CNX Cinch Nut is designed to limit story drifts of multi-story buildings and eliminate additional structural damage caused by loose connections in floor framing.
The MiTek Z4 CNX-Series Cinch Nut is a shrinkage compensating take-up device that keeps connections of Tie-Down Runs tight to the floor framing members when shrinkage and compression of wood fibers occur. The Cinch Nut uses an internal self-ratcheting action that permits movement, or “travel” perpetually in one direction along the length of a threaded rod. When connected to the floor framing, the Cinch Nut travels down the Z-Rod with the building as it shrinks and compresses. The CNX Series Cinch Nut is available in 1/8 inch increments for installation with threaded rods that are 3/8 inch through 1-1/2 inch diameter.
- Features perpetual ratcheting along the length of a threaded rod that is not limited like the energy stored in a spring loaded device.
- Simple, one-time installation that does not require pin or screw activation after the building is loaded.
- CNX models are matched to the rod diameter specified for optimal tolerances.
- LA City RR 25623
- FL 17456 Florida Building Code – Building
- Florida Building Code Residential
Z4 Bearing Plate Washers (BPW) are the interface between the Tie-Down System and the level of the building being anchored to the foundation. As the floor system is pulled upward by shear wall over-turning forces, pressure is applied to the BPW/CNX assembly and transferred into the Z-Rod/all thread rod (ATR). The required bearing area is based on the design uplift to minimize crushing of the wood and the plate thickness must be sufficient that bending does not limit the capacity of the system. The wood species is also a factor when sizing. The pounds per square inch (psi) of compression cannot exceed the allowable compression perpendicular to the grain of the wood species it is bearing on.
Z-Rods in the system transfer cumulative tension loads into the foundation due to overturning force and wind uplift. Z-Rods are threaded at each end for making connections to the CNX Cinch Nut and to Coupler Nuts but unthreaded in the body. Because the steel for threading has not been removed from the body of the rod, elongation from tension loading is less than it would be for an all-thread product. Z-Rods conforming to ASTM A36 are plain finish and those conforming to ASTM A193 Grade B7 are zinc plated.
The Z4 Tie-Down System begins by connecting the first level Z-Rod to the hold down anchor in the foundation with a Coupler. At upper levels Couplers are used to connect Z-Rods end to end to create a continuous load path. Reducers are Couplers that connect two Rods that are different diameters.
The Anchor Tie is a structural component designed for connecting Z4 Tie-Down Runs to steel members. Anchor Ties are fabricated from ASTM Grade A36 steel plate and include a pre-welded nut, making the Tie-Down connection quick and easy. ATs are available in 9 and 12 inch heights. Other heights available upon request. The 9 inch version with 1/4 inch plate steel legs is available for connecting 5/8” through 1-1/2” diameter threaded rod and the 12 inch version with twice the steel thickness at the legs is used for connecting up to 2” diameter rod.
Common applications include connecting to steel plates at concrete decks and steel beams where Tie-Down runs terminate.
- When installing at concrete decks, steel plates are designed by the Engineer of Record to resist the uplift loads.
- After concrete is poured, the AT is welded to the plate and a threaded rod is connected to the Anchor Ties’ pre-welded nut enabling the Tie-Down Run from above to attach.
- Steel beam installations are designed by the EOR.
- The Anchor Tie is welded to the beam prior to floor framing then attachment of the threaded rod and Tie-Down Run completes the installation.
The Z4 “T2” is a steel tube with a steel end plate welded to one end designed to transfer tension forces with a single concentric hold-down device. Sandwiched Installations are made by through bolting two wood members with a T2 between. The tube is then attached to a threaded rod to transfer the tension loads.