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RE: Friction factor for plastic flat bottom tank

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Note that ASCE 7-95 includes seismic coefficients for unanchored flat
bottom tanks (Table 9.3.3.2) as has the AWWA D-100 in the past (I don't
have the latest edition).  It would seem that if the tank is unanchored
it must depend on friction to avoid sliding.

Regarding the coefficient of friction for plastic, the "Standard
Handbook for Mechanical Engineers," 7th Edition (1967) gives 0.35 dry
and 0.05 greasy, as the dynamic or sliding coefficients of friction (as
opposed to the static coefficients) for "laminated plastic on steel."
No values are given for the static coefficient for this combination but
for other materials they are usually about 1/3 greater than the dynamic
coefficients.

Ed Marshall, PE
Simons  Engineering
Atlanta

> -----Original Message-----
> From:	Lew Midlam [SMTP:Lew.Midlam(--nospam--at)lcm.com]
> Sent:	Tuesday, June 02, 1998 5:35 PM
> To:	seaoc(--nospam--at)seaoc.org
> Subject:	Re: Friction factor for plastic flat bottom tank
> 
> I think there's a provision in the code that prohibits using friction
> to resist lateral loads, but I couldn't find it in a quick flip thru
> the pages.
> 
> Lew Midlam, PE
> ==============================
> 
> ITSEKSON SASHA wrote:
> 
> > Hi,
> >
> > I am designing the anchorage of the flat bottom plastic tank 18ft
> high by 12 ft. diameter.
> > It's supposed to be supported on the existing foundation and in
> designing the anchorage (Hilti HVA's) I would like to include the
> frictional resistance at least for part of the total shear.
> >
> > I know that friction between concrete and plastic is considerably
> smaller that between steel and concrete (about 0.3).  Does anybody
> have any references in mind or have any opinions on these values?
> >
> > Thanks,
> >
> > Sasha Itsekson, PE
>