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In service, railway tracks must withstand the transverse and longitudinal forces that are caused by running vehicles and thermal loads. The mechanical design that adopts any of the track models available in the technical literature requires that the strength of the track is fully characterised. In this paper, the results of an experimental research activity on the sleeper–ballast resistance along the lateral and the longitudinal directions are reported and discussed. In particular, the work is aimed at identifying the strength contributions offered by the base, the ballast between the sleepers, and the ballast shoulder to the global resistance of the track in the horizontal plane. These quantities were experimentally determined by means of an ad hoc system designed by the authors. Field tests were carried out on a series of track sections that were built to simulate scenarios in which the ballast was removed from the crib and/or the shoulder. The results of this study indicate that the strength percent contributions from the crib, the sleeper base, and the shoulder are, respectively, equal to about 50%, 25%, and 25% in the lateral direction, and 60%, 30%, and 10% in the longitudinal direction. Moreover, the comparison of the acquired data with literature results reveals that a detailed knowledge about the testing conditions and the activated ballast failure mechanisms is needed in order to correctly use the test data for the design purpose.

During the curing process, the exothermic cross-linking reaction inside epoxy resin-based composites causes overheating and, eventually, a thermal degradation of the matrix. Thick sectioned epoxy composites require an optimized curing cycle in order to minimize the temperature raise inside the composite. However, the recommended cycle for thin laminates is often wrongly used also for thick sectioned composites, resulting in an overheating. In this work, the mechanical behaviour of laminates having different thicknesses was investigated. Specimens were cured according to a curing cycle optimal for thin laminates which causes overheating in thicker laminates. The curing temperature histories at several positions inside the laminates were monitored and recorded and, following a new methodological approach, a series of comparative interlaminar shear tests was performed. Experimental results show a decrease of the interlaminar shear strength in thicker laminates. A simple model to account for the detrimental effect of the exothermic peak on the interlaminar shear strength is proposed. © 2016 Springer-Verlag Londo

ABSTRACT. In the present paper, testing methods currently adopted to measure the in service ballast resistance are synthetically reviewed to identify the main sources of uncertainty influencing the test loads and to define an experimental methodology allowing the optimal control of the testing parameters without the introduction of spurious or parasitic actions on the track sample. An alternative testing system, which allows applying on a fullscale sample of a railway track testing loads very close the real ones, is presented. Of the new system, both the ways of use for measuring the transversal and axial ballast strength, the general procedure to carry out the experimentation and its application to a real scenario are described, highlighting its main advantages in terms both of modalities for applying the loads and of testing parameter control.

A three-parameters model for the interpolation of fatigue crack propagation data is proposed. It has been validated by a Literature data set obtained by testing 180 M(T) specimens under three different loading levels. In details, it is highlighted that the results of the analysis carried out by means of the proposed model are more smooth and clear than those obtainable using other methods or models. Also, the parameters of the model have been computed and some peculiarities have been picked out

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