Beam to beam connection question

[Mike1998]

Hello everybody,

Let’s say I have beam 1, which is connected with beam 2, which runs in the transverse direction. Beam 2 is actually hanging from beam 1 and they are connected through a bolted connection on the top flange of beam 2 and the bottom flange of beam 1. The bolts are subjected to tension, because of the reaction of beam 2 to beam 1. Given that beam 1 is subjected to negative moment (so compression on the bottom flange), should I check these bolts for shear and bearing of the plates (because of the compression force on the bottom flange)?

Thank you in advance.

 

[hokie66]

As described, I don't see the bolts receiving any substantial shear force. If the bolts are installed as normal, there will not be bearing between the bolts and the flange due to hole tolerance. So no, shear and bearing are not an issue. In your tension check, prying could be an issue, depending on the geometry.

 

[Mike1998]

Thank you for your response.
Attached you see a sketch of the connection. Beam 2 is supported by beam 1 through these plates welded on beam 1. I thought that because of the negative moment which acts in the transverse direction on beam 1, the resulting compressive force on the bottom flange would result in shear of the bolts and bearing of the plates.

 

[klaus.]

well ..it depends on the 'flow' of the forces in the structure if the bolts get shear or not...
if you do not know... or not want shear....make oversizes holes

 

[BrianE22]

Figure out what the shear stress is and then provide enough clamp load so that the shear force is taken up by friction between the 2 mating surfaces.

 

[Agent666]

BrianE22, structurally the shear load in a tensioned bolted connection still goes through the bolts, i..e cannot avoid designing the bolts for the shear force if its snug tight, tensioned for bearing or friction (Slip critical).

I don't really see how simply having the bottom flange in compression results in bolt shear as per your explanation Mike?

Bolt shear would be a function of transferring some forces from beam 1 to 2 or vice versa? Can you maybe explain a bit more about what forces are in both beams 1 & 2, and what forces are being transferred between the two beams (identify these forces and this is what you design the connection for, with allowances for prying, etc as others have noted).