Windbeanspruchung von Hochspannungs‐Freileitungsseilen in Naturmessungen,Zeitbereichssimulation und Norm

Wind load of high voltage overhead transmission line con ductors in field measurements, time domain simulations and standard. The loading of overhead lines comprises of natural actions mainly. Wind loading signifies an important load case in the design of overhead transmission line structures. Conductors spanning often several hundreds of meters contribute significantly to the overall loading of suspension towers. Those towers are often designed as a mass product to support the dead and wind load of the conductors between two dead end towers. Estimating the reaction of the conductors to strong winds, both geometric nonlinearities because of the large deformations as well as aerodynamic nonlinearities need to be considered. Particularly for design procedures, those effects should be simplified. This paper presents a thorough investigation comprising field measurements along an existing overhead line, simulations with FEM combined with wind tunnel tests and generated wind fields. It is the aim of the study to validate the actual design procedure regarding loading of wind acting on conductors. Most important herein in order to describe the extreme response are assumptions on turbulence distribution and dynamic behavior of wide spanning overhead line conductors. According to usual design procedure, by means of so called span reduction factors, relevant parameters such as span length and wind turbulence can be considered.     

Die Gänsebachtalbrücke,eine integrale Talbrücke der DB AG auf der Neubaustrecke Erfurt‐Leipzig/Halle

Die Gänsebachtalbrücke auf der Neubaustrecke zwischen Erfurt und Leipzig/Halle, Teil des Verkehrsprojektes Deutsche Einheit Nr. 8.2, ist eine integrale, also lagerlose, Eisenbahnbrücke aus Spannbeton. Sie ist für den Hochgeschwindigkeitsverkehr mit Betriebsgeschwindigkeiten bis zu 300 km/h bestimmt. Die in der Realisierung befindliche Talbrücke basiert als alternativer Entwurf auf dem “Leitfaden: Gestalten von Eisenbahnbrücken” der DB AG. Die Gänsebachtalbrücke ist eine Rahmenbrücke, ein Spannbetonplattenbalken monolithisch auf kreisrunden Pfeilern. Am Beispiel der Gänsebachtalbrücke konnte gezeigt werden, dass die alternativen Entwürfe aus dem Leitfaden der DB AG hinsichtlich Tragfähigkeit, Gebrauchstauglichkeit und Verkehrssicherheit sowie Kosten mindestens gleichwertig und damit für den Hochgeschwindigkeitsverkehr geeignet sind. Das Abweichen von der Rahmenplanung und die integrale Bauweise erforderten eine Zustimmung im Einzelfall und damit zahlreiche weiterführende Untersuchungen, welche in diesem Aufsatz ausführlich dargestellt werden, wie die Untersuchung zum dynamischen Verhalten bei Zugüberfahrten und möglicher Resonanzerscheinungen. Mit diesem alternativen Entwurf kommt eine Talbrücke zur Ausführung, die robuster ist und sich besser in das flache Gänsebachtal einfügt als der Ausschreibungsentwurf der Rahmenplanung. The Gänsebach Valley Bridge, an Integral Valley Bridge owned by the DB AG on the New Railway Erfurt‐Leipzig/Halle The new railway between Erfurt and Leipzig/Halle, part of the transportation project “Deutsche Einheit No. 8.2”, crosses the Gänsebach valley via an intregal (i.e. no bearings) prestressed concrete bridge. The bridge is designed for high‐speed traffic of up to 300 km/h. The bridge, currently under construction, is based on an alternative design in accordance with the guideline “Design of Railway Bridges” (“Leitfaden: Gestalten von Eisenbahnbrücken”) of the Deutsche Bahn AG. The Gänsebach valley bridge is designed as a frame bridge, a monolithical prestressed concrete double T‐beam on circular columns. The example of the Gänsebach valley bridge proved that alternative designs following the DB AG guideline are to be regarded as at least equivalent with regard to load bearing capacity, serviceability and traffic safety as well as cost and therefore suitable for high‐speed traffic. The deviation from the original plan and the integral design required a separate approval and consequently various further tests, such as examining the dynamic behavior under train crossings and possible resonance vibrations. These tests will be described in detail in this paper. This alternative design will result in a bridge which is more robust and will fit in more harmoniously with the shallow valley of the Gänsebach than the original commissioned design would have.     

Dynamische Steifigkeit und Dämpfung von Pfahlgruppen

Dynamic stiffness and damping properties of pile groups. The dynamic stiffness and damping properties of pile‐groups have been investigated in this paper. Also, the substantial influence of these properties on an economic structure and foundation design is demonstrated. The analysis has been carried out using the “Thin‐Layer‐Method”, which is a very efficient and powerful analysis procedure in frequency domain.     

Life time prediction of old bridges

The prediction of a realistic lifetime and the prolongation of the service life of a structure is an important task to reduce costs of civil engineering structures. The usual theoretical predictions are not very reliable. The prediction model used consists of a load model, a system‐transfer model and a damage model. The results of these sequentially coupled models are usually unreliable, especially the influence of the uncertain load and damage models controls the reliability of the result. A method based on monitoring strategies is presented, which avoids these problems. Expected trends of future traffic are considered. If the remaining life time of existing structures should be assessed, information about the strain time history of the past is needed. It is shown how these data can be generated taking into account the estimated statistics of the load in the past, the dynamic behaviour and the bumpiness of the road. Synthetic time series of the local strains are generated which include the real statistics of the process and cluster effects induced by truck convoys.