Static structures (e.g. – buildings) – Means compensating earth-transmitted force – Cross bracing
Reexamination Certificate
1999-10-18
2001-10-30
Callo, Laura A. (Department: 3635)
Static structures (e.g., buildings)
Means compensating earth-transmitted force
Cross bracing
C052S293300, C052S481100, C052S693000, C052S712000, C411S466000
Reexamination Certificate
active
06308469
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to shear walls and, more particularly, to a prefabricated shear wall panel for use in frame construction.
BACKGROUND OF THE INVENTION
Shear walls or shear wall panels are used to resist lateral forces in a structure created, for example, by wind loads applied to the side of a structure or earthquakes. Conventional shear walls typically fall into three categories: (a) braced frames, (b) moment frames and (c) frames with structural sheathing.
In braced frames, a stud wall has braces which extend diagonally from a rim joist or plate at the top of the wall to a rim joist, plate or foundation at the bottom of the wall. The braces cross one or more of the studs and therefore requires cuts in the studs to let the bracing into the wall or finish materials which can accommodate the protruding bracing member. In order to avoid cutting the studs significantly or to minimize how far the brace protrudes from the wall, the braces are typically made of a steel strip or rod or a thin wooden board. Since the bracing member is longer than the wall studs, the slenderness of the bracing member limits its compressive strength and so the bracing members are installed in pairs slanting in opposite directions to provide a tensile member to resist lateral forces in either direction. In addition to these shortcomings, the braces typically occupy significant lengths of the walls which are then unavailable for windows.
In moment frames, various corners between studs and plates or joists are reinforced, typically with triangular steel plates or wooden knees. With the corners reinforced, lateral movement is resisted by moment in the studs which must bend before one of their ends can be displaced laterally while remaining vertical. This method may be suitable for timber frame or large I-beam structures in which the studs have large cross sections, but is inefficient when applied to light framing using “2 by” lumber or light metal channels. In these applications, the studs have limited moment resistance and large numbers of stud to plate or joist connections must be reinforced.
In frames with structural sheathing, plywood or oriented strand board is nailed to the studs and any sills, headers etc. used to frame openings. The sheathing panels are resistant to lateral deformation. When properly attached to the wall, the sheathing panels transfer this resistance to the wall primarily as a shear force around the perimeter of the sheathing panel. To resist this shear force, a concentrated nailing pattern is required around the perimeter of the sheathing panel. Any openings for windows require more intensive nailing and yet still weaken the panel such that some building codes deem sections of the wall with openings to have no lateral resistance. The process is time consuming and heavily dependant on quality workmanship. Further, in recent years it has been discovered that the tightly nailed sheathing panels in combination with an interior vapour barrier trap moisture within the wall which often leads to fungus growth and premature failure of the wall.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a shear wall panel suitable for light framing, particularly in wood. It is a further object of the present invention to provide such a shear wall panel that does not require structural sheathing, that is suitable for pre-assembly in a factory, and presents reduced interference with placing windows in the structure.
The invention is directed at a shear wall panel for a building comprising,
a) a pair of spaced apart vertical members having upper ends and lower ends;
b) an upper horizontal member extending between and secured to the upper ends of the vertical members;
c) a lower horizontal member extending between and secured to the lower ends of the vertical members;
d) at least four diagonal members joined end to end in a multi-segmented assembly having at least three vertices between a first end and a second end,
wherein the multi-segmented assembly is located inside of the members in a), b) and c) above; one of the at least three vertices is secured to each of the members in a) and b) above; and, the first end and second ends are secured to the lower horizontal member.
The lower horizontal member is shear connected to a foundation or laterally stabilized wall or floor below the shear wall panel. The shear connection includes vertically oriented connectors connected to the lower ends of the vertical members to resist upward tensile forces on the vertical members. In an embodiment, these vertically oriented connectors are wooden thrust blocks, preferably oriented so that the grain of the wood is vertical with a hole through the thrust blocks to accept a rod extending upwards from the foundation or a laterally stabilized wall or floor of the building below the shear wall panel.
Upper connectors transfer shear and tensile forces from a roof, floor or wall of the building above the upper horizontal member to the shear panel. In an embodiment, the upper shear connectors comprise metal straps, a first portion of which have teeth bent out of the metal strap, a second portion of which have holes for nailing through the metal strap into the roof, floor or wall of the building. Tensile metal straps have teeth whose width is parallel to a line dividing the first portion of the metal strap from the second portion of the metal strap. Shear metal straps have teeth whose width is perpendicular to a line dividing the first portion of the metal strap from the second portion of the metal strap
The invention is further directed at a shear wall panel as described above having wooden members attached to each other with toothed plates pounded through the members. The upper horizontal member preferably has a notch or extends beyond a vertical member so that the shear wall panel may be connected to the upper plates or upper horizontal members of adjacent wall panels.
The invention is further directed at a metal strap for connecting substantially abutting wooden members comprising, (a) a first portion of the metal strap having teeth bent out of the metal strap; and, (b) a second portion of the metal strap having holes for nailing through the metal strap. An embodiment has teeth whose width is parallel to a line dividing the first portion of the metal strap from the second portion of the metal strap. Another embodiment has teeth whose width is perpendicular to a line dividing the first portion of the metal strap from the second portion of the metal strap.
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Bereskin & Parr
Callo Laura A.
Shear Force Systems Inc.
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