Recalculation of German concrete bridges considering the code ‘Nachrechnungsrichtlinie’

In 2011 the German client for highway bridges published a code which gives restrictive rules for the recalculation of old bridges in Germany, the ‘Nachrechnungsrichtlinie’ (NRR). It is based on the pre-norms of the actual Eurocodes (DIN EN 1992-1:2011-01, DIN EN 1992-2:2010-12, DIN EN 1992-2/NA:2013-04) and the so-called DIN-Fachberichte (DIN-Fachbericht 101:2009-03, DIN-Fachbericht 102:2009-03). The code ensures that all old bridges in Germany can be recalculated on a comparable level, to decide for the future which measures must be taken to use them further. Since 2011 Ingenieurgruppe Bauen has recalculated more than 50 concrete bridges in Germany, so that it is time to compile the experiences of this work. The paper deals with mechanical contemplations to show the design possibilities despite the restrictions of the code. It shows the importance of engineers having proficient knowledge of historic codes, traditional construction practices and old calculation methods. Only with this expertise can existing bridge structures be preserved for the future and remain part of the engineering heritage of society.