Verbunddübelleisten sind leistungsfähige Verbundmittel für Stahlverbundträger, die vor allem in vorgefertigten Verbundbrücken eingesetzt werden. Vorteile gegenüber anderen Verbundmitteln liegen insbesondere in der hohen Tragfähigkeit, dem ausreichenden Verformungsvermögen auch bei höherfesten Betonen und der einfachen Herstellung bei oberflanschlosen Stahlprofilen. Das Fehlen eingeführter Technischer Regeln, insbesondere für die wirtschaftlichen Klothoiden‐ und Puzzlegeometrien, führte bei Projekten immer wieder zu Vorbehalten seitens der Bauherren und zu Verzögerungen im Genehmigungsprozess. Ziel des FOSTA‐Projektes P804 war es daher, offene Fragen vor allen Dingen bezüglich des Ermüdungsverhaltens dieser innovativen Verbundmittel zu klären, ein geschlossenes Bemessungskonzept zu schaffen sowie eine offene, firmenneutrale Allgemeine bauaufsichtliche Zulassung (AbZ) zu erwirken. In diesem Artikel werden die Ingenieurmodelle und Bemessungsgleichungen der AbZ zur statischen Tragfähigkeit und zur Ermüdungsfestigkeit, konstruktive Grundsätze sowie Hinweise für die Ausführung und Herstellung vorgestellt und Hintergründe erläutert.Design of composite dowels according to the new national technical approval. Composite dowels are known as powerful shear connectors in steel‐concrete‐composite girders. More and more they are used in practice especially for prefabricated composite bridges. Advantages over other shear connectors are in particular the increased strength, the sufficient deformation capacity even in high strength concrete and the simple application in steel sections without upper flange. However, missing provisions in standards for composite dowels with the economic clothoid and puzzle shape have led to retentions of clients and delays in the approval process. Hence, the aim of the recently finished research project P804 founded by FOSTA‐Research Association for Steel Application was to solve open questions concerning these innovative shear connectors and to prepare a national technical approval available (Allgemeine bauaufsichtliche Zulassung – AbZ) for any design office and construction company. In this paper design concepts for ultimate limit state and fatigue limit state, structural design principles and instructions for production and construction are presented and background information are given.
In seismic reliability analysis the total failure probability is determined by combining the fragility curverepresenting the response of the structure to seismic excitation -with the seismic hazard curve. The determination of fragility curves has a long tradition in the nuclear industry and reaches back to the 1970s. Since the late 1990s also for ordinary buildings seismic reliability analysis became more important and formed the bases for the development of new seismic standards. Several methods are available to build fragility curves relying on different assumptions and restrictions, level of detail and type of failure modes under consideration. In this paper, different fragility analysis methods are described and their advantages and disadvantages are discussed: (i) the safety factor method, in which the fragility curve is estimated on an existing deterministic quasi-static design; the numerical simulation method, in which the parameters of the fragility curve are obtained by (ii) regression analysis or (iii) maximum likelihood estimation from a set of nonlinear time history analysis at different seismic levels; (iv) the incremental dynamic analysis which is based on numerical simulation and the scaling of accelerograms until failure. These four fragility analysis methods are applied to determine fragility curves for the 3-storey reinforced concrete shear wall building of the SMART2013 benchmark project. Advantages and disadvantages of the methods are illustrated and the impact of the simplifying assumptions (e.g. lognormal curves, scaling) are accessed.
Modern standards for constructions in seismic zones allow the construction of buildings able to dissipate the energy of the seismic input through an appropriate location of cyclic plastic deformations involving the largest possible number of structural elements, forming thus a global collapse mechanisms without failure and instability phenomena both at local and global level. The key instrument for this purpose is the capacity design approach, which requires an appropriate selection of the design forces and an accurate definition of structural details within the plastic hinges zones, prescribing at the same time the oversizing of non-dissipative elements that shall remain in the elastic field during the earthquake. However, the localization of plastic hinges and the development of the global collapse mechanism is strongly influenced by the mechanical properties of materials, which are characterized by an inherent randomness. This variability can alter the final structural behaviour not matching the expected performance. In the present paper, the influence of the variability of material mechanical properties on the structural behaviour of steel and steel/concrete composite buildings is analyzed, evaluating the efficiency of the capacity design approach as proposed by Eurocode 8 and the possibility of introducing an upper limitation to the nominal yielding strength adopted in the design
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