Civil Engineering Reference
In-Depth Information
Verification checks include:
Software verification:
: The software should be verified by
asking questions such as: Is there adequate evidence that the
software has been checked for accuracy? Have benchmark
analyses been carried out?
1.
Data checking
: Has there been sufficient resource applied
to data checking?
2.
Overall equilibrium
: Has a check been made on overall
equilibrium? For example, the sum of the total vertical
reactions should be checked against the total vertical load
that was expected to be applied to the model.
6.7 Modelling review process
Figure 6.7
shows a basic review process and
Figure 6.8
rep-
resents a full review process. The former would be used in a
standard context that is familiar to those working on the type
of model. The latter would be used in an innovative situation
where there might be significant uncertainty, complexity and/
or where the context is safety critical, for example, nuclear
power installations. Results verification is always needed
but in standard contexts validation may not need deep con-
sideration and sensitivity analysis may not be required. In a
complex innovative situation, very careful attention to all the
review activities may be essential.
3.
Symmetry
: If there is symmetry has it been checked via a
symmetric loadcase?
4.
Form of results
: Does a qualitative assessment of the
results show any anomalies?
5.
Values of results:
Are the values of the results in the
expected range?
6.
Checking models
: see Section 6.6.3.5.
7.
The fundamental verification question
: Has adequate
resource been allocated to minimise the risk of implemen-
tation errors in the model?
6.6.3.5 Checking model
Checking the model against another frame of reference - a
checking model - can be a valuable review activity. The check-
ing model may take the form of:
Predictions
Verification for
checking
loadcase
Initial
review
Initial validation
A 'back of an envelope' calculation, i.e. a hand calculation based
■
on a simplified model of the system to provide a quick check.
A simplified model of the system which requires software for the
■
Qualitative
checks
solution.
A repeat of the model using different software and/or different
Ongoing
review
Regularly challenge the adequacy
of all inputs and outputs
■
Quantitative
checks
personnel.
Simplified models should be assessed for validity. It is import-
ant that they are able to adequately represent the main features
of behaviour being investigated. Also care should be taken in
relation to correlation between two models. False correlations
are not uncommon.
Final
review
Figure 6.7 Basic modelling review process
6.6.3.6 Results interpretation
Results should be regularly interpreted to seek to develop
understanding of the behaviour of the system. This can con-
tribute to the validation and verification processes.
Predictions
Competence
assessment
Software assessment
Initial
review
Verification for
checking
loadcase
Requirements
6.6.3.7 Sensitivity analysis
Varying the model to assess the effect of the variations on be-
haviour is a very important review activity. Doing this helps to
develop understanding of behaviour which can inform both the
validation and verification processes.
Initial validation
Qualitative
checks
Re-validate
Sensititivity
analysis
Quantitative
checks
Ongoing
review
6.6.3.8 Competence assessment
It is important to ensure that those using the software have the
necessary competence.
Regularly challenge the
adequacy of all inputs
and outputs
Checking
model
Final
review
6.6.3.9 Software assessment
Software validation
: The software should be validated by asking
the question: Is the software capable of implementing the model?
Figure 6.8 Full modelling review process
