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braced frame - double angles in ETABS

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I have a concentrically braced frame modeled in ETABS. Most of the brace members are double angles. I have posed this question to ETABS and am waiting for a response. I thought I would email the server to see if anyone has any input on this. 

My brace members (double angles) are coming back as "too slender" when I complete a lateral analysis using 97UBC-ASD. When I do a hand calc of the 97 UBC slenderness requirements for Zone 3 and 4, the members are ok. I have set the unbraced length ratio in ETABs, but cannot seem to get the analysis to get past the slenderness issue. Can anyone provide some insight on this?

Gina

Gina T. Gobo, EIT
Carter & Burgess, Inc
Facilities - Structural Engineering
Seattle, WA
Ph. 425-822-7096
Fax 425-822-7246
gobogt(--nospam--at)c-b.com
http://www.c-b.com
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<DIV>I have a concentrically braced frame modeled in ETABS. Most of the brace
members are double angles. I have posed this question to ETABS and am waiting
for a response. I thought I would email the server to see if anyone has any
input on this. </DIV>
<DIV>&nbsp;</DIV>
<DIV>My brace members (double angles) are coming back as "too slender" when I
complete a lateral analysis using 97UBC-ASD. When I do a hand calc of the 97 UBC
slenderness requirements for Zone 3 and 4, the members are ok. I have set the
unbraced length ratio in ETABs, but cannot seem to get the analysis to get past
the slenderness issue. Can anyone provide some insight on this?</DIV>
<DIV>&nbsp;</DIV>
<DIV>Gina</DIV>
<DIV>&nbsp;</DIV>
<DIV>Gina T. Gobo, EIT<BR>Carter &amp; Burgess, Inc<BR>Facilities - Structural
Engineering<BR>Seattle, WA<BR>Ph. 425-822-7096<BR>Fax 425-822-7246<BR><A
href="mailto:gobogt(--nospam--at)c-b.com">gobogt(--nospam--at)c-b.com</A><BR><A
href="http://www.c-b.com";>http://www.c-b.com</A></DIV></BODY></HTML>