huangyhg

x-bracing connection bolted vs welded
i am curious what the general preference is in connecting x-bracing (tension only) members to gusset plates. the general question is bolted vs. welded. i tend to think that bolts are generally easier/faster to install than welds, and therefore cheaper. if bolts are used, then can they be snug tight with standard holes, or would erection tolerances dictate that they have to be oversize holes and pretensioned bolts (would i have to go so far as calling for slip-critical with faying surface preparation)?
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in my opinion a welded x-brace should be less work and therefore cost less. a bolted connection requires detailed layouts of holes in both the angle and gusset plate. sometimes during the installation stage gusset plates need to be trimmed in order to fit up in with other
we generally use a single bolt for erection purposes and then weld.
as a rule of thumb, welded for shop connections and bolted for field connections.
i must agree with dbuzz. field welding is expensive and i am always concerned for the quality. this is due to the varying and hard to control factors.
shop weld and field bolt is good advice.
regards,
lutfi
dbuzz and lutfi - are we talking about the same thing? i agree that in general shop weld and field bolt is the way to go, but i'm not talking about something like welding double angle shear connections at each end of each beam to columns. i'm only dealing with x-bracing connections. if you are using bolts for x-bracing connections, do you use oversize holes, and do you specify anything more stringent than snug tight? if i were using the brace as a compression brace, i think (not everyone i talked to agrees on this) it would fall under the heading of "built-up
per asd oversize round holes are for use with slip critical connections. slotted holes normal to load direction are allowed but in my opinion of little practical use because they don't help the fitup problem. while some reaming etc. is permitted during fitup, bigger holes will require bigger bolts.
-mike
i don't think there really is a better way, but just depends on the fabricator/erector preferences.
if you use bolted, keep in mind that braces are often fabricated intentionally short by a small amount. i think 1/16" is common. somebody pointed out a mistake(?) that i made once by showing oversized holes to help with fitup. the supposed mistake was that the oversized holes negated the intention of the short brace fabrication. not sure either way, but it's worth mentioning because some of the others typed about oversized and slotted holes.
dbd
as someone else mentioned, welding the x-bracing works well because when they are off by 1/2" it is no problem at all. we use welded x-bracing and never have problems with it. it is usually an easy weld as well.

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