Replies

1. 
   davidmeiland | Jan 28, 2010 07:57pm | #1

   Big ones. Really big ones.

   Seriously, how can we tell you without knowing live load and dead load requirements, tributary loads, etc.? Probably wanna take your plans to an engineer to get this done correctly.

1. 
   xxPaulCPxx | Jan 28, 2010 09:03pm | #2

   I disagree:

   Small ones, Moderately small ones.

   Of course how can we tell you without knowing live load and dead load requirements, tributary loads, etc.? You probably wanna take your plans to an engineer to get this done correctly.

1. 
   Piffin | Jan 28, 2010 10:46pm | #4

   Nope -
   Limber ones - really
   Nope -

   Limber ones - really limber lumber - that way it won't break

2. 
   Gene_Davis | Jan 28, 2010 09:22pm | #3

   Click on this link, and read the whole thread.

   http://www.contractortalk.com/f14/structural-advice-33004/

   Then contact your engineer.

1. 
   karteberry | Jan 29, 2010 05:08pm | #7

   Amen Gene, That's the best
   Amen Gene, That's the best advice....

3. 
   Piffin | Jan 28, 2010 10:49pm | #5

   Therre are about a dozen bits of information missing to even begin to imagine the answer here.

   Your Q is like asking, What tires should I put on my vehicle, one goes in the front, and the other goes in the rear.

1. 
   CapnMac | Jan 29, 2010 02:03pm | #6

   What tires should I put on my vehicle

   And only the vaguest notion of whether one means a Combine or a Volt or a Case 350.

4. 
   IdahoDon | Jan 29, 2010 09:40pm | #8

   They should be as small as possible and as large as necessary.

1. 
   Piffin | Jan 29, 2010 10:32pm | #9

   The wealth of information in that concise answer is absolutely astounding!

5. 
   Homewright | Jan 31, 2010 11:18am | #10

   High praise!!!

6. 
   junkhound | Jan 31, 2010 02:03pm | #11

   Simple end supported beam?

   Moment = sigma * zee; where sigma is the extreme fiber tensile strength of the beam material, zee is the section modulus.

   OK, simple so far. zee units = inches^3, sigma = psi

   Now ya gotta figure the moment.

   For single load in middle, M = load* length/4, little more complex if not right in the middle, lots of calc on the net if ya look.

   For distributed load in english foot inch units, M = load per inch * length^2 / 8

   Now superimpose all those and ya got the answer. Get less simple fast if you have cantilevers, continuous beams over offset supports, or if deflection is the governing code factor vs. simple strength.

   Truthfully, and decent structual engineer can do simple strength calc like that in their head, and know all the sigma numbers for different materials off the top of the head.

   Like the man said, it only took ya 5 minutes, why did ya charge me $500.00

   Ans: cause you are to lazy to learn stress of materials yourself!

   It aint rocket science until ya get to something like a composite wing structure or missile body stress and life under launch vibration fatigue.

7. 
   junkhound | Jan 31, 2010 02:25pm | #12

   to give ya ideas, 'off the
   to give ya ideas, 'off the top of my head without a calculator:

   Gonna blow this off guys and not check, so here goes.

   span 30 feet 4 inches. ..... ridge beam for the vaulted ceiling.

   OK, say the ceiling spans a floor that is 20 ft wide.

   Simplfy, only dead and snow load, say 24 psf.

   Equates to 240# per foor or 20# inch load on the beam. (10 ft load *24psi/12)

   30 ft 4 inches = 364 inches

   Hurst my brain to square 364 in my head, will guess at about 150K.

   So, M = 150K *20/8 = 3E6/8 = about 400,000 inch pounds rounded up.

   OK, look for a glu lam with outer lams of select structural DF or SYP, say 1.5K psi sigma.

   400E3/1.5E3 = say about = 300 rounded up, dats a big zee!

   Now zee or a rectangular beam is width*height^2/6 = 300

   So, width * height * height = 1800

   OK, keep the width to 10" wide, h^2 = 180.

   sqrt of 180 = about 14, so your beam height will be about 14 inches. 14x10.

   Work the other way, say a 20" high beam, width = 1800/400 or about 5" wide. Still a big beam.

   Literally, go figure

   Dats a big wonking beam.

   EDIT: One more thing, make sure the footings for the posts supporting the ends of that span dont sink into the ground and give you a leaning house of pizza

1. 
   xxPaulCPxx | Jan 31, 2010 11:36pm | #13

   You spelled Pissa wrong.

   :)

1. 
   junkhound | Feb 01, 2010 10:52pm | #14

   Sidelight

   Took the boys (10$12 at the time) to Tuscany area in 1980. Still could climb the tower then, kids gave DW the willies when they stood on the edge and dropped a couple of grapes al'a G.G.

   No railing at all, figured no liabiity attorneys there then

   The church next door looks like the footing had setteled a couple of meters before the wall was finished - masonry courses at all angles!

8. 
   Jeff_Clarke | Feb 03, 2010 08:19am | #15

   What size/kind beams would be required to span 30 feet 4 inches?

   What kinds of loads are involved? A fully-loaded steel floor beam (floors on both sides) is probably going to be in the W12 x _ range. Your ridge beam is likely going to be a deep Microllam LVL.