Adjustable pier/footing cap for creating an adjustable building foundation
I have invented an apparatus for creating an adjustable foundation, for residential and light commercial structures, that are supported on concrete drilled piers or concrete pad footing supports. The apparatus is an adjustable pier/footing cap, added to conventional drilled piers/footings at the time of foundation construction; said drilled piers are commonly used to support a building foundation in expansive soil areas and/or in other areas where upper bearing soils are weak or incompetent. The adjustable pier/footing caps are partially imbedded in the concrete drilled piers/footings when the piers/footings are poured and then into the foundation walls of the building when said foundation walls are poured. Upon settling or upheaval of the foundation, the adjustable pier/footing caps can be adjusted to lower or raise the building without replacing the drilled pier/footing with an expensive remedial piering device, and without substantial excavation around the foundation.
Provisional patent application titled “Adjustable Pier/Footing Cap for Creating an Adjustable Building Foundation” filed on Jun. 9, 2006 listing Michael D. Coyle as the inventor.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot Applicable
REFERENCE TO SEQUENCE LISTING, TABLES, ETC.Not Applicable
FIELD OF THE INVENTIONThe invention is directed toward residential and commercial building foundation systems, including the design, engineering, construction, and repairs thereto.
BACKGROUND OF THE INVENTIONThe invention creates an adjustable foundation system utilizing conventionally installed drilled piers/footings, modified with the addition of adjustable pier/footing caps, and more particularly to such a system which is an improvement over conventional, non-adjustable foundation supports for residential buildings, light commercial buildings, and the like.
Foundations constructed in expansive soil areas, or areas with incompetent bearing soils, are generally founded on concrete drilled piers, or pad footings, in lieu of continuous concrete spread footings. Piers are drilled through the upper soils and into underlying bedrock, or rely on frictional interaction along the pier length for support in the deeper soils. The foundation walls typically bear only on the drilled piers/footings, spanning the distance between piers/footings above a void space, such that the foundation walls act as beams. This serves to greatly concentrate the load on the piers/footings such that any uplift pressure from expansive soil is counteracted. The void space may be eliminated in areas where expansive soils are not present. Drilled piers/footings historically contain reinforcing steel that extends upward and into the foundation wall above, thus creating a fixed and non-adjustable connection between the piers and the walls.
The geometry, size, diameter, overall minimum length of the pier, and minimum penetration distance into bedrock are typically specified by a Geotechnical Engineer based on analysis of the on-site soil conditions, as determined by sampling and testing methodologies of the profession. As such, the load bearing capacity of the drilled pier/footing is theoretically calculated and predicted, but is typically not field verified via load testing prior to construction of the foundation walls or upper structure. In theory, the piers/footings should not settle or heave, or only minimally so, but in practice it is not uncommon for minor to moderate movement to occur, and occasionally major movement occurs, due to unknown conditions and/or inadequacies of the sampling and testing methodologies.
Historically, as drilled piers/footings could not be adjusted to accommodate any such movement, structural damage has occurred to foundations and upper structures, resulting in millions of dollars in annual repair costs. Ultimately, drilled piers/footings that have experienced movement are replaced with steel piers, helical piers, or offset drilled piers, and foundation adjustments are then made to re-level the structure. These remedial actions, called underpinning, are generally effective, but also very expensive, time consuming, logistically difficult, and excessively interruptive of the normal enjoyment of the property by the owner.
With respect to foundation underpinning as a remedy to foundation movement, there are numerous devices currently utilized to underpin and re-level foundations including piering devices such as the piling system of Gregory, U.S. Pat. No. 4,754,588.
Nally, U.S. Pat. No. 5,123,209 shows a method of re-leveling a foundation after movement has occurred.
Gregory, U.S. Pat. No. 4,695,203 shows a method of shoring buildings relating to the problems set forth earlier.
In Langenbach, Jr., U.S. Pat. No. 3,902,326 shows the use of a piling member which is driven into bedrock sufficient to shore a foundation. The system utilizes a hydraulic pump and attachment to the foundation in order to shore up the foundation as shown similarly in Ortez, Freeman, III, Rippe, and McCown, U.S. Pat. Nos., 5,492,437, 5,433,556, 5,234,287, and 5,154,539, respectively.
