Pathology and assessment of existing bridges

Auscultation techniques differ according to the nature of the disorders observed, but choices are guided by the idea of the probable causes of the pathology observed. Effective auscultation must enable us to assess the quality of the material(s) in place, and to characterize the structure's current mode of operation. The assessment of materials is based both on studies and analyses of samples, and on physical methods of in-situ examination. The means used to characterize the structure's operation are also very varied, and it is often necessary to combine several of them during a single intervention. These mainly involve topographical or geometric measurements (changes in levelling, general deformation or displacement measurements under loading), direct force measurements or local operating measurements. These different methods are described below. See also the document on techniques for assessing the weathering of concrete structures, which gives for each method :

• the measurement principle ;

• usable equipment ;

• field of application ;

• conditions for interpreting measurements ;

• difficulties that may be encountered....

This dossier follows on from [C 7 402] and [C 7 403] , devoted respectively to the main problems and to equipment, including supports and protective elements.