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Re: Repost...TC Bolts

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James,

As a general comment I would say that using the TC bolts on all connections is not a bad idea as long as the contractor does so at their own cost.  Many contractors (with some notable exceptions) feel that the initial higher cost of the TC bolts is made up by a reduction in installation time.  The mantra of TC bolts is that you can tighten them from one side thus eliminating another ironworker on the other side.  This is probably true for large members such as in bridge construction but could be questionable when dealing with W8s, W10s, and W12s.

There are some other issues to be aware of:

1.  In your response be sure and state that the manufacture, installation, and inspection be in strict accordance with the latest issue of ASTM F1852, Research Council's "Specification for Structural Joints Using ASTM A325 or A490 Bolts", and any manufacturer's recommendations.

2.  Both regular A325 bolts and TC bolts are normally installed using pneumatic impact wrenches so I would not think they would be any quieter.

3.  The TC bolt socket is actually a double socket.  The inside socket grabs the spline while the outside socket grabs the nut.  They turn in opposite directions so they snap the spline part off rather quickly.  The double socket head is obviously larger than a normal socket head so if your steel is already fabricated then you can have clearance problems in tight situations especially with smaller member single plate connections.  See AISC Table 7-3b.

4.  The TC Bolt head is a dome (looks like a rivet) so if you have any plans for future extension or delayed construction then these type bolts can be very difficult to remove.  You either have to get lucky with a pipe wrench on the dome head or more likely they are torched off.

5.  For your slotted connections that are designed for movement you definitely do not want to use TC bolts.  My preference is to call out a 1/16 inch clearance and then double nut using standard A325 bolts and nuts.

Thomas Hunt, S.E.
ABS Consulting




"Kestner, James W." <jkestner(--nospam--at)somervilleinc.com>

06/10/2003 08:07 AM
Please respond to seaint

       
        To:        "SEAINT" <seaint(--nospam--at)seaint.org>
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        Subject:        Repost...TC Bolts



This is a repost from several weeks ago. I did not see any responses. Forgive me if I missed them.

I have a project where all the beam connections are designed with bolts in bearing. The wind bracing is designed with slip critical bolts.

The erector would like to use TC bolts for the entire project. This is a hospital and from what I understand the TC bolts are quiter than torquing conventional bolts (for the slip critical connections). The entire building is going to be fireproofed (so the steel will have no paint).

It seems to me that we should use conventional bolts for the bearing connections and TC bolts for the slip critical connections, and not TC bolts for the entire project. I would rather have the conventional bolts, installed finger tight, and therefore able to slip into bearing at lower levels of load (like when the building is under construction) rather then TC bolts highly torqued that then are required to slip at higher load levels (like after the building is occupied). I don't really know if using TC bolts for bearing connections can contribute to bolt banging (after occupancy), but I certainly want to avoid any possibility of this.

In addition, we have some shear tab connections with short slotted holes, that are designed for higher loads (than those shear tabs with standard holes). It seems that it may be possible to overstress some welds and plates if those connections were installed with highly torqued slip critical bolts instead of bearing bolts. Also, we have some connections to the existing building where we have slotted connections for expansion where we definitely do not want TC bolts (because of the unintended restraint that could be provided).

Any thoughts or comments would be appreciated.

Jim K.