Rule of thumb when comparing ASD loads to LSD loads.

[EngDM]

Quite often when designing steel studs I come across the need to use either Simpson or Bailey clips. However, aside from a select few Simpson clips, all resistances are for allowable loads. Is there a rule of thumb I can use to compare by factored loads vs the allowable loads for the product? Typically I just compare my factored to the allowable which seems way conservative since I'm factoring loads and factoring down the clip capacity, but there are certain cases where the client requested clip cannot work unless I compare unfactored LSD loads.

Has anyone rationaled this to themselves for a safe but not overly conservative approach?

 

[WesternJeb]

1.4 is a pretty typical conversion factor from ASD to LRFD. Just be mindful when you're using it and adjust as necessary. I.e., wind loading will be more of 1.7 conversion factor, if it is primarily dead load it will be more of a 1.3 factor. edit: I misread LSD for LRFD. Please disregard.

 

[XR250]

Just like wood, I feel like metal studs are a system that should be designed using ASD.

 

[STpipe]

You can calculate a rough conversion factor since you know the magnitudes of the different loads by comparing the ASD load combination values to the LRFD/LSD loads. There is a part of the commentary or appendix in AISC that talks about the calibration that was performed so that engineers the design using both methodologies would be equivalent.

If I remember, at a LL to DL ratio of 3, you should get the same results between ASD and LRFD, while a higher ratio meant the LRFD design would be more efficient on materials.

 

[JAE]

For more wind/seismic oriented load conditions use 1.6/0.9 = 1.78....or round it down a bit to be safe using 1.6.
For more gravity-only conditions perhaps use 1.4/.9 = 1.56....or round it down again to 1.5 or 1.4.