<title>EXTRA: a new experiment-supported condition assessment method for concrete bridges</title>

Abstract

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. Acknowledgments finalize the contribution.

State-of-the-art on load testing of concrete bridges

“…A rule of thumb that was used to determine the target proof load was that the proof load should be twice the maximum allowable load [44]. Similarly, in Germany, a factor of 1.5 for the traffic loads is used [45]. More recently [46], the determination of the target proof load is determined based on equivalent sectional [48,49], and determined for different reliability levels, different span lengths, and different ratios R/R n .…”

Towards standardisation of proof load testing: pilot test on viaduct Zijlweg

“…The large loads required for proof load testing have been achieved by using military vehicles (Varela-Ortiz, Cintrón, Velázquez, & Stanton, 2010), by directly applying dead weights such as steel profiles on the bridge (Olaszek, Łagoda, & Casas, 2014), or by using an external structure (Schwesinger & Bolle, 2000). In Europe, no Eurocodes for the assessment of existing structures are available, and no vehicles for which bridges should be rated are available.…”

Belastungsversuche – Internationaler Stand des Wissens

“…Die bauaufsichtliche Grundlage für die Durchführung von Belastungsversuchen ist mit Einführung von DIN EN 1990 [40] teilweise wieder gegeben. Damit ist die Anwendung der versuchsgestützten Bemessung in Tragwerksplanung auf normativer Grundlage möglich und akzeptiert.…”

“…Gemäß Anlage 1.1/1 der Muster‐Liste der technischen Baubestimmungen dürfen die informativen Anhange B, C und D anderenfalls nicht angewendet werden [41]. Gemäß [40], Abschnitt 5.2, dürfen Entwurf und Berechnung in Verbindung mit Versuchen durchgeführt werden, wenn zum Beispiel keine zutreffenden Modelle zur Verfügung stehen oder Annahmen beim Entwurf überprüft werden sollen.…”