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RE: Steel Connections

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In microwave telecommunication towers SAE Gr 5 bolts are commonly used.
SAE Gr. 5 bolts are usually certified as ASTM A449 bolts also.  The Gr 5
heads are smaller across the flats and the threads extend down the full
length of the bolt.  As a result, the iron workers on telecommunication
towers carry fewer bolts and the head size allows for easier
installation into the 60 degree bent plate tower legs.  Bolts are
designed as bearing bolts and they are tightened to snug tight only.

The AISC allows the use of ASTM A449 with a few caveats.  Re: AISC ASD
9th Ed. A3.4 on p 5-27.  Given that the minimum tensile strength of an
ASTM A325 bolt is the same as an ASTM A449 bolt, you can generally use
the A325 N or X values in table I-D on p 4-5 to determine the allowable
shear loads.  Allowable tension values are given in table I-B on p 4-3.

Harold Sprague
Black & Veatch

From: Harry Jones
To: seaoc(--nospam--at)
Subject: Steel Connections
Date: Tuesday, August 19, 1997 3:15PM

Has anyone used Grade 5 cap scews for connections rather than A307
The tensile strength does not seem to be an issue but I can't find
in the code that allows for this.  Is the intent of the code to allow
the use of A307, A325 and A490 bolts for structural connections?