Hydraulic and earth engineering – Foundation – Columnar structure
Reexamination Certificate
2000-08-08
2003-01-07
Will, Thomas B. (Department: 3673)
Hydraulic and earth engineering
Foundation
Columnar structure
C405S233000, C405S243000, C405S257000, C249S155000
Reexamination Certificate
active
06503025
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a precast concrete structural element and to methods of making and installing same. More particularly, this invention relates to a precast concrete beam element for providing continuous footing support in building and structure foundations and to methods of making the precast element and installing it in building and structure foundations.
Several methods for providing continuous beam footing for wall and floor slab support in building and structural foundations are known in the art. Three of the most popular methods are described below.
One popular method involves excavating a trench, placing edge forms and reinforcement in the trench, and either partially casting the beam and then casting the floor slab or simultaneously casting the beam and floor slab. This method has several disadvantages. For example, the method requires an excavation that is open to weather conditions while reinforcement is being placed in the trench. This often necessitates removal of the reinforcement after inclement weather has passed in order to remove mud and water from the excavation and restore bearing capacity prior to casting. In addition, this method requires field forming of the floor slab edge and the wall ledge. Thus, the accuracy of the slab edge forming, the wall ledge forming and the beam shape are each dependent on the skill of the craftsmen executing the work in the field. Furthermore, the method uses more concrete that would be required simply for structural purposes in order to save the cost of forming a thinner wall thickness that is required structurally. This increase in sectional area of the concrete necessitates an increase in the amount of steel reinforcement required under some building codes. Also, the increase in the bearing width requires additional unnecessary concrete in the upper section of the beam.
A second popular method for providing continuous beam footing to support wall and floor slab edges involves excavating a trench, casting the continuous bearing beam in the trench, forming an upper stem wall section including a support notch for a floor slab, casting the stem wall section, removing the forms, backfilling void areas adjacent to the stem wall, and then casting the floor slab.
This second method offers some advantages over the first method discussed above in that, in the second method, the upper stem wall can be formed to the minimum thickness required for structural needs, thereby saving substantial concrete material if the bearing depth is significant. The second method also allows for a greater difference between finish floor height and the ultimate exterior grade. However, the second method also has several disadvantages. For example, it requires an excavation open to weather conditions as in the first method but in the second method the excavation is open for an even longer period while the stem wall section is formed. The second method requires labor-intensive forming of the stem wall section, often in below grade conditions which may require continuous dewatering to achieve a structurally sound installation. The second method further requires subsequent backfilling and compaction of the void areas adjacent to the stem wall. Moreover, the second method requires either a notch to support the floor slab or steel rods through the inner face form to provide shear dowels into the floor slab. In addition, the accuracy of the slab edge forming, the slab bearing notch, and the stem wall section are each dependent on the skill of the craftsmen executing the work in the field.
A third popular method for providing continuous beam footing to support wall and floor slab edges is similar to the second method discussed above, except that in the third method, the exterior walls (usually masonry) are extended to the top of the bearing beam, followed by floor casting. In an advantage over the second method, the third method eliminates the stem wall forming step. However, the third method requires an extended period of open excavation and, typically, the time required for the installation of the below-grade portion of the exterior wall is even longer than that required to form the stem wall in the second method. Furthermore, installation of the below-grade portion of the exterior wall is labor intensive. In a further disadvantage, the third method requires backfilling and compaction of the void areas adjacent to the below-grade portion of the exterior wall. In addition, accuracy is still dependent upon the skill of the craftsmen executing the work in the field.
A primary object of this invention is to provide an improved concrete beam element which integrates the edge of slab form and the wall ledge to completely eliminate the need for field forming.
Another object of this invention is to provide an improved concrete beam element which is capable of being cast with dowel rods projecting above the wet concrete instead of through the mold.
A further object of this invention is to provide an improved method of making a concrete beam element which does not require field forming.
A still further object of this invention is to provide an improved method of making a concrete beam element wherein the method uses a mold that allows for varying beam heights to accommodate varying beam depths.
Another object of this invention is to provide an improved method of making a concrete beam element wherein the method uses a mold the depth of which can be easily increased to offer additional bearing capacity or stem wall thickness as soil and loading conditions require.
Yet another object of this invention is to provide an improved method of installing a concrete beam element wherein the exposure period of the excavation site to the weather is significantly less than that required in the prior art methods discussed hereinabove.
These objects and others are achieved in the present invention.
DETAILED DESCRIPTION
One embodiment of the present invention provides a precast concrete beam element for use as a continuous bearing structural foundation member supporting wall and floor slab loads in soil. Another embodiment of the present invention provides a method of making the aforementioned precast structural beam element. In addition, a further embodiment of the present invention provides a method for installing the precast concrete beam element into a building or structural foundation.
The precast structural beam element may include a straight back face, a top surface, a bottom surface, a front face, and first and second opposite side faces disposed between the back and front faces and between the top and bottom surfaces. The front face may include: a first upper surface extending perpendicularly and downwardly from the top surface and being parallel to the back face; a second upper surface which slopes downwardly and inwardly from the first upper surface; a middle surface which is parallel to the back face and which extends downwardly from the second upper surface; a first lower surface which slopes downwardly and outwardly from the middle surface; and a second lower surface which is parallel to the back face and which extends downwardly from the first lower surface and perpendicularly to the bottom surface. The beam element may include a notch formed therein which extends lengthwise along the top surface, and/or the middle surface of the front face has a dapped surface formed therein.
The method of making the beam element may include providing a mold containing: (a) a longitudinally movable lateral side rail having an inner wall for forming the top surface of the beam element; (b) an opposite fixed lateral side rail having an inner wall for forming the bottom surface of the beam element; (c) a first longitudinal side rail disposed between the movable and fixed lateral side rails and having an inner wall for forming the first side face of the beam element; (d) an opposite second longitudinal side rail disposed between the movable and fixed lateral side rails and having an inner wall for forming the second side face of the beam element; (e) an
Mayo Tara L.
Patton & Boggs LLP
Will Thomas B.
LandOfFree
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