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Span charts for girders for ceiling only?

M

michaelj

Member
Joined
Oct 21, 2009
Messages
27
Location
North Georgia
Where could I find a span chart for a girder for a ceiling only? the situation is the two ends of a tray ceiling, girders span across a room with ceiling joist between no roof load just attic above. Thanks
 
The awc spancalc is only good for joists and rafters. I wouldn't mind if folks sent in enough requests for them to expand on that to include some for girders and headers... attn Buddy Showalter. Their WCDD manual would probably be the closest thing, it'll be under their free publications download list
 
DRP said:
The awc spancalc is only good for joists and rafters. I wouldn't mind if folks sent in enough requests for them to expand on that to include some for girders and headers... attn Buddy Showalter. Their WCDD manual would probably be the closest thing, it'll be under their free publications download list
Click to expand...
A girder is a beam and there are many beam span programs and charts, the problems occur when there are point and compound loading, and the person using the chart or program don't know what they are doing....
 
A girder is one type of beam, just as joists and rafters are types of beams. Having a program from a code referenced authority would be helpful, just as their spancalc carries some authority and links in very well with the parameters of the prescriptive tables. I suspect it would also help avoid having people repeatedly post the wrong calculator for the use requested. What I have asked for in the past is to have the contents of awc's DA6 converted to a series of online calcs. Good project for engineering students, just as their spancalc was.
 
I agree with your thoughts o the DA6....to a point. If it's used the way you've stated. Beyond that it could turn a lot of people into "Engineers" Could be fatal.
 
Notice, twice on this thread folks have posted links to joist and rafter info for a girder. It doesn't get much more dangerous than that. A list of calcs for different situations will show that there are indeed different conditions. From there hopefully either someone will use the right calc or realize they need to get someone who can tell the difference. This info is more readily available for engineered wood and steel than solid sawn lumber. The lumber industry doesn't seem to do as good a job promoting the uses of commonly available dimensional wood.
 
I use the Forte program but only for personal use, never to prescribe a size if possible. That is a job for an engineer. If the beam can't be figured out from the code tables (which I think are really bad) I also have a great table from an engineer which will give allowable lbs and end reactions for given spans and members (Uniform loads only) and of course one needs to be sure of how to calculate the tributary loads to begin with. It stops at 14' so typically if I encounter a beam with much load, greater than 14' it will usually trigger the need for a DP automatically. Unfortunately I am encountering lots of those spanning over great rooms, used to carry purlins or rafters. They are allways undersized by at least 50%.
 
By the person who decided what beam to use. Usually the builder. So far none of the projects here are engineered and the builders are using long length clear span beams, 16' or more to carry too much load based on the uniform design loads. I have yet to find a 2 ply 2x10 that didn't end up way under-sized for the application after analysis. I run into the "we've been doing it that way for 30 years" argument every day but unless my calculations are way off the numbers just don't add up. I wish they would.....my life would be a lot easier. Unfortunately most of my time is spent trying to teach someone how a beam is sized, what tables to use etc. only to learn they just want someone else to do that for them.
 
Most folks are pretty lazy, they don't really want to know how to fish, they'd just as soon you land "that fish" for them. But it is wrong IMO to throw everyone into that bucket. The situation you describe is all too common and I run into it from builder's, designer's and rdp's... part of the reason I like to be able to check. The more we all know the fewer mistakes slip through. Last week I had a conversation with a local builder wanting to replace a 6x16 glulam with a glued and screwed stack of 2x6's to save a few bucks. Happily he was pretty sharp once we talked a little bit. I had to put my foot down hard last year on a designers work. A ridgebeam was req'd and he had way too little up there. When I wouldn't budge he finally called his engineer and it was as I had calculated on my spreadsheet. This year it was an RDP muffing the roof load, just an oops but what if I hadn't checked it? If the calcs were readily available from a referenced provider it would help.
 
I agree with DRP...lazy builders not wanting to spend money on rdp, not understanding conventional vs. unconventional, etc.
 
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