For the last decades vibration based identification of damage on civil engineeringstructures has become an important issue for maintenance operations on transport infrastructure.Research in that field has been rapidly expanding from classic modal parameterestimation using measured excitation to modern operational monitoring. Herethe difficulty is to regard to the specific environmental and operational influence to thestructure under observation. In this paper, two methods accounting for statisticaland/or operational uncertainties are applied to measurement data of a progressivedamage test on a prestressed concrete bridge. On the base of covariance driven StochasticSubspace Identification (SSI) an algorithm is developed to monitor and automaticallycompute confidence intervals of the obtained modal parameters. Furthermore,a null space based non-parametric damage detection method, utilizing a statisticalc2 type test is applied to the measurement data. It can be shown that for concretebridges the proposed methodology is able to clearly indicate the presence of structuraldamage, if the damage leads to a change of the structural system.
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