EXTRA: a new experiment-supported condition assessment method for concrete bridges

In Germany a group of researchers from four universities has developed an advanced experiment supported state assessment method for short and midspan concrete bridges under the term 'EXTRA.' As a background for this work are the deficiencies of many bridges on one hand and the rising disproportions between available funds and costs for demolition and rebuilding on the other. The presented method can be used preferably in such cases, where conventional assessment methods cannot be applied successfully. The fundamental idea of this method is to determine the ultimate testing load UTL of the structure. This UTL is defined as that load, which just not reaches a level which would cause damages in the tested structure. The level of UTL can be considerably higher than the safe load. For identification the UTL special criterions has been developed. From the UTL afterwards the safe load can be derived by safety considerations. A guideline for practical use of the method for building structures will be available shortly; another one for bridges will be prepared in the near future. Methodical and technical conditions and tasks for preparation and practical realization of the test will be introduced. Main subjects are safety aspects, needed theoretical and practical pre-investigations, the test program, different criterions for UTL-identification, the loading regime and corresponding on- line information on the building response In connection with the presentation of a selected application example experiences on the co-operation with owners, authorities and uninvolved colleagues will be discussed and advises on further developments will be given. Acknowledgements finalize the contribution.