gaps for square butt weld

huangyhg

gaps for square butt weld?
hello all,
i am trying to determine the size of the gap for a square butt weld between to beams butting each other (a splice,) however the code does not seem to give guidance on exactly how much the gap should be.
is there a rule of a thumb out there?
much thanks.
have you checked the prequalified full penetration weld tables in the aisc manual?
this is always a naughty sounding topic.
i don't get it...
mike mccann
mccann engineering
as jae suggests, look at the prequalified welds in the aisc manual.  i am not sure if this is a full pen weld though, i believe it is a partial pen.
whether it is full penetration or part penetration, the required gap depends on the welding process used, the metal thickness, the joint preparation, and maybe some other things.  there lots of prequalified welded joints, so as others have suggested, if you want to know for a specific situation, refer to the aisc manual.
aws d1.1:2002 fig 3.3 lists prequalified partial pen butt weld root openings as 0 to 1/16" for up to 1/8" base metal thickness and minimum half the base metal thickness for up to 1/4" (which is the maximum metal thickness that is prequalified). these are for smaw.
full pen butt welds are listed in figure 3.4 and require backing or backgouge (smaw, fcaw, gmaw, saw). most of these list the root opening as the base metal thickness or less.
you may want to post your required joint in the aws or welding sections.
zcp
when you say "square"... are you talking about square groove weld, or are you talking about a hss box shaped   
i think he means square groove welds.
for full strength splices of closed sections, internal backing strips are necessary.
letting the fabricator deal with the type welds you need is not always good enough.  the designer should require the welds to be shown on the shop drawings for review.
on our plate welds, the joint design is done to try to minimize time required and distortion; it's a non-essential variable.  asking the people who actually do the welds can be informative.  ditto with the bevel details.
"letting the fabricator deal with the type welds you need is not always good enough.  the designer should require the welds to be shown on the shop drawings for review. "
i agree on both. let me clarify.  i was speaking about whether or not to call out the gap size on the flagging.  i would expect that you would flag and call out the type and size of weld, but not the gap unless there was a basis for not using a aws prequalified weld or only using a certain aws prequalified weld procedure.