10 Nov 05 13:19
My professor in college that taught us steel design told us that if you design a connection for slip critical then it will not fail if it slips into bearing. I don't remember what the reasoning was other than because the connection capacity as a bearing connection is higher but I do remember him saying it.
I think STR04 concern is coming from the interaction of shear and tension. The interaction would be derived from Table J3.3 (ASD) and would show a reduction in tension (or shear) depending on the shear or tension load. This may be something to consider but here is also another approach. In the connections manual pg 1-10 connections are either direct tension, bearing, fully pre-tensioned bearing, or slip critical. As WillisV pointed out the slip critical failure is related to the clamping force, which is why the pretension is what it is. But in cases where we are required to have fully pretensioned bolts in bearing connections there is no apparent reduction in shear strength due to this. So I think you can confortably not take a reduction in strength just because you are preloaded.
One other thought is that have you actually run the numbers using the AISC table (J3.3). You may be ok, assuming the slip critical bolts are not designed to the end. For instance;
I will assume that the bolts are at 75% design capacity.
17ksi * .75 = 12.75ksi shear load.
SQRT(44^2 - 4.39*12.75^2) = 34.96 ksi - (Allowable tension stress)
ft = 28 / .7854in^2 = 35.65ksi
Its close but I would certainly be ok with it based on the other criteria given above. "I would actually be ok with no reduction based on what I said above."