Replies to post #42189 on Biotech Values

[gofishmarko]

OT : Last comment by me also. My suspicion is that regardless of whatever other design peculiarities exist , e.g., locks with pumping system , etc. , the bridge is probably designed to hold a full load of water , to the brim or to overflow ports.

Flooding downpours , tsunamis , glacial melt , whatever , on the canals on either end and on the bridge itself , combined with the possibility of power / pump failures , would flood the entire structure and require a design that could support this maximum volume of water.

So , again , given this overflow capability , any number of floating objects could be supported as well , limited only by their ability to float ( i.e. draft-limited ). More stringent limitations on allowed vessels might be imposed for a variety of reasons , but not because Archimedes was nuts (even if he was ).

[cosmosman]

Let us do this correctly.

The bridge IS a closed system: there is a lock at either end, trapping the water.

If a boat were plopped into the bridge canal with the locks closed, then the bridge would carry the full weight of the water that had been in it, plus the full weight of the boat that had been added. (The water level would rise owing to the displacement by the boat. The weight of the boat would be transmitted to the structure of the bridge by the increased water pressure owing the increase in the depth of the water caused by the boat's displacement. That's high school physics.)

However, the bridge is above the local water level (it is up high over the Elbe), so presumably water must be pumped up to bridge level through the locks. The amount of water pumped to the bridge is at the control of the operator. There is no reason whatever to operate with a higher water level when the bridge is full of boats. So if the operator controls to the water to be at a constant level regardless of how many boats are in the bridge, the total weight carried by the structure will be independent of the number and weight of the boats on the bridge. If the operator lets the water level rise (or fall) the weight carried by the bridge will rise (or fall).

The weight actually carried by the bridge depends only on how deep the operator allows the water to be. (That's also high school physics.)