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Re: EBF's

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On Wed, 03 Sep 1997 08:34:42 -0800 Bruce Hopper <Bruce(--nospam--at)uskh.com> writes:

>We just designed a facility in Anchorage (zone 4), single story, with 
>an EBF.  This facility is 580' x 220' x 41' with moment frames in the 
>north/south direction (220 foot direction) and two EBF's in each of 
>the north and south walls (parallel to the 580 foot dimension).  
>
>We looked at using concentrically braced frames first, but the size of 
>the steel and foundations became prohibitive.  Using EBF's allowed us 
>to reduce costs in terms of reduced steel sizes and significantly 
>reduced foundation sizes.
>
>We were able to reduce the steel deck from 16 gage to 20 gage  on 
>130,000 square feet of structure.  Significant savings alone.
>
>The design includes two EBF's in each of the long walls.  The two 
>frames are adjacent, sharing the intermediate column.  Steel sizes 
>were drastically reduced in the EBF's over the concentrically braced 
>at the expense of more detailing and field welding.  Overall, we saved 
>money again.
>
>The greatest savings was in the foundation work.  The entire site was 
>excavated to 20+ feet and backfilled.  Overturning was a significant 
>problem which  resulted in large footings, very deep.  Using EBF's 
>allowed us to minimize the foundations and place them much nearer the 
>surface, significantly reducing costs.
>
>Word of caution, if you intend to use LRFD design, second edition 
>(silver book), you must use the 97 UBC seismic loads (1991 NEHRP) to 
>be compatible with the 1.0 Earthquake factor.  Read the preface on 
>page 6-303 in the AISC LRFD Manual, Second Edition.
>
>Bruce Hopper, P.E.
>
>USKH, Inc.
>2515 A Street
>Anchorage, AK  99503
>
>907.343.5231
>
>bruce(--nospam--at)uskh.com
>                                                                       
EBF requires the link beams to yield first and absorb energy.  It is
commonly known that Mill Test Reports (MTRs) provided by the steel mill
generally show that steel has considerably higher yield strength than the
nominal yield strength (Fy).  I am curious how you design to ensure that
yielding will occur at the link beam first?

Y. Henry Huang, <yhh-la(--nospam--at)juno.com> and <hhuang(--nospam--at)co.la.ca.us>.
"In the beginnning, (the first Civil Engineer) created the heavens and
the earth...."