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Re: Plywood Roof Diaphragms

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knee jerk method: Insult the other engineer and make religious connotations as
to why one should not talk to them. Wave your arms around while saying this,
even if it is a phone conversation.

Higher authority method: The code is the law, the statute, it requires the
detailing you are recommending. Hold out the code on your upright palm and slap
the cover with your other hand. Offer client to put their hand on the code.

Seduce with the intellect: Keep talking. Using deeper and deeper sources of
theory's, testing, physics, and levels of risk of collapse or getting caught.
Brag of the programs you wrote. Tell of the testing. Suggest that all of your
social contacts are with other engineers only.

Change the subject: and find a hobby you can share interests in. Smile. Create a
little twitch to appear more human.

Maybe client is a visual person. Show pictures... of the detail needed, of
finished projects with the detail, of your kids, of things you have never let
your kids seen.

Maybe client has quit smoking. Sneak the client a good tobacco product.

Remind client he owes you money and if there is to be a new engineer you will be
happy to give the new engineer your box of related preliminary scratch paper,
after you are paid.

Offer to design it for the client and install it for the contractor, for free.

Invest in your own property with the money paid and design it the way it should
be.

David Merrick, SE

CDaniels wrote:

> I seem to be continually running into problems on projects with regard to
> the interaction of the roof diaphragms and shear walls.  Most of the
> projects I work on are  single story wood framed buildings or at least truss
> framed roofs and CMU bearing walls.  There are no seismic loads and most of
> the time code specified nailing of roof and wall sheathing is adequate but
> lately wall heights and square footage keeps growing and I find myself
> stretching for solutions.  My experience with other engineers in my area and
> even my co-workers is that they don't do a lateral analysis or they make
> exorbitant assumptions which nullify the need to do a lateral analysis.  How
> does one explain or justify this to a client that only knows the other
> "engineer" says that he/she doesn't need blocking, drag struts, bracing etc.
> Below is a list of dilemmas I seem to be continually involved in arguing
> against or for.
>
> * How do you transfer diaphragm forces from the roof sheathing to the wall
> plates without blocking between the trusses or rafters?  The blocking is the
> first thing that the architect wants to eliminate because of roof venting
> and here in the East no drawings I've seen ever shows blocking at this
> location.  If you use hurricane ties at the trusses it is possible to
> develop enough strength to justify the design but if you have a truss with a
> raised heel is roll over of the trusses a problem?
> * On a roof with pre-engineered trusses, how is an interior shear wall
> handled?  Can the bottom chord of the truss be used as a drag strut or
> collector if the shear wall is only a fraction of the building width and
> does not extend to the underside of the roof deck?  This would assume that
> the pre-engineered truss(es) above the wall would have to behave as a rigid
> element.
> * On a roof with pre-engineered trusses, how is an interior shear wall
> perpendicular to the truss span handled? Can this even be done without an
> exhaustive design of cross bracing within the pre-engineered truss system to
> transfer forces form the roof sheathing down to the shear wall?
>
>
> Chris Daniels
> 570-323-6603
> ced(--nospam--at)larsondesigngroup.com
>
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