Fine for creating a wake: $27,500
 

bass,
I see your point. If the boat displaced enough, the resultant wave would
pack a lot more energy. But as a scuba diver I also know that a boat's wake
doesn't travel far beneath the surface. I have dove in 4 foot waves and it's
calm 6 feet below the surface. Now when diving in the keys there was a
noticeable tidal surge that would shift you back and forth for I guess 6 to
12 inches at even 40 feet down and in this instance that was the bottom. I
haven't dove in the Sanibel area so I can't comment on the state of tidal
surges in the area. Bottom line, it seems to me that nature puts a whole
lot more stress on the bridge than the average boat wake creates. It's like
how many millimeters does the boat wakes damage the bridge per year? Can't
they make it a few feet thicker so it'll last? Bass, maybe I'm ignorant of
some facts here, but if so, I wonder how many other boats feel similar. As
I'm under the Sanibel bridge in a 23 footer at planning speed, it's hard to
imagine I'm hurting this bridge. IMHO
Paul

"basskisser" wrote in message
om...
"Paul Schilter" paulschilter@comcast,dot,net wrote in message
...
bass,
Forgive me, but I have a hard time with your statement, not
withstanding
a wave caused by an underwater earthquake, which I think sets up a wave
that
goes quite below the surface, I don't understand what the difference is
between a wind generated wave and a boat generated wave. Depending on
the
wind and fetch or the size and speed of the boat one could be equal to
the
other. In short I think they should build the construction strong
enough to
last normal conditions that the bridge sees and perhaps even hurricane
conditions for these occur as well.
Paul

Paul, it all has to do with frequency, and dynamics. Wind swept waves,
in a protected area like under a bridge, are minimal. The waves from
wind will most likely be coming from somewhere beyond the bridge,
especially if they are perpendicular to the abutements. So, these
waves will be well below there initial strength when they get to the
abutement. When a boat plows through making a huge wake, five feet
from the abutement, that huge wave is almost at it's original
strength, which is likely many times greater than the wind generated
wave.

Fine for creating a wake: $27,500
 

Doug,
Thanks for your comments.
Paul

"DSK" wrote in message
...
Paul Schilter wrote:

Bill,
When rebar rust it expands?

Yes, it sure does.

Anything I've seen rusted was diminished in
size, eventually to nothing.

Well, if the rust flakes away, then sure it does. However, if the rust is
encapsulated along with the original material, the the whole thing
expands.


I thought if the rebar was encapsulated in
cement it wouldn't rust due to lack of oxygen.

That's the idea, yes. But it doesn't always work perfectly.

I thought the purpose of
rebar was to strengthen the concrete and keep it from cracking.

The purpose of the rebar is to give the concrete some strength in tension.
Concrete is enormously strong in compression, but has almost zero tensile
or
torsional strength.

The concrete can still crack from a number of causes... impact, water
penetration (especially during freeze-thaw cycles), etc etc.

Hope this helps

Doug King

Fine for creating a wake: $27,500
 

Bill,
Sure doesn't seem to be the best material to use under water. Thanks for
the info.
Paul

"Calif Bill" wrote in message
hlink.net...
Very well put. Look at rusting cast iron pipes. There are big sheets of
rust. Figure how much air is between those sheets. Same reason rebar
expands if the rust can not flake away.
Bill

"DSK" wrote in message
...
Paul Schilter wrote:

Bill,
When rebar rust it expands?

Yes, it sure does.

Anything I've seen rusted was diminished in
size, eventually to nothing.

Well, if the rust flakes away, then sure it does. However, if the rust
is
encapsulated along with the original material, the the whole thing
expands.


I thought if the rebar was encapsulated in
cement it wouldn't rust due to lack of oxygen.

That's the idea, yes. But it doesn't always work perfectly.

I thought the purpose of
rebar was to strengthen the concrete and keep it from cracking.

The purpose of the rebar is to give the concrete some strength in
tension.
Concrete is enormously strong in compression, but has almost zero
tensile
or
torsional strength.

The concrete can still crack from a number of causes... impact, water
penetration (especially during freeze-thaw cycles), etc etc.

Hope this helps

Doug King

Fine for creating a wake: $27,500
 

bass,
In light of the below statement, how does this figure when the concrete,
for the bridge, is going to be curing in salt water? I understand that a
different type of concrete is used for underwater concrete, but does this
type than have the problem you spoke of? The feeling I get from this thread
is that the concrete used for the bridge is rather fragile, the substance we
put inside to strengthen it, rebar, just destroys it instead. What's wrong
with our building techniques?
Paul


"basskisser" wrote in message
om...
deleted
Concrete will develop stress cracks just from the loss of water when
curing. Slab cracking, for one thing, is VERY hard to control.

Fine for creating a wake: $27,500
 

Greg,
Well if they double the price they'll keep twice as many of the riff
raft out. :-) BTW - It is a unique island but not worth it at twice the
price if you've been there before. Damn, I must be riff raft. :-)
Paul

"Greg" wrote in message
...
deleted
They try to keep the riff raff out.

