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Re: Redwood Tree Seismic Hazard ?

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In the Pacific Northwest there should not be any need for dynamic analysis
of trees for seismic response because Ms. Nature has provided them a climate
of perpetual, overabundant damping.  C.G., Sacramento, CA

At 07:46 AM 10/17/97 +0000, you wrote:
>Here in the Pacific NW, we have our share of problems 
>with tree foundation failures during windstorms.  Most of 
>this has been traced to an inherent instability problem of 
>not having adequate overturning resistance  in the supporting soil. 
>Other investigators have determined the root of the problem may be 
>the structural elements of the tree foundation itself.
>Local building officials have met with the designer, Ms. Mother 
>Nature, but have not been able to come to a mutually acceptable 
>conclusion.  When the matter was submitted to the Board of 
>Registration for Engineers, counsel for Ms. Nature challenged the 
>venue, claiming the matter was more appropriate for the Landscape 
>Architecture Board. While this jurisdictional issue is being 
>resolved, Ms. Nature has been allowed continue her growing practice 
>of tree design.
>The seismic response of trees is probably not too much of a 
>problem due to the period of the ground motion and the 
>fundamental period of the tree.  Perhaps a large tree house 
>would change the trees fundamental response to that of an inverted 
>pendulum, but I speculate.  Professor Spot Tedowl, 
>University of Washington Paul Bunyon Chair, had thought about 
>performing extensive studies of this issue but lack of funding and 
>quick logging forced him to change his plans.
>I believe several years back, the Dutch structural engineer, O. ver 
>Design, looked into designing houses to withstand arboreal impact, 
>but concluded that a chainsaw and common sense usually resolved the