A. Field of the Invention
The Invention is a post support for a fence or handrail post. The invention is also a retaining wall including the post support and is also a method of building a retaining wall using the post support.
B. Statement of the Related Art
As used in this document, a ‘retaining wall’ is a barrier used to achieve an abrupt change of grade of land between a higher elevation and a lower elevation. The retaining wall supports earth at a higher elevation on one side of the retaining wall and prevents the movement of the earth to the side having a lower elevation. As used in this document, the term ‘earth’ means soil of any type, including loam, sand, clay and fill material. The term ‘fill material’ includes crushed stone of any size, gravel, quarry dust, sand, rock, or masonry and includes any material imported to a location that changes the grade of the location. A properly designed and constructed retaining wall is an engineered structure that will resist the pressure of earth and fill on the higher elevation side of the retaining wall, even when the earth and fill is saturated with water.
The strength of a retaining wall may be selected for a particular application; for example, the retaining wall may be a very strong poured concrete wall used as a basement wall. Conversely, the retaining wall may be laterally weak, as in a stack wall using in landscaping. ‘Stack wall’ means a type of retaining wall composed of stones or concrete blocks that are stacked one on top of another and that are held in place by the force of gravity and without mortar. Only the weight of the stones or blocks and the mechanical interference between adjacent stones or blocks keep the stack wall in place and holds back the earth and fill material.
The abrupt elevation change across the retaining wall may present a hazard to persons, pets or other animals; namely, a person, pet or other animal may fall from the higher elevation side of the retaining wall. To avoid the potential hazard, a fence or handrail supported by posts may be installed on the higher elevation side of the retaining wall.
Where the lateral strength of the retaining wall is adequate, the posts supporting the fence or handrail may be attached directly to the retaining wall and any lateral load applied to the fence or handrail is supported by the strong retaining wall. A ‘lateral load’ is a force, for example a force applied by a person or animal, against the fence or handrail and from the direction of the higher elevation side of the retaining wall toward the lower elevation side of the retaining wall and generally normal to a plane defined by the surface of the retaining wall. Attaching the posts to the retaining wall has the advantage of providing the maximum usable ground area above the retaining wall. Where the retaining wall is not laterally strong, such as a stack wall, attaching the posts directly to the top of the retaining wall may cause the retaining wall to collapse when a lateral load is applied to the fence or handrail.
As an alternative to attaching the fence or handrail posts to the retaining wall, the bottom end of the posts may be buried in the earth or fill on the higher elevation side of the retaining wall. Where the retaining wall is laterally strong, the posts may be buried near the retaining wall, preserving the use of the ground on the higher-elevation side of the retaining wall.
Where the retaining wall is a stack wall or is otherwise not laterally strong, burying the posts close to the retaining wall may allow a lateral load applied to the fence or handrail to be transferred to the retaining wall, which may cause the retaining wall to collapse. To avoid collapse of the laterally weak retaining wall, the posts must be buried well back from the retaining wall so that a lateral load applied to the fence or handrail is supported by the surrounding earth or fill and is not transferred to the retaining wall. Setting the posts back from the retaining wall results in loss of use of ground on the higher elevation side of the retaining wall, which is not desirable.
The prior art does not teach a post support that allows the fence or handrail to be constructed immediately adjacent to a laterally weak retaining wall, such as a stack wall, and thus preserving the use of the ground above the laterally weak retaining wall.
The post support of the invention allows a post for a fence or handrail to be installed immediately adjacent to the higher-elevation side of a to a laterally weak retaining wall, such as a stack wall. A lateral load applied to the fence or handrail will not apply a lateral load to the retaining wall and will not cause the wall, fence or handrail to fail.
A platform portion and a post portion define the post support. The platform portion is configured to be buried under earth or fill on the higher-elevation side of the retaining wall so that the platform portion is generally normal to the retaining wall. The post portion extends in an upward direction from the platform portion so that when the platform portion is buried, the post portion extends to grade level or slightly above grade level. The post portion terminates in a bottom flange. When the post support is installed, the bottom flange is attached to a mating top flange that is attached to a fence or handrail post. The fence or handrail post supports the fence or handrail.