Fine for creating a wake: $27,500
 

There is galvanized and epoxy coated rebar. Both are big bucks. The is a
company that is/was making a fiberglass rebar, too. From what I understand,
they use these products in places like the Florida Keys where concrete is made
with sal****er rather than expensive "city" water that is piped down from Miami.

Dan


Paul Schilter wrote:
bass,
In light of the below statement, how does this figure when the concrete,
for the bridge, is going to be curing in salt water? I understand that a
different type of concrete is used for underwater concrete, but does this
type than have the problem you spoke of? The feeling I get from this thread
is that the concrete used for the bridge is rather fragile, the substance we
put inside to strengthen it, rebar, just destroys it instead. What's wrong
with our building techniques?
Paul


"basskisser" wrote in message
om...
deleted

Concrete will develop stress cracks just from the loss of water when
curing. Slab cracking, for one thing, is VERY hard to control.

Fine for creating a wake: $27,500
 

Nothing better at a decent price. They epoxy coat now and that will help.
Trouble is concrete is fantastic at supporting compression, but any other
direction and get failures.
Bill

"Paul Schilter" paulschilter@comcast,dot,net wrote in message
...
Bill,
Sure doesn't seem to be the best material to use under water. Thanks
for
the info.
Paul

"Calif Bill" wrote in message
hlink.net...
Very well put. Look at rusting cast iron pipes. There are big sheets
of
rust. Figure how much air is between those sheets. Same reason rebar
expands if the rust can not flake away.
Bill

"DSK" wrote in message
...
Paul Schilter wrote:

Bill,
When rebar rust it expands?

Yes, it sure does.

Anything I've seen rusted was diminished in
size, eventually to nothing.

Well, if the rust flakes away, then sure it does. However, if the rust
is
encapsulated along with the original material, the the whole thing
expands.


I thought if the rebar was encapsulated in
cement it wouldn't rust due to lack of oxygen.

That's the idea, yes. But it doesn't always work perfectly.

I thought the purpose of
rebar was to strengthen the concrete and keep it from cracking.

The purpose of the rebar is to give the concrete some strength in
tension.
Concrete is enormously strong in compression, but has almost zero
tensile
or
torsional strength.

The concrete can still crack from a number of causes... impact, water
penetration (especially during freeze-thaw cycles), etc etc.

Hope this helps

Doug King

Fine for creating a wake: $27,500
 

"Calif Bill" wrote in message nk.net...
Nothing better at a decent price. They epoxy coat now and that will help.
Trouble is concrete is fantastic at supporting compression, but any other
direction and get failures.
Bill

What about fiber reinforced concrete? What about composite-fiber type
reinforcement bars for concrete? What about using structural steel
members, embedded for tensile reinforcement?

Fine for creating a wake: $27,500
 

"Paul Schilter" paulschilter@comcast,dot,net wrote in message ...
bass,
In light of the below statement, how does this figure when the concrete,
for the bridge, is going to be curing in salt water?

It's actually quite a complex thing, when water cures underwater.
Believe it or not, the concrete still goes through the same process,
only chemical additives make it work faster. Curing from the inside
out, thermal evaporation still takes place.

I understand that a
different type of concrete is used for underwater concrete, but does this
type than have the problem you spoke of? The feeling I get from this thread
is that the concrete used for the bridge is rather fragile, the substance we
put inside to strengthen it, rebar, just destroys it instead. What's wrong
with our building techniques?
Paul

Economics!

Fine for creating a wake: $27,500
 

"Paul Schilter" paulschilter@comcast,dot,net wrote in message ...
bass,
I see your point. If the boat displaced enough, the resultant wave would
pack a lot more energy. But as a scuba diver I also know that a boat's wake
doesn't travel far beneath the surface. I have dove in 4 foot waves and it's
calm 6 feet below the surface. Now when diving in the keys there was a
noticeable tidal surge that would shift you back and forth for I guess 6 to
12 inches at even 40 feet down and in this instance that was the bottom. I
haven't dove in the Sanibel area so I can't comment on the state of tidal
surges in the area. Bottom line, it seems to me that nature puts a whole
lot more stress on the bridge than the average boat wake creates. It's like
how many millimeters does the boat wakes damage the bridge per year? Can't
they make it a few feet thicker so it'll last? Bass, maybe I'm ignorant of
some facts here, but if so, I wonder how many other boats feel similar. As
I'm under the Sanibel bridge in a 23 footer at planning speed, it's hard to
imagine I'm hurting this bridge. IMHO
Paul

Now, I'm not a wave expert, but I DO know, that when I'm fishing, and
a boat comes through where I am fishing, at speed, and around the same
distances that one would be from bridge piers and/or abutements, that
my boat takes quite a hit from these waves. Sometimes uncomfortable.
Now I've never been in wind that bobbed my boat around like that. But,
let's assume that it does happen, that wind blown wakes can have that
impact. How often does that occur, compared to how often does it occur
from boats? Also, there is more to the equation than simple erosion of
the concrete, as you say, in a few millemeters per year. There is
impact, there is erosion of the founding soils, there are wet/dry
cycles, etc., etc.