Reducing the gage at MC Channel

[patelam]

I am trying to reduce the gage at MC 12x40 to 1.75in for a 5/8" A325 bolt. The workable gage is 2.5".

How can I verify that the washers and nuts at the bolt holes will not overlap fillet radius of MC? Does maintaining clearance for tightening (C1) as given in Table 7-15 of AISC Steel Handbook ensures that the washers will not overlap? If not, how do I find the fillet radius of MC 12x40?

Please provide your suggestions.

Thank you in advance.

 

[XR250]

Don't know how to answer but it is likely AISC's recommendations taken account the variability in the dimensions of the finished product depending on which mill was used and the wear on their dies.

 

[CDLD]

Patelam, I believe the fillet radius of MC is unique to each fabricator.
You can make an approximation by extrapolating the flange slope towards the web (flange slope is 1:6).

To do this you first need to find the flange thickness, tf2, at the web:

tf2 = tf-(bf/24)+(((bf-tw)/2)/6)

The radius can be approximated by:
R = k-tf2

the fillet offset from center of web is:
tw/2 + R

Another method is to search the shape online - the radius is sometimes shown.
I looked it up and found r = 0.61".

CISC has the following for installation clearances:
You take the worst case between tightening clearance and washer to fillet distance.