Strength design versus Allowable stress deisgn in IBC
Strength design versus Allowable stress deisgn in IBC
(OP)
I have received a design from a contractor to review which is for a single storey steel framed warehouse (portal framed building).
He has used the allowable stress design load combinations (IBC section 1605.3.1) for the analysis and member designs. Generally for strength checks I always use the ultimate state combinations (1605.2.1) regardless of the building type, and use the basic load combinations for serviceability checks.
Is there anything in the code that will permit strength checks to be done using the allowable stress design method. Can anyone offer any advice on this?
Thanks
He has used the allowable stress design load combinations (IBC section 1605.3.1) for the analysis and member designs. Generally for strength checks I always use the ultimate state combinations (1605.2.1) regardless of the building type, and use the basic load combinations for serviceability checks.
Is there anything in the code that will permit strength checks to be done using the allowable stress design method. Can anyone offer any advice on this?
Thanks






RE: Strength design versus Allowable stress deisgn in IBC
RE: Strength design versus Allowable stress deisgn in IBC
About the only thing I'd be clear on is he should be technically using the allowable strength design (not stress). If he's using the 9th edition ASD (allowable stress design) then that wouldn't be acceptable.
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/
RE: Strength design versus Allowable stress deisgn in IBC
Well that is probably true in most all cases.
But if a city or jurisdiction has not updated their code in many years and the current, applicable code refers to the 9th edition then that is the legal, adopted and required specification to use.
Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies
RE: Strength design versus Allowable stress deisgn in IBC
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/
RE: Strength design versus Allowable stress deisgn in IBC
Are the changes significant?
RE: Strength design versus Allowable stress deisgn in IBC
You do mostly low-rise right XR250? If you're just sizing small beams and posts then you're not going to see much change. It's when you get into the second order effects for large structures and such things that the changes start becoming more critical.
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/
RE: Strength design versus Allowable stress deisgn in IBC
Thanks for the info
RE: Strength design versus Allowable stress deisgn in IBC
I do a fair amount of LRFD design, but when laying out my calcs, I simply keep loads in unfactored form and then apply the load factors on the same line where I calculate moment and shear.