Corrugated shearwall
A prefabricated shearwall including a central diaphragm having a height generally defined by top and bottom edges, and a width generally defined by a pair of end sections. The diaphragm further includes at least one corrugation extending in the height direction at least partially between the top and bottom edges. The corrugation increases the ductility and ability of the shearwall to withstand lateral forces such as those generated in earthquakes, high winds, floods and snow loads.
1. Field of the Invention
The present invention relates to a shearwall for opposing lateral forces on building walls, and in particular to a prefabricated shearwall including a central diaphragm having a corrugated or non-planar cross section to improve the ability of the shearwall to withstand lateral forces such as those generated in earthquakes, high winds, floods and snow loads.
2. Description of the Related Art
Shearwalls were developed to counteract the potentially devastating effects of natural phenomena such as seismic activity, high winds, floods and snow loads on the structural integrity of light-framed constructions. Prior to shearwalls and lateral bracing systems, lateral forces generated during these natural phenomena often caused the top portion of a wall to move laterally with respect to the bottom portion of the wall, which movement could result in structural failure of the wall and, in some instances, collapse of the building. Shearwalls within wall sections of light-framed constructions provide lateral stability and allow the lateral forces in the wall sections to be transmitted through the shearwalls between the upper portions of the wall and the floor diaphragm or foundation of the building where they are dissipated without structural effect on the wall or building.
In constructions such as residences and small buildings, a lateral bracing system typically includes vertical studs spaced from each other and affixed to horizontal top and bottom plates. The bottom plate is typically anchored to the floor diaphragm or foundation. The bracing system typically further includes sheathing affixed to the studs, upper plate and/or lower plate to increase structural response to lateral forces. The sheathing used is generally oriented strand board (OSB) or plywood, but fiberboard, particleboard and drywall (gypsum board) are also used. Alternatively or additionally, light-frame construction wall sections may include prefabricated shearwall sections, which can be positioned between the vertical studs and affixed to the studs and the top and bottom connecting plates. The sheathing or prefabricated panels can also be placed adjacent door and window frames to improve the response to lateral forces at these locations.
A conventional prefabricated shearwall 20 is shown in the perspective and cross-sectional views in
While a prefabricated shearwall of the construction shown in
It is therefore an advantage of the present invention to provide a shearwall having improved lateral load bearing characteristics relative to similarly sized shearwalls.
It is another advantage of the present invention to provide a shearwall having improved lateral load bearing characteristics without adding to the size or materials used relative to conventional shearwalls.
It is another advantage of the present invention to provide a shearwall having improved lateral load bearing characteristics which may be easily retrofit into existing structures.
These and other advantages are provided by the present invention which in preferred embodiments relates to a prefabricated shearwall including a central diaphragm having a height generally defined by top and bottom edges, and a width generally defined by a pair of end sections. The diaphragm further includes at least one corrugation extending in the height direction at least partially between the top and bottom edges. The corrugation increases the cross-sectional area and ductility of the diaphragm in the lateral direction in comparison to conventional shearwalls, and further improves the resistance of the shearwall to lateral forces such as those generated in earthquakes, high winds, floods and snow loads.
In embodiments of the invention, the shearwall may further include a pair of reinforcing chords affixed to the end sections of the central diaphragm. The chords may be formed of 2 inch×4 inch wooden studs having a height equal to that of the central diaphragm. The chords further improve the resistance of the shearwall to lateral forces.
In order to distribute the significant compressive forces exerted by the shearwall over a large surface area on the underlying support surface, the shearwall further includes a flat sill plate affixed to the bottom edge of the central diaphragm. In embodiments of the invention, the sill plate may have a footprint at least equal to that of the central diaphragm, the chords and any sheathing affixed to the shearwall. The sill plate may be formed of a rigid material such as steel to evenly distribute any localized compressive forces from the shearwall. The sill plate may also underlie the chords to prevent any wetness or moisture from the underlying support surface from damaging the chords.
While a preferred embodiment of the invention includes a central diaphragm with a corrugation having a constant size and shape from the top edge to the bottom edge, the corrugation may be formed so that it is larger at the bottom edge of the central diaphragm and slopes inward to become smaller toward the top edge of the central diaphragm (or visa-versa). This results in a shearwall providing even greater lateral force resistance, as the sloped lines defined by the bends at the intersection between the various diaphragm sections have lateral components that exhibit increased resistance to movement in the lateral direction.
