Static structures (e.g. – buildings) – Means compensating earth-transmitted force – Cross bracing
Reexamination Certificate
1996-01-29
2001-10-09
Safavi, Michael (Department: 3635)
Static structures (e.g., buildings)
Means compensating earth-transmitted force
Cross bracing
C052S236300, C052S656100, C052S693000
Reexamination Certificate
active
06298612
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to light frame building construction and more specifically to reinforcing components for walls or framed portions of a building.
In the construction of light frame buildings, such as houses and apartment units, wood and metal light frame construction is conventionally known. Walls are generally fabricated as constructed frames formed of upright studs which are generally parallel to each other and separated at predetermined spacing intervals. Such construction is commonly referred to as “stick-built” or “stick-frame” construction, and is typically based upon vertical members or studs spaced apart at twelve to twenty-four inch intervals.
Several methods for reinforcing stud walls are known and are described below. Reinforcing stud walls is extremely important in order to avoid damage and structural failure of the building. This is especially true in areas where buildings are subject to shear forces or lateral forces created by high winds and by ground movement created by earthquakes. In the past few years, testing as well as environmental natural disasters, such as hurricanes and earthquakes, have illustrated that current methods for reinforcing light frame buildings are inadequate or insufficient. As such, building codes have been modified or are in the process of being modified to require stronger and more effective reinforcing methods. Each of the below described methods have proved to be questionable in light of such recent testing and natural disasters.
Mortise wood braces, commonly referred to as “let-in”, are widely used for bracing stud walls. A mortise wood brace is generally formed from a one inch by four inch wooden strip fitted into the upstanding studs and extending diagonally thereacross. Such a brace requires that rectangular grooves or slots be carefully cut in each stud so that the stud can accept the brace in a manner which maintains a flush outer surface. In this respect, a flush outer surface on the wall frame is important in that sheets of wallboard are normally secured or fixed to the stud wall frame prior to installing exterior siding. The mortise brace thus produces a wall frame having a flush outer surface on which sheathing can easily be secured. It will be appreciated however, that cutting diagonal slots or grooves is very time consuming and labor intensive, and therefore very expensive.
To further reinforce such stud walls against shear forces, some light frame constructions rely upon external sheathing, such as plywood or particle board (generally 4′ by 8′ sheets) nailed to the upright studs and top and bottom plates. Additional resistance to earthquakes is achieved by adding “hold-down” hardware at each end of the wall. Such sheathing becomes an integral part of the wall and forms the surface of the wall. The sheathing additionally provides a surface upon which to apply the finish, such as wood shingles, aluminum siding, wooden plank, gypsum board and the like.
However, use of such sheathing has proved ineffective in preventing deformation of the wall under relatively moderate lateral or shear forces. Under sufficient lateral shear force, the nails securing the sheathing to the studs are loosened or are ripped loose as the vertical studs deform from a right-angle orientation to a non-square orientation. Deformation of the wall can lead to collapse of the building structure. Recent cyclical tests conducted in California along with experience gained from the Northridge earthquake in California have demonstrated that sheathing and various “hold-down” fasteners do not perform satisfactorily.
Another method of wall bracing is disclosed in U.S. Pat. No. 4,016,698 issued to Rogers. This patent discloses a galvanized steel strap which is nailed diagonally to the studs of a wall frame with ends of the strap bent over and rigidly fastened to the upper and lower wall plates. Although the metal strap provides good tensile strength, it does not have comparable compressive strength. Likewise, the strap is not completely suitable where openings, such as window and doors exist. Also, such a method is extremely dependent upon properly securing the end of the strap. Again, this method is time consuming and labor intensive and is not suitable for application in existing structures.
A further method of wall bracing is disclosed in U.S. Pat. No. 2,497,887 issued to Hilbert. This patent discloses a paneled building construction utilizing prefabricated wall sections having reinforcing beams disposed in poured concrete. The panels are fastened together to form walls and may even include apertures for windows and doors. However, the panels form the actual wall and are not configured to be placed between existing studs in light frame construction. Such panels are suited for large high-rise structures constructed using steel “I” beams and reinforced concrete. Use of the panels is particularly directed to rapid assembly of the building since the wall sections are prefabricated and are bolted into place. However, use of such prefabricated steel and concrete wall panels is very expensive and not well-suited for use in light frame construction. Additionally, such panels, even if sized for light frame construction, cannot be retrofitted into existing structures.
Accordingly, it is an object of the present invention to substantially overcome the above-described problems.
It is another object of the present invention to provide a wall strengthening component that can be retrofitted into existing structures and can be placed between vertical studs.
It is a further object of the present invention to provide a wall strengthening component that reinforces a wall against shear forces directed thereagainst.
It is an object of the present invention to provide a wall strengthening component that is fabricated by stamping, welding, casting, roll forming, molding, or the like, parts to create the wall strengthening component.
It is yet another object of the present invention to provide a wall strengthening component having a plurality of reinforcing members between the edges providing structural resistance to shear forces.
It is yet a further object of the present invention to provide a wall strengthening component where the reinforcing members are formed from truss portions having either “Z-shaped, X-shaped, or K-shaped portions.
It is a further object of the present invention to provide a wall strengthening component in the form of a solid monolith having apertures disposed therein.
SUMMARY OF THE INVENTION
The disadvantages of present reinforcing methods are substantially overcome with the present invention by providing a novel wall strengthening component.
The present invention is extremely economical as a minimum of metal is used to fabricate the wall strengthening component. Additionally, the wall strengthening component is prefabricated and well-suited for mass production techniques, thereby minimizing labor and reducing construction costs.
The use of only a few wall strengthening components disposed in the building of a light frame construction will substantially increase the structure's capacity to withstand high levels of shear force. The increase in shear force resistance could result in such a structure surviving a hurricane or earthquake with little or no damage.
One significant advantage of using the wall strengthening component is that only a few components are needed. This is because the wall strengthening component has high resistance per foot characteristics with respect to shear forces applied thereto. If the structure is being initially constructed, the wall strengthening component is placed between existing adjacent vertical studs. A “hat-channel” may be added to the wall strengthening component to provide a surface to which to affix sheathing, such as gypsum board or wallboard. Such use in new construction is extremely economical since very little additionally labor is required to install the wall strengthening components.
If an existing structure is to be retrofitted, the existing shea
Safavi Michael
Welsh & Katz Ltd.
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