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Re: Ron Gallagher's Comments in SEAOC Plan Review

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Here's the facts with regard to the rigid diaphragm requirement,

Refer to your 1988 UBC (yes that's right 1988!!)

Section 2312 sub para 5.
The desgin story shear Vx, in any story is the sumof the forces Ft and Fx
above that story.  Vx shall be distributed ot he various elements of the
vertical lateral force resisting system in proportion to their rigidities,
considering the rigidity of the diaphragm....

Section 2312 sub para 6.
Provision shall be made for the increased shears resulting from horizontal
torsion where diaphragms are not flexible.    Diagphrams shall be
considered flexible for the purpose of this paragraph when the maximum
lateral deformation of the diaphragm is more than two times the average
story drift of the associated story....

Seem familiary????

Also Ron Gallagher is not the Seismology chair.  So - I don't think he was
agrandizing himself.

Charles Greenlaw <cgreenlaw(--nospam--at)> on 05/07/99 04:42:38 PM

Please respond to seaint(--nospam--at)
 To:      seaint(--nospam--at)                                   
 cc:      (bcc: Ron O. Hamburger/EQE)                         
 Subject: Re: Ron Gallagher's Comments in SEAOC Plan Review   

Neil, can you clarify where in '94 UBC Sec 2314.1 that the quoted item
appears. I cannot even find mention of the adjective words rigid or
in connection with the term diaphragm, and this section is on wood shear
walls and diaphragms. I have the May 1, 1994 second printing of the 94 UBC.

At 11:04 AM 5/7/99 -0700, you wrote:
>1.  Both the 1994 UBC and the 1997 UBC referring to sections 2314.1 and
>2315.1 respectively state "DIAPHRAGMS, WOOD - Not acceptable as rigid

Wherever it appears, I ask, "Not acceptable as rigid, compared to what?"

Suppose the wood diaphragm is the floor platform atop upwardly cantilevered
piles in an irregular array of lines, or mixed with other means of
resistance? -- Like for a house sittin' on the dock of the bay. Do we
distribute shears to each pile according to the distance to the next pile?

Seems stupid to refer to diaphragms all these years by offhand, shortcut
stereotypes, and then apply ill-stated, shot-from-the-hip-in-the-dark
formulas to assign precise distinctions to such terms. In due course
engineers will be prosecuted, and their licenses lifted and their savings
drained, because they fell below a "standard of care" in using this mongrel
provision that can't admit of one itself in its own heritage.

As for Dennis, when someone is upset, they are apt to behave somewhat like
an upset person behaves. Even the best doughnuts have holes in them. Cops
still buy them in spite of it.

Great weather here in and around Sacramento, too.

Charles O. Greenlaw  SE   Sacramento CA