the threaded nut 26 serves only as a clamp by means of a bolt 25 to a specially formed foundation plate 28 which in turn is connected to the foundation by anchor bolts 30. (See FIGS. 4, 6, and 9 of U.S. Pat. No. 4,603,531)
Referring to FIG. 3 of Nash, the sides of elongated nut 26 have no part in directing the flow of tension forces from the seat penetrated by opening 24 of mounting bracket 20 around the right angle bend to the upright members of mounting bracket 20 which hold wood vertical member 10.
Millions of sheet metal eccentric holdowns have been successfully used in building structures in the United States since they were first introduced in the late 1970's and became commonly used during the 1980's.
Bothare generally superior to the eccentric holdowns because the momentum forces are minimized.
But even eccentric holdowns must be carefully designed. The upward force in a prior art concentric holdown is initially resisted by the upright portion or straps of the concentric holdown connector which pull upwards on the outside edges of the flat holdown seat. These upward forces, if unrestrained, would quickly bend a prior art holdown connector seat into the shape of the letter “U” and crush the cross grain wood mud sill members when the weight of the building crashes back down on the mud sill resulting in failure of the connection and possibly leading to the destruction of the building.
Some work has been done to improve the flow of forces through holdown connector members from