Computational Engineering / Validation, verification and model assurance
Two different questions
Validation and verification, separated properly — and why a model that passes one can fail the other completely.
Lesson review: expert verification remains open
This lesson has received a full-context editorial review and a check of its technical explanations. Selected arithmetic has been checked separately. This is not independent engineering sign-off.
Checks needed for project use
- A computational engineering reviewer must check algorithms, convergence claims, statistical assumptions and numerical examples beyond the cases explicitly recorded.
- Confirm truss web layout and diagonal angle in the 24 m worked example; 63.4° is not established by the stated eight panels and 3 m depth.
- Formal checking categories and project acceptance criteria require the responsible engineer.
These are educational models and exercises. Check their assumptions before using the results. The full technical content and every diagram have not yet been independently verified.
Concrete and steel calculations retain their stated first-generation Eurocode teaching basis. Use the standards and amendments specified for your project; do not mix generations without an appropriate design basis.
Read the lesson register and outstanding review notesWhy this matters
'Checking' covers two activities that need different people, different evidence and different timing, and conflating them is how a thoroughly checked model turns out to be a model of the wrong structure.
The distinction has a standard form and it is worth learning in that form, because it is what a reviewer will expect and what a model record has to demonstrate.
By the end of this lesson you should be able to
- Define validation and verification precisely
- Classify a given check as one or the other
- Give an example of a model that passes verification and fails validation
- Recognise software invalidity as distinct from software error
What you should already know
- The diagnostic checks of Module 12
- Deflected shapes and load paths from Structural Behaviour, which Stage 1 relies on
Verification and validation
Verification asks whether the equations and numerical procedures are implemented and solved correctly, including solution accuracy. Input checks against the intended geometry, properties and loads are part of practical model assurance. Validation asks whether the model adequately represents the behaviour needed for its intended use, using appropriate physical evidence and stated uncertainty. Both can use structured plans and professional judgement.
A correctly solved first-order model may still be unsuitable for a sway-sensitive structure. Conversely, an appropriate idealisation can be implemented with a misplaced load. These checks address different questions, but one comparison does not establish that an entire model has passed either process.
Software scope
Check that the selected formulation and design modules cover the required behaviour. A tool may correctly implement its documented scope while omitting a required punching, stability, connection or local-response check. Record exclusions and arrange the missing assessment.
Hartford Civic Center (1978), Sleipner A (1991) and the CTV Building (2011) have published investigations relevant to structural modelling and assurance. Consult those investigations for case-specific conclusions. The diagnostic cases in this course are fictional teaching examples.
Check yourself
A reviewer confirms that a model's geometry matches the drawings, its sections match the schedule, its loads match the load schedule, and equilibrium is satisfied. What has been established?
Practice
In the idealised amplification model, αcr = 3.0. By what percentage is the estimated second-order lateral displacement greater than the first-order value? Use α/(α−1).
Worked example
Verification and validation on the same model
Given
- A floor model gives a midspan deflection of 18 mm
- A hand calculation on the same idealisation gives 17.6 mm
- The completed floor is measured at 27 mm
Find
What each comparison establishes
Check yourself
What does a successful verification establish?
Summary
- Validation: is this the right model? Verification: was it built as intended?
- Verification is listable and largely mechanical; validation needs judgement
- A perfectly verified model of the wrong structure passes every verification check
- Software invalidity is usually a capability the user assumed and the tool never claimed
- Ask what a tool does not do, and whether you would know