Doubler Plate design for beam web

[BAGW]

Hi,

I have a situation where I need to splice the existing beam. I cannot add flange plates due to construction restraints and need to transfer the splice forces through the beam web splice plate only. The tension force is 300k and the beam web is 0.5''. Beam web does not work for block shear strength. So I am planning to add doubler plate at the web to account for thicker web. Any inputs? Is there any resources out there which talks about the design?

Thanks

 

[CANPRO]

I believe there are two block shear considerations here. The bolt group would have to pull out the web + doubler plates. The doubler plates plates would have to pull out the web at the welds. Because of your restricted access, the doubler plates are only engaging an extra few inches of web and you're only getting a marginal increase in capacity compared to the bolts engaging just the web (no doubler plates). What is the beam size?

 

[KootK]

I believe there are two block shear considerations here. The bolt group would have to pull out the web + doubler plates. The doubler plates plates would have to pull out the web at the welds.

This was especially well articulated so I'm going to piggy back onto it by adding one critical piece. The part of the block shear that went into the beam web in the first check, is still in the beam web for the second check in my opinion. Hence the inefficiency of the concept.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[BAGW]

@ CANPRO and Ktook

I completely agree. Have to check two block shears as CANPRO pointed out. Thanks

 

[CANPRO]

I see kootk's point. It would be similar if you had a retaining wall that was tied back with a deadman anchor, but your deadman didn't extend past your failure wedge of soil. You're basically trying to anchor into something that is eventually just going to be going along for a ride.

 

[KootK]

I completely agree.

Really? So soon? That's an impressive degree of mental plasticity for a structural engineer. It takes most folks 100+ posts to get past their egos.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[sandman21]

If you are adding a welded doubler plate that takes the full capacity of the connection, why just use that and eliminate the bolts.

 

[BAGW]

@ Ktook

LOL. I was missing the point for the doubler plate shear break out at the beam web. Thats what will control now. The Bolt region is fine with doubler plate.

 

[rb1957]

see if I've got this right ...

we're welding the doubler to the web, either under the splice plate or on the opposite side, so we have to check "block shear" around the perimeter of the doubler (to verify that the beam is ok).

then we have to check block shear in the splice plate for some %age of the load (some load sheared into the doubler).

of course, we have to check net section (doubler + splice plate) where all to load has left the beam; presumbly the beam net section is already checked.

and we have to check the fasteners (shear and bearing) and the welds.

so it sounds as though the critical failure now (prompting this redesign) is block shear in the beam, (cause the doubler takes some of the beam load away) ... but we don't gain much;
secondary failures could be splice plate area (if beam block shear is ok, then thicker plates would work) or fasteners (bigger bolts could work ?).

another day in paradise, or is paradise one day closer ?