Doreen Streicher

COMPLEMENTARY APPLICATION OF RADAR, IMPACT-ECHO, AND ULTRASONICS FOR TESTING CONCRETE STRUCTURES AND METALLIC TENDON DUCTS

Nondestructive testing of concrete structures plays an increasing role in civil engineering, although until now the full potential of such techniques has not been tapped. For posttensioned structures, the investigation of tendon ducts is one of the most essential testing problems. The location of tendon ducts, the determination of concrete cover and, especially, the detection and quantification of ungrouted areas inside the ducts are the relevant questions. Recent developments and opportunities of radar, impact-echo, and ultrasonics for the investigation of tendon ducts are presented. Although the obtained results on positioning and concrete cover determination are sufficient, the location of ungrouted areas is still a matter of research. Thus, new approaches for this testing problem have to be considered. Additionally, the combined use of complementary techniques offers a high potential to increase the reliability of results. Data will be displayed on the combined application of acoustic and electromagnetic impulse-echo methods and of data fusion related to the investigation of tendon ducts.

Bridge Inspection and Condition Assessment in Europe

The European infrastructure asset has developed historically and is characterized by nation-specific construction processes. Inspection, condition assessment, and maintenance procedures differ from country to country. Because of historical and political circumstances, national infrastructure assets are maintained at different levels, too. Since the budget for maintaining the bridge infrastructure less and less meets the demands of a growing bridge stock, bridge inspection, maintenance, and life-cycle considerations gain higher importance. The need exists to develop effective diagnosis tools for early detection of construction faults, defects, and deterioration processes during inspection, to keep the bridge infrastructure at an acceptable level, from structural safety and economic viewpoints. An overview on the latest research projects and integrated bridge management systems in Europe is given. The potentials of nondestructive testing (NDT) are presented, with special focus on technical advances of NDT applications to reinforced concrete (RC) and posttensioned concrete bridges. Although NDT is not regularly integrated in these processes, the application brings valuable information on the current condition of the inner structure in called-in special inspections. NDT-automation and the application of imaging echo methods, combined with advanced data processing, produce a surprising level of information about the inner structure of massive RC slabs up to a depth of about 60 cm. Detected inhomogeneity and scatterers of acoustic or electromagnetic waves can be visualized in vertical or horizontal slices through the structure or animations. The fusion of different three-dimensional data sets of processed data improves the interpretability and accuracy of the results.

New Possibilities for Ultrasonic Imaging of Concrete Elements

In recent years the combination of measuring large concrete areas with dry ultrasonic transducers and reconstruction calculation imaging the location of construction elements and defects has been further developed and presents itself now as a precise tool to survey the inner condition of concrete elements. Examples of large area applications at test specimens and post-tensioned concrete bridges are presented.