huangyhg

welding of beam plate
i have a existing beam without vertical load..
it is failing due to horizontal load.. wind load on column..
i added plate at the bottom to make it pass..
i am not confused how to design the welding of the plate to beam..
i understand vq/i where v is the vertical shear..
but the max moment of beam here are at the ends.. and it is not caused by the vertical load on the beam..
can someone enlighten me..
thanks,

i am not confused how to design the welding of the plate to beam..
should have been
i am now confused
i assume there is a point load at the top of the column? if you check the shear diagram, there will still be a vertical shear in the beam at the ends even without a vertical load on the beam. use that shear in your vq/i.
i'm going to guess that you have a moment connection of some sort at each end of the beam and that the moments are equal in quantity and direction. in order to develop those end moments, you have to have end shears acting in the opposite direction. make a free-body diagram at the end of the beam to find the amount of shear that you have. this shear is what you have to develop the flange plate weld for.

ok thanks.. yeah the column is continuous..
another question is, in this case maximum moment is at the ends.. if i add plate.. how do i welding plate to the moment connection end plate of the beam.. or do i need to..

i'm not sure i understand your last question.
well you add plate to where maximum moment is..
in this case maximum moment is at the ends..
this is a moment connection frame..
so if i add plate at the ends up to the x distance
should this added bottom plate also be welded to the existing moment connection end plate?
up to how far should the bottom plate be from existing moment connection end plate to be effective..
by the way.. looks like the moment connection was the one that caused vertical shear per penpal97. even without point load.
is the beam failure a physical thing (bent flange, bent web, etc)? or a code failure?
physical - can't really address that w/o further details
code failure - you only need the plate where the demand moment exceeds the unreinforced capacity, so the plates may not need to be that long. in terms of right at the moment connection, you will have to tell us more detail of the actual moment connection detail (flange plates, flange angles, welded flange to column, etc).
if it is an end-plate moment connection:
1) bring reinforcing plate as close to end-plate as possible (do not hit the existing weld)
2) reinforce the end-plate with a vertical stiffener, turning the end-plate moment connection into a seated end-plate moment connection. the vertical stiffener should overlap the reinforcing flange plate. the vertical stiffener can take the additional shear at the connection; the flange plate can take the additional shear away from the connection.
there is a lot more detail involved in part 2 of that explanation, but you should get the idea.
another question..
if i have a column failing in axial..
and i added flange plate
how do i transfer axial from additional flange plate to existing base plate?
thanks,
i think you may need to have another engineer look at this??

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