# Floor Girder Problem?



## Jobsaver (Jan 12, 2011)

Why is there no span chart for a built-up girder comprised of (3) 2x6's, or (4) 2x6's.

Single-story pier and beam having 20' building width. Piers are constructed of double 8x8x16 cinderblock, solid grouted, 7' oc. Longest span between pier edges is 68".

Table R502.5(2) allows for a minimum girder of (2) 2x8 to span 5-9.

The circumstance is that the builder set the foundation up for a 5.5" height girder.

Solution A: Lower pier height to accomodate 2x8's.

Solution B: Build-up sill plate 1.75" so top of sill will match 2x8 girder height.

Solution C: Build-up multiple ply 2x6 girder.

How many 2x6 plies?


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## fatboy (Jan 12, 2011)

Not specified in the IRC = engineer's analysis for the 2 X 6 built-up girder. Do you have anchor bolts to accomodate an additional 1.75" sill build up? If not, again, engineering solution. About the only non-engineered solution would be to lower the pier, but solid grouted? Ugh, won't be fun.


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## GHRoberts (Jan 12, 2011)

Perhaps you can notch the ends.

But it should be easy enough to use a thicker bottom plate. Nail 2 2x's together and drill the top one for the nut, bottom one for the bolt.

---

Is this an inspection or your construction? Inspectors should not be offering solutions.


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## DRP (Jan 12, 2011)

AWC's (AF&PA) Wood Structural Design Data;

http://awc.org/technical/spantables/index.html

This section of the multi part download would include the tables for that span;

http://www.awc.org/pdf/wsdd/c2b.pdf


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## KZQuixote (Jan 12, 2011)

GHRoberts said:
			
		

> Perhaps you can notch the ends. But it should be easy enough to use a thicker bottom plate. Nail 2 2x's together and drill the top one for the nut, bottom one for the bolt.
> 
> ---
> 
> Is this an inspection or your construction? Inspectors should not be offering solutions.


Sill plate is PT. Doubler sill plate is a regular 2X6. Put a coupling nut on the AB and run a 1/2" bolt down into the coupling nut through the doubler sill.

Bill


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## KZQuixote (Jan 12, 2011)

> Originally Posted by GHRoberts. " Inspectors should not be offering solutions".


 This is the real world right? Where folks try to get along and find solutions that allow all the parties to save face.Bill


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## GHRoberts (Jan 13, 2011)

KZQuixote said:
			
		

> This is the real world right? Where folks try to get along and find solutions that allow all the parties to save face.Bill


I agree with you. But tell me "Who is responsible when the inspector gives 'wrong" advice?"

---

I did s search using "wood girder span tables" A responsible source gives the following allowable loads for girders spanning 8':

4x6 223 pounds/ft

6x6 237

2x8 412

It would appear that 6" of depth is not going to do it.


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## Jobsaver (Jan 13, 2011)

Thanks for the ideas. Good ideas for anchoring the double plate GH and Bill.

DRP: I looked up both of these charts before posting. I did not find them helpful. How does one go about applying these particular documents to the problem? To be clear, I am asking this question earnestly.

Also, puzzle me this everyone: 2006 IRC TableR502.5(2): One floor only:

How is it that a 2-ply 2x8 girder will span 5-9, a 3-ply will span 7-2, but a 4-ply will only span 5-10?

Next, technically, the code allows us, _for widths between those shown_, to interpolate spans. Now, I don't interpolate, I decipher (think Jethro Bodine - Beverly Hillbillies, it is what we do in Arkansas). My deciphering is as follows:

One can increase the span by 24.5% by adding one additional ply to a 2-ply 2x8 girder (5-9 to 7-2). One can increase the span by 25% by adding one additional ply to a 2-ply 2x10 girder 7-0 to 8-9.

It stands to reason that one can increase the span by about 25% if one adds one additional ply to a 2-ply 2x6 girder, and, for damn sure, if one adds two additional plys to a 2-ply 2x6 girder.

In my example in the OP, I need to get from 4-6 (2-ply 2x6 girder) to 5-8, a 25.7% increase in span.

Comments?


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## DRP (Jan 13, 2011)

George, It would depend on load, span and material. Notice the species in George's post is unknown, white oak or balsa? Span you just quoted is 8' where the OP is spanning <6'... quite a difference.

your idea of notching would be a prescriptive solution as would the WSDD if the load is within the table's range.

Checking section properties;

section modulus of a double 2x8-26.28"^3

                      of a quad 2x6- 30.25"^3... stronger in bending if identical grade

Moment of inertia of a double 2x8-95.27"^4

                         of a quad 2x6- 83.19"^4... greater deflection if identical grade is used

The codebook table would be using the weakest species combination listed, AR is SYP country.

I just posted on top of you jobsaver, I'll get back with what I can. Is this a center girder under the floor only?


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## Jobsaver (Jan 13, 2011)

DRP said:
			
		

> I just posted on top of you jobsaver, I'll get back with what I can. Is this a center girder under the floor only?


Center girders. Assume a uniform load. (Aren't these the assumptions of Table R502.5 (2)?).

