Tuesday, June 23, 2009

Re: Anchor rods set too low (again!)

Drew,
 
Weld length: pi*1.25 = 3.92"
Weld capacity: 0.75*0.6*70*3.92*0.7071*0.5=44K for 1/2" weld, and 55K for 5/8" weld.
 
V. Steve Gordin, SE
Irvine CA
 
 
----- Original Message -----
Sent: Tuesday, June 23, 2009 12:54
Subject: Re: Anchor rods set too low (again!)

I considered this, but I could only get about 22 kips (1 1/4" x pi x 4 x 1.394 kli/16th).  If I use the weld plus the threads engaged I would be mixing welds plus shear/bearing of the nut/bolt interface.  It would seem that the thread/nut would not be engaged initially until the weld broke.  This appears to be the same as the prohibition of mixing welds and snug tightened connections.


SGE Structural wrote:
Can you weld the rod - as is, below to the top of the nut - to the nut?
SG
----- Original Message -----
Sent: Tuesday, June 23, 2009 10:42
Subject: Re: Anchor rods set too low (again!)

Unfortunately, there is only about 1/8" to 1/4" of clearance between the anchor rods and the inside of the base plate holes.  I need the connection to be good for about 45k (strength).

SGE Structural wrote:
Drew,
 
Welding of this steel does not appear to be a problem.  You may not need an extension: a 1/2" thick weld of the 1-1/4" rod to the baseplate (inside the hole) will be good for about 45K (LRFD). This may be sufficient even without claiming the combined action.
 
V. Steve Gordin, SE
Irvine CA
----- Original Message -----
To: SEAINT
Sent: Tuesday, June 23, 2009 10:15
Subject: Anchor rods set too low (again!)

I have a case where the anchor rods have been set too low (again). They are F1554-36 1 1/4" diameter.  To make things worse, the columns have fixed bases and have been installed with the grout below the base plate installed.  I'm not sure why the contractor even bothered to call this in this late. 

Typically, if the rod head is flush with the top of the nut, we use the full strength of the rod. Is there a way to determine what the connection strength is between the nut and the rod if less than the entire rod is engaged?  I can't enlarge the holes in the baseplate for couplers without affecting the anchor rods and I am leery of welding on an extension of the threaded rod.
at