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Wood stud deflection - FBC - wind

engjg

Structural
Jan 2, 2015
95
In the context of:
  • exterior wood wall stud with typical window components
  • FBC 2023 code (IBC 2021 with amendments)
  • interior gypsum wall board
  • flexible exterior finishes
What is correct FBC interpretation/application for deflection ratio and wind load factor?:
  1. 0.42xW and L/120 (Table 1604.3 including footnote f)
  2. 0.42xW and L/180 (Gypsum wallboard controlled)
  3. 0.6xW and L/175 (Glazing controlled, IBC §2403.3 & Table 1604.3 footnote f)
Regarding #2; I do not know the source of the deflection ratio but have seen it used when gypsum applied; not sure if it is in code or an gypsum industry recommendation.
Regarding #3; While I have not found where code clarifies, I believe this is not applicable for typical preassembled window units. I believe the intent is for large glazing walls and the design of the mullions and frames directly receiving the glass.
 
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For ASD, I do 0.7W and L/240 min. unless I am trying to get something existing to pass.
 
Thanks for the response;. On the topic of 0.7 I will note it is my belief you are using a relic of older code editions referencing allowable wind loads (ASCE 7-05). The 0.7 was an adjustment to take the 50 year MRI down to a 10 year MRI for deflection considerations. Current IBC which used ultimate wind loads notes 0.42 instead of 0.7 in the footnotes or 0.42 = 0.7 x 0.6; in similar manner reducing 700 MRI (RC II) ultimate wind loads down to 10 yr MRI.
 
I still use ASD because the actual wind pressures have not meaningfully changed since 7-05
 

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