Static structures (e.g. – buildings) – Assembled in situ-type anchor or tie – Sheet or wire tie
Reexamination Certificate
2001-09-01
2003-11-04
Chapman, Jeanette (Department: 3635)
Static structures (e.g., buildings)
Assembled in situ-type anchor or tie
Sheet or wire tie
C052S714000, C052S715000
Reexamination Certificate
active
06640516
ABSTRACT:
BACKGROUND—FIELD OF INVENTION
DESCRIPTION OF PRIOR ART
On the windward-side of hurricane-force winds, wind pressure creates tremendous force on the wall of a building. The house can be pushed off the foundation by wind pressure. On the leeward-side of hurricane-force winds, negative pressure can bow out the wall and detach it from the building.
Adjacent walls can tilt or rack when the windward and leeward walls are being pushed and pulled. Wall sheathing helps prevent the wall from racking, or tilting. Sheathing that is tightly secured to the walls, helps transfer lateral forces to the foundation.
Earthquakes generate lateral movements on the walls, causing them to rack or twist off the foundation. If the wall sheathing fails by being pushed in, pulled out, or rocked laterally, the walls can collapse because they can not stand when weakened and supporting the heavy load of the roof.
Failure of the wall sheathing is common during strong winds and seismic movements, mainly because of inadequate fastening of the wall sheathing to the underlying structural members. Sheet metal joints perform better than nailed joints in high winds and during seismic activity.
Hurricanes
Studies of damage after Hurricane Andrew show several problems with the attachment of wall sheathing that this invention solves. Some sheets of wall sheathing that were blown off houses had staples or nails that had rusted away, and on some sheets the nails had just pulled out from the studs.
The engineering staff of the American Plywood Association provided technical personnel to assess the damage from Hurricane Andrew in Florida. The majority of wood structural sheathing failures were attributed to improper connection details, and in every case investigated, the sheathing loss was a result of improper nailing (Keith, 1992). These problems have not been solved because staples and inadequate nailing schedules are still used to tie down sheathing.
Earthquakes
During an earthquake, the floor, wall, and roof diaphragms undergo shearing and bending. The shear forces from the roof boundary members are transferred to the top of the shear wall by way of toenails or blocking to the top plate. To withstand and transfer the shear loads, plywood sheets have to be spliced together to prevent adjoining edges from sliding past or over each other (Gray, 1990).
Butted together on the centerline of a 2×(nominally 1½-inches-wide), you've only got ¾ inch bearing for each plywood sheet, so the nail has to be ⅜ inch from the edge. This leaves little margin for error, and nailing has to be done with care to avoid splitting the plywood and missing or splitting the underlying member (Gray, 1990).
Tests at the University of California show that plywood secured by overdriven nails, nails that penetrated the plywood beyond the first veneer (usually by a powered nailgun), failed suddenly and at loads far below those carried by correctly nailed plywood panels (Gray, 1990).
Steel connectors, between different components of a wood-frame building's superstructure, provide continuity so that the building will move as a unit in response to seismic activity (Yanev, 1974).
PRIOR ART
A number of connectors have been developed to tie together the structural members of a house under construction. Up until this invention, nobody had seen how to make a compact connector that could tie two or more sheathing sheets together and to the underlying structural members of the stud and sill plate.
Some prior art prevents uplift, but this invention not only prevents uplift between the stud and sill plate during hurricane-force winds, but prevents lateral movement during earthquakes.
The Simpson Strong-Tie Co.'s January 2000 catalog (page 37) lists a PSCL Plywood Sheathing Clip. This clip provides a gap and aligns sheathing but does not tie the sheathing to underlying structural members or prevent uplift or lateral movement. No other sheathing ties were found in their catalog, but they do show several mudsill connectors (pages 10-13) that tie the sill plate or stud to the concrete foundation.
The Simpson catalog also shows a Strong-Wall™ Shear wall (pages 14-17). This complicated system ties the wall stud and sill plate to the foundation, and includes the sheathing. It appears that the Shear wall is purchased and installed as a complete system.
The Simpson catalog also shows hold-downs (pages 19-22) that use bolts imbedded in the foundation concrete to hold down a sill plate. Their other hold-downs (pages 23-25) must be inserted into wet concrete. None of the above hold down sheathing that is installed on site.
Timmerman's U.S. Pat. Nos. 6,244,004 and 6,158,184 are Lateral Force Resisting Systems, but they do not tie down the wall sheathing.
Leek's U.S. Pat. No. 5,732,519 is a one-piece foundation-to-frame connection, but it too does not tie down the wall sheathing. In order to form the wall into a shear-wall, the wall sheathing must be held tightly to the wall stud and sill plate.
A prior art roof securing system by Llorens, U.S. Pat. No. 5,390,460 ties down a single sheet of roof sheathing to a support beam. This is a good connector, but it is long, and can only tie down one-size of sheathing. It must be hammered around the beam from below, but panels are installed from above the roof. Although Llorens' 460 could be used on a wall, it can only tie down one panel and provides little lateral support.
Another sheathing strap and alignment guide by Nellessen, U.S. Pat. No. 5,423,156 shows an apparatus for securing sheathing using a long strap, connecting bands, and saddles. This is a good connector, but it is long, complicated, and must be installed from below the roof. With sheathing in place, this is difficult. Although Nellessen's 156 could be used on a wall, it can only tie down panels of one size.
According to the magazine Fine Homebuilding, October/November, 1998, sheathing courses should begin with either a full or half sheet. The course of sheathing at the top row and beginning row are often odd-size, in order to get a reasonable width of sheathing on the top row (by the top plate).
OBJECTS AND ADVANTAGES
Accordingly, several objects and advantages of my invention are that it helps secure the sheathing on the roof and wall, to keep the building from being destroyed by hurricanes, tornadoes, and earthquakes.
This invention helps prevent the wall of a building from detaching from the wall studs during a hurricane or earthquake. It makes the wall into a stable shearwall, transferring shear forces into the foundation and ground.
This invention helps prevent the roof of a building from detaching from the rafters or roof trusses during a hurricane. It ties the roof sheathing securely to the underlying rafter or roof trusses, transferring lateral and uplift forces to the walls and to the foundation.
This invention helps prevent the floor of a building from detaching from the floor joists during an earthquake. It makes the floor into a horizontal shear wall, and helps the floor resist lateral forces in its horizontal plane. It also makes sure that any forces transferred from the roof and wall can be managed by the floor and transferred properly to the ground.
One object of this invention is to make each sheathing structure on a house into a shear-wall, that is, able to transfer forces without breaking or disconnecting. By tying the plywood securely to the underlying structural member, the plywood can reliably transfer and dissipate shear, lateral, and uplift forces to the ground.
During an earthquake or a hurricane, another object is for the building with my invention to move as a sturdy unit, resisting and transferring destructive forces to the ground. Mounted on the roof sheathing and rafter, my invention resists uplift, the most destructive force during a hurricane. Mounted on the wall stud and wall sheathing, my invention prevents the wall sheathing from being blown off or sucked out by the extreme negative pressure of a hurricane. Mounted on the floor sheathing and floor joists, my invention prevents
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