Wide Flange Beam to HSS Column Connection

[learning2banengineer]

Hi, my question is related to wall doubler plate used for wide flange beam to HSS Column moment connection. Hollow Structural Section Connection and Trusses design guide (FROM CISC) talked about the design of this kind of connection by checking a few failure modes. Failure mode (d) discussed on P. 324 relates the length of the doubler plate. However, it is not clearly defined what Lp reprent in the formula (please refer to attached sketch). Was is the total length of the doubler plate or just the extension for the flanges plates? In addition, how much of the weld between the doubler and the HSS wall can we use to transfer load from flanges plates to the HSS wall?(please refer to attached sketch)? Can anyone shine me some light on this, thanks!

 

[learning2banengineer]

Sorry did I posted this in the wrong forum that's why there is no reply at all? thanks.

 

[BAretired]

I believe that L_p refers to the total length of doubler plate. In your sketch, I assume you are using a cap plate on the top of the HSS, so Failure mode (d) will apply only at the bottom of the plate.

BA

 

[Den32]

Sorry, not familiar with CISC Provisions.

AISC (American Steel) has specific formulae for check HSS Faces wtih Concentrated forces.

Like BA said, do you have a Column cap plate? If so, drop cap plate so it is near top flange of W-shape and that is taken care of.

Not sure sizes or member heights, but it may be worth bumping up the HSS thickness vs. adding a thick doubler with welds.

 

[learning2banengineer]

Thanks for the reply. I couldn't drop the cap plate down becaise there is ano beam coming in the perpendicular direction and it's moment connected to the column as well, so I am connecting top flange of that beam with the cap plate directly. Den32 you are right, I haven't checked if I can just connect flanges directly to column face withough doubler plate. The deisgn guide has formula to do that too, but IMO, it's not totally clear. Since I am in Canada, connection deisgn is seperate from structural design, sometimes it's just annoying and time consuming to go back and forth with consultants to change member size. However, if a doubler plate is really needed, how much of the weld between the doubler plate and HSS wall I can use to transfer flange load?
As per my sketch, the double plate can be extend longer only at the bottom, but I guess if the doubler plate is not long enough and cannot be extended further up, I can probably go for a thicker plate to increase the resistance.