TY - CONF A1 - Helmerich, Rosemarie A1 - Moldenhauer, Laura A1 - Voigt, Gerrit A1 - Köppe, E. T1 - Considerations for identification of moisture in building materials using Bluetooth (R) N2 - The vulnerability of low-quality concrete of some bridges to ageing and deterioration while they are exposed to environmental conditions during their service life, influence of growing population and climate changes, is a well-known effect and requires survey. For survey, the development of a low cost, cost-efficient sensor network to be embedded for continuous or attached to the surface for periodic monitoring is essential. Changing ground water conditions, flood or even leakage in fresh or disposal of waste water can lead to in-creased moisture content in building materials and structural elements as walls or floors. Moisture allows the transport of other adverse chemicals that might reduce the durability of structures. The paper presents a feasibility study about the capability of microwave modules as bluetooth® or ZigBee with frequency range at 2,4 GHz to create advanced Wireless Sensor Networks (WSN) for estimation and visualization of moisture distribution in infrastructure assets. It was found that the value of the received signal strength indication (RSSI) depends on the moisture content and can be the basis for the moisture distribution inside a massive structure. The microwave modules may be used to compose networks outside and inside of building materials or structural elements. The higher the number of connections between BLE modules, the more precise and the more distant information can be obtained from the network. Mesh networking was applied to increase the quantitative information. T2 - 9th International Conference on Bridge Maintenance, Safety and Management (IABMAS) CY - Melbourne, Australia DA - 09.07.2018 KW - Structural Health Monitoring KW - Moisture KW - Bluetooth PY - 2018 SN - 978-1-315-18939-0 SN - 978-1-138-73045-8 SP - 2752 EP - 2759 AN - OPUS4-50340 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Köppe, Enrico A1 - Moldenhauer, Laura A1 - Haamkens, Frank A1 - Helmerich, Rosemarie T1 - Feuchtemessung in Bauteilen und anderen Strukturen mit Bluetooth Low Energy N2 - Die Langzeitüberwachung von Bauteilen (Structural Health Monitoring, SHM) ging in den letzten Jahren zunehmend von verkabelten Sensoren zu kabellosen Sensornetzwerken (WSN) über. Frühwarnsysteme sollen rechtzeitige Signale senden, wenn Schädigungsprozesse einsetzen, wenn ein Bauteil z. B. zu feucht wird (Deiche, Staumauern), oder wenn Feuchteprozesse in Bauteilen auftreten, die den Transport von schädlichen Stoffen ermöglichen. Mittels handelsüblicher multifunktionaler Sensoren wie einem Bluetooth Low Energy (BLE) wurden erste Machbarkeitsuntersuchungen zur Massenfeuchtemessung durchgeführt. Die untersuchten Parameter sind der sogenannte Received Signal Strength Indicator (RSSI) eines Bluetooth-Low-Energy(BLE)-Signals und die abgestrahlte Sendeleistung eines eingebetteten BLE-Moduls. Das BLE-Modul kommuniziert mit einem mobilen smarten Empfänger wie einem Tablet oder einem Smartphone als SmartHub. Die Veränderung des RSS-Indikators ist ein Maß für die Veränderung der Feuchte im Bauteil, während die ausgesandte Signalstärke konstant bleibt. Wenn das BLE-Signal einen feuchten Bereich im Baumaterial durchläuft, verändert sich der RSS-Indikator. Nach erfolgreicher Machbarkeitsstudie wurde nun ein aus dem Netzwerk MI4G (Modern Industry for Germany) zwischen der Bundesanstalt für Materialprüfung und dem Klein- und mittelständigen Unternehmen LinTech GmbH heraus beantragtes ZIM-Projekt bewilligt. Der Bericht zeigt erste Ergebnisse von Voruntersuchungen und gibt einen Ausblick auf weitere Forschungsaktivitäten. KW - Bluetooth KW - BLE KW - Feuchtemessung KW - Bauteil KW - Bluetooth Low Energy PY - 2016 UR - http://onlinelibrary.wiley.com/doi/10.1002/bate.201600074/epdf DO - https://doi.org/10.1002/bate.201600074 SN - 0932-8351 A 1556 VL - 93 IS - 10 SP - 747 EP - 751 PB - Ernst & Sohn CY - Deutschland AN - OPUS4-38163 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hong, Shuxian A1 - Wiggenhauser, Herbert A1 - Helmerich, Rosemarie A1 - Peng, B.D. A1 - Xing, D. F. T1 - Long-term monitoring of reinforcement corrosion in concrete using ground penetrating radar N2 - A new method for periodically monitoring reinforcement corrosion in concrete with Ground-Penetrating Radar (GPR) is proposed and a ten-year long-term corrosion periodic monitoring experiment is reported. GPR historical data was taken in different years, under different conditions. In order to align and normalize the obtained images properly prior to effectively performing any automatic defect detection, image registration techniques based on mutual-information are employed, and a new signal processing scheme is proposed for normalizing the intensity of GPR images. Then, the processed image results can be used to compare and find out the change of GPR detection due to corrosion. KW - Steel reinforced concrete KW - Atmospheric corrosion KW - Pitting corrosion PY - 2017 DO - https://doi.org/10.1016/j.corsci.2016.11.003 SN - 0010-938X VL - 114 SP - 123 EP - 132 PB - Elsevier Ltd. AN - OPUS4-38346 LA - eng 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 - TY - JOUR A1 - Hong, Shuxian A1 - Lai, W.