TY - CONF A1 - Wolf, Julia A1 - Milmann, Boris A1 - Helmerich, Rosemarie A1 - Köpp, Christian A1 - Mielentz, Frank 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. ED - Xu, Y. L. ED - Zhu, S. ED - Xia, Y. ED - Ni, Y.Q. ED - Law, S.S. ED - Yin, J. H. ED - Su, Z.Q. T1 - Ultrasound based monitoring system for concrete monolithic objects N2 - Ultrasound sensors should be embedded into concrete for monitoring concrete properties. These new longitudinal wave sensors with a center frequency of 60 kHz were examined regarding their suitability for ultrasonic measurements in concrete structures in terms of emission characteristics, sensitivity and frequency ränge. For the measurement of the radiation patterns, the sensors were embedded vertically and horizontally in concrete cylinders. The directivity pattern was measured using a laser vibrometer. The sensitivity of the sensor was determined in water using different sensors of the same type. It shows changes in the signal amplitude as well as variations in the frequency ränge for different transmitter-receiver combinations. The attenuation of the concrete affects the achievable resolution of the measurements and thus, the maximum possible spacing of the sensors within a concrete element. Experimental tests helped optimizing the distances with respect to the required resolution and the effort of embedding the sensors. The signal attenuation in the concrete was measured in the frequency ränge of 60 kHz in response to various degrees of reinforcement and grain size. For this purpose, the sensors were cast at different distances in the specimens studied. The recorded Signals were evaluated for their amplitude and frequency spectrum. T2 - SHMII-6 - 6th International conference on structural health monitoring of intelligent infrastructure CY - Hong Kong, China DA - 09.12.2013 KW - Ultrasound KW - Concrete KW - Monitoring system KW - Ultrasonic network KW - Embedded sensor PY - 2013 SN - 978-962-367-768-4 SP - 1 EP - 6 AN - OPUS4-29642 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Helmerich, Rosemarie A1 - Niederleithinger, Ernst A1 - Wiggenhauser, Herbert T1 - Toolbox with Nondestructive Testing Methods for Condition Assessment of Railway Bridges KW - Non-destructive testing KW - Automated scanning KW - Condition assessment KW - Bridge assessment KW - Ultrasonicecho KW - Impulse radar KW - Impact echo PY - 2006 SN - 0361-1981 IS - 1943 SP - 65 EP - 73 PB - National Research Council CY - Washington, DC AN - OPUS4-14293 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bien, J. A1 - Helmerich, Rosemarie ED - Jasienko, J. T1 - Theoretical and experimental analysis of historical bridges T2 - SAHC 2012 - 8th International conference on structural analysis of historical constructions CY - Wroclaw, Poland DA - 2012-10-15 KW - Historical bridges KW - Theoretical analysis KW - Experiments KW - Diagnostics PY - 2012 SN - 978-83-7125-216-7 SN - 0860-2395 VL - 1 SP - 45 EP - 63 PB - DWE CY - Wroclaw, Poland AN - OPUS4-26830 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 - 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 - 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 U6 - 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 - CONF A1 - Hong, Shuxian A1 - Lai Wai-Lok, Wallace A1 - Helmerich, Rosemarie A1 - Milmann, Boris ED - Biondini, F. ED - Frangopol, D.M. T1 - NDT-based monitoring of accelerated steel corrosion in concrete T2 - IABMAS 2012 - 6th International conference on bridge maintenance, safety and management CY - Stresa, Lake Maggiore, Italy DA - 2012-07-08 KW - Concrete KW - Reinforcement corrosion KW - Nondestructive testing KW - Ground penetration radar KW - Ultrasonic echo PY - 2012 SN - 978-0-415-62124-3 SN - 978-0-203-10338-8 SP - 1 EP - 8(?) PB - CRC Press CY - London, UK AN - OPUS4-29581 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Helmerich, Rosemarie A1 - Niederleithinger, Ernst A1 - Trela, Christiane A1 - Bien, J. A1 - Kaminski, T. A1 - Bernardini´, G. T1 - Multi-tool inspection and numerical of an old masonry arch bridge N2 - 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. KW - Masonry bridges KW - Non-destructive testing KW - Bridge inspection KW - Finite element method PY - 2012 SN - 1573-2479 VL - 8 IS - 1 SP - 27 EP - 39 PB - Taylor & Francis CY - London [u.a.] AN - OPUS4-27425 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Helmerich, Rosemarie A1 - Niederleithinger, Ernst A1 - Trela, Christiane A1 - Bien, J. A1 - Kaminski, T. A1 - Bernardini, G. T1 - Multi-tool inspection and numerical analysis of an old masonry arch bridge N2 - 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. KW - Masonry bridges KW - Non-destructive testing KW - Bridge inspection KW - Finite element method PY - 2010 U6 - https://doi.org/10.1080/15732471003645666 SN - 1573-2479 SN - 1744-8980 IS - NSIE_A_465075 SP - 1 EP - 13 PB - Taylor & Francis CY - London AN - OPUS4-22838 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -