Transverse strength of railway tracks : Part 2. Test system for ballast resistance in line measurement

© Gruppo Italiano Frattura 2014. This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: https://creativecommons.org/licenses/by/4.0/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 full-scale 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.Peer reviewe

Selection and ranking of the main beam geometry of a freight wagon for lightweighting

The traditional freight wagons employ I-beam sections as the main load-bearing structures. The primary loads they carry are vertical (from loading units) and axial (from train traction and buffers). Ease of manufacturing has played an important role in the selection of the I-beam for this role. However, with lightweighting increasingly becoming an important design objective, an evaluation needs to be done to assess if there are other existing or new section profiles (geometry) that would carry the same operational loads but are lighter. This paper presents an evaluation of 24 section profiles for their ability to take the operational loads of freight wagons. The profiles are divided into two categories, namely ‘conventional – made by wagon manufacturers (including the I-beam)’ and ‘pre-fabricated’ sections. For ranking purposes, the primary design objectives or key performance indicators were bending stress, associated deflection and buckling load. Subsequently, this was treated as a multi-criteria decision-making process. The loading conditions were applied as prescribed by the EU standard EN 12663-2. To carry out structural analysis, finite element analysis was implemented using ANSYS software. To determine the validity of the finite element analysis results, correlation analysis was done with respect to beam theory. Parameters considered were: maximum stress, deflection, second moment of area, thickness, bending stiffness and flexural rigidity. The paper discusses the impreciseness related to the use of beam theory since the local stiffness of the beam is neglected leading to an inaccurate estimation of the buckling load and the vertical displacement. Even more complicated can be the estimation of the maximum stress to be used for comparison when features such as spot welds are present. The nominal stress values computed by means of Navier equation lead to an inaccurate value of the stress since it neglects the variations in the local stiffness, which can lead to an increase in the bending stress values. The main objective of the paper is the applicability of particular section profiles to the railway field with the aim of lightweighting the main structure. Sections commonly adopted in civil applications have also been investigated to understand the stiffness and strength under railway service loads. The common approach reported in literature so far makes use either of the beam theory1 or topological finite element approach2 to determine the optimised shape under the action of the simplified loading conditions. Although the previous approaches seem to be more general, the assumptions made affect the optimisation process since the stress state differs from that attained under the actual service load in the real structure. In this paper, the use of complex shape cross sections and detailed finite element models allows to take account of the real behaviour in terms of stiffness distribution and local stress effects due to manufacturing features like welds. The structural assessment carried out with the detailed models also allows for the proper comparison among the considered sections. Analysis of the results showed that three out of the 24 section profiles have the highest potential to be fitted as the main load-bearing beams for freight wagons, with the pre-fabricated Z-section being the optimum of the three.Peer reviewe

Analisi del settore ferrotranviario

Indice - Il settore ferrotranviario - Analisi strutturale del settore - La domanda - L'offert

Transverse strength of railway tracks : Part 1. planning and experimental setup

© Gruppo Italiano Frattura 2014. This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: https://creativecommons.org/licenses/by/4.0/Several studies have been carried out until now by various Research Agencies and Railway Administrations to quantify the effects of the track-bed geometrical characteristics on the transverse strength of the track. Unfortunately, not all the possible scenarios in terms of track components, track-bed cross profile, operating conditions etc. have been investigated and not all the relevant variables have been directly measured. Therefore data available from the literature have different degrees of reliability. With the aim of enlarging the knowledge on the track stability and covering much of the possible relevant scenarios, an experimental research program has been developed in the framework of a cooperation between RFI, Italcertifer and DII. In order to perform the investigation under quite general conditions and to reduce the experimentation costs, n. 28 significant scenarios have been identified and reproduced on as many independent track segments. By applying on each track segment a transversal load, the strength of the ballast-sleeper interface has been determined. The results relative to the first four scenarios are presented in terms of applied load vs. lateral track displacement diagrams and in more synthetic numerical tables.Peer reviewe

