huangyhg

flange to web welds calculation of wwf
if the flange to web welds is not develop the full capacity of web. how to check the weld strength?
let say, web=30mm, bending f=0.6fy, shear ft=0.2fy, how to calculated the weld thickness?

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shear flow.
q = vq/i
you're right.
some time i'm not confident to the result. i had a gider with 26mm web. full strength weld thickness =26/.7/2=19mm(2 sides), shear capacity design only need 10mm thickness (2 sides). the weld strength is only 54% strength of web.
wait...
back to mechanics of materials. pure bending:

q=dm/dx=0
not connection need?
do you actually have pure bending? that is an idealistic case that i have personally never encountered. moments are virtually always a result of differential shears.

in pure bending there is no shear flow, so no weld required. that is correct, but as structuraleit points out, that situation is idealistic. i have never seen it either.
burtonstr, the flange to web weld requirements om beams are usually smaller than web thickness. normally shear differencial is gradual (except at supports).
in many cases i have seen the weld size being determined by the minimum weld size requirements rather than capacity.
even if you could get pure bending with no shear, then the flanges would be acting as tension and compression
can someone post an example calc
to structuraleit,
we consider pure bending, the idealistic situation. if not connection, how can the flanges and web work together? bending for 3 plates separately or "w" shape is total different
unless you have a moment connection at the beam support/connection, then you only have tension in the top flange, tension in the top half of the web, and compression everywhere else (well, that's a simplified version...actually a bit more complicated, but not significant for this case). then you have the shear in the connection, which will likely prevail.
given that, design your weld for those conditions. don't forget to combine the conditions for a compatibility check.
i got it。
thank every.
to jrstructural eng
v=9000kn, web=3000mmx20mm, weld:e49xx
q=v/h=3kn/mm
required fillet welds thickness
d=3/0.156=19.2mm
used 2x10mm fillet welds

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