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Re: SEAOC seismology opinion regarding 10/Lw factor for calculating rho

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At 12:21 PM 11/22/99 -0800, you wrote:
>During the Sept 29 seismology meeting, the committee voted to submit a code
>change proposal for the 2001 IBC Supplement No. 1, with the following language:
>"In light-frame construction, the value of the ratio of 10/Lw need not be taken
>greater than 1.0."
>Please note that this is just a proposal, which is subject to possible
>during upcoming ICC hearings.

This proposal is appreciated and would appear to help in houses and other
small buildings, etc., but leaves ambiguous what happens in a basically
light-frame building where a proprietary steel diagonally braced frame is to
be used in lieu of a wood shear wall, or some other non- "light frame"
element like a Simpson Strong Wall or a steel moment column or moment frame
is to be used. The 2:1 wood panel shear wall ratio limit forces a lot of
these things into the designs. A remedy for the rather glaring 10/Lw fiasco
needs to address the entire situation. The habitual, longstanding
disadvantage of Seismology Committee not reaching out to the light frame and
residential engineering community still shows in this proposal's wording. 

Although the earliest formal code change may be the 2000 IBC Supplement No
1, what about recommending to the Calif Bldg Stds Commission and other
adoption-mandating bodies, and to ICBO, and IBC, that this rho factor
element for light frame projects was a mistake from the beginning, and
deserves to be corrected forthwith. Then local adoptions can be amended to
suit, and good sense can regain legality.

This last step may seem unusual, but when a criminal in prison is discovered
to be innocent, a pardon can be arranged without first waiting for the
minimum sentence to have been served.

Charles O. Greenlaw  SE   Sacramento CA