Formulas for sizing timber moment

[GoodnightKiwi]

Hi -

I'm a geotech engineer so go easy on me with this one.

Having designed a tied-back retaining wall, I am trying to find a method whereby I can calulate the required timber pole moment for the horizontal waler that the tie-back tendons connect to - and thereby determine the minimum required pole size of that horizontal member. In this instance the uprights are at 1 metre centres and the tendon connects to the waler mid span (i.e. 0.5m from the upright either side of it).

Sketches are attached.

Sketch 1 is for a continuous horizontal beam (i.e. more than 1 tendon attached)
Sketch 2 is for a horizontal beam with only 1 tendon attachment.

Thanks in advance

 

[rowingengineer]

GoodnightKiwi,
I assume you in NZ, I think your local timber company can help. Carter halt Harvey have a program for engineers.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[PEinc]

If you place the tie rods right next to the soldier beams, you nearly eliminate the bending moment in the wale. It may not be the "look" you want, but it does reduce the wale size.

If you conservatively assume the wale has a simple span between soldier beams, the moment M = PL/4. For a continuous wale with concentrate loads at the mid-spans, check AISC's 14th Edition (or earlier) Steel Constrruction Manual, page 3-212, which shows that Mmax = 0.171PL (5-span), 0.175PLK (3 span), or 0.187PL (2 span) with Vmax = 0.66P (5 span), 0.65P (3 span), or 0.69P (2 span).

http://www.PeirceEngineering.com