stitch weld

huangyhg

stitch weld
i have a composite t-section that is composed of a 1/4"x3" plate with a 3/8" x 4" stem plate. a 3" @ 12" stitch weld, staggered on opposite sides, holds the plate together.  the section is subjected to an axial load.  the question i have concerns the variables q and i in the shear flow equation v=vq/i. question 1: do i consider my i over the entire top area of the stem plate? or just the 3" weld area? question 2: when calculating q over the entire top section of the stem plate, with considering my neurtal axis at the center, q=0 for one side of the stitch weld. any suggestions would be appreciated.
  
v=vq/i is not appropriate for your application.  that formula is for horizontal shear flow originating from internal shear forces that are perpindicular to the longitudinal axis (taking loads in shear and bending, not axial loads).  if the entire load is applied through one of the plates, then just figure out how much load the welds need to tranfer into the other plate and design the welds for that shear force.
you need to design the connection based on discrete shear connectors, found in any mechanics of materials.  
structuraleit is correct.  for axial load conditions, the vq/i formula doesn't apply.
if you have bending, with the associted shear force v varying across the span length, then the q = vq/i is applicable where v is the vertical shear, i is for the overall section (the whole t section) and q is the area of the "t" flange plate times the distance from the centroid of the "t" flange to the centroid of the overall shape.
dwha, i think ccb1 used the term "composite" to imply the two plates work together, not that there was a concrete slab with shear connectors.

assuming you are using aisc, section e6 "built-up members" has requirements for connections between compression elements.  
thanks for the information. i appreciate it.