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RE: Drift limitation

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I think my question was more rhetorical as I recognized your contribution
and those of the others who have participated. However, my point was that it
has taken two years to either discover the confusion or to rectify it in the
professional community.
While we have discussed this and you have been, most certainly, as helpful
as Ben has been in the issues, less than 2% of the professional community
obtains their information from the SEAINT List. What provisions are brought
forth to clearly define the intent of the code to the rest of the community.

As one suggestion, how about answering the questions and giving clear
direction in each monthly newsletter from each chapter and on the Web
services. While I can't expect SEA to extend their reach to non-members, it
would be in the best interest of the entire profession to create an on-going
FAQ (Frequently Asked Questions list that chooses issues such as this or the
Rho discussion from Gary Searer) and makes an attempt to bring the issues to
the professional community.

What is gained is a growth of faith that there is a renewed link between
code writers and practioneers who have felt left out in the cold by the lack
of formal and clearly defined direction on issues such as this.

Martin, you have made progress, since leaving the Chair position of the
Seismology Committee, to respond to the members on the List and I commend
you for this. However, it is important to have a formal response on
interpretations of the code so that there is no incorrect way to design.

Dennis S. Wish, PE

-----Original Message-----
From: Martin W. Johnson [mailto:MWJ(--nospam--at)]
Sent: Tuesday, February 06, 2001 8:42 AM
To: seaint(--nospam--at)
Subject: Drift limitation

from Dennis:

"Martin, if you can't comment who will and who should or are we simply to
time hunting for the information or drawing our own interpretation."

Actually, I thought the discussion yesterday pretty well covered the basics.

The topic of whether 30-7 should be excepted came up at the last seismology
meeting, and I was very much surprised when I heard Bob Bachman agreeing
John Hooper that there had been talk about allowing the exception at the
convention.  However, Charlie Kircher, who chairs the ground motion
recalled that the concerns of Hall & Heaton about velocity pulses were also
being reviewed by the committee at about the same time as the IBCO
and that the perservation of the 30-7 equation was considered at that time
as a
measure of protection for tall buildings.

I really can't tell you exacty what agreements may or may not have been
made - I
was not there, and I have heard some conflicting recollections myself.

The fact is that the requirements for drift of tall buildings have already
relaxed in the 97 UBC even when Eqn 30-7 is considered because in the 94 and
earlier codes the force used to check for drift was greater.  I personally
not think that it is appropriate in zone 4 to push the envelope further and
remove the 30-7 limitation. Whether it had any different meaning or purpose
earlier codes is irrelevant, it is it's relevance today that matters.