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Re: Simplified Seismic Design Trends

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I have been following the thread on "Code Simplification" and would like to   share with the list subscribers the SEAOC board mandate for the Code Streamlining Committee and where we are in the process of developing a streamlined Earthquake Design Manual for Low Rise Building Structures:

The seismic design provisions in the 1997 Uniform Building Code (UBC) have introduced several changes and revised many of the requirements from the 1994 UBC.  These modifications include strength level seismic load demands, a redundancy factor, an overstrength factor, and a height dependent force for attachment of elements and components.

The cumulative effect of these new provisions has introduced a high degree of complexity coupled with the potential for ambiguous interpretations. This has led a great number of design professionals with varying degrees of experience to voice serious concerns about the provisions as they apply to simple, low rise structures constructed from any of the common building materials (wood, concrete, masonry, and steel).

The 1997 UBC seismic design provisions are intended to cover a broad spectrum of structure types and sizes, and various conditions that can occur in building structures. However, many of these requirements are only applicable to very specific conditions found in a limited number of buildings. Also, whereas seismic load demand provisions are predominantly listed in Chapter 16, the material design provisions are scattered throughout the Code.  Because of this complexity, the potential exists for misinterpretation and misapplication of these provisions.

In order to reduce these complexities as they apply to low rise structures, SEAOC initiated the Code Streamlining Committee with a mandate to reformat the seismic provisions of the 1997 UBC in order to make them more user friendly as they are applied to the most common low rise building structures.  

The Manual is not a “simplification” approach, nor a reduction in the seismic standards. It is a reorganization for process and information. This is the essence of streamlining. Its purpose is to locate in one concise document the information on the seismic design provisions that are applicable to new low rise buildings since they comprise the great majority of the building stock.  These provisions have been pooled from 1997 UBC Volumes 1, 2 and 3.  The Manual covers seismic design only.  It does not cover wind design.  It includes design aid tables and commentary on contentious issues such as flexible vs. rigid diaphragm in wood frame construction, the Rho factor, etc... 

As practitioners, we must keep in mind that we are bound by State law to use the applicable building codes.  The Manual is intended to be available to use immediately upon publication since it is actually Code language.  A simplification process (which I think is still needed) is very lengthy and may or may not make it in the next adopted Code, whatever that Code may be (NFPA, IBC, ...). So this manual will be a handy GO TO reference manual for seismic designers.

The Manual is in its final draft and is being reviewed by the Structural Standards Committee and Building Code Committee.  I hope that it will be ready for publication by Mid-Summer.  

Also, SEAOC is considering preparing another manual that will serve as a seismic design primer, an earthquake design 101 for practitioners.  

I hope you find this information helpful.  Please send me any feedback.

Janah A. Risha, S.E.

PS: Please note my correct email - jrisha(--nospam--at)risha.com

<<Barry - SEAOC has formed a committee titled "Code Streamlining" currently
chaired by Janah Risha jrisha(--nospam--at)risha.com

Similarly, BSSC has a "SIMPLIFIED PROCEDURES TASK GROUP" Chaired by Bill
Holmes.

FYI, Fred>>
-- 

Janah A. Risha, S.E.
President
Risha Engineering Group, Inc.
"Your Structural Connection"
410 East Cypress Avenue
Burbank, CA 91501
Voice		818-729-9777
Fax		818-729-9779

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