When a lateral load is applied to the fence or handrail attached to the buried post support, the fence or handrail post and the post portion act as a moment arm that tends to rotate the platform portion about a fulcrum in response to the lateral load. The fulcrum generally will be defined by the edge of the platform portion closest to the retaining wall. The weight of the earth and fill above the buried platform portion resists that rotation of the platform about the fulcrum and acts generally upon a second moment arm extending from the center of the platform portion to the fulcrum. If the weight of the earth and fill above the platform is adequate, the platform will not move and the fence or handrail will resist the lateral load without movement.
The earth and fill immediately above the platform portion is not the only earth and fill resisting the lateral load applied to the fence or handrail. Force applied by the platform portion to the earth and fill directly over the platform portion will cause the earth and fill to apply a force to the earth and fill located between the platform portion and the retaining wall. The weight and friction of the fill and earth between the platform portion and the retaining wall contributes to the resistance of the platform to a lateral load applied to the fence or handrail. In addition, friction between adjacent grains of the earth or fill will resist motion of the platform portion, as will turf roots or roots of other plants growing in the earth or fill over the platform portion.
The platform portion may have a configuration to prevent earth or fill from moving through the platform portion. For example, the platform portion may have a solid surface or a grid surface where the openings in the grid are too small to allow the passage of earth or fill.
Alternatively, the platform portion may define openings large enough to allow soil and fill to pass through the openings. In the event the platform portion defines openings large enough to allow soil or fill to pass through, a geotextile fabric may be disposed above and below the platform portion when the platform portion is installed. The geotextile fabric is selected to have openings that are adequately small to prevent motion of the earth or fill through the platform portion.
The post portion terminates at its upper end in a bottom flange. The bottom flange is configured for connection to a mating top flange that is attached to the fence or handrail post. The bottom flange is in a spaced-apart relation, both vertically and horizontally, from the platform portion. The vertical separation between the bottom flange and the platform portion allows the platform portion to be buried adequately deeply so that the weight of the fill and earth on the top of the platform portion will adequately resist deflection of the post portion when the post portion is attached to a fence or handrail post.
The vertical separation distance may be selected to allow the platform portion to be buried below the frost line. The frost line is the location in the ground below which water does not freeze during cold weather. The depth of the frost line varies by location, depending on the local climatic conditions. A buried object that is above the frost line is subject to ‘frost heave,’ which is displacement of the object by the expansion of water as the water freezes. A platform portion that is buried below the frost line is not subject to frost heave and will not be disturbed by freezing and thawing conditions. The vertical separation distance may be selected based on the depth of the frost line for the particular location in which the fence or handrail post will be installed.
The horizontal separation distance between the platform portion and the bottom flange is selected so that when installed the platform portion is set back by a sufficient distance from the retaining wall that the earth and fill located between the platform portion and the retaining wall adequately resists lateral movement in response to a lateral force applied by the earth and fill located above the platform portion and so that the earth and fill located between the platform portion and the retaining wall will not transmit force to the retaining wall.
The lower part of the post portion may define a curve or other shape to reduce the length of the post portion that is immediately adjacent to the retaining wall. By using a curve or other shape, in the event of overloading the post portion in the lateral direction so that the post portion presses against the retaining wall, only the topmost portion of the retaining wall engages the post portion and only the topmost portion of the retaining wall is damaged. Providing that the lower part of the post portion defines a curve or other shape to reduce the length of the post portion adjacent to the retaining wall eases the task of repair of the retaining wall in the event of failure of the post support due to overloading.
As a second embodiment, the post portion may extend vertically from the platform portion so that the bottom flange is not displaced laterally from the platform portion. In this second embodiment, only the weight of the fill and earth immediately above the platform portion resists a lateral load applied to the fence or handrail post. For this embodiment, the platform portion may be larger than in the first embodiment so that a greater weight of fill and earth is above the platform portion. Alternatively, the platform portion may be buried deeper in the fill and earth, also so that a greater weight of fill and earth is above the platform portion.
As noted above, the platform portion tends to rotate about a fulcrum when a lateral load is applied to the fence or handrail. As a third embodiment, the fulcrum may be defined by a separate fulcrum member that is in a spaced-apart relation to the platform portion and that is disposed between the platform portion and the retaining wall when the post support is installed. The separate fulcrum member provides a longer moment arm between the fulcrum and the platform portion, allowing a smaller platform portion to resist the same lateral load or allowing the same platform portion to resist the same lateral load while buried under less earth and fill than the first or second embodiments.
Because the platform portion is buried by fill and earth and generally will be installed on a base of crushed stone, the bottom flange may not be level when installed. A mechanism is provided to allow the fence or handrail posts to be plumb, even when the bottom flange is not level. Any suitable mechanism may be used. One possible leveling mechanism comprises a top flange that is attached to the fence or handrail post and that is configured for engagement with the bottom flange. Jackscrews may engage both the top and bottom flange. The jackscrews may define a first end having a right-hand thread and a second end having a left-hand thread. Each jackscrew between the first and second ends defines a tool connection, such as a hex-shape to receive an open-ended wrench. Each of the top and bottom flanges is threaded to receive one end of each jackscrew. Turning a jackscrew in one direction while the jackscrew is in threaded engagement with the top and bottom flanges will increase the distance between the flanges. Turning the jackscrew in the other direction will decrease the distance between the flanges. Four jackscrews have proven suitable in practice, but three or more jackscrews also are suitable. Locking screws may fix the two flanges in position once the jackscrews are adjusted.
For applications where adjusting the height of the fence or handrail post is not critical, the adjustment mechanism may comprise two jackscrews combined with a single pivot of a pre-selected height. Other alternatives include shims between the top and bottom flanges and a ball-and-socket joint between the top and bottom flanges. Any mechanism known in the art for adjusting and angle or height between two objects is contemplated by the invention.
The post support 2 of the invention allows a fence or handrail 4 to be installed immediately adjacent to a stack wall 6 while preventing a lateral load 8 applied to the fence or handrail 4 from damaging the stack wall 6 or resulting in failure of the fence or handrail 4.
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For any of the embodiments, the lateral load 8 that may be accommodated by the post support 2 without rotating the platform portion 10 and without damage to the stack wall 6 may be selected by selecting the volume 50 of earth or fill 24 above the platform portion 10, and hence selecting the weight resisting motion of the platform portion 10. Selecting either the depth of earth or fill 24 over the platform portion 10 or selecting the platform area 18 will select the weight of the earth or fill 24 above the platform portion 10.
The platform portion 10 also has a configuration to prevent earth or fill 24 from moving through the platform portion 10 from the top side 20 to the bottom side 22 when the platform portion 10 is buried under earth or fill 24. The configuration may be that the platform portion 10 presents a solid barrier such as a continuous sheet of metal that prevents passage of the earth or fill 24 through the platform portion 10. As a first alternative to a solid barrier, the platform portion may define openings 56 communicating between the top and bottom sides, but that are too small to allow the passage of earth or fill 24. As a second alternative, and as shown by
In the alternative embodiment of
Any other apparatus to adjustably support one object with respect to another is contemplated by the Invention for the adjustable attachment of the top and bottom flanges 28, 26.
The platform portion 10 and the post portion 12 may be composed of any suitable material. Stainless steel has proven suitable in practice. Stainless steel is durable when in contact with earth or fill 24 and does not depend on coatings for that durability. Stainless steel also may be readily formed and welded. Any other suitable material may be used. For example, molded, cast or pultruded polymer resin, whether or not the resin is fiber-reinforced, may form the platform portion 10, post portion 12, bottom and top flanges 28, 29, the fence or handrail post 36 or the fence or handrail 4.
The following is a list of numbered elements identified in the drawings and specification.
Number | Name | Date | Kind |
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5431372 | Kostelecky | Jul 1995 | A |
7823348 | Leiva | Nov 2010 | B1 |
20040020713 | Fregosi | Feb 2004 | A1 |
20060213722 | Cunningham | Sep 2006 | A1 |
20090159864 | Perris | Jun 2009 | A1 |
20100171085 | Webster, IV | Jul 2010 | A1 |
20140105686 | Southworth | Apr 2014 | A1 |
Number | Date | Country |
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2127927 | Dec 1997 | CA |