thoughtofthis
Structural
- Jan 16, 2012
- 31
So ponding analysis is covered in AISC K2 and SJI has a direct ponding analysis tool, but there are limitations to both. For instance, they're only applicable to rectangular bays with evenly spaced framing.
I understand that ponding stability is iterative for an exact solution, but why can't this be accomplished directly with a software like RISAfloor? Build a roof and set the deflection requirements to l/180 or whatever governs. Add a rain area load equal to the depth of the appropriate water head plus the l/180 deflection of the longest member in that bay. RISAfloor sizes the roof members to limit deflection to l/180 and checks the strength of the members.
For example, say you have a roof bay that is 30 by 30. The depth of water that can be impounded is 3 inches. l/180 at 30 ft is 2 inches. So input a rain area load of 62.4pcf*(3in + 2in / 12 in/ft)=26psf. Use the load combo D+(Lr, S, R).
I understand that ponding stability is iterative for an exact solution, but why can't this be accomplished directly with a software like RISAfloor? Build a roof and set the deflection requirements to l/180 or whatever governs. Add a rain area load equal to the depth of the appropriate water head plus the l/180 deflection of the longest member in that bay. RISAfloor sizes the roof members to limit deflection to l/180 and checks the strength of the members.
For example, say you have a roof bay that is 30 by 30. The depth of water that can be impounded is 3 inches. l/180 at 30 ft is 2 inches. So input a rain area load of 62.4pcf*(3in + 2in / 12 in/ft)=26psf. Use the load combo D+(Lr, S, R).