I recently bid on a job in Southern California that I did not get. Not
unusual in a competitive market. However, it wasn't the fee that was the
primary culprit. It was the Architect's fantasy that I told him I could not
recommend attempting that lost the job for me.
The Architect wanted to construct a wall around the perimeter of a
restaurant. The wall was to be 4' wide by 8" thick and 22' high spaced at 8'
o.c. with iron mesh design material in between the cantilevered wall
sections. I did not do any calculations prior to bidding. I simply
recommended that the wall system be braced into the roof (which was also to
be at 22' height) and approx. 5' and 18' away from the new restaurant
Well you win some and you lose some. That was okay because I am doing other
work for this same Architect. However, the other day I was at his office and
we finished the project we were working on and he asked me a question. He
wanted to know if it was usual for the roof system to experience large
horizontal deflections. The roof area is about 35' by 85'. He stated that he
was on the roof and the roof seemed to move quite a bit. He played with
making the roof move and during that time measured a horizontal deflection of
plus or minus 1/2".
The roof system is for a one story portion of the building. The lateral
system is apparently W8x?? columns with a much larger beam between the
vertical columns. It doesn't take a rocket scientest to know that a 1/2"
deflection caused by a 190 lb individual is a lot of deflection. He asked me
the question because he was concerned about the deflection causing problems
with the large glass panels between the columns.
I don't want to engineer a building for free that I already know is not going
to figure. My point in bringing this condition to the attention of other
engineers is that there is some engineers out there that don't use very good
judgement. On the surface it would seem to me that this building will not
sustain Code provisions for lateral loads. How many of these buildings are
His concern made me think back to the 4' wide vertical concrete panels set at
8' o.c. cantilevering into the stratosphere a distance of 22'. I asked him
how the panels were constructed. He said that they precast them on the slab
and then dowelled into the new footings with re-bar and set the panels with a
crane and epoxy and braced them for a couple of weeks.
It would seem to me that the cantilever calls for Z = 0.40 for Southern
California per Table 16-I; and an I = 1.00 per Table 16-K; and a Cp = 2.00
per Table 16-O in the 1994 U.B.C. The resultant seismic factor is 0.80. And
this sucker is 22' high. Without running the calculations it is not something
that I would design. I guess what I am saying is that when you lose some, it
might be a good thing.
I know of one restaurant that I will never dine at in Southern California.
How many more are there?