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RE: ASCE7-05 240 ft ordinary braced frames in seismic design category D?

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Will:

I think this is what ASCE7-05 seems to be shooting for but the wording is
poor and I don't like it.  I wonder if there is an errata on this?  

It seems ridiculous to me that you can't use an ordinary steel braced frame
in a shoe box two story building that is 36 feet tall.

Scott.
 

-----Original Message-----
From: Will Haynes [mailto:gtg740p(--nospam--at)gmail.com] 
Sent: Wednesday, April 09, 2008 4:06 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: ASCE7-05 240 ft ordinary braced frames in seismic design
category D?

I also think the intent is that the braced frames which are indicated in the
table as limited to 160 ft are allowed to be increased to 240 ft, not the
ones that are listed in the table as 35 ft (the ordinary frames).

Will

On Wed, Apr 9, 2008 at 6:53 PM, Haan, Scott M POA
<Scott.M.Haan(--nospam--at)usace.army.mil> wrote:
> It used to be in ASCE7-02 that ordinary braced frames were limited to 
> 35 feet  with an exception that they could be as high as 240 feet as 
> long as any  braced frame grid did not carry more than 60% of the 
> seismic forces in that  direction and that not more the 20% of the 
> force in a braced frame was from  torsion.
>
>  ASCE7-05 section 12.2.5.4's wording seems to muddy the waters for me.  
> It  says height limits in Table 12.2-1 are permitted to be increased 
> from 160  feet to 240 ft in seismic design category D?
>
>  Does this mean I can can have an ordinary braced frame in seismic 
> design  category D with a 35 ft height limitation increased to between 
> 160 feet and  240 feet per ASCE 7-05?
>
>  Special braced frames and eccentrically braced frames have a height 
> limit of  160 feet in seismic design category D.  It seems like the 
> intent of ASCE 7-05  is only to allow special braced frames and 
> eccentrically braced frames to use  the height limit exception because 
> of the wording "increased from 160 feet to  240 feet."
>
>  Thanks.
>  Scott
>
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--
Will H.

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