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RE: Tilt-Panel Bottom Connections

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Jake,
I also do not know of any code provision for this but I have had experience with a building which could fail due this condition during a large earthquake.
There was an architect in Los Angeles who designed a large number of industrial tilt up buildings during the l980's.  He used  several independent structural engineers to design the panels and the wood roof system but did all of the drawings and other design himself.  After the Northridge earthquake (1994) the facilities manager called me and said that there was a crack in the slab floor that got wider after every shake that occurred.  Upon observation, it was 4.5 feet from the south wall, 1/4" to 3/8" wide.  Although the conditions on the other three sides were the same, it did not occur there.  On the plans there was a dowel from the 30'+ high concrete wall and from the slab into the 3" wide pour strip, but no reinforcing in the slab itself.  The crack occurred at the inner end of the dowels in the slab.  The reason it occurred there was because the ground sloped 2 to 3 feet down from north to south.  The north footing was embedded into firm natural soil whereas the south footing was on top of it with fill (well watered landscaping) which was supposed to resist lateral movement of the footing; it didn't.
The problem therefore is whether you can depend on the soil to restrain the footing or not.  Therefore since it is a question involving both the wall/slab and the soil it is not as common a failure as the roof/wall case where you know there is nothing else to restrain the outward force of the wall.  I think that a code provision that required the designer to either show that the surrounding soil can resist the forces or include engineered ties into the slab would be appropriate.
Richard Hess
-----Original Message-----
From: Jake Watson [mailto:jake.watson1(--nospam--at)gmail.com]
Sent: Monday, February 19, 2007 9:09 AM
To: SEAINT
Subject: Tilt-Panel Bottom Connections

Our local SEA is looking at tilt-panel to foundation / slab connections and code requirements.  Because of this I have spent a fair amount of time researching the recent code history (97 UBC +).  Each code cycle has changed the wording and methodology.  FEMA 368 & 450 also take different approaches.  Because of this, I have assumed there must be a historic precedent of panel failures.  Two days of online research hasn't turned up a single report addressing the issue.  I can't seem to find a single reference which discusses panel performance at the bottom (good or bad).  Numerous papers, articles, and reports discuss diaphragm and out-of-plane anchorage.  But I couldn't find a single report dealing with the bottom.  That said, I am at home and haven't gone through recent ACI or TCA publications.

Can anyone point me to a reference which reviews the performance of panel bottom connections?

Jake Watson, S.E.
Salt Lake City, UT