TY - JOUR A1 - Klinger, Christian A1 - Michael, Thomas A1 - Bettge, Dirk T1 - Fatigue cracks in railway bridge hangers due to wind induced vibrations - Failure analysis, measures and remaining service life estimation N2 - Unexpected wind-induced vibrations of the hangers have caused an early fatigue crack on specific steel components and joints of a railway bridge over the Elbe River at Lutherstadt Wittenberg, Germany. During regular periodic inspection a fatigue crack of approximately 240 mm length was found near a butt weld of the longest hanger. The hanger was immediately secured by welded butt straps across the crack. Based on experimental investigations of hanger vibrations additional bracings were added between the hangers to avoid wind-induced vibrations. The weld heat influence zone which was affected by high cyclic stresses was replaced by new material. Nevertheless it was impossible to determine sufficient remaining service life for those remaining bridge components that were exposed to extreme high real load cycles. The grinding of the affected steel surfaces was the key element of the remedial actions. Furthermore, additional fracture mechanic calculations were carried out in order to assess the remaining service life of the welded joints. In this respect, the calculation approach used by Deutsche Bahn AG was compared to further procedures from the mechanical engineering field. These investigations showed that the studied, repaired components have both, bearing and fatigue capacities within the validity of standards. KW - Bridge hangers KW - Wind induced vibrations KW - Undamped structural elements KW - Fatigue crack KW - Remaining service life PY - 2014 U6 - https://doi.org/10.1016/j.engfailanal.2014.02.019 SN - 1350-6307 SN - 1873-1961 VL - 43 IS - Special Issue 'A Tribute to Prof. A. Martens' SP - 232 EP - 252 PB - Elsevier Science Publ. CY - Oxford AN - OPUS4-31318 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Klinger, Christian T1 - Failures of cranes due to wind induced vibrations N2 - Self-excited vibrations with large amplitudes in natural wind may occur at slender structural elements with low damping. Because of the different designs (e. g. using solid sections today instead of cables for tension elements in the past) the susceptibility to wind induced oscillations has increased. Those wind induced vibrations of profiles with specific cross section geometry which are motion induced and therefore self-exciting are called 'galloping vibrations'. Especially systems with elements that are highly tensile loaded and undamped, like hangers of bridges or tension bars of cranes, are sensitive to wind induced vibrations. Therefore more and more fatigue problems caused by galloping oscillations have occurred in the 1990s. This paper describes exemplary the collapses of two modern cranes of different design and manufacturers. During standstill periods, both cranes suffered from wind induced vibrations of the tension bars, which bear up the counterweights. The failure analysis process to identify and explain the fatigue fractures as well as the comparative experiments and simulation to verify that they were caused by wind induced galloping-vibrations is described. It is shown, which parameters led to galloping-vibrations of the tension bars and how their onset wind speed and the amplitudes can be estimated with more accuracy by a non-linear and non-stationary approach. Furthermore it is shown that such dynamic stresses caused fatigue failure of the tension bars for the counter weights and subsequently collapsing of the cranes. For loss prevention knowledge and results gained by these investigations should be put at disposal to engineers working on this field of design. In the meantime, a contribution to development of appropriate technical standards on structural steelwork was given by the research works on galloping. Although new standards were introduced, which consider wind induced vibrations, such failures still occur. (Reference to the paper 'Fatigue crack in railway bridge hanger due to wind induced vibrations – failure analysis, measures and remaining service life estimation' in this same Special Issue 'A tribute to A. Martens' 2014). KW - Wind induced galloping vibrations KW - Onset wind speed KW - Undamped structural elements KW - Crane tension bars KW - Fatigue fracture PY - 2014 U6 - https://doi.org/10.1016/j.engfailanal.2013.12.007 SN - 1350-6307 SN - 1873-1961 VL - 43 IS - Special issue: 'A tribute to A. Martens' SP - 198 EP - 220 PB - Elsevier Science Publ. CY - Oxford AN - OPUS4-31595 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -