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

Re: Report on Wood Diaphragm Issues

[Subject Prev][Subject Next][Thread Prev][Thread Next]
After reading your post I now know that given the opportunity I will not do
work in Big Bear as long as that idiot is there.  Several of our local
building officials (we have 5 separate jurisdictions around Lake Tahoe)
tried the Exp D nonsense when it first came out.  Fortunately there is a
good design example in the Wind commentary put out by SEAW (as well as a
careful reading of UBC 1616) that clearly shows that D cannot apply, that we
were able to use to combat this kind of illogic.  As far as combining snow
with seismic there are several papers that have done a probabilistic study
of combining snow and seismic.  They all support the use of the minimum 1/4
as suggested in the code.  We (us local Tahoe engineers) have used this
information to actually reduce the amount of snow used as DL during seismic
in Placer co. (North shore) and we are working on El Dorado Co.(south
shore).  If there is no engineer on staff at the Big Bear building dept. you
might let the official know that you are willing to file a complaint with
the board for practicing engineering without a license.  I have found this
to be a very effective tactic when dealing with non-professional +ACI-Barney
Fife+ACI- type building officials.

As far as your last paragraph, in one of this past summers' SEAOC on line
issues, Dennis reprinted an old article by Charles Greenlaw which reviewed
+ACI-The Death of Common Sense+ACI- by Philip K. Howard.  I would highly recommend
all to read this well written article as well as the excellent book.  The
book gives insight into why we are having to deal with such an overly
complex code as well as how petty bureaucrats have come into so much power.
It is a good read but also depressing.

Randy Vogelgesang S.E.
South Lake Tahoe

-----Original Message-----
From: ken
Date: Friday, January 07, 2000 4:34 PM
Subject: Re: Report on Wood Diaphragm Issues

+AD4-It is a sad day when we allow attorneys and building officials to dictate
+AD4-how we are to design structures. Anytime the code allows for a choice in
+AD4-engineering design, the building officials will always opt for the more
+AD4-conservative method. Case in point is the wind exposure definition of case
+AD4-or case c which has resulted in Exposure +ACI-c+ACI- being required as the standard
+AD4-throughout Southern California. But to argue for Exposure +ACI-b+ACI- is futile
+AD4-(aerial topo maps,etc). Along with some jurisdictions requiring 90 mph wind
+AD4-speed and Exposure +ACI-c+ACI- results in designing for a Class 2? hurricane. The
+AD4-City of Big Bear Lake, which has a non-engineer building official, has
+AD4-required the following criteria for lateral design for projects close to
+AD4-lake: 80mph Exposure +ACI-d+ACI- , 100psf snow load and no 75+ACU- reduction for snow
+AD4-loads for seismic design ( dl  100+ACU- snow).
+AD4-So if we allow the Building Officials the choice between flexible or rigid
+AD4-diaphragms, they will always opt for the more conservative method. To use
+AD4-the UBC Standard 23-2 for the calculations of the diaphragm and shear wall
+AD4-deflections along with their wide range of assumptions and parameters can
+AD4-never accurately determine rigidity or flexibility.
+AD4-To try and explain the 1997 UBC earthquake design chapter 16, along with
+AD4-sections 2320.5, 2320.11.4, 2:1 aspect ratio for plywood walls to the
+AD4-general public results in appearing to be stupid.
+AD4-Somehow sound engineering judgement, common sense and  practical design
+AD4-experience, have been replaced by code formulas and ambiguous requirements
+AD4-that just don't work in the real world.