Static structures (e.g. – buildings) – Openwork; e.g. – truss – trellis – grille – screen – frame – or... – Three-dimensional space-defining
Reexamination Certificate
2000-02-09
2001-04-10
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Openwork; e.g., truss, trellis, grille, screen, frame, or...
Three-dimensional space-defining
C156S257000, C052S749100, C052S690000
Reexamination Certificate
active
06212846
ABSTRACT:
BACKGROUND—FIELD OF INVENTION
This invention relates to an isosceles joist suitable for use in construction of frame buildings as roof joists, floor joists or rafters, and particularly to wooden isosceles joists having dimensional grade lumber or engineered laminated wood flanges and webs.
BACKGROUND—DESCRIPTION OF PRIOR ART
Where strength is required in both the vertical and horizontal directions, considerable savings of weight and material cost may be accomplished by using joists arranged in the form of a triangle. This general design provides required strength to support compressive and tension loads generated by application of vertical loads to the top of the joist structure displaying the characteristics of a series of interconnected triangular truss units providing diaphragm strength for horizontal wind or seismic loads.
Various metal triangular joist arrangements are shown in prior art such as the following U.S. Patents:
Brown
U.S. Pat. No. 3893276
Beam and build-
July 8, 1975
ing
Theault
U.S. Pat. No. 3978635
Self-supporting
Sept. 7, 1976
element
Salas
U.S. Pat. No. 4178736
Housing module
Dec. 18, 1979
and
Rooney
U.S. Pat. No. 4282619
Truss structure
Aug. 11, 1981
Seaburg
U.S. Pat. No. 4435932
Alternating V-
Mar. 13, 1984
Truss
Lautensleger
U.S. Pat. No. 4349996
Integrated roof
Sept. 21, 1982
system
Metal triangular joists have a completely different design and use metal components. With this in mind, within their strength range, wooden isosceles joists are often superior. Wooden isosceles joists cost less and are more easily cut to fit. Since wooden isosceles joists don't require special fasteners, they are better adapted to wood frame construction such as homes and small commercial buildings.
There are also various wooden joists, beams, and trusses made of dimensional lumber or laminated materials shown and constructed extensively in the prior art, having a cross section resembling the capital letter “I”, and called an I-beam.
Keller
U.S. Pat. No. 3991535
Pressed-in dovetail
Nov. 16, 1976
Peters
U.S. Pat. No. 4336678
I-Beam truss
June 29, 1982
structure
Lambuth
U.S. Pat. No. 4413459
Laminated wooden
Nov. 8, 1983
Eberle
U.S. Pat. No. 4456497
Wooden I-Beam
June 26, 1984
Brightwell
U.S. Pat. No. 4715162
Wooden Joist with
Dec. 29, 1987
web
Onysko
U.S. Pat. No. 4974389
Wooden Structural
Dec. 4, 1990
Scarlett
U.S. Pat. No. 5323584
Structural beam and
June 28, 1994
These are typically characterized by a multitude of wooden joists, beams, and trusses running parallel to one another or angled relative to one another to form a roof incline, with the webs spanning the upper and lower flanges in a vertical plane. A wooden joist, beam, or truss of this design can only carry a load imposed in the vertical direction, it cannot resist horizontal loads, such as wind or seismic. This type of structure requires cross-bracing to be stable.
Couture, U.S. Pat. No. 4,888,934, Beam structure, issued Dec. 26, 1989, shows a wood beam of V-shape cross section with a cable along the bottom designed as a retrofit to replace wood joists in floors or roof rafters, but does not use a rectangular top and bottom flange and web design.
Zetlin, U.S. Pat. No. 3,906,571, Structural member of sheet material, issued Sep. 23, 1975 shows a structural member formed entirely of sheet material with a V-shape cross section. This invention uses the stress skin design, and does not use a rectangular top and bottom flange and web design.
OBJECTS AND ADVANTAGES
One object and advantage of the present invention is to provide a structure comprised of two or more interconnected isosceles joists which are able to support loads while spanning relatively large distances.
A still further object and advantage of the present invention is to provide a structural member of the above type which has a triangular configuration suitable for imparting rigidity and strength to the structure in which it is used.
Another object and advantage of the present invention is to provide a structural member having the above characteristics and which also displays a high strength to weight ratio.
Another object and advantage of the present invention is to provide a structural member which, while possessing the above characteristics, may be fabricated from low cost recycled materials, such as plastic/wood fiber mixtures.
Another object and advantage of the present invention is to provide a structural member which, while possessing the above characteristics, may be fabricated from carbon fiber composite materials or other synthetic material which produces the strength required.
Another object and advantage of the present invention is to provide a structural member having the above characteristics, which can be put into position by erecting individual two plane half-joist sections into position on the building.
Another object and advantage of the present invention is to provide a structural member having the above characteristics, which can be put into position by assembly on the ground prior to being positioned, a multitude of isosceles joists, and lifting the assembly into position on the building.
Still another object and advantage of the present invention is to provide a lightweight, easily transportable, relatively inexpensive structural member of the above type which is comprised substantially or entirely of mass-produceable modular elements of engineered laminated wood materials.
Another object and advantage of the present invention is to provide a structural member having the above characteristics, where the need for cross-bracing between joists is eliminated and highly effective shear resistance is developed to support vertical loads at the roof or floor. Consequently, isosceles joists are inherently capable of transferring wind or seismic loads (horizontal forces in a given direction) to load support systems such as provided by adjoining walls of the structure, thereby solving a structural problem with roof systems having low diaphragm strength without the necessity for extensive cross-bracing.
Another object and advantage of the present invention is to provide a structural member having the above characteristics, which is of modular construction and whose modular elements may be prefabricated off site as two plane half-joists, each having a single top longitudinal flange and a single bottom longitudinal flange interconnected by a web fitted into a groove along the diagonal of the flange by a continuous adhesive joint, easily transported to, and easily assembled at the site consisting of diagonally disposing the half-joist sections relative to each other, where the facing surfaces of the top and bottom flange members can be juxtaposed and physically secured by a bolt during assembly.
A concomitant object and advantage of the present invention is to provide a structural member having the characteristics described above and which may be readily assembled with similar members to form a load carrying isosceles joist structure, such as the roof structure or the floor joists on a building.
The foregoing objects and advantages of the invention will become apparent from the following description of the preferred form and from the following illustrations of those forms, in which:
SUMMARY
In accordance with the present invention, a system of longitudinal flanges and webs connected along the flange diagonals, of dimensional graded lumber or engineered laminated wood material, are interconnected at each respective top flange and bottom flange which forms a composite, integrated, isosceles joist structure displaying the characteristics of a series of interconnected triangular truss units providing the rigidity and stability incident to structural triangulation. The isosceles joist develops highly efficient shear resistance to support vertical forces from roof or floor loads and horizontal forces from wind and seismic loads to a load support systems such as adjoining walls of the structure. An isosceles joist roof structure provides diaphragm strength without a structural roof decking to support a structural metal roof systems.
REFERENCES:
pa
Friedman Carl D.
Varner Steve
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