Wind Load Case A and B 4

[spud22]

I am doing design on an open building with monoslope roof. ASCE 7-05, Figure 6-18A has values for Cnl and Cnw, but it references Load Case A and B. I can find no clarification of what Load Case A and B are in the document. Can anyone help? Thanks

 

[msquared48]

A and B I couldn't find either in a quick search.

However, you do have the load cases 1 thru 4 listed on
Figure 6-9, and the additional applications shown on Figure 6-6.

Mike McCann
MMC Engineering

 

[woodman88]

Basicly you have to check both cases. If you go to this post - thread507-219092 - they talk about it more.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[ron9876]

A and B are opposite wind directions. See wind dorection in the diagrams.

 

[OldPaperMaker]

spud22,
The commentary to ASCE 7-10 does a better job of explaining the case A & B. on page 552, C27.4.3, 2nd paragraph says:
" Two load cases, A & B, are given in Figs. 27.4-4 through 27.4-6 (old Fig 6-18B to D). These pressure distributions provide loads to envelop the results from detailed wind tunnel measurements of simultaneous normal forces and moments. Application of both load cases is required to envelop the combinations of maximum normal forces and moments that are appropriate for the perticular roof shape and blockage configuration."

I think this means that use use the factors from the two load cases that give you the maximum wind pressures. I suppose that they could have called them case 1 or 2.

 

[spud22]

Thanks to everyone for their input. My thought is for a publication like this to put in such a load factor and then not define how they intended it to be interpretted is bizarre. We will use the worst case conditions and muddle on.