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Re: Plan Irr. for Shear Walls

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Larry:
 
Since we are running strength level force calculation within the section 1630 and the Em is used to represent the maximum earthquake force that can be developed in the structure, I will use the "ultimate capacity" with the section 1612.4 load combinations in your case. However, you may want to verify with the holdown manufacturer how they got the "ultimate capacity" in the current catalog. Those numbers usually do not represent bolting/ nailing the holdown devices to the wood posts condition if you are designing wood structures.
 
You may want to checkout other components(i.e. nail, strap, anchor bolt, shear wall) to find out which one will control your design. There have been some difficulties for us to obtain those "ultimate capacity" to be used in the design. Also make sure the ratio of the "ultimate/allowable" is less than the Omega-o factor so you will not design for force higher than the Em. The allowable stresses can be increased by 1.7 along with the 1.33 duration of load increase permitted in Chapter 23 for wood structure working stress design.
 
By the way, how will you limit the vertical deflection for a beam supporting shear wall under the Em or "ultimate capacity" force?
 
 
Regards,
Julian Chu
----- Original Message -----
To: seaint
Sent: Friday, April 14, 2000 8:50 AM
Subject: Plan Irr. for Shear Walls

If I have a plan irregularity, (i.e. offseting shear walls), I must comply with Section 1630.8.2 using the omega factor to design the supporting elements below except that Em need not exceed the maximum force, etc, (Exception 1). Does this mean that if a holown for the shear wall above has an allowable "capacity" of 5.0 kips, that this is the maximum force necessary to design to, or is it the holdown ultimate capacity, or what??
 
Thanks in advance,
 
 
Larry Hauer SE