Zum Biegedrillknicken von Kranbahnträgern aus winkelverstärkten Walzprofilen

Lateral‐torsional buckling of crane runway beams built‐up by rolled profiles combined with angle sections on the top flange. Crane runway beams of overhead travelling cranes are subjected to biaxial bending and torsion due to the crane operation with the wheel loads ane the eccentric horizontal loads. The crane runway girders are proned for lateral‐torsional buckling due to this loading situation. Therefore the verification for lateral‐torsional buckling is often dimensioning for the design of crane runway beams for overhead travelling cranes. In the case of the application of rolled sections, the required lateral stiffness of the top flange is often not sufficient even for light crane operations and medium span lengths. In order to increase the lateral stiffness on the top flanges of these crane runway beams, the rolled sections can be strengthened by welding angle profiles on both sides of the top flange. This type of construction is a widespreaded application for crane runway beams especitally for medium and heavy crane operations. However, the assessment method for lateral‐torsional buckling is for this type of crane runway beam more difficult because of the simple symmetrical cross‐section togehter with the the loading situation with biaxial bending and torsion. Within the scope of this article, the different possibilities for the assessment methods of lateral‐torsinal buckling are shown for crane runway beams built‐up by rolled profiles combined with angle sections on the top flange and are compared on the basis of a example calculation. In addition the results of a comprehensive parameter study [1] on the effectiveness of the different assessment methods are summarized.     

Stabilitätsnachweis für Tragpfähle von kombinierten Stahlspundwänden nach EC 3

Dieser Beitrag stellt die Ergebnisse einer Kurzstudie [17] vor, in der das Stabilitätsverhalten der Tragpfähle von kombinierten Stahlspundwänden untersucht wurde. Zunächst werden die neu entwickelten Bemessungsregeln für Stabstabilität nach Eurocode 3 vorgestellt. Erste Beispielberechnungen zeigen, dass mit dessen Anwendung nicht nur der Berechnungsaufwand ansteigt, sondern auch das Bemessungsniveau konservativer wird. Wird die Stützwirkung des Bodens in Form einer Federhalterung angesetzt, ist ein großer Anstieg der rechnerischen Tragfähigkeit zu verzeichnen. Für die Spezifizierung der Federsteifigkeit des Baugrunds wurden beispielhaft Momenten‐Verdrehungsbeziehungen ermittelt. Die erforderlichen Drehfedersteifigkeiten, die notwendig sind, um das alte Bemessungsniveau zu erreichen, können von den Werten für die vorhandene Steifigkeit überschritten werden. Es konnte gezeigt werden, dass die Entwicklung eines Verfahrens für die effiziente Stabilitätsbemessung der Tragpfähle von Stahlspundwänden sowohl notwendig als auch möglich ist. Stability verification of H‐Sections used in combined quay walls according EC 3. This contribution presents results of a small research project [17] analysing the stability aspects of king‐piles of combined steel sheet piles. First of all the, new design rules according to Eurocode·3 are explicated. Exemplified calculations have shown that with the use these rules not only the effort for design increases but also the verification level will be more conservative. The embedment of the surrounding soil being considered in the form of a spring support, a big rise of the bearing load is observed. For the specification of the spring stiffness derived from the soil embedment exemplified moment‐rotation relations were developed. The stiffness exceeds the required rotational stiffness necessary for reaching the old level of bearing load respectively based on the existing codes. Thus, it was possible to show, that the development of a procedure for the efficient stability design of combined steel sheet pile walls is necessary as well as feasible.     

Repräsentative Vorkrümmungen e0 für das Biegeknicken – Ergänzende Untersuchungen

Equivalent geometrical initial bow imperfections e₀ for flexural buckling – additional investigations. According to Eurocode 3 Part 1‐1, a member subjected to an axial compression force may be verified by two different approaches: a verification by the equivalent member method or a cross sectional verification. Concerning the second possibility bending moments according to second order theory must be calculated, where initial bow imperfections e₀ must be taken into account, which should be taken normally from EN 1993‐1‐1, table 5.1. The values e₀ used up to now should be changed, because they are partly unsafe, this was shown earlier by intensive investigations [5]. The results of additional investigations are explained here concerning test results and analytical values for high strength steel S700. Furthermore comments are given to values e₀ calculated depending on the non‐dimensional slenderness λ .     

