[Towertalk] (no subject)

[kr7x@attbi.com]

Mike:

I free recommendation is to burn off the leg stubs. Have 
a new base plate fabricated from 1/2" steel plate sized 
to match the dimensions of Rohns pier pin plate. Find a 
1 foot top section of your Rohn 25 that is still 
straight and not warped so it will mate up with a new 
section. Have the 1 foot section welded to the new plate 
to use as an attachment pin like the pier pin base.

Have 3/4" hole drilled in the base plate in the 4 
corners a minimum of 1" in from the edges and drill and 
epoxy grout in 4 - 5/8" diameter threaded rods that are 
embeded a minimum of 5 inches into the concrete base.

This is from the Hilti catalog and is the HVA Adhesive 
anchoring system using HAS rods. The resulting system 
will have 13,000 plus pounds of shear capacity. Since 
your tower is guyed there is basically no moment at the 
base to worry about and the plate being sized as the 
Rohn pier pin base will be adequate for the compressive 
load from the tower.

This is all based on the assumption that your new 
installation will be the same as the old.

Actually you could use 1/2" diameter HAS rods also, with 
5/8" holes in the plate.

Look up your local Hilti supplier in the yellow pages 
and talk with them.

I concur with all the other suggestions that you use 
epoxy anchors to reattach to the existing base.

73

Hank Lonberg, S.E.,P.E.
KR7X