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RE: Rigid plywood diaphragms

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>One other thing we forgot to discuss - How do we contend with a gap that
>continues to grow wider between Engineered solutions and Conventional

This has been troubling me for several years and not necessarily in the
specific design area you are discussing but in all areas of design codes.
Non-engineered "Design" Solutions such as Conventional Framing must  be
conservative compared to the Engineered Solution. The whole logic should be
that if you are not going to pay for an engineer to optimise the design and
accound for all variations from the norm, then the resulting "design"
should have a higher factor of safety and thus be more expensive.

This applies in many other areas such as prestressed concrete (my
speciality), concrete design in general and other design areas where the
"deemed to comply" rule is actually less conservative than the properly
calculated result from a theoretically correct calculation. 

This has crept into many design code rules over the years as more advanced
theory and the use of computers for much more complicated calculation has
allowed the Code Committees to intorduce more complicated design solutions 
in many areas. At the same time,  they have also left in the Code the old
simplified "deemed to comply" rules that we all know off by hard for those
who want to take short-cuts and not use the new methods. 

Unfortunately, the old simplifications often result in higher capacities or
less reinforcement or material so that those who are taking the trouble to
do the proper calculations are penalised.

Simplified rules MUST be conservative at the expense of backward
compatibility with old codes and long-remembered rule-of-thumb methods.

In your case, the Conventional Framing methods must move with the times and
be conservative despite the protests of the uninformed.

Regards  Gil Brock
Prestressed Concrete Design Consultants Pty. Ltd.
5 Cameron Street Beenleigh Qld 4207 Australia
Ph +61 7 3807 8022		Fax +61 7 3807 8422
email:	gil(--nospam--at)