I can do the math using the tables provided, but I am unclear how a multiply 2x6 built-up beam relates to, say, a 6x6 on the span chart?

Interestingly, I am looking at a 1989 CABO One and Two Family Dwelling Code, Table R-602.2.1a, Allowable Span for Girders Supporting One Floor Only, and Table R-602.2.1b, Allowable Span For Girders And Required Size Of Columns And Footings To Support Roofs, Interior Bearing Partitions and Floors.

Note: One problem with blogging about engineering principles is that it seems that every other sentence one begins to type as a statement ends up being another question.


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## DRP (Jan 13, 2011)

In some surroundings it never hurts to clarify that one is speaking earnestly  

I've been typing and have just checked for your response so some of this duplicates what you have confirmed.

My '06 reads 2 ply 2x8- 5-9, 3 ply 7-2, 4ply 9-0... either a misprint in yours or you jumped a line while reading?

Assuming this is a center girder supporting one floor only... the description of the table.

The girder is supporting halfway to the exterior wall on the left, 5', and halfway to the exterior wall on the right, 5'. The total width of floor being supported is 10'. The codebook lists the load as 40 psf plus the dead load of 10 psf...50pounds per square foot total load.

50 psf x 10' of tributary width= 500 plf, pounds per lineal foot, bearing on the beam.

The girder is spanning roughly 6'... 6x 500 lbs=3000 lbs total load

Go to the table I posted, run down to 6x6... 4 plies (6" w x 5.5" tall) is greater than a 6x6 (5.5"x5.5") and we are getting some increases for multiple members and dimensional lumber, in other words this is quite conservative.

Run across the table until w>500 and W>3000... second column. Look up , you need a species and grade with Fb >1000. Look down in that cell E needs to be >.981, Shear >76psi

Go to Lowes and pick up some #2 SPF... from the awc- Fb-1308, E-1.4, Fv-135.

I'd slide over to the SYP pile #2 Fb-1437, E1.6, Fv-175

Now go back to the WSDD 6' span table, look at the 4x6 (3.5" x 5.5") Look at the Fb 1600 column, a 3 ply is 4.5"x5.5". That would work in SYP, you can ask for #1 if you want to clearly pass without cyphering further.

This is actually the way the old CABO 1&2 family table was set up. I've tried to keep this prescriptive, we can discuss how to check it using accepted engineering practice if you'd like. Make sense?


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## DRP (Jan 13, 2011)

LOL, just saw your edit. in the CABO look at S=10', 40 psf...6-6"

Do you have footnote 3 in your edition?


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## GHRoberts (Jan 13, 2011)

DRP said:
			
		

> George, It would depend on load, span and material. Notice the species in George's post is unknown, white oak or balsa? Span you just quoted is 8' where the OP is spanning <6'... quite a difference.


My post was to indicate that according to some sources the benefit of multiple plys seems to diminish quite quickly. And that 8" depth seems to be beyond the reach of multiple plys of 6".

I am very happy to accept that the obvious engineering that says 3 plys will support 50% more load (plus the 15% property increase) than 2 plys. But there appear to be engineers who use the same engineering references that do not rely on the obvious engineering and get a much different answer.


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## dhengr (Jan 13, 2011)

Jobsaver:

Part of the reason that there isn’t a table for various built up girders made up of multiple 2x’s is that fastening them together to truly act as a unit becomes a little tricky.  And, we also start to worry that there might be unanticipated loads on them, something other than a nice uniform load in lbs./ft. from the joists, or that the joist loading on one member is not being properly transferred to the other members of the girder.  It just really becomes difficult to tabulate everything, to fit every situation, under every circumstance, as more possible variables enter the picture and should be considered for a proper design.  I haven’t had time to study every detail of DRP’s posts, but they certainly look about like the advice I would give.  If you know what you are doing with section properties, stress grades of the lumber, accumulation of loads on the girder, any special loading considerations, deflection considerations, you can do just what he is suggesting.  The trick is to watch out for any exceptions that the tables don’t cover, or don’t allow for.  Watch out for notching any members to fit, that’s a very special case and generally not allowed, and follow directions for nailing the girder together.

What are your loads on that girder?  Certainly, they will be at least 10' of floor area (width), unless the fl. joists are continuous over the girder, then the girder loading will be greater.  Is their a wall line over or near the girder, what’s its loading per ft.; and walls crossing the girder are concentrated loads on the girder, do these walls carry any ceiling loads, attic loads, or roof loads?  Any jamb loads from 1st fl. openings are concentrated loads on or near the girder, which really can’t be accounted for in a simple tabulation.  Once you have a firm handle on these types of questions, and there may be others which a plan review would reveal, you can take a first shot at the problem (generally a conservative approx.) by looking at the joist tables.  Table R502.3.1 (2) shows a #2 SPF 2x6 will span 10'-3" and carry 50#/sf or 50#/lf at 12" spacing.  And, as a rule of thumb 3 or 4 of them will carry a proportionally greater load.  Actually, you see that a #3 SPF 2x6 spaced at 24" is carrying 100#/lf (that’s 2 x 50#/sf) and that’s closer to your span length.  You should be careful what controls your design, bending, shear or deflection, and duration of loading should be considered too.  So, while this is a reasonable first approx. as a way to look at your problem, you should be careful that there is nothing which prevents this from being reasonable.  How do you tie these girders together over the piers, or are they continuous over the piers, and that’s a whole different problem, although not impossible either.

