provides a simple way to form a level support surface for a building. In addition, the spikes reinforce the piers and provide other advantages discussed below.

Since the concrete is poured into the holes on site, the present method eliminates shipping and handling costs associated with using precast concrete elements. In addition, this method allows the builder to adapt to changes in soil conditions or topography. For example, if soil conditions require deeper holes, deeper holes can simply be excavated and more concrete poured. Thus, building in expansive soil is no longer a problem since the pier^' can be constructed to go deep into the ground where significant soil expansion generally does not occur. It also should be understood that by using enough piers and by modifying the tube length and diameter of the spikes, any strength requirement can be met.

Pouring the concrete on site to form the piers in excavated holes also advantageously molds the pier to the configuration of the hole. As a result, the foundation exhibits strength in tension as well as compression. More specifically, pouring the concrete in the hole allows the concrete to flow along the contours of the hole as well as into cracks or crevices in the ground. This forms an interface between the pier and ground that tends to prevent the pier from being lifted out of the hole when placed under tension such as when the building is subjected to high winds. In contrast, precast piers typically have smooth side walls to facilitate being driven into the ground and, thus, are more prone to being lifted from the foundation holes when placed under tension.

The pier constructed according to the present invention also provides significant protection against shear and bending stresses generated by the building when subjected to high winds or seismic disturbances, for example. Since the spike, which is coupled to the building, is embedded in the concrete and the concrete is molded in the ground, the pier foundation provides excellent stress transfer from the building to the ground. The spike also provides the concrete with reinforcement and enhances the tensile strength of the concrete block.

Unlike some pier foundations which do not provide a mechanism for securing the building to the piers, the spike of the present invention includes a bracket for coupling the building to the piers and maintaining the coupling during seismic disturbances or other severe weather conditions such as high winds or tornadoes.

The method of the present invention also advantageously results in a preleveled pier foundation that permits a simple pier-to-floor connection.

According to one embodiment of the invention, the positioning step is accomplished by driving the spikes into the ground. The spike support surface positions are measured and any spike may be driven further into the ground if the support surface is above the selected elevation or retracted if the support surface is below the selected elevation. As evident from the foregoing, the spike positions can be quickly adjusted without the need for heavy machinery which may be required to reset a precast pier, for example.

In another embodiment, the positioning step is accomplished by attaching the spike support surfaces to a rigid member such as a beam before or after placing the spikes in the holes. In either case, the elongated member is leveled (i.e., oriented to be parallel to the horizontal) before the solidifying fluid is poured. After the fluid has solidified, the beam is ready to support floor joists. One advantageous aspect of this method is that the spikes need not be driven into the ground since they are suspended by the beam which can be supported by conventional means. This is particularly advantageous when hard earth formations are encountered and it would be difficult to drive the spikes into the ground. A modification of this embodiment comprises attaching the spike support surfaces to a rigid flooring support member or structure instead of the beam. The flooring support member can be designated as alternative to conventional girder (beam) , joist and flooring sheet type flooring support structures. In this case, the flooring support member, which can include a foam material sandwiched between parallel plates, is similarly leveled before the solidifying fluid is poured.

The above is a brief description of some deficiencies in the prior art and advantages of the present invention. Other features, advantages and embodiments of the invention will be apparent to those skilled in the art from the following description, accompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a longitudinal section of a foundation pier constructed according to the principles of the present invention;

Figs. 2A, B and C are diagrammatic views illustrating a method of constructing the multiple pier foundation of the present invention;

Fig. 3 is a side elevational view of the foundation pier of Fig. 1 with a section of floor support structure attached thereto and wherein the spike has an alternate tube configuration;

Fig. 4 is a transverse section taken along line 4-4 in Fig. 3; Fig. 5 is a side elevation of another bracket assembly for the spike of Fig. 1;

Fig. 6 is a diagrammatic view illustrating another method of constructing a multiple pier foundation according to the present invention; and Fig. 7 is a top plan view of a multiple pier foundation constructed in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in detail, where like numerals indicate like elements, a multiple pier foundation as well as the structure of the individual piers formed thereby is shown in accordance with the present invention. Each pier 1 generally includes an elongated member or spike 2, that is embedded in concrete element 3.

Referring to Fig. 1, spike 2 comprises an elongated tubular member 4 and a bracket assembly 6 which can generally comprise an angle bracket as illustrated in the drawings. Spike 2 preferably is metal, but can comprise other materials such as carbon composites, for example. Tubular member 4, which can have a square or round transverse configuration, can be crimped to form circumferential grooves 8 and provide an enhanced concrete-grabbing surface that strengthens the interconnection between the spike and the concrete. Bracket assembly 6, which provides a support surface for a flooring support structure, as will be discussed below, is secured to one end of tubular member 4 by welding, for example, as designated by reference numeral 10. It should be understood, however, that other mechanisms differing in configuration from bracket assembly 6 can be used to form the desired structural support surface without departing from the scope of the invention. The other end 12 of tubular member 4 is pointed and forms a stake for penetrating into the ground. The method of constructing the multiple pier foundation of the present invention generally involves positioning a plurality of spikes at a desired depth in holes formed in the ground so that their upper support surfaces form a level (i.e., parallel to the horizontal) framework for supporting a structure such as a home or commercial building. After all of the spikes are in the desired positions, concrete is poured therearound to form the completed piers. Alternatively, one spike can be positioned at the desired position and concrete poured therearound, the next spike positioned and surrounded by concrete, and so forth, until the multiple pier foundation is completed. The steps for carrying out the method are discussed in detail below.

