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Re: Performance-Based Seismic Design, Po

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Bruce Shephard wrote:

. > The New Zealand Building Code is based on performance criteria.
. > 
. > Various codes for loading, materials etc are deemed 'means of 
. > compliance'.   
. > 
. > The codes specify minimums for facilities,  usually based on life safety 
. > and post disaster functionality.  Design is not constrained to code 
. > application but alternative innovations may be accepted with 
. > justification.
. > 
. > Some building owners take the option of design and construction beyond 
. > the minima.  This is usually to protect very valuable contents (Museum of 
. > New Zealand - Te Papa) or to ensure business continuity  (telephone, 
. > newspaer printing),  or to enable post disaster function (Government, 
. > emergency servies).  For example most base isolation applications have 
. > been for more than 'minimum' earthquake performance.
. > 

Isn't this what the current codes do?  The codes specify the minimum 
requirements, but don't prohibit you from providing something better.

It is my understanding that the *entire* building code is targeted for 
"performance based design" which would not be limited to structural 
adequacy.  In an article by Jim W. Sealy, FAIA, the July-August 1997 issue of 
"Building Standards" had the following example of how the IBC Performance 
Code would be worded concerning guardrails:

"Objective:

A barrier shall be provided where a person could fall from one level to 
another [30 inches (762 mm) or more].

Functional Statement:

To prevent people from _unintentionally_ falling from an opening in the 
building's envelope, or from one level to another.

Performance Requirements:

Barriers shall:

1. Be continuous for the full extent of the hazard.
2. Be of appropriate height.
3. Be of adequate rigidity.
4. Be of adequate strength to withstand foreseeable loads, both static and 
impact.

Solutions:

A. Roofs with permanent access shall have permanent barriers.
B. When barriers have openings, they shall be of an appropriate size:
   1. To prevent people from falling through.
   2. To restrict passage through, when barriers are located in areas likely 
      to be frequented by children under 6 years of age."

I can see nothing in this that establishes minimum requirements that have 
been found necessary through experience.  It leaves it up to the designer to 
determine the "appropriate height," "adequate rigidity," "foreseeable loads," 
etc.  Since the purpose of the barrier is to prevent a person from 
"unintentionally" falling from one level to another, they would not be 
required in places where people would commit suicide (e.g., Empire State 
Building).

A. Roger Turk, P.E.(Structural)
Tucson, Arizona