Also, what is the condition of the bearing surface on the conc. blk. piers and how do you tie the girder down to the pier?  You say double 8x8x16 blk. pier; is every other course laid perpendicular to the previous course so you have a bonded pier, or do you really have two piers side by side?


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## jar546 (Jan 13, 2011)

Adding layers of nominal lumber to increased width does not help as much with deflection as adding depth which is probably why there are limitations on layers in the prescriptive charts


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## DRP (Jan 13, 2011)

It actually has to do more with what dhengr said, getting the girder to act as a unit... which really only matters if the joists are side hung. If the joists are resting on top I could go wider than the table, with engineering, not efficient, but efficiency isn't the controlling requirement here. If the joists are on top the girder simply needs to be attached together but not neccessarily "knitted" into a unit.



> My post was to indicate that according to some sources


"or in accordance with AF&PA/NDS"

 I've been referring to that source for my info as per code.

The rest of the concerns are addressed by reading the tables, code and NDS.

You may notch a girder, if you do I would follow the NDS and traditional practice, slope the notch rather than making a sharp 90* corner to avoid splitting at that re-entrant corner.

If you are worried about acting as a unit it can be a solid sawn 6x6, just be aware that design values change to heavy timber above a 5x5... a #2 6x6 carries lower design values per square inch than a dimensional 2x6.


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## Jobsaver (Jan 13, 2011)

DRP said:
			
		

> LOL, just saw your edit. in the CABO look at S=10', 40 psf...6-6"Do you have footnote 3 in your edition?


3. Spans and girder sizes may be computed independently of the above table when designed in accordance with accepted engineering practice and substantiating data are provided and submitted as required.

Yes. I read footnote 3 to say; Do the math to determine all imposed loads on each individual girder, determine deflection per species, etc. . . . as dhengr outlines in his post:



			
				dhengr said:
			
		

> . . . becomes a little tricky . . .  start to worry . . . It just really becomes difficult to tabulate everything, to fit every situation, under every circumstance, as more possible variables enter the picture and should be considered for a proper design.  . . . , you can do just what he is suggesting. . . . The trick is to watch out for any exceptions that the tables don’t cover, or don’t allow for. If you know what you are doing with section properties, stress grades of the lumber, accumulation of loads on the girder, any special loading considerations, deflection considerationsWhat are your loads on that girder?  Certainly, they will be at least 10' of floor area (width), unless the fl. joists are continuous over the girder, then the girder loading will be greater.  Is their a wall line over or near the girder, what’s its loading per ft.; and walls crossing the girder are concentrated loads on the girder, do these walls carry any ceiling loads, attic loads, or roof loads?  Any jamb loads from 1st fl. openings are concentrated loads on or near the girder, which really can’t be accounted for in a simple tabulation.


If you know what you are doing with section properties, stress grades of the lumber, accumulation of loads on the girder, any special loading considerations, deflection considerations . . . I don't.



			
				GHRoberts said:
			
		

> My post was to indicate that according to some sources the benefit of multiple plys seems to diminish quite quickly. And that 8" depth seems to be beyond the reach of multiple plys of 6".I am very happy to accept that the obvious engineering that says 3 plys will support 50% more load (plus the 15% property increase) than 2 plys. But there appear to be engineers who use the same engineering references that do not rely on the obvious engineering and get a much different answer.


Are you happy to accept that 4 plys will span the extra inches in the equation at hand?



			
				jar546 said:
			
		

> Adding layers of nominal lumber to increased width does not help as much with deflection as adding depth which is probably why there are limitations on layers in the prescriptive charts


.Still, it would be convenient for me right now if the tables did include the same calculations for muti-ply (x3 & x4) 2x6's, as they do for multi-ply 2x8, 2x10, and 2x12.

Somewhere between the engineer, who knows what reference material and what math to use to solve equations, and the builder, who says, "this historically works", lies _this_ building inspector, who has to try to explain in plain language why doubling the size of a thing doesn't necessarily add a bit more span to it.

Thanks all for the perspectives. I need to go back to school so I can better help fix the residential code in places that matter.


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## GHRoberts (Jan 13, 2011)

"Are you happy to accept that 4 plys will span the extra inches in the equation at hand?"

(yes) I am happy to accept the engineering that DRP outlined. It is what I would do. (I did not read his post with any more care than to determine that his approach is the same as mine.)


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## jar546 (Jan 13, 2011)

If there is no roof load and just a 40 lb live load + 10 lb dead load, If your tributary load is only 10' and your span is only 5.67 feet, (3) 2x6 will work fine.


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## DRP (Jan 13, 2011)

I agree,

This is my "spreadsheet" for simple beams and might help explain things one step deeper jobsaver. It's just the AWC beam design formulas written into a simple script;

http://www.windyhilllogworks.com/Calcs/beamcalc.htm

Enter:

Load 3000 lb

Span 68"

Width 4.5"

Depth 5.5"

Fb 1308 - #2 SPF

E 1.4

Fv 135

Click "show result"

Works just fine, deflects  1/8" + a blond one under the entire load.

