Return to index: [Subject] [Thread] [Date] [Author]

RE: Field Observations - Stupid things I've seen

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I've read a lot of the crazy stories people have sent in but I believe
this one is close to the top of the list.

I designed a 4 story precast parking deck that was to be inspected by an
independent testing company.  I performed several perfunctory site
visits during construction of the foundations.  The contractor was
falling behind schedule and started working two shifts per day.  Before
my next visit was scheduled, I was called out to the jobsite because
"the entire structure had collapsed".  Upon arriving at the job site, my
initial observations was that the contractor had installed all the
prestressed columns and the first three levels of double T's.  The
contractor took me over to several columns and sure enough, the entire
structure had fallen approximately six inches and was barely supported
on the concrete pier "stumps".  Upon investigation, two things
immediately became evident.  The first was that the contractor was in
such a hurry that he had installed and leveled all the columns with 4 ~
1 1/8" diameter bolts as required by the shop drawings but neglected to
grout between the columns and the piers.  As the anchor bolts became
more and more loaded, the compressive capacity of the bolts came under
question.  Unfortunately, the second thing that the contractor neglected
to do was install the ties in the piers that restrained the anchor
bolts.  The inspector approved the installation and concrete was poured.
 When the anchor bolts failed outward by buckling outwards in the
direction of least resistance , the piers failed and a majority of the
structure settled approximately six inches.  Within two hours the
contractor was working around the clock to cut welds and disassemble the
precast sections to rebuild the piers in accordance with the structural