Einflussfaktoren auf das Tragverhalten randnaher Verbunddübelleisten/Influencing parameters on the load-bearing behaviour of composite dowels positioned close to the free surface of concrete slabs

Abstract

Zusammenfassung Verbunddübelleisten bieten im Stahlverbundbau eine wirtschaftliche Alternative zu klassischen Verbundmitteln wie Kopfbolzendübeln. Moderne Verbunddecken werden in zunehmendem Maße filigraner ausgeführt und darüber hinaus werden oftmals haustechnische Funktionen in das tragende Deckenbauteil integriert. Um die hierfür erforderlichen geringen Deckendicken zu realisieren, können Verbunddübelleisten horizontal innerhalb der Betonplatte positioniert werden, woraus ein geringer seitlicher Abstand zum freien Betonplattenrand resultiert. Bisherige Untersuchungen beschreiben unterschiedliche Versagensbilder von Konstruktionen mit Verbunddübelleisten, beispielsweise Spalten der Betonplatte, Ausstanzen eines Betonkegels oder Plastizieren der Stahlzähne. An der Technischen Universität Kaiserslautern wurden im Rahmen eines gemeinsamen Forschungsprojektes mit der RWTH Aachen Push-out-Versuche durchgeführt, anhand derer das Tragverhalten von Verbunddübelleisten mit randnahen Einbaupositionen untersucht wurde. Hierbei wurden bisher unbekannte Versagensmechanismen beobachtet, die durch bestehende Bemessungsansätze für Verbunddübelleisten mit konventionellen (randfernen) Einbaupositionen nicht abgedeckt sind. Im Rahmen dieses Aufsatzes werden die Einflüsse der Parameter Betonfestigkeit, Plattendicke und Bewehrungsführung auf das Trag- und Verformungsverhalten randnaher Verbunddübelleisten analysiert und eine mechanische Modellvorstellung zum Lastabtrag randnaher Leisten vorgestellt.

Crack propagation and residual load‐bearing behavior of composite dowels – effects on the global behavior of composite girders under cyclic loading

“…In addition, 15 geometric functions were determined which also vary depending on the above-mentioned parameters. Figure 8(b) also shows approaches according to equation (7) which limit the scatter band to both sides. The upper limit curve is to be regarded as critical for the crack propagation.…”

“…In addition, an integration into the European standardization process via a so-called Technical Specification (CEN TS) is currently being sought in order to enable the use of composite dowels in building and bridge construction in the long term. In addition to the existing design concept of longitudinal shear resistance, approaches for the resistance of composite dowels in cracked concrete [3], [4], under tensile or mixed shear-tensile loads [5], [6] as well as under edge influences [7], [8] are currently being developed.…”

Development of a Consistent Design Concept for Composite Dowels

“…This observation is caused by two overlapping effects. Firstly, it is due to the pulverization of the concrete in the quasi-hydrostatic compressive stress zone directly below the steel teeth, which is also reflected in the predominant concrete deformation in the slip composition of the 100 mm thick specimens (figure 5d) and was described more detailed in [18,19]. Secondly, the 4 mm thick steel teeth reached their yield strength at the said load level, resulting in the large total slip of the 200 mm thick specimens, their load-bearing capacity was ultimately limited by the steel resistance and not by edge failure.…”

“…This article summarizes the test program of the small-size specimens within the research project as well as the resulting design model including the underlying engineering models. A more detailed description of individual topics has already been given in [18][19][20]. Furthermore, large-size component tests were carried out to verify the transferability of the design equations which are presented within the final report [21].…”

Development of a new design approach for composite dowels positioned close to the concrete surface

“…As an alternative, composite dowels can be used with the rules given in a German technical approval [1]. Existing investigations under monotonic [2], [3], [4], [5], [6], [7], [8], [9], [10], [11] and cyclic loading [12], [13], [14], [15], [16] and regulations on composite dowels include various failure modes of the structure. Specifically, if the position of the composite dowels is close to the concrete surface, as to be seen in Figure 1, an additional failure mode can occur in which the concrete cover at the edge of the concrete slab spalls (Figure 2).…”