Bei Brückenlaufkranen werden die Radlasten in die unterstützenden Kranbahnträger über deren Obergurte eingeleitet. Die Konstruktionsdetails im Obergurtbereich, d. h. die Anschlüsse und Verbindungen, erfahren dabei einen mehrachsigen Spannungszustand infolge der Radlasteinleitung und der gleichzeitigen Biegung des Kranbahnträgers. Zu diesen Konstruktionsdetails zählt bei geschweißten Kranbahnträgern die Flansch‐Steg‐Verbindung, die Gegenstand dieses Beitrags ist. Die wiederholte Überrollung von Kranbahnträgern durch Radlasten führt aufgrund der konzentrierten Lasteinleitung und der geometrischen Kerbwirkung der Konstruktionsdetails zu einer mehrachsigen Ermüdungsbeanspruchung. Da diese mehrachsige Ermüdungsbeanspruchung durch eine Phasenverschiebung der Spannungskomponenten gekennzeichnet ist, wird sie als nichtproportional bezeichnet. Die für den Ermüdungsnachweis erforderlichen Ermüdungsfestigkeiten im Eurocode 3 – aber auch in den ehemaligen nationalen Normen – beruhen bislang auf Analogiebetrachtungen zum Doppel‐T‐Stoß, dem Kreuzstoß, unter Zugbeanspruchung und stützen sich nicht auf Versuchsergebnisse am eigentlichen Konstruktionsdetail ab. Im IGF‐Forschungsvorhaben FOSTA P895 wurde die Ermüdungsfestigkeit von Kranbahnträgern mit nicht durchgeschweißter Flansch‐Steg‐Verbindung durch eine Kombination aus Ermüdungsversuchen mit überrollender und ortsfest schwellender Radlast ermittelt. Ziel der Untersuchungen war es, die nichtproportional mehrachsige Ermüdungsbeanspruchung der Flansch‐Steg‐Verbindung zuverlässiger bewerten zu können.Test‐based fatigue strength of constructional details with wheel load application – Investigations on partial penetration flange‐to‐web connections. In case of bridge cranes, the wheel loads are applied to the supporting crane runway girders through their top chords. The constructional details of the top‐chord region, i. e. the joints and connections, are subjected to a multiaxial stress state due to the wheel load introduction and the global bending of the crane runway girder. For welded crane runway girders, the flange‐to‐web connection is one of these constructional details and subject of this article. The frequent travelling of wheel loads over a crane runway girder leads to a multiaxial fatigue stress due to the concentrated load introduction and the notch effect of the constructional details. As the multiaxial fatigue stressing exhibits a phase shift between the stress components, it is referred to as nonproportional. The fatigue strengths of Eurocode 3 being necessary for the fatigue evaluation were derived in analogy with the tension‐loaded cruciform joint and are not test‐based for the considered constructional detail. In the IGF research project FOSTA P895, the fatigue strength of partially penetrated flange‐to‐web connections were determined through a combination of fatigue tests on crane runway girders with travelling and stationarily pulsating wheel load. The project aimed at a more reliable evaluation of the nonproportional multiaxial fatigue stress of the flange‐to‐web connection.

No abstract

Titanium and niobium stabilized austenitic stainless steels X6CrNiTi18-10S (material number 1.4541, correspondent to Alloy 321) respectively X6CrNiNb18-10S (material number 1.4550, correspondent to Alloy 347) are widely applied materials in German nuclear power plant components. Related requirements are defined in Nuclear Safety Standard KTA 3201.1. Fatigue design analysis is based on Nuclear Safety Standard KTA 3201.2. The fatigue design curve for austenitic stainless steels in the current valid edition of KTA 3201.2 is essentially identical with the design curve included in ASME-BPVC III, App I (ed. 2007, add. July 2008 respectively back editions). In the current code revision activities of KTA 3201.2 the compatibility of latest in air fatigue data for austenitic stainless steels with the above mentioned grades were examined in detail. The examinations were based on statistical evaluations of 149 strain controlled test data at room temperature and 129 data at elevated temperatures to derive best-fit mean data curves. Results of two additional load controlled test series (at room temperature and 288°C) in the high cycle regime were used to determine a technical endurance limit at 107 cycles. The related strain amplitudes were determined by consideration of the cyclic stress strain curve. The available fatigue data for the two austenitic materials at room temperature and elevated temperatures showed a clear temperature dependence in the high cycle regime demanding for two different best-fit curves. The correlation of the technical endurance limit(s) at room temperature and elevated temperatures with the ultimate strength of the materials is discussed. Design fatigue curves were derived by application of the well known factors to the best-fit curves. A factor of SN = 12 was applied to load cycles correspondent to the NUREG/CR-6909 approach covering influences of data scatter, surface roughness, size and sequence. In terms of strain respectively stress amplitudes in the high cycle regime, for elevated temperatures (>80°C) a factor of Sσ = 1.79 was applied considering and combining in detail the partial influences of data scatter surface roughness, size and mean stress. For room temperature a factor of Sσ = 1.88 shall be applied. As a result, new design fatigue curves for austenitic stainless steel grades 1.4541 and 1.4550 will be available within the German Nuclear Safety Standard KTA 3201.2. The fatigue design rules for all other austenitic stainless steel grades will be based on the new ASME-BPVC III, App I (ed. 2010) design curve.

The assessment of the influence of the LWR coolant environment and postulated chloride transients on the crack growth is of importance for ageing management with regard to safety and reliability. Aim of the investigations was to determine cyclic crack growth rates at LWR conditions and to study possible size effects and the impact of chlorides on environmentally assisted cracking.Crack growth experiments were performed with fracture mechanics specimens of different size in simulated BWR water of high purity and under the effect of chloride transients with RPV steel 22NiMoCr3-7.Subsequent to a phase of cyclic loading, the specimens were exposed to static load, interrupted by partial unloadings.All cyclic crack growth rates da/dN vs. ∆K in high purity water were in good agreement with ASME XI water curves.No significant influence of specimen size on the crack growth behavior and with regard to SCC could be detected in high purity water environment. Cyclic induced crack propagation immediately stopped when turning to static load. Under static load the chloride transients did not cause crack initiation by SCC.Load transients in chloride containing environment initiated significant SCC-induced crack growth. A "chloride memory effect" with regard to a preceding chloride transient at static load, leading to SCC-induced crack propagation during subsequent load transients in high purity water environment did not arise.

No abstract