The PLUS class notation includes extended scope of fatigue strength verification for hull structural details. The PLUS notation is primarily intended for tankers, gas carriers and container vessels of conventional design operating in harsh environments. The notation may also be applied to other types of vessels.

Purpose

The objective of the PLUS notation is to document the fatigue life of critical areas in the vessel. Critical areas subjected to analysis are the longitudinal stiffener – web frame connections, stringer heel and toe, bottom and side shell plating, deck openings and some ship specific details. The calculation will indicate areas that need upgrading in order to obtain the target fatigue life in service area specified by CSR or Nauticus(Newbuilding) notation.

Benefits

Fatigue cracks are the most common damage on vessels, the cracks may cause oil spill into ballast water or sea and repairs have high cost and very time consuming. A vessel complying with the PLUS notation will obtain enhanced fatigue strength and the likelihood for fatigue problems during service life is reduced. Particularly vessels trading in harsh environment and therefore have an increased probability for fatigue problems would benefit from this notation.

Features

• Expected fatigue life is calculated for:
  • Longitudinal stiffener connection to web frame at aft-, amidship-, and forward-frame.
  • Stringer heel and toe o Deck openings and details.

  • Bottom and side shell plating

• Ship specific details:
  • LNG: Upper and lower chamfer, upper hopper knuckle and longitudinal girder at cofferdam bulkhead.

  • LPG: Lower and upper side brackets

• All locations analysed should comply with the target fatigue life for the vessel to be assigned the PLUS notation.

• Finite element calculations are used to determine the hotspot stresses at critical locations.

• The calculations are carried out according to procedures specified in the DNV Classification Note 34.2 “PLUS Calculations”.