From: Jim Kestner <jkestner(--nospam--at)somervilleinc.com>
Date: Fri, 11 May 2001 13:13:50 -0500
I have run across a number of older systems thru the years including the
SMI system that you mentioned. I will mention a few other oddities....
Many of the older flat slabs had 4 way reinforcing (orthogonal plus
diagonal strips). Certain areas were over-designed and others under
designed by today's methods. I understand that there was also a 3 way
system but I never saw one.
I encountered a concrete building one time that was well detailed and it
was interesting to note that the stirrups were reversed in areas of
reverse bending. Perhaps the thought was that the continous bottom part
of the stirrup had to occur in the tension zone.
A building in Virginia had some oval shaped bars. These were round
equivalents. I understand that Bethlehem rolled these in the 30's so
that they could be field bent easier. This same building was well
detailed for the beams and columns but the slab had all bottom bars (no
top bars) and there were cracks over all the beams.
I worked on an old building that had all smooth bars. The contractor was
able to knock off all the concrete and leave all the bars hanging in
place. The lack of bond between the bars and the concrete made quite an
impression on me!
I worked on an existing building that had "star columns". There were 2
steel angles with the points projecting in all 4 directions. The angles
were connected together by batten plates. These columns are torsionally
very weak so if they are hit by a fork truck, watch out!
I also worked on a heavily loaded multi-story industrial building built
before the turn of the century with buckle plate floors. This was
typical in bridge construction but very unusal in buildings.
Jim Kestner, P.E.
Green Bay, Wi.
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