"Calif Bill" wrote in message link.net...
"basskisser" wrote in message
om...
"Calif Bill" wrote in message
ink.net...
"basskisser" wrote in message
m...
"P.Fritz" wrote in message
...
"Calif Bill" wrote in message
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"Gould 0738" wrote in message
...
I would have agreed with the width/length of the tank/dam
doesn't
matter
...
but ... then why are dams so thick at the top? Dams can be 20 /
30 /
...
feet thick at the top where the water is only a few inches deep.
There
is
more to this than me thinks!


Many dams have a service road across the top, a place to stage
heavy
equipment
if need be for repairs, etc. That will require a certain
practical
width.
You
also need some structural mass to frame spillway gates, etc-
often
located
near
the top of the dam. Hoover Dam has a highway across the top, and
so
is
probably
75 feet "thick" many feet above the surface. :-)


And parts of the dam are hollow.

Because a solid mass is not necessarily the most efficient use of
material
WRT strength. (like a roof truss)

Hmm, really? When speaking of "strength", just what aspect are you
talking about, Fritz? Stress? Strain? Axial unsupported compression?
Axial supported compression? Tension? Compression perpendicular to the
plane?

Dam's are also thick, in case water rises above the top. Avoids erosion
causing breaks. Also, you may have to have a thick section not too far
down. Freshwater is about 15 psi for every 33', and the gradual
decrease
to the top, will make for thicker top.

Also, usually, the bottom of the dam is restrained by rock, while the
top of the dam is restrained only at the ends.

What does this have to do with the question.

Everything, but, depending on WHICH question you'd like answered.

You would only need thickness
at the ends if this was the reason.

Nope, absolutely wrong. I simply said the bottom is restrained by
rock, usually, or in the case of earthen dams, even skin friction.
This is true. AND, it also has no bearing on the thickness in the
middle, completely different set of circumstances, or in a way you may
understand, apples, and oranges.

You could save cost via material and
material moving with a thin center top.

Again, why would you assume that, because the bottom of a dam is
restrained by mechanical means, either rock strata, skin friction,
caissons, etc., that that somehow means there are smaller forces
acting on the "center top"???