Wind load per ASCE 7-05: Envelope procedure

[rkhandekar]

In ASCE7-05, Wind load Section 6.5.12.2.2 is applicable for low rise (<60ft) rigid buildings only (this is clearly mentioned in ASCE7-10 release).
However, all the PEB industry still use Section 6.5.12.2.2 even for flexible buildings (actually almost all PEB building will fall under flexible building category)
Note that wind load from both sections differs significantly.
Please provide some clarity on this.
Thanks
RK

 

[JAE]

Are you sure your building is flexible?
Per ASCE 7-10, section 26.9.2, low rise buildings can be considered as rigid.

 

[r13]

See ASCE7 for definition of flexible buildings - having fundamental neutral frequency less than 1 Hz. Also see the linked blog for definition of "rigid" building, which the most PEBs are belong. Link

 

[rkhandekar]

Hi JAE,
Yes. The building is flexible. I have observed that most of the PEB buildings (even though low rise) are flexible building due to lower stiffness of steel framing (at least in portal direction).
Refer to attached where conditions (limitations) for using Envelope procedure are given.

Thanks,
RK

 

[JAE]

So you'd performed an analysis determining the building's natural frequency?
I guess I could see it being possibly flexible for a portal frame system.