Steel Beam Moment Connection

[Veer007]

Hey guys, Can double row shear bolts resist moment without connecting top and bottom flanges of beam? If so, can i provide bolts continuously with 3" spacing?

Thanks in advance!!

 

[skeletron]

I wouldn't call that a moment connection with only the web connected. Theoretically the bolt group, plate, and weld will contribute to some rotational resistance, thus providing some moment resistance. But I wouldn't count on it for anything substantial. The detail also shows welding to the face of an HSS which would be more flexible than the flange of a W-column. So...I will double down on there being no substantial moment resistance.

 

[Toby43]

Moment Resistance? Yes
Rotational Stiffness? NO - Thus won't attract moment and not to be relied upon to reduce actions in beam or provide lateral stability.

 

[Veer007]

i could think that same, but our engineer says this as moment connection, that's why i asked.
Do u accept this will take some moment resistance? Please explain

Thanks in advance!!

 

[Toby43]

What I'm saying is that it has moment resistance, but in a framed structure it would not attract moment. If the beam was a cantilever with a connection like this at its "root" it would take the moment due to it been required by statics, but the rotation could be significant.
Moment Resistance - Product of Bolts in shear capacity (plate tearout, bolt shear etc...) by the lever arm of the connection.
Moment/Rotational Stiffness - Must account for connection slippage and deformations. Thus bolts in shear inherently have slippage, as opposed to bolts in tension clamping "stiff" plates together. Also as Skeletron mentioned, the HSS wall would add flexibility.
I'll see if I can hunt out an old plot of moment attracted vs rotational stiffness and post it up so you can see the relationship.

 

[skeletron]

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1556859553/tips/design_and_behaviour_of_shear_tabs_fx2haa.tiff[/url]

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1556859607/tips/endrotation_sjnzbe.tiff[/url]

 

[Veer007]

thank you for your brief explanation, it may helpful for me if u get me the relationship.

Thanks in advance!!

 

[Toby43]

Image below shows the Classification system for joint stiffness according to the Eurocode for steel joints and the plot below it demonstrates, that even with a "rigid" classification, the moment developed could indeed only be 80% of the fully rigid model. The plot is created considering a symmetrical single bay moment frame under uniform UDL with the following notation
Kj= Joint stiffness relative to the beam stiffness
Kc= Column stiffness relative to the beam
gamma m = percentage of attracted moment at knee joint relative to infinitely rigid connection
In this instance due to symmetry of frame and loading the beam stiffness = 2EI/L
[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1556860419/tips/Moment_rotation_w2zrc9.pdf[/url]

 

[GC_Hopi]

To expand on Toby43's remark: at the shear plate connection you have proposed consider the plowing/bearing action of the bolts caused by their local stress concentration. The connection will start to have plastic yielding at the shear plate due to plowing of the extreme/top and bottom bolts,ie the ones with the maximum lever arm, and this will preclude the connection from providing substantial moment capacity beyond the moment bearing of the extreme bolts. I would recommend reviewing the established literature from AISC or similar organizations.