TY - CONF A1 - Wolf, Julia A1 - Mielentz, Frank A1 - Milmann, Boris A1 - Helmerich, Rosemarie A1 - Köpp, Christian A1 - Wiggenhauser, Herbert A1 - Kurz, J.H. A1 - Moryson, R.M. A1 - Samokrutov, A. A1 - Alekhin, S. G. A1 - Alver, Ninel A1 - Sazak, H.Ö. T1 - An ultrasound monitoring system for concrete structures N2 - The research project "Ultrasonic Net for Concrete Monitoring (UNeCOM)" aims at developing a methodology for an embedded ultrasonic network for the condition assessment of infrastructure constructions. Civil engineering structures made of concrete, which are located in tectonically active regions or undergo special loading conditions, may require continuous monitoring. It is important to assess the condition of the building and its stability to recognise and classify the effect of a seismic event or evolving damage at early stages before failure occurs. Embedded ultrasonic sensors offer the possibility to detect changes in the material and degradation mechanisms from inside the structure in areas which are difficult or impossible to inspect otherwise. In contrast to conventional ultrasonic testing methods, where the concrete surfaces are scanned with ultrasound probes, this new approach uses sensors, which are embedded into concrete, eliminating the effect of variable coupling conditions between sensors and concrete. This method allows an integral detection of changes in the concrete structure, for example due to seismic activities, to detect mechanical impacts, as well as degradation of the material due to overloading. Such methods have great relevance especially for the monitoring of constructions like power plants, bridges, offshore structures and other structures with high technical safety requirements. The sensor network can be controlled remotely through the internet which is also being used for data transfer. The embedded sensor network is designed to monitor structural damage and concrete degradation globally with high sensitivity. T2 - Istanbul bridge conference 2014 CY - Istanbul, Turkey DA - 11.08.2014 KW - Ultrasound KW - Concrete KW - Monitoring PY - 2014 SN - 978-605-64131-6-2 SP - Paper 32, 1 EP - 9 AN - OPUS4-32028 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Helmerich, Rosemarie A1 - Zunkel, Astrid T1 - Partial collapse of the Berlin Congress Hall on May 21st, 1980 N2 - The Berlin Congress Hall was a gift of the United States of America to Germany for the Berlin World Exhibition in 1957. The elegantly double-curved roof was made from an advanced prestressed concrete construction. The construction followed the design by the American architect Hugh Stubbins with special structural modifications to comply with German construction rules. No early indications for failure initiation were detected before a sudden partial collapse. On May 21st, 1980, the Southern external roof overhang collapsed. In December 1980, Jörg Schlaich and his co-authors published a summarizing expert opinion about structural causes of failure. The present paper mainly introduces results of cause analysis made at the Federal Institute for Materials Research and Testing (BAM), mandated by the Public Prosecutor at the Berlin District Court to specify the causes of the sudden failure. This paper refers to BAM-publications about analyses that were performed under this mandate and published – most of them in German language – within the first years after failure. The expert's opinions comprise structural considerations materials investigations, metallographic analyses and corrosion. Nowadays experts have learnt from the failure and built a slightly modified roof in the original shape at the 750th birthday of the city of Berlin and re-opened the former Berlin Congress Hall to the public on May 9th, 1987. The Hall is now serving as the House of the Cultures of the World, following the initial intention of the hall. KW - Partial collapse KW - Berlin Congress Hall KW - Analysis KW - Stress corrosion cracking KW - Reconstruction PY - 2014 U6 - https://doi.org/10.1016/j.engfailanal.2013.11.013 SN - 1350-6307 SN - 1873-1961 VL - 43 IS - Special Issue 'A Tribute to Prof. A. Martens' SP - 107 EP - 119 PB - Elsevier Science Publ. CY - Oxford AN - OPUS4-30863 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Portella, Pedro Dolabella A1 - Helmerich, Rosemarie T1 - Adolf Martens and his contribution to materials engineering N2 - Adolf Martens (1850–1914) was a pioneer of materials engineering. After his studies in Berlin he joined a railway company being responsible for the technical equipment. His interest for the basic mechanisms of mechanical strength and fracture of metallic materials led him to the development of the basic concepts for metallography; his papers published between 1878 and 1889 laid the fundament of this technique. In 1880 Martens changed to the Royal Industrial Academy in Berlin and by 1884 he was designated as director of the Materials Testing Laboratory at the Technical University Berlin. Under his guidance this institution acquired an excellent reputation in all relevant areas of the German industry, forming the nucleus of the Bundesanstalt für Materialforschung und -prüfung (BAM) – the Federal Institute for Materials Research and Testing. Martens developed equipment in many different areas as mechanical testing of metallic materials and of paper, characterization of the wear behavior of materials and viscosity of lubricants. His overwhelming contribution to materials engineering was recognized as early as 1895 by Floris Osmond, who denominated martensite a metallographical constituent resulting from quenching of steels. In 2000 ISO designated the value obtained from the instrumented indentation method as Martens Hardness – HM. KW - Adolf Martens KW - Microscopy KW - Metallography KW - Mechanical testing KW - Quality assurance in materials testing PY - 2014 U6 - https://doi.org/10.1016/j.engfailanal.2014.03.001 SN - 1350-6307 SN - 1873-1961 VL - 43 IS - Special Issue 'A Tribute to Prof. A. Martens' SP - 2 EP - 10 PB - Elsevier Science Publ. CY - Oxford AN - OPUS4-30865 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Helmerich, Rosemarie A1 - Herter, Jürgen T1 - Root cause analysis of cracks in old steel viaducts and retrofitting N2 - Following the long tradition of the Federal Institute for Materials Research and Testing (BAM) since Adolf Martens has created first routines in failure analysis (Ruske, 1971), BAM has been frequently called-in by the Berlin Traffic Association (BVG) to carry out root-cause analyses of the Berlin suburban train line (Frahm, 1902), reported in Helmerich and Herter (1999), Helmerich (2000), Nega and Winkler (1998), Helmerich et al. (2002) and Herter et al. (2002). This was also the case in the 1990s, when BVG-inspectors found cracks in hanging, barrel-like shaped ballast plates of the Berlin underground steel viaducts during regularly scheduled inspections. Cracks were located parallel to the riveted connection between the ballast plates and the upper chord of the viaduct cross girder steel profiles. For safety reasons, the operator BVG immediately stopped the cracks by means of drilling stop holes at the crack tips. As intermediate measures, longitudinal steel profiles were spanned below the rail axes between the cross girders affected to stabilize the track in longitudinal direction. The inspection period was shortened from years to few weeks. BAM was mandated to measure strains under regular train traffic to analyze the cause of the cracks. Strains were measured in identical connections as the damaged details, which did not suffer from cracks at the time of the measurement. The traffic-induced strain cycles and thus the resulting strain differences in the questionable cross sections were higher than expected and resulted in stresses of max. 85.8 MPa. Calculations showed that the credible remaining fatigue life for this particular structural detail was exceeded after 68 years according to nowadays standards. Extensive discussions, further field and laboratory tests followed to develop a rehabilitation plan for retrofitting the structure with minimum interference of the traffic. Finally, a method with minimum intervention to the structure was elaborated by a consortium of the operator BVG, BAM and producers based on further laboratory and field tests at BAM. Now, the viaduct is saved for the future. KW - Riveted viaducts KW - Fatigue cracks KW - Strain measurement KW - Rehabilitation KW - Non-ballasted track PY - 2014 U6 - https://doi.org/10.1016/j.engfailanal.2014.03.003 SN - 1350-6307 SN - 1873-1961 VL - 43 IS - Special Issue 'A Tribute to Prof. A. Martens' SP - 150 EP - 170 PB - Elsevier Science Publ. CY - Oxford AN - OPUS4-30897 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hong, Shuxian A1 - Lai Wai-Lok, Wallace A1 - Wilsch, Gerd A1 - Helmerich, Rosemarie A1 - Helmerich, R. A1 - Günther, Tobias A1 - Wiggenhauser, Herbert T1 - Periodic mapping of reinforcement corrosion in intrusive chloride contaminated concrete with GPR N2 - This paper presents an experimental effort for developing a novel reinforcement corrosion monitoring technique based on Ground Penetrating Radar (GPR). Experiments were carried out to periodically monitor the accelerated reinforcement corrosion process with GPR. The data were processed in both time and time–frequency domains to investigate the tendencies of GPR signal attribute changes related with corrosion, moisture and chloride contamination. Data processing methods were proposed to visualize the reinforcement corrosion and chloride distribution with target specified signal attribute mapping. Half-Cell Potential (HCP) and Laser-Induced Breakdown Spectroscopy (LIBS) methods were employed to verify the GPR observations. KW - Reinforcement corrosion KW - Chloride contamination KW - Periodic monitoring KW - Ground penetrating radar PY - 2014 U6 - https://doi.org/10.1016/j.conbuildmat.2014.06.019 SN - 0950-0618 VL - 66 SP - 671 EP - 684 PB - Elsevier Science CY - Amsterdam AN - OPUS4-31397 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Helmerich, Rosemarie A1 - Milmann, Boris A1 - Wöstmann, Jens T1 - Condition of CFRP-strengthening of concrete bridges years after aplication T2 - 31st DANUBIA-ADRIA Symposium on Advances in Experimental Mechanics CY - Kempten, Allgäu, Germany DA - 2014-09-24 PY - 2014 AN - OPUS4-33076 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Helmerich, Rosemarie A1 - Milmann, Boris A1 - Wöstmann, Jens T1 - Bond durability of CFRP-laminates on concrete bridges N2 - Trans-European corridors for transport of people and goods require strengthening of bridges to carry increased axle loads in terms of absolute axle loads and of their frequency. Most of the bridges along highways are reinforced or prestressed concrete bridges. Since the late 1990s, CFRP laminates have been applied to box girder and T-beam bridges to increase the overall capacity. Although regular inspections are carried out, no special method was available to test the bond condition of CFRP laminates after being in Service for more than ten years. The German Center of Competence in Civil Engineering is aware of this need and funded a research project to investigate the bond condition by means of advanced non-destructive testing (NDT). T2 - 31st Danubia-Adria Symposium on advances in experimental mechanics CY - Kempten, Germany DA - 24.09.2014 KW - Concrete bridges KW - Strengthening KW - Non-destructive testing KW - CFRP KW - Durability KW - Inspection PY - 2014 SN - 978-3-00-046740-0 SP - 1 EP - 2 AN - OPUS4-33116 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -