Methoden zur Reduktion des Teilsicherheitsbeiwerts für Eigenlasten bei Bestandsbrücken.

Methods to reduce the partial safety factor concerning dead loads of existing bridges The recalculation guideline for existing concrete bridges allows to reduce the partial safety factor for dead loads from γG = 1.35 to 1.20 which matches a conservatively estimated model uncertainty factor. Pre-requisite is that geometry, concrete's specific weight and reinforcement ratio are known from sufficient und representative measurements on-site. In recalculation according to the guideline, the dead load variation driven by these three factors is considered directly by the load distribution. However, no details on required accuracies of the measurements are specified at all. This paper shows how tailor-made partial safety factors can be derived from on-site measurements and supplemented with empirical data from literature. For existing bridges, it seems appropriate to measure the geometry and to estimate the variation of concrete's specific weight while the reinforcement ratio is taken from construction drawings. For application a reference bridge is jointly measured in cooperation with the land surveying office of the state capital city Düsseldorf. 3D laser scans and multicopter over-flights deliver a digital model. In general, the presented approach is relevant for recalculation, modification and deconstruction matters of existing bridges. [ABSTRACT FROM AUTHOR]