Structural monitoring for safeguarding the remaining life time of a bridge building endangered by stress corrosion cracking. Initial point of the structural monitoring of the bridge over the railway in Waren (Müritz) were the results of recalculation and the investigations of the prestressed wires. In this regard it was documented, that the bridge is in fact endangered by stress corrosion cracking, but ductility provides a sufficient prior notice of failure. Thus the further use of the bridge is possible, provided of a shortened inspection interval. Due to ongoing use the inspection of the building is possible to a limited extend only, the necessary frequent visual assessment was replaced by a structural monitoring. So the focus was not on the complete measurement based observation of the building. The main aim of the structural monitoring rather was the purposeful and economical registration of possibly developing bending cracks. During the monitoring period of two years the development of a bending crack under service load was detected and thereby the real arise of the crack-before-failure-criterion was confirmed. The paper shows the principle procedure of collecting information as basis for a safe decision making as well as on planning, execution and evaluation of structural measurements and their integration into the assessment process of the structure.