Structural efficiency

From Narciki
Jump to: navigation, search


Part of a series on vessels'

Structure

Icon-structure.png
Concepts

Strucutral Efficiency

Structural efficiency is a function of the weight of structure to the afforded ships strength. Naval architects strive to maximize structural efficiency by minimizing the weight, while still providing adequate strength (it is not a matter of structural minimization). Scantings, materials, etc. can all be varied to achieve this goal (see stuctural design for the design process).

Contents

Efficient Structure

The most efficient structure is realized when all design criteria are met, including deflection and strength requirements. Class requirements are generally not optimized - to accurately size, first-principal calculations can be used.

First Principals

  • Direct/manual calculations
  • FEA

Factors

Factors which influence structural efficiency:

  • Ship loads & loading cycles (i.e., fatigue requirements)
  • Margins for abnormal events (i.e., accidents should be reasonably survivable)
  • Future usability, either by refit or resale.

Constructibility

Constructibility refers to the ease at which a shipyard is able to build the vessel. Difficulty in the build process can come from exotic materials, poor access, weldments which by size or weight are difficult to handle, excess precision, or reliance on unusually high quality materials. These factors require additional materials testing, more labour, more skilled labourers, higher wastage, more dangerous working conditions, etc. which may result in a more expensive vessel, longer lead times, more difficult maintenance, etc. which may outweigh the benefits of a smaller or lighter structure.

Excessive Sections

While it is possible to select structural sections optimized for local stresses, the number of sections has to be held to a reasonable value, at reasonable increments of change. Too many sections require the shipyard to order many small batches, increasing lead times, increasing wastage, and introducing logistical problems such as storage & identification.

Aesthetics and Durability

Above and beyond class rules or other regulations, heavier scantlings may be used where deformation may be routine or noticeable. Light plating, for example, will deform locally where stiffeners or bulkheads are welded & this will show. For interior bulkheads, or screened locations, this may be acceptable however exterior plate may electively increased in thickness or corrugated for aesthetic reasons. Similarly, working decks may use special grades or thicker plate to decrease dimpling or deformation from wheeled vehicles, cargo, etc.

See also

Personal tools