Zum Feuerwiderstand von Stahlbetonstützen

Fire Resistance of Reinforced Concrete Columns This contrubution shows studies to fire resistance of reinforced concrete columns, based on a structural analysis with an advanced calculation model. The analysis covers simply supported columns as well as cantilever columns with buckling length in case of fire up to 20.0 m. For simply supported columns in multistorey‐buildings a new classification table will be suggested because of the general storey height of approximately 4.0 m. Cantilever columns can be classified in fire resistance classes in compliance with praktice conditions (Level‐1 method). Finally safety considerations for reinforced concrete columns will be performed, which show, that existing concrete columns, which are designed in conformity with the minimum dimensions of german standards (table 31 in DIN 4102‐4), are stable in case of fire, if they are planned and built in compliance to acknowledged rules of technology.     

Zuverlässigkeitsbetrachtung exzentrisch belasteter Stahlbetonstützen

Reliability Assessment of Eccentric loaded Columns The resistance of eccentrically loaded columns whose cross sections are loaded by a combination of bending couple and normal forces is characterized by a mutual relation between the axial force N and the moment M. The aim of the examination on hand was to verify the partially closed solutions for known eccentricities e. Since in practical design interaction diagrams based on these solution formats are frequently used and since new approaches of the nonlinear calculations are recently established in the Eurocode 2, in the opinion of the authors the necessity was given to this examination.     

Anwendung der Zonenmethode für brandbeanspruchte Stahlbetonstützen

Die Heißbemessung von Stahlbetonstützen mit der Zonenmethode (Vereinfachtes Verfahren) ist nach Eurocode grundsätzlich möglich und in verschiedenen europäischen Normen bereits eingeführt. In Deutschland wird das Verfahren für die Stützenbemessung in Zukunft jedoch voraussichtlich abgelehnt, da sich die Ergebnisse teilweise nicht mit denen der anerkannten Allgemeinen Verfahren decken. Ein Grund für die Diskrepanz der Ergebnisse der verschiedenen Methoden liegt nach Einschätzung der Autoren in der teilweise nur unzureichenden Dokumentation bzw. Regelung der Zonenmethode. Dass z. B. die Zonenmethode als Verfahren der Plastizitätstheorie angelegt ist, jedoch als nichtlineares Verfahren verwendet wird, führte bereits zu wesentlichen Fehlinterpretationen bzw. Missverständnissen. Dieser Aufsatz zeigt daher eine kurze Darstellung der ursprünglichen Annahmen sowie eine Herleitung der Zonenmethode nach Hertz. Im Hauptteil des Aufsatzes wird anhand von dokumentierten Eichbeispielen gezeigt, wie die Zonenmethode für Druckglieder in der Praxis anzuwenden ist, damit die Traglast und das Last‐Verformungsverhalten bezogen auf die Allgemeinen Verfahren ausreichend genau bestimmt werden können. Use of a Simplified Method (Zone Method) for Concrete Columns Exposed to Fire Eurocode 2 provides a fire resistance check for concrete columns called zone method (simplified calculation method). Some European countries already allow this check. Germany will probably reject this method for concrete columns, as the results from the zone method partly differ from the accepted advanced method. In the authors' opinion, one reason for the differences might be lack of documentation or lack of detailed rules for the zone method. Using the zone method as a nonlinear method – even though it is based on the assumptions of plastic theory – already lead to decisive misinterpretations or misunderstandings. Hence, this article shows briefly the original assumptions and derivation of basic formulas for the zone method according to Hertz. The use of the zone method for compression members is demonstrated with documented calibrating examples. It is displayed, how to calculate the ultimate load and the load‐bearingbehaviour with adequate accuracy.     

Probabilistische Modellierung hochfester Stahlbetonstützen in Hochhäusern

Probabilistic Modelling of HPC Slender Columns in High‐Rise Buildings In Germany high strength concrete is used successfully since 1990. The extremely high compressive strength of this material allows considerable reduction in cross‐sectional dimensions of reinforced concrete columns and accordingly accomplishes highest architectural and functional requirements. This leads in many cases to extremely slender structures and therefore increases the risk of failure due to loss of stability. Because of the positive experience with high strength concrete up to now, the current study questions the initial conservative design provisions. In this context code procedures of DIN 1055‐3 and DIN 1045‐1 are compared with the results of probabilistic analysis and potential optimization will be indicated.