Bolts Tightened to Full Pre-Tensioned Load - Axial Capacity? 1

[Norby_acn]

Good morning, all. I have a little bit of an odd situation come up.

I am working on a structure which has thousands (not an exaggeration) of angles as a part of horizontal trusses that are a part of the lateral system. They are all required due to the nature of the structure and providing continuity for the load path. However, they generally experience very little load, something on the order of 1,000 - 1,5000 lbs or less typically. The angles come in at an angle to the truss chords and the connections require slotted holes for tolerances. Field welding is absolutely not an option. I've provided a sketch in the attachment.

Due to the number of connections, the nature of the structure, and other factors, slip critical bolts are not an option. Also, the geometry, orientation, and elevation of the beams/columns is set. There is a small amount of play for adjustment of the angle brace. Can standard A325N bolts which have been tightened to their full pre-tensioned load be expected or designed to have as a shear capacity? Due to the nature of pretensioning the bolts, there has to be some capacity. I just can't find any information on what that capacity might be or how to calculate it.

Any help is greatly appreciated. Thank you,

 

[CANPRO]

You need to rotate your slot so it is perpendicular to the load, then you have direct bearing with the bolt.

 

[Norby_acn]

I should also mention that the bracing has all be designed as "compression only", but I am aware that a brace doesn't actually know that it is "compression only" and will likely experience some limited tension loads at certain points in its working life.

 

[klaus.]

what is the sense of the slotted hole ???

 

[Norby_acn]

CANPRO: I hate it when its such an obvious solution and I just have to think "Why didn't I think of that!?!?!?". Thank you very much, that is a great idea!

klaus: I'm not sure what you mean by "sense"?

 

[Tomfh]

What’s the point of a slotted hole perpendicular to the angle?

 

[BAretired]

If slotted holes are used, they should be parallel to the brace. Alternatively, oversized holes could be used without slots.

BA

 

[Norby_acn]

Tomfh: The purpose is to provide some flexibility for erection in the field. The angles are pre-cut and need to be able to be installed in the field.

 

[Tomfh]

Norby, what I mean is: how does a perpendicular slot provide tolerance?

 

[canwesteng]

What makes this job special that you need slotted holes? Is your fabricator particularly dimensionally challenged?

 

[KootK]

I don't believe that all of your stated requirements can be satisfied concurrently. Allow welding, allow slip critical bolting, abandon the notion of significant installation tolerance, or sacrifice reliable axial force transfer. Something has to give.

 

[GC_Hopi]

Are you able to break the structure into discreet sections? This will allow a tolerance for each section and prevent a error from accumulating.

Have the installer field drill some or all of holes for the bracing. This can be used break the structure into sections, see previous comment.