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Re: Plwd: Rigid Diaphragm Analysis - Opinions Wanted

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> 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.