Английская Википедия:Air draft
Шаблон:Short description Шаблон:Other uses
Air draft (or air draught) is the distance from the surface of the water to the highest point on a vessel. This is similar to the deep draft of a vessel which is measured from the surface of the water to the deepest part of the hull below the surface. However, air draft is expressed as a height (positive upward), while deep draft is expressed as a depth (positive downward).[1][2]
Clearance below
Шаблон:Main The vessel's clearance is the distance in excess of the air draft which allows a vessel to pass safely under a bridge or obstacle such as power lines, etc. A bridge's "clearance below" is most often noted on charts as measured from the surface of the water to the under side of the bridge at the chart datum Mean High Water (MHW),[3][4] a less restrictive clearance than Mean Higher High Water (MHHW).
In 2014, the United States Coast Guard reported that 1.2% of the collisions that it investigated in the recent past were caused by vessels attempting to pass under structures with insufficient clearance resulting in bridge strikes.[1]
Examples
The Bridge of the Americas in Panama limits which ships can traverse the Panama Canal due to its height at Шаблон:Convert above the water. The world's largest cruise ships, Шаблон:MS, Шаблон:MS and the Шаблон:MS will fit within the canal's new widened locks, but they are too tall to pass under the bridge, even at low tide (the two first ships are Шаблон:Convert, but do have lowerable funnels, enabling them to pass the Шаблон:Convert Great Belt Bridge in Denmark). New vessels are rarely built not clearing Шаблон:Convert, a height which accommodates all but the largest cruise and container ships.
The Suez Canal Bridge has a Шаблон:Convert clearance over the canal.
The Bayonne Bridge, an arch bridge connecting New Jersey with New York City, undertook a $1.7 billion modification to raise its roadbed to Шаблон:Convert.[5]
See also
- Structural clearance
- Structure gauge
- Tower Bridge
- Cargo ship size categories
- Chart datum
- Bridge strike
References
- ↑ 1,0 1,1 Ошибка цитирования Неверный тег
<ref>; для сносокuscgне указан текст - ↑ Шаблон:Cite book
- ↑ See: NOAA Navigation Chart #12335, Hudson and East Rivers, Governors Island to 67th Street, Revised October 1, 2019, "HEIGHTS: Heights in feet above Mean High Water"
- ↑ See: U.S. Coast Pilot 5, Chapter 8, p. 354, Structures across the Inner Harbor Navigation Canal, New Orleans, 15 December, 2019, "Vertical clearance measured at Mean High Water"
- ↑ Bayonne Bridge rededication ceremony marks end of $1.7 billion project