Now for grins, back out the 4.5" width and insert 1.5", back out the 5.5 depth and insert 9.25"... we're trying a single 2x10. Watch the deflection number as you click "show result". Less timber and the deflection dropped about in half. Remember Jars comment above? Old carpenters say "deeper is cheaper"

Oh, if they want to use a solid 6x6 timber it'll need to be a #1 in SYP


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## Jobsaver (Jan 13, 2011)

DRP said:
			
		

> a blond one


LOL!

Thanks again for all of the comments. Also, DRP, for the beam calc link (cool!).


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## Jobsaver (Jan 14, 2011)

GHRoberts said:
			
		

> Is this an inspection or your construction? Inspectors should not be offering solutions.


The reality is that I have lived in this community as a working adult in trade-oriented work for thirty years. People ask my advice, and I believe it is my civic duty and job to give it, carefully.



			
				KZQuixote said:
			
		

> This is the real world right? Where folks try to get along and find solutions that allow all the parties to save face.


And, the building community is happy to call when they discover a problem, in order to correct the problem, before the problem becomes a bigger problem. Virtually always, it is a given at this point, that a mistake has been made in the "design" of the construction. So, Bill is right. It is about helping people with whom one has a good working relationship save face in light of an error they made, without compromising the integrity and intent of the code, permitting, and inspection processes.



			
				GHRoberts said:
			
		

> I agree with you. But tell me "Who is responsible when the inspector gives 'wrong" advice?"


Not having a design professional to assume responsibility, the permit holder is responsible; It is no different when an inspector misses something entirely when performing an inspection. The inspector loses credibility, but the permit holder is still responsible for his project. This is one of the reasons we strongly encourage individuals "building thier own home" or project to cause the trades they are hiring to pull the permit, unless, they are truly willing to accept full responsibility as thier own contractor.

The circumstances that caused the establishment of this thread:

One of our very reputable builders made a mistake, confusing what used to work under the SBCCI codes he worked under for many, many years, (see the CABO code referenced earlier in this thread), but that is not in any obvious way prescriptive since the regional codes were consolidated into the IRC. He set up a foundation for 2x6 girders.

Upon working with his framer, another very reputable tradesman in this community, to put together the framing package delivery, the "mistake" of not being able to meet the prescriptive requirements of the IRC girder table was discovered. An hour later, the builder called me and explained the situation looking for possible solutions. Of his own accord, he ruled out sideloading the girders instead of toploading them as planned, (hence I did not even mention this option in the OP).

As is my custom, I put forth some effort to offer solutions that I will accept as a building inspector, to remedy a specific one-time problem, with the caveats that this particular solution *will not become a new construction practice in my ahj, and that I am offering my best advice only as a Building Inspector, not as a Design Professional.* I try to do enough research to the best of my ability and means, to only offer consevative solutions that will fulfill the intent of the code.

Also, my Department Head and direct supervisor is a P.E. She directs me to carry on in my usual manner in which she has placed her confidence.

The folks that hire and use the inspectors that respond in this forum have placed a confidence. And, as inspectors, our reputations and credibility are at stake. This is a powerful incentive to carefully proceed to offer good advice where it counts, in the field, onsite, talking to the men and women that build things for a living.

This forum and the people responding here comprise another great resource for my town. Thanks.


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## dhengr (Jan 14, 2011)

Jobsaver:

I applaud you for trying to be helpful and for trying to solve a builder’s problem rather than just red flagging it and walking away with a ‘when you get it fixed, call for another inspection, and we’ll see.’  But, he shot the bull, you didn’t, and unless you know what you are doing you probably shouldn’t stick your neck out a mile to solve his problem, you might get accused of committing Engineering, and we all know what a crime that can be.  Alternatively, it seems like a great working relationship within your JHA, when buildings will come to you having discovered their own error, rather than trying to hide it and hoping you’ll overlook it, or it’ll go away.

Your problem isn’t rocket science, it’s a fairly clean and simple engineering problem, and we about beat “designed in accordance with acceptable engineering practice” to death in another thread, and unless you know what that is and how to do it, you might not be doing it acceptably, and thus probably shouldn’t be doing it.  The loads aren’t tough math, they are just a more complete accumulation and understanding of the loads and load paths, concentrated loads, etc., a thorough mind set during that process.  Bending moments, shears, bending and shear stresses and deflections are real engineering, but still fairly elementary engineering, for your problem.  And, one way to start to approach this problem is as DRP, George and I have suggested, by using tables that were not exactly done to meet your problem.  But, here too, the trick is that you have to know what you are doing, you have to know about how the tables were developed; in particular, any limitations or exceptions or special considerations.  Most of these tables are for uniform loads only, because any concentrated loads can be located anyplace on the beam and can have a significant affect on the beam’s design.  DRP has done a very nice job of laying out the basic steps for approaching your problem, but again, the disclaimer at the bottom of his spreadsheet is pretty important to understand.  It isn’t usually the well laid out calculation steps in the spreadsheet that go wrong, it is the input and assumptions made in compiling the input or the interpretation of the results.  And, having the experience and intuition to know when an output answer just doesn’t look right.  To pull DPR’s leg a bit, I usually don’t worry about more than 4 or 5 decimal places for stresses and defections, since I’m not that sure of my load assumptions.  You never did comment on any unusual loadings, concentrated jamb loads, wall loads and the like, and that’s important because they are deviations from what the tables or DRP’s spreadsheet are calculating or are based on.  And, then the assembly and installation of the girder become an important issue too.  An interesting exercise on your part, now that you have DRP’s spreadsheet, might be to go back to the joist or girder span tables and see if you can agree with their results for loads and span lengths, etc. and see which stress or deflection controls the design, and report back to us.

