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Fire testing of loaded carbon tension members The application of carbon tension members is motivated by extraordinary well fatigue behaviour and high tensile strength of the material. Compared to steel, cross sections can be reduced. Steel tension members used for network arch bridges shall be replaced in perspective. The loadbearing behaviour of carbon tension members in case of fire is still unknown. Therefore, fire tests were performed to investigate the failure mechanisms. Based on the derived test data the comparability to conventional steel tension members was estimated. This paper describes real scale fire testing of mechanically loaded carbon tension members, carried out as a part of the joint research project NeZuCa. The test setup consisted of four carbon tension members with circular cross sections and diameters of 36 mm and 51 mm. In absence of a prescriptive fire scenario for the application case intended in the research project and to ensure comparability, a fire exposure according to standard temperature/time curve was chosen. The elongation of the tension members as well as the temperatures of the specimen and the furnace were recorded. [ABSTRACT FROM AUTHOR]

Damage equivalence factors for deck slabs of steel railway bridges According to EN 1993‐2, the fatigue verification of railway bridges can be based on internal forces due to the standard load model 71. These internal forces are to be multiplied by a dynamic coefficient Φ2 and a damage equivalence factor λ. In this paper, factors λ1 allowing for the damage effect of traffic on quadrilaterally supported plates with torsionally flexible supports at the longitudinal edges as encountered in single‐track railway‐brides in a span range between 10.0 and 27.5 m are derived for three standard traffic situations. The required damage equivalence factors λ are obtained from the factors λ1, considering the annual traffic volume and the requested service life. [ABSTRACT FROM AUTHOR]

Unexpected fatigue cracks at main girders of a railway bridge – strain measurements under service and analyses based on fracture mechanics At a steel railway bridge, erected and taken into service in 1960, fatigue cracks were detected at some transverse stiffener to web connections at the lower flange of the main girder. These findings were surprising, because this specific connection detail was suggested in previous national design standards for fatigue. The paper presents the comprehensive strain measurements under service to show the local stress field at the critical detail within the web plate of the main girder, indicating the well‐known phenomenon of distortion‐induced fatigue, but with unexpectedly high resonance‐like bending stresses in the web. Based on fracture mechanics analyses, with implementation of the measured strain/stress data due to local and global effects at the transverse stiffener connection, as well as the measured material properties (fracture toughness and crack growth parameters) the remaining fatigue life was analysed. The positive results allow an unrestricted train operation in the future. It also turned out, that the mixed‐mode effects must be taken into account and considering only mode I at the crack tip may lead to unsafe results. [ABSTRACT FROM AUTHOR]

Abstract: Modern railway bridges as thick‐plate trough bridges – Optimization of fatigue design and life‐cycle analyses. Innovative improved design solutions of bridge constructions increasingly aim at maintenance reduced structures where the utilization and surrounding traffic routes are affected only in minor extent by rehabilitation and maintenance works. As part of the FOSTA‐AiF‐research project „Holistic Assessment of steel‐ and composite railway bridges according to criteria of sustainability” (P978) specific investigations were carried out in order to optimize different railway bridge types by improving single structural details and construction variants types. To assess the benefits of these optimized constructions within the life‐cycle of the bridge, the conventional and improved constructions were compared with each other by applying sustainability analyses. This paper deals with the evaluation of the trough bridges with thick track plates which was especially developed for rail traffic constructions and which is also known as thick‐plate trough bridges. It focusses on questions related to the fatigue design, uses large scale tests for verifications and provides recommendations for the construction and design. [ABSTRACT FROM AUTHOR]

Abstract: Modern heavy plate solutions for bridge constructions for sustainable, efficient constructions. In many European countries infrastructure – road as well as railway infrastructure – needs intensive investments to follow the growing demands of mobility and goods traffic. Steel or steel composite bridges offer in this context viable and very sustainable solutions. Due to its unlimited recyclability steel can in general be seen as the ideal material for such sustainable constructions, but especially when designers or fabricators consistently exploit the potentials nowadays available thanks to smart product developments during steel production very cost‐efficient and remarkable constructions are realizable . It therefore pays off to select modern and innovative grades and high‐quality steels, like longitudinally profiled plates or higher strength thermomechanically rolled or quenched and tempered steels, as early as the planning and design phase. Modern innovations in steel permit not only highly efficient, cost‐optimized fabrication but also more slender and architectural aesthetics. This paper will highlight some of these possibilities in heavy plate production for bridge building. [ABSTRACT FROM AUTHOR]

Abstract: Trough girders are widely accepted in engineering on account of lowing construction depth and protection against traffic noise pollution, but most of them are used for simple‐supported girder bridges with a span of generally less than 30 m. On the railway line of Nanjing–Qidong in China a new railway bridge will be built which has a span of over 64 m but a construction depth of less than 2.4 m on which Shanghai–Nantong railway line is also passed, so the type of concrete‐filled steel tube tied‐arch bridge with trough girder was chosen. For such a new structure hardly used in engineering, there are no research results yet available about mechanical properties of the structure. This paper therefore makes for the bridge an experimental model of 1:4 geometric scale in order to test mechanical properties under operation load, cracking load, and ultimate load such as cracking diagram, load‐carrying capacity, stress distribution, and failure mechanism. According to the experimental results, when the model is subjected to longitudinal bending moment, the failure mode is similar to that of pure bending of a girder, and when the model is subjected to transverse bending moment failure mode behaves like the flexural failure mode of the traditional reinforced concrete structure. A non‐linear element analysis is also made on the model with the results in good agreement with that of the experiment. The same modeling method is applied to the finite element analysis of the real bridge, considering various load in design. In the analysis, it is finally verified that this new type of bridge meets specification requirements in strength, rigidity, and resistance to cracking. [ABSTRACT FROM AUTHOR]

Abstract: 50th anniversary of the Bonn‐Nord (Friedrich‐Ebert) Bridge across river Rhine. This bridge, opened to traffic on June 28, 1967, was the world's first cable‐stayed bridge with a central multicable system (80 locked coil ropes) and has a main span of 280 m. The 36.3 m wide bridge deck consists of a central steel box girder and wide cantilevers, the 49.4 m high towers are also from steel. The side spans were erected on the final and auxiliary piers and the main span by free cantilevering. The paper deals with the design, shop fabrication and erection of the bridge, a recent structural health monitoring and the results of calculations according to the actual Eurocodes. Although the bridge does not meet some of the actual requirements, no major structural defects have been detected. So, the life time of the bridge may not be determined by the structural but by the traffic capacity which may require a wider bridge in about 2040. [ABSTRACT FROM AUTHOR]