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Jointless Concrete Bridges - Development of a Flexible Abutment

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Abstract

For bigger concrete bridges the jointless construction hasn't been established up to now. Concerns regarding the durability still exist since constraint stresses as a result of temperature alterations and shrinkage lead to crack initiation. With the use of the new flexible abutment these restraint stresses and occurring cracks can be reduced significantly. An efficient decoupling of abutment and subsoil is reached by introducing a buffer layer of polystyrene and a geogrid reinforced backfill. Full size tests and non linear calculations show that only little deformations arise at the backfill material.

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... In this type of bridge, relatively large forces caused by the earth pressure and cracking due to imposed deformations may arise in the abutment wall when the bridge expands or shortens. Constructional solutions have been proposed to increase the flexibility of the abutments of integral bridges or to decrease the earth pressure behind them [5], [10], [16], [17], [18], [19]. ...
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This paper presents the results of an experimental test series on the soil-structure-pavement interaction in the vicinity of the transition slab at the end of an integral bridge. The main function of transition slabs is to ease the transition between the bridge deck and the embankment in case of differential settlements. Additionally, in the case of integral bridges, they can solve the problem of moderate imposed longitudinal deformations at the bridge ends. In this case, the displacements imposed to the transition slab can lead to vertical and longitudinal surface displacements and to cracking of the pavement. Based on the observed behaviour, some recommendations are proposed for the geometry and surface conditions to optimise the behaviour of the transition slabs.
Article
Die gekrümmte Grundrißform läßt sich optimal mit der fugenlosen Bauweise kombinieren. Denn Zwängungen aus Temperaturschwankungen und Betonschwinden lassen sich durch horizontales “Atmen” des Überbaus auf niedrigem Niveau halten. Damit können aufwendige technologische und konstruktive Maßnahmen zur Beherrschung der Rißbildung vermieden und Kosten gesenkt werden. Zudem eröffnen sich neue Gestaltungsmöglichkeiten. Im folgenden Beitrag wird gezeigt, daß zum Entwerfen gekrümmter Betonbrücken bereits wenige Parameter ausreichen. Parameters for designing jointless concrete bridges with curved geometry in plan The curved geometry in plan shall be advantageously combined with the jointless construction method. Constraints due to temperature and shrinkage can be considerably reduced by horizontal “relaxation” (movement) of the superstructure. In this way complicated concrete technology and constructive measures on site can be avoided to decrease cracking and reduce costs. Additionally it offers an improved aesthetic. The following contribution shows, that few parameters are sufficient for designing curved concrete bridges without bearings and joints.
Article
Die fugenlose Bauweise eröffnet dem häufig als massig und plump charakterisierten Beton neue Perspektiven. Dies gilt besonders für Brücken, da sie über einen langen Zeitraum nicht nur störungsfrei funktionieren, sondern auch von Nutzern und Anwohnern als Artefakte akzeptiert werden sollten. Obwohl mittlerweile umfassende Erfahrungen vorliegen, stößt diese Bauweise noch immer auf Skepsis. Entscheidender Einwand ist die Frage nach der sicheren Beherrschung der durch Zwängungen verursachten Risse im Beton. Im ersten von zwei Beiträgen wird gezeigt, daß bereits mit dem Tragwerksentwurf (conceptual design) entscheidende Schritte zur Entschärfung dieser Problematik möglich sind. Jointless Concrete Bridges with Flexible Abutments The jointless construction method offers new prospects for the often as massive and bulky characterised concrete. This is particularly relevant for bridges as they shall not only function perfectly for a long period but also be useful and accepted as artefacts by residents. Although in the meantime there are comprehensive experiences, this construction method does still cause scepticism. A decisive objection is the question about the reliable control of cracks in the concrete due to constraints. The first of two contributions shows that with the conceptual design important steps for an ease of the problems are possible.
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