DRP.....    Several of your posts here are really a nice presentation of this problem, from a builder’s perspective.  You are making me a convert, less of a doubting Thomas; but we’ll still have to talk a bit more about long shed dormers, without much roof sheathing and without rafter ties.  I think we could work together quite well, and understand each other in the process.  It’s usually a pleasure working with builders who have a bit more than the normal builder’s intuition about why something works or what size a beam has to be.  I said before that I thought you got screwed on your oversized cedar deck beam, and now I really believe that if you applied the same finesse to that problem as you have here.  If you showed me that, as a BO, I would not have made you get an engineers stamp on it.  The BO probably didn’t know as much about the problem as you do, so then he didn’t know what to do if it didn’t exactly follow the code tables.  Your post #20, shows exactly the process the engineer would normally go through with the 2x10 and 6x6 as possible options, to try to hone in on a best solution.


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## jar546 (Jan 14, 2011)

This is what the "engineers" gave to me.  Comment?

http://inspectpa.com/download/GirderSample1.pdf


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## GHRoberts (Jan 14, 2011)

jar546 said:
			
		

> This is what the "engineers" gave to me.  Comment?http://inspectpa.com/download/GirderSample1.pdf


Looks like you typed in the proper loading.  I assume the results are correct. I don't like the format, but ...


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## dhengr (Jan 14, 2011)

Jar:

Given your twitter like brevity, what comments, by whom?  That looks like just another way to skin the same cat.  But, the engineers didn’t really give you this printout did they, they licensed the program to you, with some instructions about how to use it, and with some disclaimers too, right?  Is there some mysterious difference btwn. pages 1 & 2 of your attachment, I couldn’t find any?

I keep screaming for a full accounting of the loads on that girder, so far we have the 1st fl. DL (10#/sf) and LL (40#/sf) on two 10' long simple span joists framing into that girder for a 10' tributary width, leading to a 500#/ft. uniform loading on the girder; the joists are not 20' long and continuous over the girder;   and there are no partitions, 1st fl. opening jamb loads, no ceiling, attic, or roof loads being added to that beam; and I doubt that.  Without seeing the plans and having some real involvement in the project, or sufficient experience working with that builder so I know the quality of his work and how he interprets what I tell him to do, I don’t know if I’m getting the full story, and I do know who’ll be hung out to dry if things go wrong.  Because your very own statement, “This is what the “engineers” gave to me.” would me misinterpreted.  I’ll usually give my opinion and general guidance on the problem, as best I understand the word picture that you have presented, but I just can’t (won’t) do real engineering over the internet.

As to your printout, I don’t particularly like the format either, but could probably get used to it after using the program for a while.  I would like to see what you input, it looks like all the answers are there, but I want to study them a bit more before commenting.  That is usually the case with any of the programs or spreadsheets out there, you have to use them often enough to get comfortable with the input and output format, and what you can expect from them.  Also, their limitations, exceptions and the like must be kept constantly in mind when using them.  Your’s or DRP’s might not be exactly the way I’d write the program, or the input or the output, but we should all get basically the same answer to a given problem.  So, now we have the IRC tables for joists and girders, we have DRP’s spreadsheet, and we have your BeamChek v2010 program which purports to comply with NDS 2005, which I don’t have a copy of, but I think I can muddle through, if you guys give me a clue now and then.  I suggest you use your program, just as I did Jobsaver, to work out a few of the tabulations in the IRC joist and girder tables, and lets see how they compare and if we can explain any differences.


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## DRP (Jan 14, 2011)

Jar, nice, I tried the demo a few years ago, nice. Beamchek is more elegant than my efforts but the formulas are the same. It checked allowable compression perp to grain and gave minimum bearing area to avoid crushing the side of the beam. It then adjusted the span length and load to account for half the required bearing length at each end to arrive at the "true" span as per NDS. Curious why you , or it, didn't take the repetitive member increase, it is allowed here.

I was needing something that allowed me to input timbers of many species and sizes. I have a sawmill and one of the most diverse forests on the planet right outside my door. That was the limiting part of the programs I tried and what I and a few others needed. Try figuring a heavy timber barn swapping out a variety of sizes and species at the kitchen table manually. I've done it at a friends kitchen table with 7 kids running in and out, the mill idling in the background and we were trying to resize because the logs were opening up differently than planned. I wrote a few scripts and put them online. If I can get on their computer we can play "what if" a whole lot quicker than punching numbers on a calculator. I've written versions with drop down species lists that then automatically input the design values for common timbers but this is the simplest, so most versatile, we just used it with dimensional lumber, it'll work with lvl's as well.