BRIEF DESCRIPTION OF THE DRAWINGSThe present invention will now be described with reference to the drawings in which:
The present invention will now be described with reference to
Referring now to
Some alternative embodiments of the central diaphragm are shown in
In embodiments of the present invention, the central diaphragm may have an overall height of 93¼ inches, an overall width of 12 inches, and a depth of 2½ inches. It is understood that each of these dimensions may be varied in alternative embodiments, both proportionately and disproportionately with respect to each other. For example, in one alternative embodiment, the central diaphragm may have an overall width of 18 inches. Each of the sections 104, 106 and 110 through 118 is preferably the same height. In embodiments where the overall width is 12 inches, end sections 104 and 106 may each be 2½ inches wide, rear planar sections 110 and 112 may each be 3 inches wide, the angled sections 114 and 116 may each be 4¼ inches wide, and the front planar section 118 may be 1½ inches wide. It is understood that each of these dimensions for the sections 104, 106 and 110 through 114 may vary in alternative embodiments, both proportionately and disproportionately with respect to each other. In embodiments of the present invention, the central diaphragm 102 may be formed of 7-gauge sheet steel (0.1875 inches). Other gauges, such as for example 10-gauge sheet steel, and other materials of comparable strength and rigidity may be used in alternative embodiments. One such alternative material may be expanded metal.
In a preferred embodiment, the rear planar sections 110, 112 may be coplanar with a back edge of the diaphragm 102 and front planar section 118 may be coplanar with a front edge of the diaphragm 102 so that the corrugation 108 traverses the entire depth of the central diaphragm. As explained in greater detail below, the corrugation 108 need not traverse the entire depth of the central diaphragm in alternative embodiments.
Referring now to
In embodiments of the present invention, the shearwall 100 may further include a pair of reinforcing chords 120 and 122 affixed to the end sections 104 and 106, respectively. The chords may be formed of wood, such as for example sawn lumber from lumber groups including spruce-pine-fir, Douglas fir-larch, hem-fir and southern pine. The chords 120, 122 may alternatively be formed of engineered lumber, such as glulam and wood composites. Other types of wood are contemplated. The chords may have a height equal to that of the central diaphragm 102 and channels 119 and 121 together, and may be 4 inches wide by 2 inches deep. Various affixing mechanisms may be used to affix the chords to the central diaphragm, such as for example a plurality of ¼ inch×½ inch Simpson Strong-Drive® screws. Other types of screws and affixation methods are contemplated. The screws in one embodiment may be provided in each chord along a single column and spaced apart 6 to 12 inches from each other. It is understood that the screws may be provided in more than one column, or not aligned in a column, down the length of the chords 120, 122, and may be spaced apart more or less than 6 to 12 inches in alternative embodiments.
Affixation of the chords to the central diaphragm as described above further improves the resistance of shearwall 100 to lateral forces. While a single chord is shown on each side of the central diaphragm, it is understood that more than one chord may be provided at each end. For example, 2 to 4 (or more) such chords may be affixed together and mounted to each side of the central diaphragm. It is also understood that chords of less than 2 inches deep and 4 inches wide may be used in alternative embodiments. Sheathing (not shown) may be affixed over the front and back surface of the central diaphragm and chords, and affixed to the chords by a variety of affixing mechanisms including Simpson Strong-Drive® screws. It is further understood that the chords 120, 122 may be omitted in alternative embodiments.
Shearwall 100 further includes a sill plate 124 affixed to the bottom of the central diaphragm. This allows shearwall 100 to have a lower load bearing surface with a sufficient surface area to allow distribution of the shearwall compressive forces over a sufficiently large area on the underlying floor diaphragm or foundation. If the compressive forces from the shearwall are concentrated, for example in a situation where the bottom plate is small or is shaped with channels so that only a portion of the bottom plate lies in contact with the underlying support surface, the resulting compressive forces can damage or cause failure in the underlying support surface.
Accordingly, sill plate 124 is provided as a flat plate with a relatively large surface area. The plate 124 has a length which is preferably equal to that of the central diaphragm and the chords 120 and 122 together, and a width that is equal to the width of the chords 120 and 122. This width dimension is greater than the width of the U-shaped channel 121 in embodiments of the present invention. In such embodiments, this provides a sill plate which is 16 inches long and 4 inches wide. It is understood that the length and/or width of plate 124 may be larger in alternative embodiments. For example, in embodiments of the invention not including chords 120, 122 and/or channel 121, the footprint of the sill plate may be the same size as the footprint of the central diaphragm.
Sill plate is also rigid enough to allow even distribution of any localized compressive forces from the shearwall 100. In one embodiment of the present invention, the sill plate 124 is formed of ½ inch thick steel. In embodiments of the invention, sill plate 124 may be affixed within channel 121 by affixation methods such as welding. The rigidity of the sill plate 124 as well as the rigid affixation of the sill plate 124 to the channel 121 further prevents buckling of the shearwall under laterally applied loads. It is understood that sill plate 124 may have thicknesses other than ½ inch in alternative embodiments.
