Corrosion resistance of uplift connectors

[gould]

Currently there is a discussion before the Florida Building Commission Structural Technical Advisory Committee in regards to the requirement (or non) of corrosion resistance of hardware used to resist uplift and moment turnover. Where as there are several code references that would substantiate the support of a galvanization specification for the conventional sheet metal connectors, the meat of the discussion has been focused on the codes lack of specifications for threaded rod (continuous from roof to foundation)type connectors which are becoming more prevalent in the market. It has always been my contention that a connector is a connector and they should all be corrosion resistant, but the argument is being made that rod type connectors should not be required to provide corrosion resistance. FEMA TB 8-96 clearly recommends 2 levels of galvanization and their uses at various exposures and geographical locations, but never provides the allowance of no galvanization. In my efforts to support and see to the maintenance of the galvanization specification, even for rod (1/2&quot type systems, I am looking for any additional documentation that will substantiate the need for galvanization, the negative effects of not galvanizing, or other information relative to the cause.

 

[Kramer]

California is much less humid than Florida, but this might be of interest. In the 1999 edition of the SEAOC "blue book" the commentary on wood lateral force resisting elements (page 254) discusses moisture caused damage at the bottom of exterior shear walls and makes the following comment:
"Detailing to protect the sheathing is also needed. Where this decay issue exists, there is often also a problem of extensive corrosion at strap-type tie-downs connecting the framing to the foundation."
I typically use Simpson PHD anchors with threaded rod anchors instead of strap-type tie-downs because I feel the strap-type anchors are suseptible to corrosion and because I feel the PHD anchors have less deflection. Since the rods are buried in the wall they are not exposed to the exterior elements.