I believe my program will come up more conservative on joist or rafter span lengths that are limited by deflection due to the fact that I am running the "pass/fail" on total load rather than LL only. Beamcheck should click right in with the awc spancalc. I can manually change the input to LL only and run again if I want to push the line, I don't feel a need to tell everyone that. If you're using this for conventional joists and rafters you're backing up to begin with. I let the javascript run out to the limits on decimals for simplicity, it could round but personally I just ignore beyond thousandths and convert to fractions in my head. You can view the code by right clicking a blank area on the calc and then click "view source".  I bang nails for a living, feel free to modify the code and post your improvements.

Getting back to the original problem. If you run some checks against the girder table you'll see that a triple 2x6 is running a good bit less conservative than their trend or than a solid sawn 6x6 with the WSDD grade specs. I suspect they are leaving some wiggle room for the unknown potential conditions dhengr described and for the possibility that the girders in the prescriptive table may be side loaded. The math can be shown to work at 3 ply but there's certainly nothing wrong with 4 ply, there is no need to pass by the skin of our teeth.

Dr's Woeste, Bender and Loferski at VA Tech taught a short course on the '05 NDS and mixed in some other short topics, one was on floor vibration frequency... annoying floor vibration. The combination of joists designed to the limits and exacerbated by girders near the limits can produce some really annoying floors. When you run those calculations a spongy girder can easily screw up an otherwise acceptable set of joists. They suggested designing girders for L/600. Assuming 2x8 joists this floor is ok with either 3 or 4 ply vibrationwise since the spans are short but it did pick up >3 Hz going from SPF and 3 ply to all SYP and a 4 ply girder, a noticeably "tighter" feeling floor.


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## GHRoberts (Jan 14, 2011)

DRP said:
			
		

> I am running the "pass/fail" on total load rather than LL only.... annoying floor vibration.


One nice part of being an engineer is that you can write up a spread sheet to "do it your way."


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## Jobsaver (Jan 15, 2011)

GHRoberts said:
			
		

> but ...


But . . . what?



			
				dhengr said:
			
		

> Is there some mysterious difference btwn. pages 1 & 2 of your attachment?


I looked at the second page expecting to see calcs for a 4-ply beam?



			
				dhengr said:
			
		

> I keep screaming for a full accounting of the loads on that girder.


Respectfully, why?  The balance of prescriptive spans, combined with the other elements prescripted in the IRC are thought to be conservative enough not to worry about a full accounting of the loads on an individual girder. In other words, if the codebook formulas are derivative of conservative engineering, then it is not necessary to have a full accounting of the loads in order to use the tables. I always imagined that when engineers, architects, and other design professionals were designing framing elements for a home, something as basic as described in this thread, that even you guys turned to span charts here and again.

Note the following:



			
				Jobsaver said:
			
		

> It stands to reason that one can increase the span by about *25%* if one adds one additional ply to a 2-ply 2x6 girder, and, for damn sure, if one adds two additional plys to a 2-ply 2x6 girder. In my example in the OP, I need to get from 4-6 (2-ply 2x6 girder) to 5-8, *a 25.7% increase in span*.





			
				Jobsaver said:
			
		

> the builder, who says, "this historically works"





			
				DRP said:
			
		

> The math can be shown to work at 3 ply but there's certainly nothing wrong with 4-ply, there is no need to pass by the skin of our teeth.


It seems to me that we are all saying the same thing. And, that every party is reaching the same conclusion: A 3-ply girder will probably work okay, but it is close, and depending on where the walls are . . . you might want to make it a 4-ply just to be sure.


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## jar546 (Jan 15, 2011)

In all actuality and in real life, the poor planning of the masonry contractor would have to bear responsibility for the costs to be incurred for engineering services if they want to build outside of the prescriptive code requirements.

I would need a stamped spec sheet from a PE if they did not want to comply prescriptively.  That is truly the bottom line.


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## GHRoberts (Jan 15, 2011)

jar546 said:
			
		

> I would need a stamped spec sheet from a PE if they did not want to comply prescriptively.  That is truly the bottom line.


As a "PE" I do not work for the AHJ. I provide information to my clients. That information is never stamped. My clients have the option of passing the information on to the AHJ if they desire. (Unless I am doing the actual physical construction the engineering is for "informational" purposes only.)

I believe the code requires "engineering" not work by an engineer. Certainly not work containing an engineer's "stamp."

---

The nice part of engineering is that anyone can do it for themselves. Most people don't have a "stamp."


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## jar546 (Jan 15, 2011)

Little thread drift.