-L. A1 - Helmerich, Rosemarie T1 - Experimental monitoring of chloride-induced reinforcement corrosion and chloride contamination in concrete with ground-penetrating radar N2 - In this article, we present a laboratory experiment to monitor the accelerated corrosion in concrete using ground-penetrating radar (GPR). Four concrete test specimens were cast with rebars of different size and placed at different depths. The lifetime decades of reinforcement corrosion process were accelerated into 18 days by using the impress current technique. The electrochemical corrosion process was periodically monitored with GPR. Two control specimens were also prepared to investigate the influence of chloride contamination on GPR signal. The measured data were analysed both in time and frequency domains. In time domain, the peak-to-peak amplitude of a wave reflected by a rebar was calculated to investigate the relationship between an increase in signal amplitude and the degree of corrosion. In frequency domain, the time–frequency representations of the signal were computed by using S-transform. The results show that reinforce corrosion increased the amplitude of reflected signal in time domain but did not change the peak frequency in frequency domain while chloride contamination attenuates the signal to smaller amplitude and lower peak frequency. Based on the results, a novel process is finally proposed for GPR-based corrosion detection. KW - Non-destructive KW - Reinforcement corrosion KW - GPR KW - Chloride KW - Moisture KW - S-transform PY - 2015 DO - https://doi.org/10.1080/15732479.2013.879321 SN - 1573-2479 VL - 11 IS - 1 SP - 15 EP - 26 PB - Taylor & Francis CY - London [u.a.] AN - OPUS4-33085 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Helmerich, Rosemarie A1 - Milmann, Boris A1 - Wöstmann, Jens T1 - Non-destructive detection of surface-bond defects in carbon composite-strengthened concrete structures N2 - For almost 15 years, carbon fibre-reinforced polymer (CFRP) plates and sheets have been used for strengthening and repair of civil engineering structures. CFRP plates were applied to upgrade structures for change in use or increasing traffic load. CFRP laminates have also been used to repair deteriorated structures such as multi-storey parking or bridges. The execution quality and condition of the strengthening measure in terms of bond integrity were neither monitored nor tested systematically. Inspectors eventually applied simple hammer knocking during regular main inspection for subjective noise distinction as a measure for eventual insufficient bond. This paper presents the feasibility and the limitations of low-frequency transversal ultrasonic waves with dry-coupling point-contact sensors for inspection and defect detection between CFRP laminate and concrete surfaces. The German Centre of Competence in Civil Engineering (DIBt) has initiated a national research project [Helmerich et al. (2012). Condition analysis of bonded CFRP-applications on concrete structures by means of non-destructive testing [in German: Zustandsuntersuchung von CFK-Klebeverstärkungen an Betonbauteilen mittels zerstörungsfreier Prüfung (ZfP)]. Final, internal project report], carried out at the Federal Institute for Materials Research and Testing (BAM), Germany. The aim of the project was to present a potential non-destructive testing method for bond defect detection as a measure for the durability of the strengthening system more than 10 years after application. KW - Concrete bridges KW - Strengthening KW - Non-destructive testing KW - Composite materials KW - Durability KW - Inspection PY - 2015 DO - https://doi.org/10.1080/15732479.2013.879322 SN - 1573-2479 VL - 11 IS - 1 SP - 3 EP - 14 PB - Taylor & Francis CY - London [u.a.] AN - OPUS4-33086 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 DO - 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 - 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 DO - 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 DO - 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 DO - 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 -