From: Roger Turk <73527.1356(--nospam--at)compuserve.com>
Date: Tue, 18 May 1999 00:44:40 -0400
I trust that you posted this message in the hopes that the appropriate
building department will see it, recognize the unusual building and check it
out. Maybe you already know that members of that building department are
members of this list.
This type of situation puts structural engineers in a dilemma. The building
is obviously inadequate; the 22 ft high wall panels are probably inadequate
for wind, let alone earthquake, but you didn't design it, so what do you do?
Our professional responsibility is to protect the health, safety and welfare
of the public. Knowing what you know and just never going into the building
does not fulfill that responsibility.
I think that if I were in your situation, I would write the architect and
tell him that based on what I was told, I am very concerned about the
structural adequacy of the building and recommend that he have the
structural design reviewed by an independent competent structural engineer. I
would also provide the names of several structural engineers that I feel
would do a competent review of the project and would emphasize that I am not
to be considered to perform such a review.
Based upon what the architect has already told you, I believe that he
already has questions about the structural adequacy and wants some
reinforcing of that opinion.
A. Roger Turk, P.E.(Structural)
John Ott wrote:
. > 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
. > building.
. > 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 out there?
. > 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?
. > John Ott