Structural design

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Part of a series on vessels'



Structural Design

The purpose of structural design is to design the most efficient structure that will allow the vessel to perform it mission. An efficient design takes into consideration both initial build costs as well as life-cycle costs. In a purely commercial vessel the most efficient design is one that will allow for the greatest earning capacity; while a military vessels structure is typically designed to maximize weight savings.


Structural Design Process

The structural design is just one stop on the design spiral and as the design spiral itself it is an iterative process. The five key steps to designing structure for efficiency are:

  1. Development of preliminary scantlings & arrangement
  2. Analysis of the above design - check loads, deflections, stress concentrations, including FEA for complex or heavily loaded structures.
  3. Compare design to the required criteria - Class, Safety Factors
  4. Redesign of structural arrangement to meet the above criteria ~ over/under built?
  5. Repeat steps 1-4 until an acceptable optimum is reached


Factors which influence the structural design, and which may be varied during the design process, include:

Arranging Structure

See structural layout method for an example process

  • Limit stress concentrations, i.e., by ensuring structural continuity
  • Minimize abrupt structural changes, i.e., by canting structure
  • Minimize discontinuities, i.e. by modifying arrangements, aligning bulkheads, etc.
  • Where possible, limit spans by effective use of pillars and bulkheads

Optimizing Structure

The priority of needs which drive an optimal structural design vary with the vessel type, use, and ownership. While these vary with specific projects, some typical examples:


  1. Reliability/Safety
  2. Structural Weight (Deeper scantlings are more efficient, but may limit usable space)
  3. Lifecycle Costs
  4. Initial Construction Cost
  5. Performance


  1. Performance (Decreased weight increases speed, detectability)
  2. Survivability (Compartmentalization, flammability, etc.)
  3. Life Cycle Costs
  4. Initial Construction Cost

Government Agencies

  1. Longevity
  2. Initial Construction Cost


  1. Initial Construction Cost
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