Documentação Técnica

Documentação Técnica
* Engenharia de Dragagem, Sinalização Náutica, Batimetria, Projetos de Canais Navegáveis, Meio Ambiente, Cartas Náuticas, Software de Navegação, Topografia Básica e outros assuntos técnicos.

* Os leitores poderão ter acesso e fazer download do material na parte inferior desta página.

segunda-feira, 15 de agosto de 2011

NM Santa Katarina: Maneuvering Area (Port Planning)

When a vessel enters the harbor basin, its speed needs to be reduced to proceed with anchoring and berthing maneuvers. In practical terms, these maneuvers may be conducted at a normal speed of 8 to 11 knots over a length of 2 to 3L, L being the vessel length, although larger distances may be required for larger vessels with modern hydrodynamic shapes. A significant consideration in determining the required length for minimizing speed is the vessel’s fittings in maneuvering equipment, as well as the type of propeller; if the latter is of variable pitch, the distance can be reduced to 1.5L. The maneuvering area is located either in the outer harbor, situated between the port entrance and the main port, or in the main harbor basin closest to the entrance.

Apart from reducing speed during an initial stage of straight movement, the vessel conducts maneuvers for positioning itself appropriately for the berthing position, which has been determined beforehand. This expanse of sea, called the maneuvering area or circle, should have dimensions calculated on the basis of the harbor’s design vessel. If the port is sufficiently large, more than one maneuvering area may be designed and located at intervals of about 1 km. Figure 1.6 depicts the layout of a large artificial port with a maneuvering circle.


The diameter of the maneuvering circle required is affected directly by the type of rudders and propellers with which a vessel is equipped, whether or not tugboats will be employed, or whether anchors or wrapping dolphins will be used. For unfavorable maneuvering conditions, no tugs, and vessels with only one rudder, a 4L diameter is required, whereas in favorable conditions with modern navigation systems, a 3L diameter may suffice. Instead of a circle, maneuvering requirements may be satisfied by an ellipse with 3L and 2L axes, the main axis being lengthwise of the vessel’s course. If maneuvers are conducted with the aid of tugboats, the minimum diameter of the maneuvering circle may be reduced to 2L. A corresponding decrease is also achieved if the vessel is fitted with a second rudder or a lateral propeller, usually a bow thrust.

During towage, a vessel’s engines usually are stopped or are in excellent synchronization with the tugboats. Furthermore, if a vessel has the ability to use bow and stern anchors or wrapping doplhins, the diameter of the maneuvering circle may reach the minimum dimension of 1.2L.

In the maneuvering area, the sea surface is generally calmer than that at the entrance, and it is advisable that the lateral currents in this area be weaker than approximately 0.15 m/s. Furthermore, the reduction in available draft due to squat is insignificant in the maneuvering circle. Consequently, the required draft in the maneuvering area may be somewhat smaller than that at the entrance. In most cases, a safety margin of about 1.5 m below the maximum draft of the design vessel is sufficient.

To avoid accidents, the maneuvering area should be surrounded by a safety zone from fixed structures or vessel moorings. It is accepted that the width of this zone is a minimum of 1.5B, where B is the design vessel’s beam, and in any case it should be above 30 m.

Fonte: Constantine D. Memos, National Technical University of Athens Zografos, Greece.

***

The stranding of the ship Santa Katarina in the river port of Porto Alegre involves joint analysis of the concepts "turning basis" and "maneuvering area" because the shipping channel passes in front of the berths. See more in Encalhe do NM Santa Katarina.

Turning basin alternative designs

Fonte: Engineering and Design - Hydraulic Design of Deep Draft Navigation Projects. U.S. Army Corps of Engineers (EM 1110-2-1613).

Nenhum comentário:

Postar um comentário