Acie Chance wrote;
<I have jest started my first braced frame structure under the 97 UBC.
Section 2220.127.116.11 limits the width to thickness ratio of angles to 52/Fy^1/2.
This puts the minimum thickness of a 6 in. angle at 3/4 inch. Under the 94 UBC
Table B5.1 the width to thickness ratio was 76/Fy^1/2. The 94 UBC would allow a
6 in. angle to be 1/2 in. thick. I would like to know of any reports of
failures and/or testing which brought about this change. Most of my structures
are not buildings and I could use section 2213.8.3. However there size and cost
makes it desirable for these structures to go through a major earthquake with
out following down or needing major rework.>
The 1997 UBC slenderness ratio for angles was changed to agree with that
prescribed in the AISC Seismic Provisions, Sections 13.2d and 14.2d. In
general, compact section criteria are more restrictive in high seismic zones in
order to minimize the detrimental effects of local buckling during repeated
inelastic cycling. this is most noticeable for angles and HSS members.
Rick Drake, SE
Fluor Daniel, Aliso Viejo, CA