Why I like BeamChek V2010:

1) OK so it is relatively easy to use but relative is a relative word.  I still find myself calling up the experts to verify I am inputing the correct data

2) I get updates about 3 times a year as the manufacturers specs change which make for better accuracy

3) Just about all manufacturers are on there.  Have yet to not have an LVL make/model present

4) We can look at heavier solid lumber such as 4x6, 6x8, etc

5) It does steel beams

6) It does more than just simple spans

7) It can do concentrated loads

8) It is an all around versatile program

Now WHY I we use the program (this is where I expect to be flamed)

1) To check submissions that are not prescriptive yet come from an architect and not an engineer.

2) For my own personal enjoyment.

Here is an example of a recent use:

We had a recent submission for a 24' wide ranch home with clear span roof trusses.  The main girder in the basement was specified by the architect as a (3) 2x10 spf with 1/2" ply in between.  The vertical support posts were 9'5" apart.  The bedrooms were split up by bathrooms, hallway and a laundry room so there was no particular area where it was all bedrooms.

Table R502.5(2) Prescriptively shows that this beam is inadequate for supporting 1 floor whether he attempts to reduce to the 20' width column, bump up to the 28' column or interpolate in between.

I cannot verify what the plywood will do, especially when it is not prescriptive and there will be obvious joints not over supports for this multi-span.  Bottom line, I cannot take that into consideration.

To give the architect the benefit of the doubt, I inputed the girder he planned into BeamChek  and it still failed.

When I sent the plan review back, he argued that the prescriptive table does not include 24' wide and he just put this in another town with no problems during plan review.  I told him that his problem was beyond the prescriptive code and that I ran it on beam check to see if it would pass and it of course failed.  That did not stop the argument from him so I said to either change the beam to meet the code prescriptively or hire and engineer and provide a stamp and calculations for our records.

Basically, I just wanted to see how close the prescriptive tables were and also use it to re-enforce my decision since I was dealing with a DP.

BTW, he later submitted the same plan to another town that used me to do the plan review and he never learned his lesson and failed again.


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## jar546 (Jan 15, 2011)

GHRoberts said:
			
		

> As a "PE" I do not work for the AHJ. I provide information to my clients. That information is never stamped. My clients have the option of passing the information on to the AHJ if they desire. (Unless I am doing the actual physical construction the engineering is for "informational" purposes only.)I believe the code requires "engineering" not work by an engineer. Certainly not work containing an engineer's "stamp."
> 
> ---
> 
> The nice part of engineering is that anyone can do it for themselves. Most people don't have a "stamp."


George, you are really working hard to find something to be a detractor about, huh?

BTW, I don't care who hires or pays the PE or who the PE is working for as it is the permit applicant who must submit it to the AHJ before work can continue or begin.


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## GHRoberts (Jan 15, 2011)

Jobsaver said:
			
		

> But . . . what?


The "But" indicates it is not up to me to accept it or reject it.

I am happy with a list of beams and loads and the word "OK" by each. That is all I ever show.


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## GHRoberts (Jan 15, 2011)

jar546 said:
			
		

> George, you are really working hard to find something to be a detractor about, huh?BTW, I don't care who hires or pays the PE or who the PE is working for as it is the permit applicant who must submit it to the AHJ before work can continue or begin.


You said you require an engineer's stamp. Show me the code section that requires an applicant to provide a stamp.

----

I am amazed that you admit you don't know how to enter data into Beam Check, but you accept the results you get from doing so.


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## Jobsaver (Jan 15, 2011)

jar546 said:
			
		

> I still find myself calling up the experts to verify I am inputing the correct data.





			
				GHRoberts said:
			
		

> I am amazed that you admit you don't know how to enter data into Beam Check, but you accept the results you get from doing so.


Given a choice, should I be counting on someone, I'd put my confidence in the man that is not afraid to ask a question, and understands the meaning of a sentence.


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## DRP (Jan 16, 2011)

We've shown that the engineering on this is pretty basic, we have general agreement on methods, results and interpretation of the results. Code interpretation is a bit more mixed. I don't feel a need to make the contractor get a stamped design for a simple girder. Jar shows that blindly trusting a RDP's stamp might not be wise. Knowing how to design a simple beam is much more useful for all parties. Out of the box software, or using my calc has it's benefits, it gets you up and running quickly. It has some drawbacks, you may or may not understand what it is doing. That has been my point in participating in these threads, either sharing what I know or learning from those who know more. I'd be more than happy to continue that part of the discussion. It is counterproductive to decide that we cannot discuss engineering topics because we might miss something, using that approach we will most certainly miss everything every time!

As for the code interp. Look at the stipulations on grading... pretty clear and focused ( I happen to disagree with them as well), now look at the call for engineering... much broader. I pointed out footnote 3 in your CABO for a reason. The intent is clear, simply show that you have considered non prescriptive methods in a rational way. Just as with those grading requirements you are slowly rewriting the law through commentary and interpretation.  Jobsaver, you sound alot like our old BO. If I ran into trouble he was my first call. I know the answer now will be "get an engineer" so I don't bother him much. It is a two way street and unless the inspector has all the time in the world he simply isn't going to look in all the right places. When we were working together he already knew the places I was concerned with.


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## Jobsaver (Jan 16, 2011)

DRP: Your post sums up my thinking as well. I prefer to be a resource, not just another link in the chain of bureaucracy. And, to be a good resource, one needs good resources.

