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Re: LADBS Info Bulletin ST-12

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The City of Los Angeles Department of Building and Safety has published a
draft of an Information Bulletin, dated January 27, 2000 and revised May 15,
2000. It is entitled "Interim Alternate Method for Distribution of Lateral
Forces in Wood Frame Buildings Assuming Flexible Diaphragms." The scope of
this bulletin is to address the issue of the code requirements for diaphragm
flexibility and story drift in wood-frame buildings.

This draft bulletin gives the option of using the Basic Static Force
Procedure, employing shear wall displacement analysis and story drift
limitation, or using the Simplified or Alternate Basic Static Force
Procedure, employing "Conditions for Assuming Flexible Horizontal
Diaphragms."

For anyone who is up on this stuff, my first question is: has this draft
document since been revised? Secondly, has there been further explanation
given for the last condition listed: "shear panels and hold-downs provided
shall be designed to exceed the design load by at least 20%."?

Specifically, I cannot for certain determine just what is the "design load".
Is this 75% of the values listed for vertical shear panels in the Los
Angeles Building Code? If this is the case, then are we to take 20% off of
these reduced values, resulting in 60% of the listed capacity? And, the same
for the holdown hardware?

Thanks in advance for your informative response.

Richard L. Flower, P. E.
Los Angeles


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