Notch Effect on the Fatigue Behavior of a Hot Dip Galvanized Structural Steel

Исследовано влияние гальванического покрытия на усталостную прочность конструкционной стали S355. Несмотря на наличие в литературных источниках экспериментальных данных по гладким образцам из этого материала с покрытием, почти отсутствуют таковые по образцам с концентраторами напряжений. Выполнен сравнительный анализ образцов с центральным отверстием, подвергнутых гальванизации методом горячего погружения, и исходных образцов той же геометрии. Усталостные испытания проводились при двух постоянных значениях асимметрии цикла нагружения. Получено и проанализировано 60 новых экспериментальных данных.Досліджено вплив гальванічного покриття на втомну міцність конструкційної сталі S355. Незважаючи на те, що в літературних джерелах є експериментальні дані щодо гладких зразків із цього матеріалу з покриттям, майже відсуті дані щодо зразків із концентратором напружень. Виконано порівняльний аналіз зразків із центральним отвором, ще зазнали гальванізації методом гарячого занурення, і вихідних зразків такої ж геометрії. Випробування на втому проводились при двох постійних значеннях асиметрії циклу навантаження. Отримано і проаналізовано 60 нових експериментальних даних

Notch Effect on the Fatigue Behavior of a Hot-Dip Galvanized Structural Steel

We investigate the effect of a galvanizing coating on the fatigue strength of S355 structural steel. Although some results on fatigue tests of unnotched specimens are available, those on notched components are scarce. A comparison is carried out between hot-dip galvanized specimens weakened by a central hole and untreated specimens of the same geometry for two nominal load ratios R = 0 and R = −1. In total, over 60 new experimental data are summarized and analyzed in the present contribution

Weigh in Motion Measurement and Experimental Fatigue Assessment of a Railway Bridge

Fatigue represents one of the most diffused failure modes in steel railway bridges. Phenomena such as "vibration induced" and "distortion induced" fatigue are still only partially covered by design codes and represent critical aspects for the assessment of existing bridge and the design of new ones. The European research project FADLESS "Fatigue damage control and assessment for railways bridges" is directed towards defining innovative technical guidelines for the assessment and control of existing and new bridges with regard to fatigue phenomena induced by vibrations and distortions. In this paper, the experimental methodology applied for the fatigue assessment of an Italian case study, the Panaro Bridge, is reported. Such a methodology consists of: preliminary execution of the fatigue assessment of the bridge; experimental structural characterisation; installation of a developed structural monitoring system including a properly designed weigh in motion system

FATIGUE TESTS ON RIVETED CONNECTIONS

To estimate the fatigue strength of riveted joints represents a problem of primary importance both for the re-analysis of old bridges and the assessment of relatively recent structures. Even if the riveted solution is going to be progressively substituted by bolted and welded solutions, the behaviour of riveted members remains a matter of considerable economic importance. Technical specifications available in the Standards in force give to engineers engaged in fatigue design problems a reference curve relating to only one detail and the recommended values appear to be very different. In particular, recent re-analysis reported in the literature showed that the value suggested by the Eurocode 3 for shear splices that use non pre-loaded high strength bolts is strongly non-conservative when applied to riveted connections taken from old bridges. The paper presents the results of fatigue tests carried out on 3 different riveted joints and compares them to the design curves reported by some European and American Standards in force

Global and local dynamic behaviour of the Sesia viaduct, a steel-concrete composite railway bridge on the HS line Turin-Milan,

Steel-concrete composite bridges have become an important alternative to concrete structures in the development of new high speed railway lines throughout Europe, due to considerable advantages concerning design, construction time, durability and costs. Nevertheless design process highlighted many still open problems related to the estimation of dynamic and fatigue effects due to the HS train passages lacking reliable numerical models and suitable assessment methodologies. In the framework of the recently launched research project "DETAILS" (funded by European Commission), that aims at analyzing dynamic interaction phenomena and fatigue behaviour of these types of bridges, the Sesia Viaduct, a steel-concrete composite box girder bridge, has been deeply investigated by means of a wide experimental modal analysis campaign in operational conditions. In the experimental campaign, three spans of the bridge were instrumented by accelerometers covering 103 sensor locations and by optic fibers, to obtain detailed mode shape information for correlation and updating of Finite Element models. Furthermore the accelerometer locations have been designed in order to identify the global dynamic behaviour and the ones of particular substructure and elements (i. e. the bottom steel plate, the diagonal of the cross girder, the bottom flange stiffener etc.). Fiber optic sensors have been used to measure the strain field at two stations of the bridge in order to analyze the distortions of the cross section under the train passages. The paper present the acquired vibration data under ambient and train excitation, showing Operational Modal Analysis results and providing a comprehensive description of the dynamic behaviour of the whole structure and relevant structural elements

Train-induced vibrations of masonry railway bridges

Experimental data used to carry out structural identification (either artificial or natural), usually consist of time-histories both of the excitation and of the response; however, in the civil engineering field it can be sometimes necessary to refer only to the measured response, due to difficulties to measure the forcing action, as it happens for wind-induced loads or for traffic (road or rail-road) induced loads

A 24-bit permanent monitoring system for bridges: development and initial results

Steel-concrete composite bridges are an important alternative to concrete bridges due to considerable advantages regarding the design, construction time, durability and costs. Therefore, they are largely used in high-speed lines of the European railway networks. The recently launched EC research project "DETAILS" aims to remove actual uncertainties on dynamic effects and interaction phenomena, fatigue loadings, structural modeling, fatigue life and damage assessment of these types of bridges. In the frame of the project, 3 European bridges will be instrumented and monitored during a long period. This paper describes the permanent monitoring system that has been developed for the Sesia Viaduct located on the new Italian high-speed line between Torino and Milano. The aim of the vibration monitoring system Is to follow the evolution of the bridge dynamic properties in time and in relation to temperature and humidity and to evaluate the bridge response under high-speed train loading. Next to a description of the system, also the results of a preliminary detailed dynamic assessment will be shown

Experimental dynamic analysis of steel concrete composite railway bridges: the Sesia viaduct on the high speed line Turin-Milan

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