Fatigue assessment of rail track detail on movable bridge in Estonia based on 2D/3D Finite Element Modelling using hot-spot stresses
D.A. Rikeros Orozco (TU Delft - Civil Engineering & Geosciences)
Milan Veljković – Mentor (TU Delft - Steel & Composite Structures)
P.A. de Vries – Graduation committee member (TU Delft - Steel & Composite Structures)
M. A.N. Hendriks – Graduation committee member (TU Delft - Applied Mechanics)
Klaas Wiersma – Graduation committee member (Witteveen+Bos)
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Abstract
There are several methods to perform fatigue assessment as described by the Eurocode 3 and the International Institute of Welding (IIW). The codes establish the relation between stress ranges and their respective number of cycles until failure of the detail. This method is called S-N curves, however this is based mainly on nominal stresses. A different approach is analyzed in this project, the hot-spot stress method. The hot-spot stress is used to analyze stress distribution caused by geometrical discontinuities on a welded connection. Finite element modelling (FEM) is used in order to ascertain and calculate the hot-spot stress for different details. This method consists on performing a stress extrapolation based on read-out points to avoid any peak stress caused by the finite element analysis itself.
This project focuses on a project-specific welded connection in a rail track for a movable bridge located in Tallinn, Estonia, designed by the company Witteveen+Bos. Initially, the company performed a model of the complete rail track used in the movable bridge, where the welded connection is located. This project takes a more specific scenario and develops the analysis of the local model of the connection itself. The hot-spot stress approach is taken to analyze this structural detail by means of two different finite element software, RFEM and ABAQUS, to perform a validation between these programs. In this report, a comparison is performed between modelling using shell elements and solid elements as well as mesh refinement. The extrapolation of the hot-spot stress is performed by taking the normal stresses at the surface of the element. Based on the results obtained from the analysis, this project provides recommendations when performing this type of analysis on welded connections. A design check is also performed to establish if the detail design is sufficient against fatigue, caused by the motion of the movable bridge.