Load model of historic traffic for fatigue life estimation of Norwegian railway bridges
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Material fatigue is the primary damage mechanism in steel railway bridges and ultimately causes material fracture and eventually component and system failure. It is essential that the infrastructure owner can predict and monitor the state of material fatigue in the bridge stock to avoid bridge collapse due to the catastrophic consequences to human life and environment as well as economic cost. Fatigue life assessment of railway bridges is also necessary to ensure that limited funds for maintenance and renewal of the infrastructure is managed in the most efficient manner. Given the vital role of a well managed, reliable and safe railway infrastructure to a functioning modern society and the large number of steel railway bridges in the railway infrastructure, fatigue life assessment of steel railway bridges is of key importance to industrialized countries all around the world. The state of the fatigue damage mechanism depends strongly on the loading history of the material. The loading history of the material is determined by the historic traffic on the railway infrastructure, and the remaining fatigue life of a railway bridge therefore depends on the historical traffic conditions at the bridge site. Historical traffic conditions in the railway infrastructure has long been a neglected field of research on fatigue life assessment of railway bridges. Furthermore, the traffic conditions in a railway network is strongly heterogeneous, data on traffic conditions at one site in a railway network is therefore generally not applicable to the traffic conditions at another location in the railway network. This thesis considers historical loads on the Norwegian railway network and establishes a conservative load model of the historical loads for fatigue life estimation of steel railway bridges. The available data on historical loads on the Norwegian railway network between 1854 and the present is compiled. The load conditions in the railway network is established through documentation of the geometry and loads on the rolling stock, permissible loads and speed on the lines in the network and rules for train operation. It is concluded that the precise load conditions at a particular bridge generally cannot be determined due to lack of relevant data. A novel methodology to find the most damaging train, given all possible locomotives and wagons for a particular period and traffic type is developed. The methodology determines the conservative load case and allows prediction of the remaining fatigue life of railway bridges with the available data. The significance of historical traffic on fatigue life of railway bridges is considered and it is concluded that traffic prior to 1900 can be neglected in fatigue life estimation of Norwegian bridges. Passenger and freight traffic after 1900 has a significant contribution to fatigue damage due to moderate fatigue damage potential for some structural components and relatively high number of train passages on certain lines in the railway network. A general framework for establishing and calibrating a load model to the conservative load case is presented. The framework is used to develop a conservative load model of historic freight and passenger traffic for efficient assessment of bridges in the Norwegian railway network.
Består avPaper 1: Frøseth, Gunnstein Thomas; Rønnquist, Anders. Evolution of load conditions in the Norwegian railway network and imprecision of historic railway load data. Structure and Infrastructure Engineering 2019 ;Volum 15.(2) s. 152-169 https://doi.org/10.1080/15732479.2018.1504087
Paper 2: Frøseth, Gunnstein Thomas; Rønnquist, Anders. Finding the train composition causing greatest fatigue damage in railway bridges by Late Acceptance Hill Climbing © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/) https://doi.org/10.1016/j.engstruct.2019.109342
Paper 3: G. T. Frøseth and A. Rönnquist. Load model of historic traffic for fatigue life estimation of Norwegian railway bridges.