LRFD Design in the NDS and Deflections

[bigmig]

I'm trying to make the jump to the ASCE7-10 Windload provisions, which are all strength based.

When I calculate my shearwall and diaphragm deflections based on the NDS Deflection equation (4.3-1) in the new 2012 NDS
do I need to convert my unit shear to a service level shear values? I was taught that all deflections are calculated with
service level loads. In NDS 2012 Section 4.3.3 they say that the ASD Unit shear is the Ultimate Shear divided by 2.0.

Is it as simple as dividing my ASCE 7 values by 2.0?

 

[lexpatrie]

The diaphragm values you want are in SPDWS. The properties (E, G/in, etc,) don't change for LRFD/ASD. As to the forces, you have to drop those to ASD level to check deflections. Generally in 7-2010 you use 0.6 W for ASD (and deflection calculations).

I don't think you're using any values from ASCE 7 as to the diaphragm. If you mean loads, no. You're using 1.0 W for LRFD and 0.6 W for ASD. That's not dividing by two. The divide by two is accurate for (capacity) of diaphragms in SPDWS, but doesn't pertain to deflection calcs. Diaphragm capacity in SPDWS for LRFD is multiplied by some ASCE specific value that's not 1.0. I don't know it, but it's not 1.0. It's a phi or a lambda or a time effect factor or something.

--Brian

 

[bigmig]

Brian, Where do you get the 0.6W for ASD to LRFD conversion?