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Organisationseinheit der BAM
Eingeladener Vortrag
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Practical applications of recent BAM-research results of NDT and monitoring in civil engineering
(2018)
Nondestructive testing and monitoring was of mayor interest in BAM-research related to the survey of civil engineering structures during the last two decades. Three case studies about research projects carried out at BAM were presented. All three projects focussed on the survey of parameters and safety related tasks in bridge engineering and inspection. First, the monitoring of the Berlin main station was presented with focus on the sensors developed specifically for this project. The second case study presented and application of guided ultrasonic waves to CFRP-strengthened bridges. The method was sucsessully applied to two of four different strengthening measures carried out min. 10 years ago. The last project presented the feasibility study of a network consisting of simple Bluetooth modules to survey changes in the moisture content in sand and massive concrete.
Current measurement methods for dertermination of moisture analyse near-surface moisture distribution. During an externally funded research project, microwaves in the Bluetooth(R) frequency band width were utilized for Setting-up a module network. Without additional sensors, the feasibility study confirmed that threedimensional data can collected to obtain a threedimensional data set as basis for the estimation of moisture distribution inside massive building materials.
Active thermography
(2017)
Active thermography is introduced as tool for diagnostics in civil engineering structures. Aside from basic information, examples for applications of active thermography in different types of structures was presented. Active thermography was applied in historic structures to reveal former components or even ancient openings. Other examples present active thermography as a tool for nondestructive detection of debonding in CFRP strengthened structures. The way is explained, how the system was optimized for different materials.
The Berlin Main Station was built between 2000 and 2006. At the occasion of the 10th anniversary after the Berlin Main Station was officially opened to train traffic, a view back on eight years of monitoring was given. For the period of the construction with different load cases, the monitoring system was required by the Railway Authorities (Eisenbahnbundesam, EBA) to survey differential vertical displacements between neighbouring supports of the glas roof and the partially prestressed middle bridges. 128 sensors were installed.The data was published in the Internet with access restricted to the BAM scientists and the owner of the station, the German Railways DB AG.
Civil engineers, who are involved in nondestructive testing have to solve an essential task: the transfer of the results of NDT-research into practice. NDT in civil Engineering is a quite new discipline. The results must meet the needs of the infrastructure owners to convince them about the usefulness of NDT. The issue of reliability of the NDT-data was discussed.
Bridges represent a crucial part of traffic infrastructure networks for both, freight transport and transport of people. None the less, sometimes it is not easy for infrastructure owners to manage or extract data and knowledge of interest about specific bridges from bridge management systems, e.g. along a line. In case of search for a special material parameter or for a recent strengthening measure, the selection of the wanted information may be time consuming. The search process depends on the complexity of the selected issue.
The paper presents the applicability of ontologies, a new tool from artificial intelligence transferred to bridge engineering issues. Current modern ontologies consider the rules from the World Wide Web consortium (W3C), use a defined Web Ontology Language (OWL) and the Dublin Core Metadata Initiative (DCMI®) to describe the members of a domain and the relations between them in a machine readable manor. Any information, data as well as text information is broken down to a simple triple (RDF) in a subject- predicate- object relation to organize the link between them. Advantage over any type of data base is processibility due to the use of restrictions and axioms. Visualization plug-ins, as OntoGraph or GraphViz, can visualize the structure of the ontology or parts of it and the described relations.
In the recent years, ontology editors like e.g. Protégé, were developed to enable domain experts to structure a specific domain. The editor is still under development. None the less, the study shows exemplarily, how an ontology for riveted steel bridges could consider results from testing in the laboratory and in the field. Besides typical materials, typical damage processes defects and structures, applicable methods are formalized, classified and described. Queries using e.g. DL-Query may address tasks of interest and extract it from the ontology.
Active Thermography
(2016)
Active thermography is a nondestructive testing method for identification of near surface defects and signs of early deterioration. The presentation explains the potential and Limits of the method and the equipment for application to concrete structures. Advanced data analysis can increase the quality of imaging of the measurement. The method is usually applied once for analysis of the current condition. If applied periodically, the method can be used for observation of a deterioration process.
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.
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.