Black Locust Design Values

[XR250]

I have an Arch. that wants to use 2x Black Locust for decking. My job is to figure out how far we can span it with Assembly loads. The info on the internet is pretty slim. I found this:

https://www.woodworkingnetwork.com/wood/wood-explorer/black-locust

Gives the MOR of 19.4 ksi. Does anyone know how to convert that to an allowable bending stress?

Thanks!

 

[Ron]

XR250....Check Chapter 4 of The Wood Handbook. Available online at following link....

Chapter 4

 

[XR250]

Thanks Ron,

That gives me the same ol' 19.4 ksi value. Looks like there is a factor of safety of about 5.0 on the values based on what I use for pine. I may just use 3 ksi. Serviceability may control anyway
The decking is a literally 4 inches off the ground on sleepers so I don't know that I really should worry about strength :>

 

[Ron]

XR250....M_R is f_b at ultimate failure, so I don't see an issue with using the pine values or with using the ratio of pine values (M_R for pine relative to allowable f_b for pine).

 

[XR250]

Thanks Ron

 

[OldBldgGuy]

I don't have the design values for you to use, but I can tell you that black locust is multiples of the strength of any softwood used to produce decking and showing in any set of tables. It's harder, stronger, and tougher. Anyone milling oak would tell you that red oak is softer and weaker and white oak is comparable if they did a comparison, but the toughness is in a completely other realm. I don't know how that translates into allowable stresses, but I'd have no qualms using D-fir or Larch values and being confident that it was very conservative.