To: seaint(--nospam--at)seaint.org, aec-residential(--nospam--at)polhemus.cc
Subject: Re: Exposure D Wind/Seismic Loads under IBC
From: Charles Greenlaw <cgreenlaw(--nospam--at)speedlink.com>
Date: Wed, 07 Jun 2000 17:02:19 -0700
At 11:07 AM 06/07/2000 -0700, you wrote:
>While we're at it, I'm dealing with "build-for-expansion" difficulties
>for a hospital in Little Rock. The IBC with increase my forces 6 TIMES
>over SBC. (1.5 for hospital and 1.5 for lack of redundancy included).
>What is this doing to people in other parts of the country, incl. CA?
To answer the last question, a PE friend who specializes in woodframe
residences in Zone 4 Coastal California visited last weekend, and said that
the 97 UBC has caused him to have to submit to others double the quantity of
structural calculations that were sufficient under the 94 UBC. But there is
no material change in the design forces, or in the construction provisions
he finds it necessary to specify.
He said that all the building departments he deals with admit that they do
not understand the 97 UBC seismic sections, and so they want the engineers
to submit calculations covering every last code provision that they think
might plausibly pertain. The result is that he now creates great stacks of
paperwork which simply confirm that the usual members and details are OK,
same as they were before the 97 UBC took effect.
The building department personnel tell him they like his work, but say to
him that no two engineers follow the code in the same way; there is no
settled consensus what it means or requires. This is worrisome, because it
means that other engineers can more credibly be hostile expert witnesses
against you, in both civil litigation deep pocket picking, and in
overzealous PE license disciplinary attempts.
You asked about the 2000 IBC, not the 97 UBC, but in seismic the 2000 IBC is
an evolution of the 97 UBC. Site seismicity and how to reckon with it has
been recast, as Harold Sprague explained straightforwardly, and that change
appears to reflect much improved technical knowledge, plus uniform
application of risk.
The two 1.5 factors in contrast come from California SEAOC Seismology
Committee philosophy that is other than technical. The 1.5 importance factor
reflects a view that some occupancies deserve a higher factor of safety than
others, but got its incentive impetus when two hospitals came to grief in
the 1971 San Fernando CA earthquake. A new state bureaucracy was created as
The other 1.5 factor is new for the 97 UBC, and a great deal of unrest has
been one result. On its face, it is a piece of "social engineering" like tax
policies openly are: it is to encourage engineers to provide a greater
number of separate seismic resisting elements than the codewriters believe
has been the trend. Unfortunately, engineers aren't owners or architects,
and merely get caught in the middle as bearers of bad news to their clients.
There are many e-mail messages in the Seaint website's archives, among other
writings, that expose the Rho factor as lacking technical merit, and as
producing irrational, anomalous, grossly inconsistent, absurd, ridiculous,
and counterproductive results. Now there is a fight going on between some of
the Rho-originating SEAOC committeemembers and their successors, the latter
wanting to correct the former, for 2003 IBC purposes, and being opposed.
Neil Moore observed that these provisions are "project killers." Quite so.
But they also can be project creators. Your "build-for-expansion" hospital
might have to have existing portions (if any) torn down and replaced. You
might instead have to design retrofit strengthening of it. If you design in
anticipation of expansions having to conform to 2000 IBC, go overboard.
Future editions could be yet more severe and complicated, in part because
some influential engineers push code changes their firms have developed
peculiar capabilities to comply with, compared to competitor firms.
Now for another unavoidable cheap shot: local officials in your state or
local jurisdiction might just choose to waive the offending code provisions,
either officially or covertly. Either way, it is a form of rebellion other
than the armed kind Fountain Conner wrote of. If waived covertly, the
engineer is not helped; it only puts the middleman engineer at risk of being
sued and prosecuted as a scofflaw for not furthering the locally unwelcome
social engineering aims of remote codewriters and ICC-level code adoptors.
Ultimately, public policy and its discretionary enforcement belongs to
elected officials and their subordinates. The recent Elian Gonzales vs INS
appellate court decision affirmed that emphatically. Let your own public
officials declare on the record what parts of the code apply to your
project, and what don't, so you can proceed with your work. The buck and the
heat should stop with them.
Charles O. Greenlaw SE Sacramento CA