Static structures (e.g. – buildings) – Sheetlike element assembled parallel to existing wall,... – Mounting means attached to facer; e.g. – upholstery panel
Reexamination Certificate
2001-02-28
2002-11-26
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Sheetlike element assembled parallel to existing wall,...
Mounting means attached to facer; e.g., upholstery panel
C052S112000, C052S509000, C052S202000
Reexamination Certificate
active
06484468
ABSTRACT:
BACKGROUND—FIELD OF INVENTION
This invention relates to innovative connectors and fasteners that make buildings stronger, and helps protect them from earthquakes, hurricanes, tornadoes, and strong winds.
BACKGROUND—DESCRIPTION OF PRIOR ART
BACKGROUND
Recent studies of earthquake damage on wood-frame buildings indicate that the outside wall sheathing is the most important structural member in preventing destruction to a home. Sheathing that is tightly secured to a house, stiffens the vertical components against damaging deformations.
The initial failure location on buildings during hurricanes is at the roof to wall connection, or at the wall to floor connection. This invention uses the outside wall sheathing to help tie the roof and floor to the walls, and stiffens the wall to distribute wind loads to the roof framing and end walls.
Failure and loss of the roof sheathing is common during hurricanes, mainly because of inadequate fastening of the roof sheathing to the underlying structural members. The roof system provides stability to a house by supporting the tops of exterior and interior load-bearing walls.
Sheet metal joints perform better than nailed joints in high winds and during seismic activity. Strong connectors, secured by sturdy fasteners, will insure that the major structural members of a house are securely tied together. Rigid outside sheathing, securely fastened to the walls, strengthens the link between the horizontal and vertical components of a structure.
Earthquakes
Earthquake studies of a single-family building showed that failure was mainly due to the improper connection of wall studs to sole plates; the failures were attributed to nail withdrawal from the framing (Goers, 1976).
Tests of wall studs to sole plate connections showed that the studs were uplifted from the sole plate, and the nails which connected the bottom of the plywood sheathing to the sill were punched out of the sheathing (Kamiya et al., 1981).
The outside sheathing allows the naturally flexible wood wall studs to deform just enough to absorb the earthquake forces without cracking. When the outside sheathing is secured tightly to the studs, top plate, rafter, and sole plate, without becoming disconnected, it increases their load-bearing strength.
Steel connectors, between different components of a wood-frame buildings superstructure, provide continuity so that the building will move as a unit in response to seismic activity (Yanev, 1974). Outside sheathing helps transfer earthquake forces to the ground while greatly strengthening the resistance to lateral seismic motions (Yanev, 1974).
Hurricanes
In 1974, wind-study testing of a full-scale house showed that the initial failure location was at the roof to wall connection, or at the wall to floor connection (Tuomi and McCutcheon, 1974). The stiffness of the wall influences the distribution of wind loads to the roof framing and end walls (Polensek, 1976).
In 1990, tests were done on (prior art) rafter/top plate connectors (hurricane clips) that are installed on a house during construction; it was found that hurricane clips are sometimes three to five times stronger than conventional toe-nailing under uplift loads (Canfield, 1990). Retrofit of prior art hurricane clips is difficult or impossible on existing houses.
Studies of damage from Hurricanes Andrew and Iniki show that most of the wind damage to a gable end of a home was from the difference in pressure inside and outside the home. Almost all pictures of damaged wood or masonry buildings show the gable end blown away from the building. (FEMA reports FIA-22, FIA-23)
Pictures never show the gable end blown into the building. This is due to the Bernoulli Effects, where the pressure differential between wind blowing around and over a building, and high pressure air inside, blows out a wall or roof.
An airplane rises due to the pressure differential of faster air moving over a wing, compared to the high pressure of slower moving air under a wing. So too does the side walls blow out of a house due to the Bernoulli effects of wind blowing perpendicular to the wall. Gable ends blow out of a house, because of higher pressure in the house compared to the extremely low pressure on the leeward edge of the wind direction.
Once the side wall or gable end of a house is blown out, the rigidity of the roof and entire house is compromised due to wind getting into the house. Driven rain, along with the wind can damage everything in the house, along with damaging the structural integrity of the roof and walls of the house.
Loss of the roof sheathing was consistently observed after Hurricane Iniki and Hurricane Andrew. The primary cause of sheathing damage was inadequate nailing into the underlying structural members of the roof. There was evidence of missing, corroded, misapplied, and too few nails or staples attaching the roof sheathing to the rafters, purlins, or trusses.
Outside Sheathing
If an earth tremor is strong, the nails holding the outside wall sheathing may be inadequate in size or quantity. Many nails are driven into the edge of the sheathing where the wood can split and lose connection with the underlying studs.
If the outside sheathing detaches from the wall studs, the walls cannot transfer lateral forces or transverse loads and the building can rack and collapse. When the outside sheathing is sufficiently attached to the structural framing, the sheathing and structural framing function together.
A sturdy wall system absorbs, resists, and transfers forces imposed by wind and earth movements. Improperly secured sheathing may not function effectively in resisting transverse loads and lateral forces.
Previously, framers did not understand the structural importance of outside wall sheathing. Improper nail size, length, or type, along with an improper fastening schedule, could jeopardize the anchoring ability of the outside sheathing. Plywood can still be applied with power-driven staples.
Many times, the exterior sheathing is applied to the wall when it is constructed on the ground, then raised in place. This helps keep the wall from racking when raised, but is heavier to lift and may be weaker than sheathing applied to a wall in place.
Part of my co-pending application, Ser. No. 08/191,852, filed on Feb. 2, 1994, ties the rafter to the outside sheathing and underlying top plate. This is one of the weakest failure points on a house during a hurricane.
This continuation-in-part application has unique connectors to tie together major structural members of a house using the important outside sheathing. These major structural members include the gable end rafter and joist, the sole plate and walls, and the corner post, rafter, and top plate. These unique connectors are held to the outside sheathing, and underlying or exposed structural members using unique fasteners, or nails, screws, and bolts.
Roof Sheathing
The stability of the walls is dependent on the roof for top lateral support. The roof sheathing can be composed of boards or plywood. It ties the rafters and roof trusses together, and prevents the roof from racking. The roof sheathing may have been applied carelessly in the past, as it was felt that the weight of the roof cladding would keep the roof on tight.
Previously, framers did not understand the structural importance of roof sheathing. Improper nail Haze, length, or type, along with an improper fastening schedule, could jeopardize the anchoring ability of the roof sheathing. Plywood may be applied with power-driven staples. In humid or salt-air climate, the nails or staples can corrode and lose holding power.
Prior Art
A number of connectors have been developed to tie together the roof rafter and the top plate, or wall stud and sole plate. Previous connectors were made to be used during construction of the structure and covered by the outside sheathing.
These connectors cannot be retrofitted to existing structures without extensive dismantling or damage to the inside wall board or outside sheathing. Without dismantling the walls, a homeowner can't tell if hurricane clips are correctl
Friedman Carl D.
Katcheves Basil
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