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Organisationseinheit der BAM
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.
Berlin Main Station is the largest multi-level station in Europe. Its daily passenger number amounts to over 300.000. Structures built for such a large number of people require a high-level safety standard. The station was built on the inner city site of the historic Lehrter Bahnhof. The conditions for building and start of operation were challenging by several reasons. The typical sandy ground with a high level of groundwater makes the permanent static stability of such a complex structure difficult. Several completed, ongoing, and planned construction activities in the immediate vicinity of the station influence the ground settlement of the whole area. On basis of the structural design an impact prediction was calculated, which expected certain vertical displacements particularly between the single columns of the outer concrete bridges of the building. These columns support the glass roof construction, which only allows a defined limit of displacement. In order to avoid damage, a concept for monitoring and adjusting potentially occurring displacements was developed for installation at the outer bridges of the station.
Condition assessment of old railway bridges, a scientific cooperation between Berlin and Wroclaw
(2009)
Two years ago, the East Prussian and the Low-Silesian Railway lines celebrated their 160th anniversaries. The history of both first railway connections in the Eastern railway network development in the whole region in the 19th century is presented together with information about the railway between Berlin and Wroclaw. Special attention is paid to the railway bridges built in this period. The first large iron bridges and typical masonry arch structures are presented. Special attention is paid to masonry arches. The condition appraisal of existing masonry arches requires new developed technical methodologies, effective tools and procedures for the description of the bridges current state and function. Their current technical condition as well as service-ability is described.
Opportunities and limitation of non-destructive testing in condition assessment of bridge structures
(2009)
The amount of new knowledge about bridges, materials they are made of, deterioration processes for the different materials, resulting defects, methods for early detection of them and related causes for damage increases day by day. Often the knowledge remains in the heads of ageing specialists leaving the inspection teams or universities. This paper presents a feasibility study about application of a new tool from artificial intelligence to model and organize bridge engineering knowledge from a domain expert´s view. Exemplarily, knowledge and not only data from bridge testing in the field and in the laboratory were formalized for the presentation of the functionality of ontologies.
The amount of new knowledge about bridges, about the materials they are made of, deterioration processes for the different materials, typical defects, methods for early detection of them and related causes for damage increases day by day. Often the knowledge remains in the heads of ageing specialists leaving the inspection teams or universities. This paper presents a feasibility study about application of a new tool from artificial in-telligence, ontology, for modeling and organizing bridge engineering knowledge from a domain expert´s view. Exemplarily, knowledge and not only data from bridge testing in the field and in the laboratory were formalized for the presentation of the functionality of ontologies. The open source ontology editor Protégé was ap-plied to test the feasibility.
In 1882, the East-West suburban train viaduct was built through Berlin as part of the public traffic solution in the late 19th Century. Today, the only left over iron arch bridge is a pair of two arches Crossing the Spree river in the middle of Berlin. Before dismantling the former parallel two original pairs of iron arches and rebuilding new arches for the high-speed railway line through Berlin in 1997, BAM was involved in an extensive test program of the heritage iron arch structure. Especially the estimation of accumulated damage in critical details and the verification of the old material properties at early stage was important information to the bridge owners. The testing program included two strain and displacement measurement campaigns, non-destructive testing, materials testing and microscale metallographic analysis of critical details. The measured strain cycles were significant lower in number and size than expected. Most of the cycles were compression stress cycles only. The work was planned in Cooperation with the Berlin consultancy Professor Hilbers that was responsible for the design and calculation of the reconstruction measures. Additionally, after calculation of the possible reuse of the old arches, we compared measured data from strain measurements with the results from calculation.
The measured data and the calculated data show a good qualitative correlation.
Cast iron arch bridges were built in the late 18th and early 19th century across Europe. After the famous Iron Bridge in the Ironbridge Gorge in Coalbrookdale in England, being now part of the UNESCO world heritage, many cast iron bridges followed and substituted timber bridges. A series of cast iron bridges has been built in central Europe, in Laasan, Breslau, (now Wrocław), in Berlin, Potsdam, Bad Muskau and Schwerin. The paper gives an overview about the current state of some remaining cast iron arch bridges, typical damage cases, material properties and rehabilitation. Most of the old cast iron arch bridges serve as pedestrian bridges. Some of these bridges have been strengthened to increase the traffic load. Different rehabilitation measures as substitution of parts of the bridges and strengthening using Carbon Reinforced Polymers (CFRP) are discussed.
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.
In this research, laboratory experiments were carried out to investigate the feasibility of using ground penetrating radar (GPR) for corrosion detection and/or monitoring, and the mechanism of corrosion caused GPR signal changes, taking into account the influence of several parameters: Chloride, rebar size and cover depth. With the understanding of the mechanism, a novel method for detecting reinforcement corrosion in concrete with GPR is proposed, together with a series of signal processing toolkits for corrosion visualization and image comparison.
Monitoring accelerated corrosion in chloride contaminated concrete with ground penetrating radar
(2012)
Within the presented research project, experimental and numerical investigations were performed to develop a thin-shelled, modular, mobile element system made of a micro-reinforced ultra-high-performance ductile concrete (DUCON®). Material parameters were experimentally determined to adapt the material model within the numerical analysis applying the Drucker-Prager relationship. Afterwards, for validation of the numerical models, quasi-static and high-velocity impact tests were performed on plate-like structures. Finally, a suitable geometry of transportable barrier elements will be designed, which provides a maximum of resistance against impact by a minimum of weight and a maximum of mobility.