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RE: Beam Splices

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Alden,
 
The ideal place for splices is in near zero moment areas.  The idea behind that is to make the moment carrying requirements of the splice as minimal as possible.  I am unsure as to whether the dimension you give are from the ends of the beams or the depths of the members. 
 
Assumptions:
   - dimensions are the member and/or splice depth
   - beams are solid web built up members (fabricated from plates or bar stock) with the flanges welded to the web
   - using splice plate connections (typ. bolted)
 
The fabricator's shop and equipment can often detemine what is reasonable... for a lot of (automated) shops beam depths over +- 60 to 70 inches may require manual welding.  Conrac or pull through welders typically can not weld beams deeper than this.  If the beam depth is over 6' then you might consider open web frames or more interior columns as cheaper alternatives.
 
Other considerations for splices and splice locations:
1) make sure beam sections are not too heavy for the cranes to be used for erection (or typically available)
2) make sure beam sections are not too flimsy for erection (doesn't sound like the case here)
3) deep bolted splices may require additional bolt rows just to "flatten out the splice plate".  Large spaces (>24" to 26") could allow the splice plate to be cupped between bolt rows.
4) keep the beam lengths consistent with available material... since most plates or bar stock are available in 20' or 40 ft lengths try to avoid lengths like 21' and the like.  It might be cheaper material wise to beef up the splice (for additional moment and shorter length) then to weld the extra web and flange sub-assemblies together.
5) keep beam length reasonably long... (sounds wierd... i.e. don't provide (20) 5 ft beam sections for a 100 ft long beam)
6) keep in mind that different load combinations could have different locations for zero moment... try to use the most critical combinations for zero moment areas.
 
Well, my ideas are fading faster than I can type them in so I hope this helps some...
Greg Effland, P.E.
KC MO
 
 
 -----Original Message-----
From: Alden Manipula [mailto:amanipula(--nospam--at)novagroupinc.net]
Sent: Wednesday, July 11, 2001 2:24 PM
To: SEAINT Listserve
Subject: Beam Splices

a recent phone discussion with a steel detailer has arisen some questions i have.
 
i usually locate beam splices in a beam line where the moment is zero, typically it's somewhere around 4'-0" to 6'-0".  but the particular project i was discussing with the detailer has larger spans than what i'm used to seeing and splices came out to be lager than 6'-0", for example, i have one at 8'-8" and a few 7'-0".  the detailer seemed to think these were not pratical locations, ie he's never seen ones this long before.  but maybe he hasn't done a large building yet? 
 
my questions are, am i wrong in placing splices so far?  is there some praticallity issue in regards to erecting a beam line with a splice this large?  any 'rules of thumb' i haven't learned?  is there a maximum and minimum distance in the steel manual?
 
TIA

Alden Manipula
Structural E.I.T.
www.novagroupinc.net