I am currently a mediocre resource aspiring to become a good one. To know all of the methods, each of the interpretations, is the goal. Until then, I will sustain my ambition by asking a lot of questions to those accomplished that know more than I.


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## GHRoberts (Jan 16, 2011)

Jobsaver said:
			
		

> Given a choice, should I be counting on someone, I'd put my confidence in the man that is not afraid to ask a question, and understands the meaning of a sentence.


Did you notice that in post #24 Jar had the span wrong, the tributary "width" wrong, and the dead load wrong?

You might notice that in post #32, Jar indicated that he would accept his own unsealed unlicensed opinion if BeamChk (improperly used - wrong span, wrong tributaqry "width", and wrong dead load) gave "OK"s. But if a licensed professional submitted the same it would need a seal. (Read all that Jar writes about what he does. Not just those points that support your point of view.)

Perhaps you could be helpful and tell us why the numbers are wrong. (It is impossible to determine some of the correct numbers from the information given.)


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## Jobsaver (Jan 16, 2011)

GH: The span given in the OP is 68". Jeff's beamchek printout shows the beam span to be 5.67'. This is correct. I do not understand much of the balance of the printout. Where is the tributary width indicated? The dead load? At the bottom of the table portion of the document, I see printed, Uniform LL:400, and, Uniform TL: 500 = A, but these fiqures do not mean anything to me as presented.

I do not read post #32 the same as you. While anyone can make a mistake entering data, it appears to me that Jeff is particular to say that he has not mastered making the determination of which data is required in every circumstance, (I have experienced the same problem using beam sizing software, and will sometimes call someone more proficient to guide me through a particular equation.)

Also, he is particular to say in what two circumstances he (his company) uses the program:

"Now WHY I we use the program (this is where I expect to be flamed)

1) To check submissions that are not prescriptive yet come from an architect and not an engineer.

2) For my own personal enjoyment."

Then he proceeds to give a specific historical incident that includes checking a beam designed by an architect that seemed suspect, and that did not meet the prescriptive requirements of the code, rendering it further suspect, while dealing with an architect, who in effect, instead of doing and producing the math, said, "this is the way we always do it". Should that same architect have produced an appropriate solution in writing, sealed (professional verification), the solution would be accepted.

Making an issue of whether or not a Certified DP's document, or opinion, has to be stamped or not is a nonsensicle argument . . . of course _*it is in the BO's prerogative to require a stamped document before accepting a solution.*_

Lastly, concerning Jeff's post #32, he stated, "this is where I expect to be flamed". Maybe . . . from a registered DP that cannot admit the possibility of self-error.


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## DRP (Jan 16, 2011)

Jar did it right, lets work it longhand;

10' trib width x #40LL= 400 plf LL

10' trib width x #10DL=100plf DL

LL+DL= 500PLF TL

Max bending Moment= WL/8

W= (5.67'x #500)+#34 = #2869

M= (#2869 x 5.67')/8= 2033 ft-lbs

2033 ft-lbs x 12 =24396 in-lbs

section modulus = bd2/6

3-2x6's... (4.5 x 5.52)/6 = 22.69"3

24396/22.69= 1075 psi extreme fiber stress in bending.

the extreme fiber is the one furthest from the neutral axis, the strap of wood along the bottom edge of the beam has 1075 psi of stress. Look at Jars adjusted allowable stress, 1138 psi... we're safe. I took issue here, since there were 3 plies he could have adjusted upwards another 15% giving an Fb of 1308.

Blueberry muffins just got out, class dismissed


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## jar546 (Jan 16, 2011)

Nice work guys.  Looks like we all came to the same conclusion using our own methods, mine of which is a licensed software program.


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## Jobsaver (Jan 16, 2011)

Jobsaver said:
			
		

> I see printed, Uniform LL:400, and, Uniform TL: 500 = A, but these fiqures do not mean anything to me as presented.





			
				DRP said:
			
		

> Jar did it right, lets work it longhand;10' trib width x #40LL= 400 plf LL
> 
> 10' trib width x #10DL=100plf DL
> 
> ...


Thanks again DRP. I owe you an apple.

Now I see I missed the footnote at the bottom of the Beamchek document, "Uniform and partial uniform loads are lbs per lineal ft."


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## Richard (Jan 24, 2011)

It is unlikely that such a beam would be a simple span (ie discontinuous over the supports).. A continuous built up member would be even stronger.


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## jar546 (Jan 24, 2011)

Richard said:
			
		

> It is unlikely that such a beam would be a simple span (ie discontinuous over the supports).. A continuous built up member would be even stronger.


True, unless you strategically place spliced where there is neither negative nor positive moment.  The baseline of the curve so to speak.


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## Richard (Jan 25, 2011)

Joints would, of course, be over the supports but for such small spans only one of the 3 members would need a joint at each support which would crate a much stronger and more stable girder.  I realize the builder will use continuous lengths anyway and there is nothing wrong with exceeding the code reequirement for strength and deflection but it demonstrates why the prescriptive tables can be a poor substitute for god engineering design.


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