A bridge in Sweden carries the Gota Canal over a highway. What, if anything happens to the load on the bridge when a boat passes across it in the canal?
it increases slightly, due to the water height increasing slightly.
Ignoring waves and pressure variations due to velocity, nothing at all. The weight of the boat displaces an equal weight of water.
The water level does not go up, steady state. It is a canal, not a closed basin.
OK, I agree with Prof Damon, if it is an open canal, water level is constant.
When a boat passes across a bridge that carries the Gota Canal over a highway in Sweden, the load on the bridge does not change significantly. This is because the bridge is designed to accommodate the weight and movement of the boats. However, let me explain how the load on the bridge is managed in such cases.
Bridges that carry canals over roadways are typically designed as movable or bascule bridges. These types of bridges have a movable section known as a "span" or "leaf" that can be raised or lowered to create clearance for boats passing underneath.
When a boat approaches the bridge, the span is raised by mechanical or hydraulic systems to create an opening for the vessel to pass through. This way, the boat can traverse the canal without obstruction. Once the boat has passed, the span is lowered back into its original position, and the bridge returns to its regular load-carrying state.
Throughout this process, the main load-bearing structural elements of the bridge, such as the piers and abutments, remain unaffected by the passing boat. These components are designed to support the weight of both the bridge itself and any vehicles that use the roadway.
In summary, the load on the bridge is carefully managed through the use of movable spans that allow boats to pass without significantly impacting the overall structural integrity of the bridge.