From: "Sprague, Harold O." <SpragueHO(--nospam--at)bv.com>
Date: Fri, 21 Jan 2000 17:00:57 -0600
Your timing is perfect. I just returned from the BSSC annual meeting held
this week in Las Vegas. This issue was presented and debated at length
yesterday. Gerry Jones presented the general issue, Jim Harris outlined the
idealized procedure, and Ron Hamburger expanded on the vision of the intent
of the NEHRP Provisions process. The question posed was should the BSSC
develop standards or continue with "... Recommended Provisions..."
The BSSC through the CRDC, CRSC and other committees assembled the 1997
NEHRP into the IBC at the request of the 3 model codes. Admittedly, there
are some warts that made their way through. And the speed and consensus
process is a concern. The speed is the most amazing thing.
Developing code is a tight rope act. By default, writing code establishes
what is perceived as the state of the practice. Procedures for design are
presented and debated in the Building Seismic Safety Council which proceed:
1. Through Technical Subcommittees
2. Through the Provision Update Committee
3. Through the members of the Building Seismic Safety Council
(about ready to begin)
These design procedures are beyond mere theory, but often are not quite
ready to be a standard. The NEHRP was intended as "...Recommended
Provisions ..." and is traditionally viewed as not even a "Pre-Standard". A
true ANSI consensus process was not the original intent of the BSSC NEHRP
Codifying prevalent practice should be a consideration, but only that. If
it is wrong, the degree of prevalence is irrelevant (Thoreau's majority of
one). A properly developed code weighs the state of the practice (as
opposed to state of the art), and looks at the prevailing practice. My
subcommittee went through this daily, weighing many standards against what
the seismology maps and Seismic Design Procedure Group were doing.
Jim Harris announced yesterday that the "standard" ASCE 7-98 (no this is
not a typo) will still be coming, but is obviously late. Originally
intended to be out in 1998, changes and the consensus process mandate the
late delivery. In its current configuration, the ASCE 7-98 will include the
1997 NEHRP Provisions with few modifications. Some of the modifications
were born out of the development of the 2000 NEHRP.
S. K. Ghosh presented the ACI 318-99 which went out as scheduled in 1999,
but the anchorage was not included due to time constraints. The ACI has
developed a separate document on anchorage design. The ACI 318-99 included
most of the NEHRP changes in concrete so that the IBC could incorporate the
ACI 318 directly. ACI is now on a 3 year cycle parallel to the IBC and the
Coordination is essential among all the entities that develop the code
including the materials code promulgators, due to the seismic response of
materials and assurance of proper detail consideration.
The FEMA 343 assessment of the FEMA 273 was also presented, which is the
first real stab at structural seismic performance. It showed some of the
holes in implementation, and some of the strengths. It was a very good
study, and a must read. (No NY Post review yet. Humor intended) The FEMA
343 showed what it was like to rehabilitate buildings by practicing
engineers using the FEMA 273. The engineers were not specialists, experts,
researchers, or ...... dare I say ... code writers. Many of the engineers
had little or no experience in seismic design. The results were very
enlightening and useful.
In regard to nonbuilding structures mandatory regulations must be the norm.
If regulations are voluntary, owners will only look at the cost, and safety
will be a topic for the lawyers in a back room. Safety should not be a
function of the law firm that represents the owner. If designs have any
semblance of voluntary provisions or options, the performance must be
obvious to the public, the building official, and the owner. Unfortunately
we are not ready for performance standards yet.
The practicing structural engineer must always be kept in mind. The level
of sophistication should not require a nonlinear dynamic analysis on every
element on a building. We can provide bounds to allow for simple model
development for the accuracy we need.
I use myself as the acid test. If I can understand it, any EIT should be
able to. I'm just a guy who was to clumsy to continue being an iron worker
(broken bones and scars to prove it).