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Re: UBC Sect 1807.2 - Interconnection of Pile Caps

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The seismic sections of the IBC are based on the 1997 Edition of 
the "NEHRP Recommended Provisions for Seismic Regulations for New 
Buildings and Other Structures."  These provisions are being 
coordinated with the 1997 UBC requirements to develop the IBC.

Section 1807.2.23.1 of the November 1997 draft of the IBC has a tie 
requirement very similar to the current UBC requirement.  
Clarification of what level of seismic hazard requires ties is 
provided (Seismic Design Category C or higher).

Based on the latest mapping, most structures in Honolulu will be 
Seismic Design Category B or C, depending on the occupancy and soil 
type.  This would indicate that ties would be required for some (in 
SDC C) and not for others (in SDC B).

You wrote:
> I have been researching code requirements for the interconnection of 
> pile caps to answer a Contractor who is questioning the need for the
> ties because an SE out of Seattle has been designing buildings here
> (Honolulu - Seismic Zone 2A) without interconnection of all the pile 
> caps with tie beams.
> 
> I want to make sure I have all the "answers" when questioned about this
> issue.  Structural Safety is of course my first concern but I do not
> want to be overly conservative either.
> 
> The research I have done is as follows, the UBC requires "every
> structure subjected to seismic forces shall be interconnected by ties"
> Since every structure (except maybe Zone 0) would be subjected to
> seismic forces all strucutres would require inteconnecting ties.  
> 
> The ASCE 7-95 requirements however relate this requirement to the both 
> theuse and seismic risk - for example a non essential building in Zone 
> 2Awould not require ties per ASCE 7-95.  
> 
> The 2000 edition of the UBC (IBC 2000 DRAFT) sect 1807.2 has been 
> replaced w/  "Three or more piles connected by a rigid cap shall be 
> considered as being braced,..." which appears to indicate that 
> interconnection of the pile caps would not be required in this 
> situation.
> 
> Is there a good source of info for where the IBC DRAFT revisions are 
> coming from?  Is there a new version of the "Blue Book" that has gone 
> into more detail about pile interconnection?

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Michael Valley                                   E-mail: mtv(--nospam--at)skilling.com
Skilling Ward Magnusson Barkshire Inc.                  Tel:(206)292-1200
1301 Fifth Ave, #3200,  Seattle  WA 98101-2699          Fax:        -1201