welded splice connection to transfer the momen

huangyhg

welded splice connection to transfer the moment
i would like to connect two w18 beams together using a welded connection.  the web will have a full penetration weld, and the top and bottom flanges will have a certain size plate fillet welded over and centered at the interface of the two beams.  it is intended to be a moment connection.  my question is analyzing the fillet welds to the top flange, and analyzing the plate itself.  i was going to take the moment at the connection point, and turn it into axial (compressive and tensile) loads acting on the welds and plates by dividing it by the the depth of the original beam.  so say a w12x58 is the size of the beams being connected and the moment at this point is 120 in-kips, then i would use 10 kips of axial load acting on the weld.  is this the only load i need to use to determine length of weld and size of plate i need?  should i also add into account shear flow?
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why not full pen the flanges as well?  no design needed.  is this a beam splice with the same size beams or are they different sizes.
the web weld will take the beam shear since it is full pen welded.  you are correct to calculate the flange force in the beam to size the plate and the fillet weld.  the plate should be checked for gross tension and compression.  the weld on each side of the joint should just be checked for the flange force.  there really isn't shear flow as in two   
thanks, that is what i figured.
regarding the full pen welds, we feel it will be difficult to get all of the backing plates installed and lined up properly.  part of the beam is being cut out and removed because it is heavily corroded.  the new beam will be installed and spliced in place.  this beam occurs at an expansion joint, so there is another beam offset about a foot away.  this makes it very difficult to access the inside of the joint, so we are trying to limit parts and/or work inside the joint.  we actually decided to do a partial pen weld on top and bottom, grind it down, and then put a plate over top of it.
do you need to transfer the full moment capacity?  if so, then can you use temp clip angles to bring the surfaces into 'bearing' and use full penetration welds?
if you don't need full capacity, why a full penetration on the web?  usually a simple butt weld is sufficient.
can you use end plates welded to each w18?  these can be connected using fillet welds.  remember that a 3/4" multi-pass fillet weld is normally less costly than a complete penetration.  you can then bolt the end plates together with hs bolts.
dik