Using the appropriate vessel information is a key step in evaluating the energy of a berthing vessel. Information pertaining to the vessels size, shape, and mass are critical inputs to all proceeding calculations.

When certain vessel information is unknown it is useful to use statistical information for similar sized vessels. All suggested values on this sheet are from PIANC's publication of the "Guidelines for the design of Fender Systems 2002" Appendix C for a 75% confidence level.

Glossary:

How a vessel is allowed to berth and in what conditions the vessel berths can have a bigger impact on the energy calculations than any other input. Site conditions including but not limited to wave action, tidal range, weather conditions, facility design, and facility appearance should all be considered as inputs to the berthing conditions.

It is suggested that extreme care be used when considering the inputs for this section. Any overrides to suggested values, especially berthing velocity, should be made with confidence before moving forward.

Glossary:

As a vessel comes in contact with a fendering system the vessels center of mass will rotate around the point of contact through an angle equal to that of the approach angle. In order to rotate through this angle a certain amount of energy must be used. The amount of energy used reduces the berthing energy of the vessel and is accounted for by the calculation of the eccentricity factor.

Glossary:

A vessels hull will always slightly deflect under the contact reaction of a fendering system. This slight deflection in the ship's hull is capable of absorbing as much as 10% of the vessels energy. In order to account for this energy absorption the softness factor is applied. Softness factor is determined by the relative strength or rigidity of the ship's hull to the reaction force of the fenders. However due to the regular uncertainty in hull rigidity versus fender reaction the softness factors is often times ignored and left at 1.

Vessels moving through the water will always have a certain mass of water traveling along with it. This mass of water must also come to rest during the berthing of a vessel. The Virtual Mass factor accounts for the amount of water affecting the travel of the vessel and the additional energy required to bring this mass of this water to rest. Vessel dimensions along with the free space for water flow under the ship's hull will affect the virtual mass factor.

The most common methods for calculation of the virtual mass factor is the Shigeru Ueda, Vasco Costa or the PIANC 2002 method. If no definitive reason to do otherwise is given the PIANC 2002 method is recommended.

Glossary:

Similar to the Virtual Mass Factor which considers the water moving with the vessel the berthing configuration Factor considers the water that gets trapped between the vessel and the approaching dock. The water trapped in this vicinity will act as a cushion for the oncoming vessel and will absorb some of the vessels berthing energy and contributes to the berthing configuration factor.

For facilities where the berthing angle is greater than 6 degrees the berthing configuration factor is generally neglected. However for facilities which berth vessels with approach angles less than 6 degrees and in an area where water can be trapped relatively easily the reduction in energy can be as much as 10%.

Designers should apply an appropriate Factor of Safety (FOS) to account for abnormal impact. The FOS should take into consideration any potential risk associated with berthing and navigational conditions, the consequence of failure associated with the particular berth, hazardous cargoes, load sensitivity of the structure and any other factor that may affect the ability to safely berth the vessels.

General guidelines as indicated in PIANC 2002 are indicated below. Please note, however that common practice within the Marine Industry is to adopt a factor of safety of 2.0 for structures associated with hazardous cargo (ie Berthing Dolphins for LNG, OIL, CHEMICALS etc.)

Glossary: