  While purely data-driven assessment is feasible for the first levels of the
Structural Health Monitoring (SHM) process, namely damage detection and
arguably damage localization, this does not hold true for more advanced
processes. The tasks of damage quantification and eventually residual life
prognosis are invariably linked to availability of a representation of the
system, which bears physical connotation. In this context, it is often
desirable to assimilate data and models, into what is often termed a digital
twin of the monitored system.
  One common take to such an end lies in exploitation of structural mechanics
models, relying on use of Finite Element approximations. proper updating of
these models, and their incorporation in an inverse problem setting may allow
for damage quantification and localization, as well as more advanced tasks,
including reliability analysis and fatigue assessment. However, this may only
be achieved by means of repetitive analyses of the forward model, which implies
considerable computational toll, when the model used is a detailed FE
representation. In tackling this issue, reduced order models can be adopted,
which retain the parameterisation and link to the parameters regulating the
physical properties, albeit greatly reducing the computational burden.
  In this work a detailed FE model of a wind turbine tower is considered,
reduced forms of this model are found using both the Craig Bampton and Dual
Craig Bampton methods. These reduced order models are then used and compared in
a Transitional Markov Chain Monte Carlo procedure to localise and quantify
damage which is introduced to the system.
