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FW: Seismic Retrofit Questions

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> Joseph,
> 
> It is hard to make an old building conform with new code detailing
> requirements.  I've had the exact same questions that you have now,
> and I'm anxious to see how the list responds on the wall detailing
> question.  I agree, that you must attach the diaphragm to the shear
> wall in the newer section.  I think I've used Hilti's to the masonry
> and welding from below to connect the steel deck to the angle
> (assuming the deck gage is adequate).  If that can't be done, have the
> roofing membrane pulled up and do it from above (the hard way).
> 
> Just for interest, you might try looking at NEHRP Guidelines for the
> Seismic Rehabilitation of Buildings, along with the commentary for
> that document.  They are FEMA-273 and FEMA-274, and can be ordered for
> free at (800) 480-2520.  FEMA also has a few other documents you might
> want, including:  FEMA-149, Seismic Considerations of Elementary and
> Secondary Schools; FEMA-178, NEHRP Handbook for the Seismic Evaluation
> of Existing Buildings; and FEMA-310, Handbook for the Seismic
> Evaluation of Buildings - A Prestandard.  The 310 document will
> eventually replace 178.  These are all free documents.  I think what
> you'll find with FEMA-273 and 274 is that they might be more
> appropriate for rehabilitation than the UBC.  The 178 and 310
> documents will be very conservative, and if you use their checklists
> for evaluation, some items may show as deficient.  However, the reason
> I put those in, is because of the Non-Structural checklists.  I think
> we often get tasked with looking at the "structural" items in a
> building, and one of the major problems during an earthquake is
> non-structural stuff falling on people, blocking egress, etc.
> Suspended ceilings, bad connections for utilities (especially gas
> lines), book cases and shelves that could topple and block egress.
> These things could be especially important to look at for a school.
> If your client hasn't thought about the non-structural issues, you
> might bring it up.  
> 
> Hope some of that helped,  
> 
> Mike Ritter
> 
> ps, Often when tasked with seismic studies or upgrades, I will
> recommend to the client to have us look at wind also.  A lot of older
> buildings simply used, say 20 psf on everything with no consideration
> for uplift or other issues that are addressed in the newer codes (ie,
> ASCE 7).  Have you considered wind effects on the school building?  It
> probably would be pretty easy to run a quick number just for
> comparison.
> 
> 
> -----Original Message-----
> From:	Joseph R. Grill, PE [SMTP:jbotch(--nospam--at)micron.net]
> Sent:	Tuesday, September 19, 2000 8:18 PM
> To:	SEAINT
> Subject:	Seismic Retrofit Questions
> 
> I am in the middle of an investigation of an old school in my area.
> The
> main concerns are with seismic safety, although in the process I've
> found
> other problems.  I'm not in the process of doing calculations for an
> actual
> retrofit, but my findings will be used by the school officials to help
> decide the future of the school.  At the moment I have two questions
> to pose
> to the list.
> 
> In the oldest portion of the school (5 additions since the early 60's)
> there
> are some load bearing masonry walls.  Checking the walls for load
> combinations in UBC (sorry guys using WS design) I have found that the
> reinforcing provided in the walls is adequate strength wise although
> severely lacking in minimum reinforcing requirements for a zone 3
> structure
> if it were being designed today.  I am at a loss as to how to approach
> this
> in the report.  Do these walls need an upgrade in capacity in some
> way, or
> not.  I'm sure I will be pressed on this matter.
> 
> Another question was posted in a similar situation last June, although
> I
> think I remember the metal decking wasn't required as a diaphragm.  In
> this
> school (a newer addition) steel joists were used to support metal
> decking.
> There is no direct connection from the diaphragm to supporting CMU
> walls
> below.  I will be looking for supplying shear transfer from the deck
> to the
> walls, hopefully without disturbing the roofing membrane which is
> fairly
> new.  Back in June Stan Caldwell listed some molly bolts with a
> supplier in
> Denver, although the bolts had no ICBO certification.  Does anyone
> have any
> ideas for an attachment of this sort.  Angles installed below and
> attached
> to the deck from below?  The school district is low on cash, Just
> built a
> new high school, so cost is an issue.  Also, the community has become
> very
> aware of the issues, and it would be nice to have the ICBO thing or
> something substantial to be able to back up the method used.
> 
> Thanks, Joseph Grill, PE
> 
> 
> 
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