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Plan Irregularity Type 5

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The concern is that you design the building such that it will perform
satisfactory if the earthquake forces are not parallel to the primarily
axis of the structure.

The SRSS provisions are typically used when you are performing a response
spectrum analysis and not for wood structures.  What you do is analyse the
structure in two perpendicular directions.  You then combine each term by
taking the SRSS of the results from each analysis and using the combined
term to check compliance.  

Note that after you have performed the SRSS combination that the results
are not in equilibrium.  This is not a problem if you have performjed a
response spectrum analysis since you have already lost equilibrium after
the effect of the several modes have been combined.

It is my opinion that a Type 5 Plan Irregularity does not indicate that the
structure will perform poorly.  As a result I do not believe that this type
of structure should be considered irregular.

Mark Gilligan

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