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Eingeladener Vortrag
- nein (56)
The active approach for non-destructive-testing in Civil Engineering (NDT-CE) with infraredthermography (IR), developed at the Federal Institute for Materials Research and Testing (BAM), is described in part one of this contribution. The active IR-approach is based on the principles of impulse- (IT) and pulse-phase-thermography (PPT). The concept is a direct result of a research project at the BAM in cooperation with the Technical University of Berlin (TUB) and was funded by the Deutsche Forschungsgemeinschaft (DFG). In the second part results of the new thermography-scanning system (thermo-scanner) of BAM on debonding of multi-layered structures, especially carbon fibre reinforced plates (CFRP) on concrete are presented. Both, the thermo-scanner developed at BAM, and the investigations carried out, are part of the
EU-Project Sustainable Bridges. In the third part of the paper the characteristic frequency of the optimum phase-contrast as a means for the characterization of defects depth in CE by means of PPT is introduced. A new quantitative approach is tested and discussed on concrete structures with defects of polystyrene and gas concrete.
A toolbox with non-destructive testing methods for the condition assessment of railway bridges
(2006)
The unified economic structure of the European market requires a unified transport infrastructure to ensure seamless and barrierfree transportation of passengers and goods. The European commission is funding the European Integrated Project Sustainable Bridges to comply with future traffic demands. The main objective of the project is to reliably assess and upgrade the bridge infrastructure for the required increase of axle loads and transport volume. 32 Institutes from 12 countries develop unified procedures for the assessment and improvement of the existing railway bridge stock under the guidance and review of six major European railway companies.
Non destructive testing (NDT) is given a high priority. One of the work packages concentrates on the potential of advanced NDT-methods and creates a toolbox with advisable methods for the condition assessment of all types of railway bridges. Although NDT-methods are implemented in the quality assurance process in many industries, their application in the railway infrastructure is not common. Only a few countries have included selected NDT-methods into advanced condition assessment procedures for the management of their bridge stock.
This paper describes also current activities to enhance pulse-phase thermography, impulse-radar and acoustic methods. The advanced methods enable infrastructure owners to verify construction plans, to assess structures, repair and strengthening quality or to identify in-service damages. Latest development is an automated scanning system for combined acoustic and electromagnetic measurements. The results are then combined through data fusion techniques to further increase their value for the bridge owners.
Complex special inspection of an old masonry arch bridge according to the Guideline on Inspection and Condition Assessment of Railway Bridges and numerical analysis of the structure are presented. The guideline summarises recommendations for the step-by-step investigation of railway bridges applying enhanced methods developed during the EU-funded project Sustainable Bridges. For the investigation of the arch barrel, the ballast parameters and the inner structure of the backfill behind the arch barrel a number of various advanced non-destructive and minor-destructive testing methods were applied. Deformation of the structure during load tests was measured using three independent measuring systems: laser vibrometer, LVDT and microwave radar. Results of calculations performed with 2D and 3D models based on FEM are compared with the field load tests. Sensitivity of the ultimate load of the structure to investigated parameters is studied in FE model. Some general conclusions according to methods of testing and modelling of masonry arch bridges are presented and discussed.
Inspection of steel bridges
(2007)
Assessment of existing steel structures - A guideline for estimation of the remaining fatigue life
(2007)
In many countries and regions, traffic infrastructure projects suffer from low funding. The budget is tight for new infrastructure building and, thus, the importance of inspection, maintenance and assessment of the existing traffic infrastructure increases. A new fatigue assessment guideline for the estimation of the remaining fatigue life of steel bridges has been written by technical committee 6 of the European Convention of Constructional Steelwork (ECCS). It will be a useful tool for the complementation of bridge management systems, used commonly for condition assessment.
Design specifications and rules are harmonised throughout Europe. They are under constant development, but there is still a lack of forwarding and concentrating experiences as well as developing rules for the fatigue assessment on existing steel structures. This paper presents a guideline with a proposed fatigue assessment procedure for existing steel structures embedded in information about old materials and non-destructive testing methods for the evaluation of details (ECCS 2004, Assessment of existing steel structures). Particular attention is paid on remedial measures which are proposed for weak details and damages caused by fatigue. The developed fatigue assessment procedure can be applied to existing steel structures under cyclic loading in general, but the guideline concentrates on the existing traffic infrastructure made from old steel, because of the public importance. The proposed procedure summarizes, regroups and arranges the knowledge in the field of assessment on existing steel to be applied by practicing engineers. The procedure is a milestone in knowledge transfer from a state of scientific knowledge to state-of-the-art.
Assessment of existing steel structures - Recommendations for estimation of remaining fatigue life
(2008)
Acoustic measurement methods
(2008)
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.