It is a further feature of the sill plate 124 to underlie the chords 120, 122, thereby preventing their contact with the underlying support surface. In embodiments of the present invention where shearwall 100 is mounted on a foundation, the sill plate 124 isolates the chords from wetness and moisture from the foundation which may otherwise weaken and erode the chords. The provision of the sill plate 124 under the chords also allows the compressive forces exerted specifically by the chords to be evenly distributed over the sill plate and onto the underlying support surface as described above.
Referring now specifically to
Shearwall 100 may similarly include openings in the top edge of the central diaphragm 102 and channel 119 for affixation to a top plate of a wall as by bolts or other anchoring mechanisms described above. As also indicated above, shearwall 100 is prefabricated so that it may be easily located within a wall in any desired location simply by affixing the shearwall to the underlying support surface and top plate. The shearwall may be installed initially during construction of a building, or retrofit after completion of construction.
Shearwall 100 including corrugated central diaphragm 102 is capable of withstanding greater lateral loads in comparison to conventional shearwalls. Moreover, the corrugation(s) improve the ductility of the shearwall in the lateral direction.
Up to this point, the corrugation 108 has been disclosed as having constant dimensions between the top edge 101 and the bottom edge 103. That is, the intersection between the rear planar section 110 and angled section 114, and the intersection between the rear planar section 112 and angled section 116, form lines that extend vertically between the top and bottom edges parallel to each other. Similarly, the intersections between the angled sections 114, 116 and the front planar section 118 form lines that extend vertically between the top and bottom edges parallel to each other.
In an alternative embodiment of the present invention shown in the front view of
In addition to lateral force resisting characteristics of the shearwall 100 shown in
Although not shown in
In a further alternative embodiment of the present invention shown in FIGS. 17 though 19, the central diaphragm may include apertures 260 provided through the surface of the diaphragm. The apertures may be various shapes and sizes in alternative embodiments, and may be formed in the diaphragm before or after the corrugation is formed. The shapes may be oval, oblong, circular, quadrilateral, polygon or irregular from the front view in alternative embodiments. The size may also vary such that the aperture 260 extends as far out as the rear planar surfaces 210, 212 (as shown in
Up to this point, embodiments of the present invention have been shown as including a central diaphragm with a single corrugation 108, 208 or 308 as shown in
As shown in
As an alternative to a single unitary piece of material that extends the length of the diaphragm, the central section 406 may be comprised of more than one piece as shown in
The embodiment shown in
Although the invention has been described in detail herein, it should be understood that the invention is not limited to the embodiments herein disclosed. Various changes, substitutions and modifications may be made thereto by those skilled in the art without departing from the spirit or scope of the invention as described and defined by the appended claims.
Claims
1. A shearwall, comprising:
- a central diaphragm, including a top edge and a bottom edge generally defining a height of said central diaphragm, first and second ends, extending between the top and bottom edges, generally defining a width of said central diaphragm, and a corrugated section extending at least partially between said top edge and said bottom edge in between said first and second ends, said corrugated section forming at least one corrugation.
2. A shearwall as recited in claim 1, further comprising a sill plate affixed at said bottom edge of the central diaphragm and having a footprint at least as large as the footprint of said central diaphragm.
3. A shearwall as recited in claim 1, further comprising first and second chords affixed one each to said first and second ends.
4. A shearwall as recited in claim 3, wherein said first and second chords are each formed of 2 inch×4 inch wood.
5. A shearwall as recited in claim 3, further comprising a sill plate affixed at said bottom edge of the central diaphragm and having a footprint at least as large as the combined footprint of said central diaphragm and said first and second chords together.
6. A shearwall as recited in claim 1, wherein said central diaphragm is formed of 7-gauge steel.
7. A shearwall as recited in claim 1, further comprising a channel in which said central diaphragm is seated.
8. A shearwall as recited in claim 7, further comprising a sill plate affixed to a bottom edge of said channel and having a footprint at least as large as the combined footprint of said channel and said first and second chords together.
9. A shearwall as recited in claim 1, said at least one corrugation being defined by a pair of angled sections extending along said height dimension from a first plane at a back edge of the central diaphragm and angling inward toward each other, said angled sections terminating in a second plane at a front edge of the central diaphragm, and said at least one corrugation further being defined by a front planar section in said second plate and extending between said pair of angled sections.
10. A shearwall as recited in claim 1, said at least one corrugation extending from said top edge to said bottom edge.
11. A shearwall as recited in claim 1, said at least one corrugation extending from said bottom edge and terminating at a position between said bottom edge and said top edge.
