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RE: Plwd: Rigid Diaphragm Analysis - Opinions Wanted

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Your comments are true when designing a small building with small forces
on good soil, but the higher forces apply to all elements in the LFRS.
The 20% cost increase was just a correlation (not having much info on
costs) but it would seem that the extra time spent in the design
outweighs the construction cost increase.  I work mostly on tilt-up
structures that are priced in cost per square foot of coverage in a
general sense. If I'm designing diaphragms, wall panels, shearwalls,
footings, collectors all to a 20% higher force level I think the cost
can be significant. Don't forget that our forces are already swelling
compared to the previous code and an additional 20% force level won't
translate well to an established developer who bases the costs on
present construction. If you are designing a house, I grant you the fact
that the costs may not be that significant.

Gerard Madden
CRJ Associates
Design Engineer, Structural Department
650-324-0691x129
650-324-0927-fax
gerardm(--nospam--at)crjarch.com


> -----Original Message-----
> From:	ASQUILALA(--nospam--at)aol.com [SMTP:ASQUILALA(--nospam--at)aol.com]
> Sent:	Tuesday, July 13, 1999 8:21 PM
> To:	seaint(--nospam--at)seaint.org
> Subject:	Re: Plwd: Rigid Diaphragm Analysis - Opinions Wanted
> 
> > I feel that if you design your buildings for a 20% higher force and
> your 
> competitors
> > spend an extra day or two doing calcs, your clients will gradually
> go
>  >elsewhere. I feel that engineering fees are nothing compared to
>  >construction costs. I recommend (not that I'm some authority) to do
> the
>  >extra calcs, save your client some money, and you'll also know the
> code
>  >a little better. If your buildings cost 20% more than the
> competition,
>  >you'll lose.
> 
> Providing extra 20% higher force doesn't translate to 20% more costs. 
> Sometimes doubling the force will not even increase the costs by 10%.
> 
> Assuming that after calculating using the long method you end up with
> shear 
> equals 275 lbs/ft. providing shear panel with 360 lbs/ft capacity.
> Then 
> using the simplified method you will come up with 330 lbs/ft, you will
> then 
> use the same 360 lbs/ft capacity.
> 
> Even if you need a little bit more stronger shear panel,  you might be
> just 
> adding thickness (it will increase the material cost but not
> necessarily the 
> labor cost), or you will make the spacing of nails closer (material
> cost and 
> labor cost will negligibly increase).
> 
> I happen to be both working in the design engineering and construction
> 
> industries.  My full time work is in construction and my part-time
> work and 
> moonlighting work are in design and engineering. It is sometimes funny
> that 
> we (engineers) think that we are trying to save the owners some money
> by 
> doing more complicated calculations. But in reality our efforts are
> not that 
> too significant.
> 
> You are right that engineering fees are nothing compared to
> construction 
> costs especially when they are in a hurry to finish the job.  The
> faster you 
> finish the design the more savings the contractor or the owner will
> gain. 
> 
> 
> Engr. Alfonso S. Quilala Jr., P.E.   
> 
> 
>  
>   
>  
>