Skip to main content

Relationships

A relationship code between a PES and an ES tells the engine how the two sit together operationally — same operating line, parallel lines, integral, or unrelated. The relationship is the gating condition for several reductions (notably barricaded ILD), and it directly chooses which Exposure Type (IBD, PTRD, ILD, IMD, etc.) applies between the pair.

Learning objectives

By the end of this lesson you should be able to:

  • Understand different relationship codes the criteria engine recognizes and what each implies
  • Predict how a relationship change moves the analysis between IBD, PTRD, and ILD Exposure Types
  • Identify which reductions are conditional on relationship status

Relationship codes​

Different criteria engines utilize different relationships codes in order to accurately model how that criteria assesses related and non-related exposures. Many are very similar and some are as simple as Related or Unrelated. DCMA, for instance, recognizes five relationship codes between a PES and an ES. Each one routes the engine to a different branch of the criteria flow.

CodeDisplay nameMeaning
unrelatedUnrelatedThe facilities are not part of the same operation. IBD or PTRD applies.
relatedRelatedRelated but not on the same operating line — typically parallel operating lines, or an ES that serves multiple PESs. ILD applies, but barricaded ILD reductions do not.
samelineSame Operating LineThe PES and ES are part of the same operating line, but the ES may serve multiple PESs. VITAL is not applied; personnel are considered essential. Barricaded ILD reductions become available.
integralIntegralThe ES is integral to the PES, or it serves only that PES. Personnel are considered essential.
idsessentialIDS EssentialReserved for Intentional Detonation Site PESs where personnel are essential to the operation.

The relationship is one of the first decisions the engine makes about a pair — change it and the Exposure Type, the available reductions, and the resulting analysis code can all shift in one step.

A common modeling mistake is to treat "related" as a single yes/no question, and for some criteria that works just fine, but for others more granularity is required. The engine distinguishes parallel-line relationships (related) from same-line relationships (sameline) explicitly, and the difference is significant:

  • Same Operating Line (sameline) — barricaded ILD reductions are available; an effective barricade between PES and ES can move the analysis from K18 to K9.
  • Related, parallel (related) — barricaded ILD reductions are not available. A barricade between the pair has no effect on the result.

This is the modeling pitfall demonstrated in the Barricaded related vs barricaded sameline exercise — the canonical example for this module.

How relationships drive Exposure Type​

Relationship codeExposure Type
unrelated (ES is an inhabited building)IBD
unrelated (ES is a public route)PTRD
related, sameline, integral, idsessentialILD (or less)

The exact required distance still depends on the type code, attributes, hazard division, and barricading — relationship is the gate that decides which Exposure Type is even in play.

Try it​

Set up a PES and an ES at a fixed distance with all other inputs constant. Cycle the relationship code through unrelated, related, and sameline and re-run analysis after each change. Note that:

  1. unrelated puts the analysis under the IBD Exposure Type
  2. related puts the analysis under the ILD Exposure Type with no barricade reduction available
  3. sameline puts the analysis under the ILD Exposure Type; adding a barricade now activates the K9 reduction

This is the most direct way to feel how a single input — relationship — reshapes the entire criteria path.