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This paper reports the development and testing of two independent, innovative techniques for measuring rail displacements. One system combines remote video monitoring with particle image velocimetry, using a webcam and a small telescope. The second uses sleeper mounted geophones that give a voltage output proportional to the velocity of motion, which can be filtered and integrated to calculate displacements. Laboratory validation tests show that the video monitoring system can measure peak-to-peak displacements to within 0.04 mm from a distance of 15 m for frequencies less than 4 Hz. The geophones measure peak-to-peak displacements to within 0.07 mm for frequencies as low as 1 Hz. Data from three different standards of railway track and/or train speeds are used to explore and quantify the limitations of each system in the field.

Fatigue tests on tubular joints have shown that as a crack propagates through the chord wall, it curves under the weld toe. This produces, at the brace-chord intersection, a doubly curved semi-elliptical crack emanating from the weld toe. A doubly curved crack in a tubular joint is a very complex geometry which has proved to be difficult to model. In consequence, previous work on the evaluation of stress intensity factors in tubular joints adopted a simplified approach, ignoring the crack curvature under the weld toe. However, in the absence of benchmark solutions, the effects of any modelling approximation on accuracy are impossible to quantify. To address this problem and as part of the research on fatigue assessment methodologies, a technique which is able to accurately model doubly curved cracks in tubular T-joints has been developed at University of Wales, Swansea. This paper describes a detailed account of the generation of the finite element model and the procedure for evaluating the stress intensity factor solutions. The validation results are also presented to demonstrate the reliability of the model developed. Notation a b e h 11,2,3 ml,2,3 nl,2,3 T t Ur Vn Wt D G K /r(I, II, III M~ Mk Mk3-D Q SCF SIF T Cf 3' A KNhs ~ nora ¢ = crack depth = plate width = crack half width = plate length = local radial direction cosines = local normal direction cosines = local tangential direction cosines = radial distance or weld toe radius = attachment thickness = local radial displacement = local normal displacement = local tangential displacement = chord diameter = elastic shear modulus = stress intensity factor = mode I, II, III stress intensity factors = correction factor for 3-D effects = 2-D attachment correction factor = 3-D attachment correction factor = elliptic crack correction factor = stress concentration factor = stress intensity factor = main plate thickness = length/half diameter (chord) = brace diameter/chord diameter = half diameter/thickness (chord) = stress intensity factor range = hot spot strain = nominal strain = parametric crack front angle 130 D. Bowness and M.M.K. Lee O'hs = hot spot s t r e s s O'nom -~-nominal s t r e s s z, = Poisson's ratio r = brace thickness/chord thickness 0 = radial angle ¢ = weld angle