Referring to Figs. 2A-C, a first embodiment of the method for constructing a multiple-pier foundation according to the invention is diagrammatically shown. At the outset, a plurality of holes 14 are formed in the ground, generally designated by reference numeral 15, with a drill, auger or other suitable excavating device. The spacing or arrangement of holes 14 will depend on the requirements for the particular building. Thus, the arrangement of holes can vary widely; the arrangements shown in the drawings are provided for purposes of example and are not intended to limit the scope of the invention. Referring to Fig. 2A, a notch 16 is formed in the center of bottom surface 18 of each hole 14 for receiving a spike 2 and ensuring that the spike is centered in the hole. This also ensures that the spike will be centered in the completed pier for alignment with the structural elements of the building to which the spike will be attached as well as for equal distribution of forces in the concrete foundation element. Such a notch can automatically be formed when using an auger having a conventional centrally positioned pilot head or lead, for example. One of the spikes is then positioned in a hole with its pointed end 12 placed in notch 16. Then, the spike is driven into the ground until the upper or support surface of lower flange or base 20 of bracket assembly 6 appears to be at elevation 24. Elevation 24 is selected according to the desired height of the flooring girders, which will be supported by bracket assembly 6.

The position of bracket base 20 is measured by any suitable means such as a conventional laser level. If the upper surface 21 of bracket base 20 is above elevation 24 (Fig. 2B) , spike 2 is driven farther until that upper surface is aligned with elevation 24 (Fig. 2C) . On the other hand, if a spike has been driven too far so that the upper surface of bracket base 20 is below elevation 24, it can simply be retracted and redriven. In some cases, the initial spike path may need to be repacked to adequately support the spike when redriven.

The other spikes are similarly driven into the ground so that the upper surfaces of bases 20 of bracket assemblies 6 form a level support surface, i.e., a support surface that generally lies in a plane essentially parallel to the horizontal, for a flooring support structure which can comprise a conventional arrangement of girders, joists and floor sheeting, for example. After each spike is properly leveled, the holes are filled with concrete, e.g., pea-gravel concrete. A paper skirt or tube can be arranged around each hole so that additional concrete can be poured to extend concrete element 3 above ground level 22 as indicated by reference numeral 25 (Fig. 3) . Raised portion 25 permits water to runoff of the pier to minimize the water's corrosive effects on the spike and provides additional strength in resisting lateral forces, e.g., bending as the additional concrete laterally supports spike 2. The minimum vertical thickness of raised portion 25 will vary depending on the application as would be apparent to one of skill in the art.

Referring to Fig. 3, after the concrete piers solidify or harden, beam or girder 26, which can be steel, is secured to a group of bracket assemblies 6 by fasteners, such as screws 28, to span across the intervals between concrete piers as shown in Fig. 7. Alternatively, beams 26 can be secured to the bracket assemblies by other means such as welding without departing from the scope of the invention. Finally, floor joists 30 are attached to steel girders 26 to form with the steel girders as flooring support structure for floor sheeting material 32 (Fig. 7) .

Referring to Fig. 4, a transverse section of the pier of Fig. 3 is shown illustrating a modified configuration of the tubular portion of the spike shown in Fig. 1. More specifically, tubular member 4' includes four radial lobes 33 that extend longitudinally to increase surface area of tubular member 4' and enhance concrete grabbing capacity of the spike. Preferably lobes 33 extend substantially the entire length of member 4• to maximize the surface area of the spike that interfaces the concrete.

Fig. 5 illustrates alternate bracket assembly 6' and flooring support structure or member 40 which can be used to directly support flooring material such as tile or carpeting. Bracket assembly 6• includes L bracket 42 and C bracket 44 which can be secured to one another by welding, for example. C bracket 44 receives composite flooring support member 40 that comprises foam material 46 sandwiched between essentially parallel and planar metal plates 48. Flooring material such as carpeting or tile can be directly attached to the upper metal plate since metal plates 48 are generally continuous members that can be square or rectangular, for example, to cover the desired area and to interconnect 3 or more piers. Generally, this flooring support structure can replace the conventional steel girder, floor joist and floor sheeting type flooring support structure and is lighter and less expensive relative thereto. It also is particularly suitable for mobile homes where a strong perimeter support foundation system is typically employed. Referring to Fig. 6, another embodiment of the method for constructing the multi-pier foundation will be described. As in the above procedure, holes 14 are formed in the ground for receiving spikes 2' ' . It will be apparent from the following, however, that the spikes need not have a pointed end since they are not driven into the ground. Accordingly, notches 16, described with reference to Figs. 2A- C, are not necessary. In this case, steel girder 26 is arranged above the holes 14 so that the bottom surface of the girder is aligned with elevation 24. In this case, the top surface of the beam is essentially parallel to the beam's bottom surface so as to provide a level surface for the floor joists and sheeting, for example. To this end, girder 26 is supported by vertically adjustable supports such as screw jacks 34. For example, the elevation 24 of a first end 36 of steel girder 26 can be measured and screw jacks 34 adjusted until a second end 38 of steel girder 26 is at the same elevation 24.

Before or after girder 26 has been aligned with the holes and leveled, spike bracket assemblies of the desired configuration, e.g., assemblies 6 illustrated in Figs. 2A-C, are secured thereto via fasteners 28, for example. Thus, spikes 2' ' can be disposed in holes 14 before or after steel girder 26 has been aligned and leveled (the sequence is not critical) . However, only after girder 26 is aligned with the holes and elevation 24 and spikes 2'' secured thereto, is concrete poured into holes 14 and allowed to cure. After the concrete is completely dry, screw jacks 34 are removed from steel girder 26 and the rest of the building can be constructed over the foundation. Alternatively, the spikes can be attached to a segment of generally planar flooring support structure 40 and the structure 40 leveled.

This embodiment of the method is particularly suitable in places where the soil is rocky or hard because it alleviates the problem of driving spikes into hard earth formations. It also has the advantages of making the concrete piers on site and pouring the concrete after the system is leveled as discussed above. In addition, the process of aligning the foundation is extremely easy. Screw jacks 34 are simply adjusted until the ends of each steel girder 26 are at the same elevation. Once the concrete dries, spikes 2'' will maintain steel girders 26 in the leveled position.

Fig. 7 shows a top view of a typical pier foundation constructed according to the present invention. A plurality of circular concrete piers 1 are disposed at spaced intervals according to soils engineering requirements. Accordingly, the invention is not limited to the configuration shown which is merely provided for purposes of example. Longitudinal steel girders 26 extend between concrete piers 1 and are supported by spike bracket assemblies 6. Joists 30 traverse and are supported thereby girders 26. Flooring sheet material 32 is placed on joists 30. Alternatively, flooring support structure 40 can be substituted for the girder, joist and flooring sheet construction as described above.

The above is a detailed description of a particular embodiment of the invention. It is recognized that departures from the disclosed embodiment may be made within the scope of the invention and that obvious modifications will occur to a person skilled in the art. The full scope of the invention is set out in the claims that follow and their equivalents. Accordingly, the claims and specification should not be construed to unduly narrow the full scope of protection to which the invention is entitled.

Claims

WHAT IS CLAIMED IS:

1. A method of constructing a foundation comprising the steps of: forming multiple holes in the ground; providing multiple spikes, each having a support surface; positioning each spike in one of the holes such that the support surfaces of the spikes so positioned are substantially at the same elevation; pouring a fluid capable of solidifying into a solid mass into the holes.

2. The method of claim 1 wherein the pouring step comprises pouring concrete into the holes.

3. The method of claim 1 wherein the positioning step includes driving the spikes into the ground to a depth such that their support surfaces form a level framework for supporting a building.

4. The method of claim 1 wherein the positioning step includes attaching the support surfaces of the spikes to a single beam and leveling the beam so as to be parallel with the horizontal.

5. The method of claim 1 wherein the positioning step includes attaching the support surfaces of the spikes to a flooring support member.

6. The method of claim l wherein the spikes are positioned at said elevation before the pouring step.

7. A method of constructing a multiple pier foundation comprising the steps of: forming multiple holes in the ground; providing multiple spikes, each having a substantially flat support surface; arranging each spike in one of the holes such that the support surfaces of the spikes so arranged are oriented in substantially the same plane; and pouring concrete into the holes to fix the position of the spikes.

8. A method of constructing a multiple pier foundation comprising the steps of: forming multiple holes in the ground; providing multiple spikes, each having a support surface; arranging each spike in one of the holes with the support surfaces of the spikes attached to a single member; and pouring concrete into the holes.

9. The method of claim 8 wherein the attaching step comprises attaching the spike support surfaces to a single beam.

10. The method of claim 8 wherein the attaching step comprises attaching the spike support surfaces to a single generally planar plate.

11. A foundation pier comprising: a concrete element having first and second opposed end faces; a spike embedded in said concrete element and extending from one of said end faces; and a bracket coupled to said spike.

12. The pier of claim 11 wherein the spike extends from both of said end faces.

13. The pier of claim 12 wherein said spike includes opposed first and second ends, said bracket being coupled to said first end and said second end being pointed.

_* 14. The pier of claim 11 wherein said pier includes a rough outer surface.