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Re: Commercial Construction Standards

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Dennis,

I will limit my comments to the embeded columns in the store front because it
has been too long since I did any design work.  I used to use this system in URM
retrofits when there was a store front which needed to remain open.  At that
time (pre-Northridge) many contractors did not want to try and develop moment
connections in the field because of the expense.  Consequently, I took the
approach you are taking and had good success.  (Some of these were in the
affected area of Northridge and performed as intended!)

Your grade beam will have to be fairly deep in order to provide the fixity you
are looking for.  The advantage is that you will use smaller longitudinal bars
which will make the contractor happy.  Watch your tie spacing and make sure you
get some "U" shaped ties that surround the column and extend into the grade
beam.  Use a good development length on these ties as this is how the moment is
trasfered to the grade beam with the column is moving towards the end of the
grade beam--in the other direction, bearing is how the moment is primarily
transfered.

Good luck, hope this helps.

Rick Ranous

Dennis Wish wrote:

> I am starting a commerical project this week. It's been a long time since I
> have done anything but custom residential, cold-form and retrofit work. This
> appears to be very easy, but I have a few questions on engineering standards
> which some of you might be able to help with:
> The project is a Starbucks Coffee and five other storefronts. Wood frame,
> TJS roof trusses (parallel chord) with sloping wall plate, tee-bar ceiling,
> three solid sides and one openfront, slab on grade. A few unique features
> such as a small parapet type tower structure (facade), and a covered portola
> (walkway).The building is essentially 57' x 120 feet long. The trusses
> (TJS)clear span the 57 feet. there diaphragm is 5/8" struct I plywood, all
> side walls are fully sheathed from plate to plate. Overall plate height
> rises from 12 feet to about 16 feet (3/8" per foot roof slope). Here are a
> few questions:
>
> 1.  Would you recommend welded wire fabric in the slab or a more durable #3
> rebar arrangment. What is the conventional layout of #3 rebar (6" o/c, 12"
> o/c or 18" o/c).
> 2. The stores are approximately 15 feet wide, however the owner does not
> want any interior partitions for load bearing. He wants to be able to
> combine stores if wanted. What is the maximum slab area for installation of
> expansion joints? What is the conventional slab thickness (4" or 6")
> 3. I intend to use embedded steel in the open front - pendulum type
> columns - which conforms with the clients past conventions. Rather than
> embedding into post foundations, I plan to use the foundation as a grade
> beam with erection pads below (which will be bearing pads as well). I want
> to develop lateral moment in the grade beam. This posses two questions:
> a) should I place the grade beam below and independent of the slab edge? I
> think it is a good idea since the grade beam will be f'c=3000 psi concrete
> with special inspection required and also it will keep the structural
> gradebeam independent of the non-structural slab. Any other thoughts?
> b) Should I follow '94 code and distribute lateral according to an Rw of 6
> or follow the '97 code and take the penalty for the pendulum condition?
> Also, if I follow '97 UBC convention should I use the lateral component for
> the entire building or just the embedded poles?
>
> 4. 3(b) leads to this question - Has the SEAOSC code committee taken a
> position yet regarding embedded column lateral design. It was suggested in
> their minutes that they intended to take the position that only the columns
> be loaded with higher shear in order to compensate for story drift. Any
> comments yet?
>
> 5. I have recomended the use of TS (Timber Strand) studs. This is a low
> budget project, but I am under the impression that the labor savings in
> taller walls with dimensionally true and straight lumber will compensate for
> the labor cost and scrap necessary to deal with crowned, warped and twisted
> studs.
>
> Any comments you might have would be greatly appreciated. At the least,
> please let me know if you think I am on the right track.
>
> Thanks in advance for all advice.
> Sincerely,
> Dennis S. Wish PE
>