12. A shearwall as recited in claim 1, said at least one corrugation including two corrugations.
13. A shearwall as recited in claim 1, said central diaphragm including at least one aperture.
14. A shearwall as recited in claim 1, said central diaphragm including at least one embossment.
15. A shearwall as recited in claim 1, said central diaphragm including at least one stiffening lip.
16. A shearwall, comprising
- a central diaphragm having a height, width and depth, each being perpendicular to each other, and a corrugation extending in the direction of said height of said central diaphragm;
- first and second chords affixed to said central diaphragm at opposed edges of said central diaphragm and extending in the direction of said height of said central diaphragm; and
- a sill plate affixed to a bottom of the shearwall, said sill plate having a footprint at least as large as said central diaphragm and said first and second chords together.
17. A shearwall as recited in claim 16, further comprising a channel in which said central diaphragm resides.
18. A shearwall as recited in claim 17, said sill plate having a width greater than that of said channel.
19. A shearwall as recited in claim 16, said sill plate being formed of ½ inch thick steel.
20. A shearwall as recited in claim 19, said central diaphragm being formed of 7-gauge steel.
21. A shearwall as recited in claim 16, said height being 93¼ inches, said width being 12 inches, and said depth being 2½ inches.
22. A shearwall as recited in claim 21, said chords each having a height approximately equal to a height of said central diaphragm, a width of 4 inches and a depth of 2 inches.
23. A shearwall as recited in claim 16, said height being 93¼ inches, said width being 18 inches, and said depth being 2½ inches.
24. A shearwall, comprising:
- a central diaphragm having a top edge and a bottom edge defining a height of said central diaphragm, first and second end sections defining a width of the central diaphragm, and a front plane and a rear plane defining a depth of said central diaphragm, said central diaphragm including: a pair of rear planar sections extending at least part way between said top and bottom edges and being adjacent, respectively, to said first and second end sections, said pair of rear planar sections having a surface residing generally in said rear plane, a pair of angled sections extending at least part way between said top and bottom edges and being adjacent, respectively, to said pair of rear planar sections, said pair of angled sections extending from said rear plane toward said front plane and angling toward each other, and a front planar section extending at least part way between said top and bottom edges and being adjacent said pair of angled sections, said front planar section having a surface residing generally in said front plane.
25. A shearwall as recited in claim 24, further comprising first and second chords affixed one each to said first and second end sections.
26. A shearwall as recited in claim 24, further comprising a sill plate affixed to a bottom of the shearwall.
27. A shearwall as recited in claim 24, first and second intersection lines being defined between said pair of rear planar sections and said pair of angled sections, said first and second intersection lines being parallel to each other.
28. A shearwall as recited in claim 24, first and second intersection lines being defined between said pair of rear planar sections and said pair of angled sections, said first and second intersection lines angling in toward each other from said bottom edge to said top edge of said central diaphragm.
29. A shearwall as recited in claim 24, first and second intersection lines being defined between said pair of rear planar sections and said pair of angled sections, said first and second intersection lines angling away from each other from said bottom edge to said top edge of said central diaphragm.
30. A shearwall as recited in claim 30, said first and second intersection lines extending from said bottom edge to said top edge of said central diaphragm.
31. A shearwall as recited in claim 30, said first and second intersection lines originating at said bottom edge and terminating between said top and bottom edges.
32. A shearwall as recited in claim 24, a first intersection line being defined between a first of said angled sections and said front planar section, and a second intersection line being defined between a second of said angled sections and said front planar section, said first and second intersection lines being parallel to each other.
33. A shearwall as recited in claim 24, a first intersection line being defined between a first of said angled sections and said front planar section, and a second intersection line being defined between a second of said angled sections and said front planar section, said first and second intersection lines angling in toward each other from said bottom edge to said top edge of said central diaphragm.
34. A shearwall having a length between a top and bottom of the shearwall, comprising:
- a first member extending in the length direction between a top and bottom of the shearwall, the first member including at least a first corrugation;
- a second member extending in the length direction between the top and bottom of the shearwall, the second member including at least a second corrugation; and
- a central section of variable width in a direction transverse to the length of the shearwall for affixing the first member to the second member.
35. A shearwall as recited in claim 34, where in the central section is a single unitary section extending at least partially between the top and bottom of the shearwall
36. A shearwall as recited in claim 34, where in the central section is comprised of a plurality of piece of sections positioned between the top and bottom of the shearwall.
37. A shearwall as recited in claim 34, where in the central section is welded to the first and second members.
Type: Application
Filed: Dec 12, 2003
Publication Date: Jun 16, 2005
Inventors: William Leek (Carmel, CA), Jose Perez (San Leandro, CA), Jerry Gridley (Grass Valley, CA)
Application Number: 10/734,870