Transverse strength of railway tracks : Part 3. Multiple scenarios test field

© Gruppo Italiano Frattura 2014. This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: https://creativecommons.org/licenses/by/4.0/In the present paper the design and construction choices of a test field for the ballast lateral resistance measurement, in order to produce data useful for the development of a numerical model able to simulate the service critical conditions of a continuous welded rail track, are described. Some construction details described herein allow to better understand the methodological approach followed in the design of experiments, the tests management philosophy as well as of the accuracy achieved in their implementation.Peer reviewe

Rotating wave approximation and entropy

This paper studies composite quantum systems, like atom-cavity systems and coupled optical resonators, in the absence of external driving by resorting to methods from quantum field theory. Going beyond the rotating wave approximation, it is shown that the usually neglected counter-rotating part of the Hamiltonian relates to the entropy operator and generates an irreversible time evolution. The vacuum state of the system is shown to evolve into a generalized coherent state exhibiting entanglement of the modes in which the counter-rotating terms are expressed. Possible consequences at observational level in quantum optics experiments are currently under study.Comment: 8 pages, 1 figure, introduction extende

Single center experience with laparoscopic adrenalectomy on a large clinical series

BACKGROUND: Laparoscopic adrenalectomy is considered the gold standard technique for the treatment of benign small and medium size adrenal masses (<6 cm), due to low morbidity rate, short hospitalization and patient rapid recovery. The aim of our study is to analyse the feasibility and efficiency of this surgical approach in a broad spectrum of adrenal gland pathologies. METHODS: Pre-operative, intra-operative and post-operative data from 126 patients undergone laparoscopic adrenalectomy between January 2003 and December 2015 were retrospectively collected and reviewed. Diagnosis was obtained on the basis of clinical examination, laboratory values and imaging techniques. Doxazosin was preoperatively administered in case of pheochromocytoma while spironolactone and potassium were employed to treat Conn's disease. Laparoscopic adrenalectomies were all performed by the same surgeon (CG). First 30 procedures were considered as learning curve adrenalectomies. RESULTS: One hundred twenty-six patients were included in the study. Functioning tumors were diagnosed in 84 patients, 27 patients were affected by pheochromocytomas, 29 by Conn's disease, 28 by Cushing disease. Surgery mean operative time was 137.33 min (range 100-180) during the learning curve adrenalectomies and 96.5 min (range 75-110) in subsequent procedures. Mean blood loss was respectively 160.2 ml (range 60-280) and 90.5 ml (range 50-200) in the first 30 procedures and the subsequent ones. Only one conversion to open surgery occurred. No post-operative major complications were observed, while minor complications occurred in 8 patients (0,79%). In 83 out of 84 functioning neoplasms, laparoscopic adrenalectomy was effective in normalization of endocrine profile. CONCLUSIONS: Laparoscopic adrenalectomy is a safe and feasible procedure, even for functioning masses and pheochromocytomas. A multidisciplinary team including endocrinologists, endocrine surgeons and anaesthesiologists, is recommended in the management of adrenal pathology, and adrenal surgery should be performed in referral high volume centers. A thirty-procedures learning curve is recommended to improve surgical outcomes

Transverse strength of railway tracks: part 1. Planning and experimental setup

Several studies have been carried out until now by various Research Agencies and Railway Administrations to quantify the effects of the track-bed geometrical characteristics on the transverse strength of the track. Unfortunately, not all the possible scenarios in terms of track components, track-bed cross profile, operating conditions etc. have been investigated and not all the relevant variables have been directly measured.Therefore data available from the literature have different degrees of reliability. With the aim of enlarging the knowledge on the track stability and covering much of the possible relevant scenarios, an experimental research program has been developed in the framework of a cooperation between RFI, Italcertifer and DII.In order to perform the investigation under quite general conditions and to reduce the experimentation costs, n. 28 significant scenarios have been identified and reproduced on as many independent track segments. Byapplying on each track segment a transversal load, the strength of the ballast-sleeper interface has beendetermined. The results relative to the first four scenarios are presented in terms of applied load vs. lateral track displacement diagrams and in more synthetic numerical tables