Dynamische Messungen an einer Eisenbahnbrücke als Stahlbetonverbundrahmen

Measurement of dynamic properties of a composite frame railway bridge – Field testing of the railway bridge crossing Salzach River in Schwarzach/St. Veit, Austria. A prefabricated composite frame bridge was measured at four different stages during construction phase and after opening to railway traffic. The performed measurements were used to analyze the contribution of backfill to dynamic behavior of the bridge under vertical excitation. At the first measurement, different kinds of accelerometers and afterwards different analysis methods were used. Both led to the same eigenfrequencies. The three subsequent measurements were analyzed with only one of those methods. At the investigated bridge, only a negligible contribution of the backfill could be observed. This paper introduces the first obtained results and discusses which observations can be transferred to other bridges.     

Neuartige Sandwichfahrbahnplatte für Eisenbahnbrücken

Innovative composite deck slab for railway bridges – Analysis of the fatigue behaviour of the shear connectors using the strain‐life method. At the Technischen Universität Wien (Vienna University of Technology), Institut für Tragkonstruktionen (Institute of Structural Engineering), Research Centre of Steel Structures, a new, extremely slender steel‐concrete‐steel composite (SCSC) plate is under investigation to meet the requirements of today's standards related to the geometric conditions and noise emission in the substitution of old railway bridges. The multi‐layer structure of the plate consists of two steel cover plates with an unreinforced concrete core, hence the name of sandwich plate. Perforated shear connectors, welded alternately to only one of the outer steel plates, work together to ensure the transmission of the shear flow between the outer plates, by the activation of diagonal, horizontal concrete compression struts between neighboring dowel bars. In addition to the distribution of the vertical loads in cross direction to the main girders, the SCSC deck slab also acts as main girder bottom flanges. Investigations on the static load‐bearing capacity as well as an explanation of the load‐carrying mechanism of the SCSC plate were made in ([1] [2] and [3]). Evaluation of the fatigue behaviour is presented in this work, focusing on the fatigue behavior of shear connectors of the SCSC plate. In the course of research a nonlinear, three‐dimensional finite element model served as the basis for a lifetime calculation using the local strain‐life method [4]. The aim was to investigate the relation between the range of traffic load (Load Model 71) and the bearable number of load cycles of the SCSC plate till crack initiation in the shear connectors. This paper provides an overview of the approaches used to calculate fatigue life of the shear connectors and gives a brief summary of the results.     

Empfehlung Nr. 5 “Punktlastversuche an Gesteinsproben“ des Arbeitskreises 3.3 “Versuchstechnik Fels“ der Deutschen Gesellschaft für Geotechnik

Der Arbeitskreis AK 3.3 “Versuchstechnik Fels“ der Deutschen Gesellschaft für Geotechnik e. V. erarbeitet Empfehlungen für felsmechanische Labor‐ und Feldversuche sowie Messungen im Gebirge und an Bauwerken. Die vorliegende Neufassung der Empfehlung Nr. 5 behandelt den Punktlastversuch an Gesteinsprobekörpern und berücksichtigt die Weiterentwicklung der Versuchstechnik und ‐auswertung seit der gleichnamigen Empfehlung Nr. 5 von 1982. Es werden die Anforderungen an die Prüfeinrichtung und die Probekörper sowie die Vorgehensweisen für die Durchführung und Auswertung von Punktlastversuchen festgelegt. Die wesentliche Neuerung besteht darin, dass nicht mehr der Lastpunktabstand allein, sondern die Probekörperfläche zur Berechnung des Punktlastindex verwendet wird. Beim Punktlastversuch wird ein Indexwert für die Festigkeit eines Gesteins bestimmt, indem ein zylinderförmiger, quaderförmiger oder unregelmäßig geformter Probekörper zwischen zwei Lasteinleitungsspitzen bis zum Bruch belastet wird. In dieser Empfehlung werden der Zweck, die Begriffe, die Prüfeinrichtung, die Anforderungen an den Probekörper und die Versuchsdurchführung erläutert. Drei mögliche Optionen der Versuchsauswertung werden aufgezeigt, die Darstellung der Ergebnisse beschrieben und mit Hilfe von Beispielen illustriert. Abschließend wird erläutert, wie die einaxiale Druckfestigkeit aus der Punktlastfestigkeit abgeleitet werden kann. Recommendation No. 5 (revised) of the Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e.V. — “point load tests on rock samples”. The Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e.V. (German Geotechnical Society) is compiling instructions for rock tests conducted in the laboratory and in‐situ, and for performing monitoring of rock masses and civil engineering structures. The revised version of recommendation No. 5 deals with the point load test on rock samples and incorporates recent developments in testing machines and testing procedures since the first version from 1982. The requirements for the testing machines and the specimens are given, as well as the procedures to perform the tests and evaluate the data. The essential modification is the use of the sample area instead of the platen tip distance alone. The point load test is used to derive an index value for rock strength. Therefore rock specimens in the form of core, cut blocks or irregular lumps are loaded until failure between a pair of load tips. In this recommendation, scope, terms, apparatus, specimen requirements and procedure of the test are explained. Three possible options of test evaluation are given, the reporting of results described and illustrated by examples. Finally it is shown, how the uniaxial compressive strength can be derived by the point load strength.