As demonstrated above, there are many methods currently used to shore up, re-support and adjust a foundation after movement has occurred, but when drilled piers/footings are present as the original support system, these remedial systems always require partial demolition, disconnection, and abandonment of the original drilled piers/footings in favor of the newly installed remedial piers.
None of the other methodologies provides a mechanism to utilize the original drilled pier/footing via incorporating an adjustable interface into the drilled pier/footing and foundation connection at the time of initial construction.
Therefore, utilization of the invention provides a superior foundation support system as compared to current drilled piers/footings, and provides a superior, simpler, and more cost effective method and mechanism for adjusting a foundation should movement occur, as compared to remedial underpinning systems.
The invention provides an adjustable foundation interface between drilled piers/footings and foundation walls in expansive soil areas, or any other areas where drilled piers/pad footings are installed as the primary foundation support.
The invention also provides a system that will allow re-leveling adjustments to be made to the foundation, with minimal disruption to the living environment, surrounding soils, and other infrastructure components.
In addition, the invention eliminates the need for installing remedial underpinning and demolition, disconnection, and abandonment of the original drilled piers/footings.
Incorporating the invention results in a dramatic reduction in the costs required to repair and/or adjust a foundation via any of the other foundation shoring and underpinning systems, as a new pier is not required and only minimal excavation is required.
The above description of the invention will be more fully appreciated by reference to the following detailed description of the preferred embodiment when taken in conjunction with the accompanying drawings wherein:
The bottom section of the adjustable pier/footing cap consists of a steel base plate 2, with a hole 3 centered in the plate of diameter sufficient to allow insertion of the threaded rod 10. Steel nut 6 and steel nut 8 are welded to the base plate 2, one on the top and one on the underside, centered on the hole 3 to accept the threaded rod 10 which is threaded through nut 6, hole 3 and nut 8 to the desired position. The rod 10 is then welded to the nuts to create a fixed connection between the rod 10 and the plate 2. Four rebar 4 are welded to the underside of the base plate 2, which imbed into the concrete of the drilled pier/footing and tie to the internal steel rebars of the drilled pier/footing, thus securing the bottom section of the adjustable pier/footing cap to the drilled pier/footing.
The bottom section of the adjustable pier/footing cap is inserted into the drilled pier/footing immediately after the concrete for the pier/footing has been placed. The plate 2 is centered on the pier/footing and is flush with the top of the pier/footing.
The middle section of the adjustable pier/footing cap consists of a steel plate 12 similar to the base plate 2, with centered hole 13 to accommodate the threaded rod 10. A single steel nut 14 is centered on the hole 13 and is welded to the plate 12. When threaded onto the rod 10, the plate 12 and nut 14 are free to spin up or down on the rod 10 as needed. The plate 12 has four additional holes 15 near the plate 12 corners to accept four bolts 16 that create a secure but removable connection between the middle section and the top section.
The top section of the adjustable pier/footing cap consists of a steel plate 18 similar to plates 2 and 12, with similar hole 19 to allow passage of the threaded rod 10. A steel tube 22 with welded cap plate 23 is welded to the plate 18, creating a cavity within which the rod 10 can slide up or down as needed. Steel rebar 24 are welded to the steel tube 22 that are imbedded in the foundation wall, creating a secure connection between the top section and the foundation wall. The plate 18 has four holes 20 drilled in alignment with the four holes 15 of the middle section plate 12. Four cap nuts 21 are centered on the holes and welded to the top plate 18. When inserted over the threaded rod 10, the top section plate 18 aligns with the middle section plate 12 and the four bolts 16 are inserted through the holes 15 and 20 to create a connection between the middle section and the top section.
At the time of forming the foundation walls and prior to placement of concrete, the middle and top sections are installed and rotated to the desired elevation such that the top section plate 18 will be flush with the underside of the foundation wall.
In the event of foundation settlement or upheaval, the affected adjustable pier/footing caps are exposed and temporary support jacks are installed under the walls and adjacent to the pier caps. The bolts 16 are then removed and the middle section plate 12 and nut 14 combination unit is rotated up or down as needed to the point where the foundation can be raised or lowered to the desired elevation. Upon successful adjustment the bolts 16 are reinstalled and the jacks removed.
It is understood that the foregoing description and alternative embodiments are merely illustrative of the best mode of the invention and the principle thereof, and various modifications and additions may be made to the apparatus and method by those skilled in the art, without departing from the spirit and scope of this invention, which is therefore understood to be limited only by the scope of the appended claims. Sizes and numbers, and strength characteristics of members, including length, width, thickness, diameter, welding, plates, nuts, rods, bolts, etc. are subject to engineering judgment and specifications to accommodate project specific loading requirements.
Description of Alternative EmbodimentThe previously described preferred embodiment describes the invention as it can be used to support foundation walls. However, the invention may also be used to support beams and/or columns/posts that ultimately transfer load to drilled piers or footings. For such alternative applications, the adjustable pier/footing cap may be inverted such that the “upper” section is imbedded into the pier or footing. The “bottom” section then becomes the attachment to the beam or column/post as the case may be, and the rebar 4 and nut 6 are omitted from the base plate 2. In this case the threaded rod 10 does not penetrate the base plate 2 and the plate 2 acts as a platform to support the beam or column/post.
In the event of beam settlement or upheaval, temporary support jacks are installed under the beam and adjacent to the pier caps. The bolts 16 are then removed and the middle section plate 12 and nut 14 combination unit is rotated up or down as needed to the point where the beam can be raised or lowered to the desired elevation. Upon successful adjustment the bolts 16 are reinstalled and the jacks removed.
Claims
1. An adjustable pier/footing cap system that adds adjustability to a conventional drilled pier/footing building foundation, comprising a plurality of steel members connected together that create an adjustable load transfer interface between the drilled pier/footing and the foundation wall;
2. The adjustable pier/footing cap system of claim 1 wherein said plurality of steel members includes a threaded rod inserted through a steel base-plate and welded thereto, said base-plate having several reinforcing steel bars attached and extending below that create a tie connection to the reinforcing steel bars typically contained in the drilled pier/footing; the base-plate being located at the top of the drilled pier, thus providing a fixed structural support;
3. The adjustable pier/footing cap system of claim 1 wherein said threaded rod extending upward from the drilled pier and base-plate, through the typical void space provided as part of conventional drilled pier/footing foundation construction, and penetrating a second, upper steel base-plate with hole centered in the plate of sufficient size to allow the threaded rod to slide through unencumbered; said upper base-plate having a steel tube welded to the upper side that creates a cavity within which the threaded rod can slide freely; said tube having several steel reinforcing bars welded thereto that extend upward into the foundation wall; said upper base-plate being located at the bottom of the foundation wall, which is also the top of the foundation void previously described;
4. The adjustable pier/footing cap system of claim 1 wherein said threaded rod containing a third plate with threaded nut welded thereto, such that the nut and plate combination spins along the exposed threads of the threaded rod within the void zone, and when raised to the position of meeting the upper base plate creates the load transfer connection between the foundation wall and the threaded rod, and consequently to the drilled pier/footing below; said adjustment plate containing holes that align with holes in the upper plate that allow for a bolted connection between the two, thus providing for continuity of load transfer in the event of uplift forces.
5. The adjustable pier/footing cap system of claim 1 wherein said adjustment plate is unbolted from the upper plate in the event of foundation movement, and the adjustment plate is rotated to raise or lower the foundation, with the assistance of temporary jacks if needed, to the desired elevation at which point the bolts are re-installed and the jacks (if used) are removed.
Type: Application
Filed: Jun 8, 2007
Publication Date: Dec 11, 2008
Inventor: Michael D. Coyle (Denver, CO)
Application Number: 11/811,336
International Classification: E02D 5/00 (20060101);
