Two monuments in Portugal are being monitoring by the University of Minho: the Clock Tower of
Mogadouro and the Church of Jerónimos Monastery, in Lisbon. Vibration sensors and temperature
and relative air humidity sensors are installed in the two monuments. Operational modal analysis is
being used to estimate the modal parameters, followed by statistical analysis to evaluate the
environmental effects on the dynamic response. The aim is to explore damage assessment in
masonry structures at an early stage by vibration signatures as a part of a heath monitoring process
to preserve the historical constructions. The paper presents all the preceding dynamic analysis steps
before the monitoring task, which includes the installation of the monitoring system, the system
identification and subsequent FE model updating analysis, the automatic modal identification and
the investigation of the influence of the environment on the identified modal parameters.(undefined