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RE: 1920's 9 story concrete frame building

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1:2:4 mix = 1 part cement : 2 parts fine aggregate :  4 parts coarse
aggregate (all by volume);  from "Practical Structural Design" by
McCullough, 3 ed., 1927.  Average strength of 1:2:4 limestone aggregate mix
= 2505 psi (varies from 2206 to 2708), 1:2:4 sandstone mix averaged 1620
psi;  from "Concrete Engineers' Handbook" by Hool & Johnson.  Seems that
1500 to 2000 psi was often used as design compressive strength for hard rock
aggregate concrete.  Obviously testing would be required to determine actual
compressive strength.

Ed Marshall, PE

> -----Original Message-----
> From:	Jeff Smith [SMTP:smthengr(--nospam--at)]
> Sent:	Wednesday, May 12, 1999 9:37 AM
> To:	seaint(--nospam--at)
> Subject:	RE: 1920's 9 story concrete frame building
> Well, the client showed up with some plans and to my surprise the first
> 5-6
> floors have square columns with #3 spiral ties at 1.5 to 3" pitch. The
> vertical reinforcing ranges from 6 3/4" dia. to  10-7/8" dia bars. Above
> the
> sixth floor there are basically 4 bars with # 2 ties at 10" o.c. Concrete
> was a 1-2-4 mix for the heavy columns (what does that mean again?)I left
> the
> plans at my office so the details are a bit sketchy. Bob, I am sure you
> and
> other SEAONC members would recognize the original Engineers, another
> colleague did. Werner (maybe) someone, someone and Russell I believe.
> Their
> offices were on Pacific. Even though I am amazed with the amount of
> reinforcing, I still would be very nervous in that building,it is very
> heavy
> with the pan joists. The aspect ratio is closer to 2.5:1 and it is sort of
> "z" shaped in plan. I have a client who is equally concerned about seismic
> safety and the view, meanwhile a frenzy is building and other bidders are
> lining up without any consultant review what so ever. Maybe my client
> found
> out about the sale too late or maybe the sellers are note allowing enough
> time for buyers review, I am not sure.
> Regards,