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Re: URM

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This is a good question. Based upon the URM question I raised, I took a
design approach that to control the stiffness of the diaphragm so as to
balance crosswall requirments and anchorage. However, how does the diaphragm
know how to act or will the diaphragm provide greater stiffness as indicated
in the UBC or will it react as predicted in the ABK methodology and limited
in the UCBC Appendix 1 Chapter 1.
Satisfying the code in this instances appears to be the most logical choice
since the debate between "Special procedure" and "General Procedure" has not
been resolved and the code provides us the alternative based upon our
judgment as to which one to use. The difference between the two is
negligible on one story structures, but is much greater the taller the
building.
Finally, isn't the purpose of a Hazard mitigation code to balance safety
with ecconomy? I don't want to create a hazard, but historically, anything
that we have done to anchor these buildings has proven to make them perform
better.  At some point adding anchors and diaphragm stiffness becomes
detrimental to the URM wall as the shear transfer increases. I don't think
the solution as to whether it is best to exceed code standards for hazard
mitigation is a simple answer.
Any other comments.
Dennis Wish PE

-----Original Message-----
From: Charles Greenlaw <cgreenlaw(--nospam--at)speedlink.com>
To: seaoc(--nospam--at)seaoc.org <seaoc(--nospam--at)seaoc.org>
Date: Thursday, January 08, 1998 9:49 PM
Subject: Re: URM


>> The code requirement for the connection of these [cross-]
>>walls to the diaphragm is only that they be connected for the crosswall
>>capacity. In most cases this can be achieved within the length of the
>>crosswall.
>>
>>Have I sufficiently baited anyone else to respond ? :)
>>
>>Regards,
>>
>>Mark D. Baker
>>Baker Engineering
>
>>if so, then you don't need to check the connection to the
>>diaphragm.
>
>
>The responses preceding this one are reasonable and well-stated, but they
>all focus on satisfying what the Code wants.  Do you also have an interest
>in the perhaps separate purpose of satisfying what the Building wants? It
>might be different enough to matter --to the building.
>
>But that's a private concern between you and the building. You get to work
>out that little relationship in your own style, without us "in-laws"
>watching. It can be a lot of fun, too. It's where you get to perform
>engineering free-style, after doing the compulsories for the judges. If you
>do this, and if it's fun, please don't let anyone know. There are several
>code-change committees out there who don't like engineers to use
independent
>judgment and enjoy it without guilt.
>
>Thanks for baiting another response on this provocative retrofit concept.
>
>Chuck Greenlaw, S.E., Sacramento CA
>
>
>
>