Regelwerke für die Werkstoffauswahl und Dauerhaftigkeit von nichtrostenden Stählen für Stahlbauten – Entwicklung und aktueller Stand

Technical regulations for the selection of materials and dura bility for steel structures – Development and current status. One of the most important changes of the revised DIN EN 1993‐1‐4 released in October 2015 can be found in the annex section A ”Selection of materials and durability“. Contrary to the previous version this annex is now normative. By means of a point system considering different key variables that influence the selection of stainless steel alloys and combines values for each to give a total corrosion resistance factor suitable alloys can be selected. The annex aims to provide a methodology for use by designers with no specialist knowledge of either corrosion or stainless steels. The paper also discusses differences and similarities with the previous valid German national technical approval Z‐30.3.6.     

Realität – Modell – Norm

Bauen stellt eine komplexe Interaktion der Gesellschaft mit der natürlichen Welt dar. Bauwerke sollen i. a. über eine sehr lange Zeit, häufig länger als ein Menschenleben praktisch nutzbar sein. Die Anforderungen an die Zuverlässigkeit, insbesondere Sicherheit, sind ungewöhnlich hoch und deutlich größer als in anderen Bereichen der Technik. Bauen unter den Bedingungen des ökonomischen Wettbewerbs erfordert Regeln und Richtlinien für die Beurteilung der zu erwartenden Zuverlässigkeit eines Bauwerkes. Modelle bilden die Interaktion zwischen Bauwerk und vorhandener Umgebung unter Nutzung probabilistischer Methoden näherungsweise ab. Die Beurteilung von Robustheit und Sensitivität der Modelle erhält eine steigende Bedeutung. Die Definition von allgemein anerkannten Regeln der Technik für die Bemessung von Bauwerken muss den aktuellen Bedingungen angepasst werden. Zukunftsfähige Normenkonzepte müssen sich an der Entwicklung der Entwurfsmethoden und der Informationsund Kommunikationstechnik orientieren. Vereinfachende empirische Formeln, Diagramme usw. verlieren ihre Gültigkeit auch außerhalb eingeführter Normen nicht und müssen nicht neu aufbereitet werden. Reality – Model – Code. Construction involves a complex interaction with the physical world and with society. Buildings are expected to be usable for a very long period of time, often longer than the span of a human life. The requirements with regard to reliability and security in particular, are extraordinarily high – considerably greater than in other technical fields. Construction, particularly under the pressure of free market competition, requires rules and regulations for the assessment of the anticipated reliability and performance of a building. To a certain degree, models can be used to anticipate the interaction between a building and its environment by applying probabilistic methods. The robustness and sensitivity of models therefore increasingly gains importance. The definition of commonly accepted technical rules for the design of buildings has to be matched to the current conditions. Concepts for developing design codes must be futureproofed such that the codes are complimentary to the progress of new design methodologies, and also to the innovation and development of information technology. However, traditional empirical simplifying formulas, diagrams, etc., are still valid and do not require updating.     

Verfahrensprüfung zur Bestimmung von Anziehparametern für vorgespannte geschraubte Verbindungen

Procedure qualification for the determination of tightening parameters for preloaded bolted connections. DIN EN 1090‐2 and DIN EN 1993‐1‐8/NA define tightening procedures for preloaded bolted assemblies tightened at the nut side by simple use thereof. However, in a multitude of applications, preloaded bolted connections are used, which for example are tightened on the head side, designed as tapped hole connections and/or are to be used several times. In these cases, a procedure test is necessary to determine the tightening parameters. The present paper describes the principal procedure for carrying out such a procedure test, in particular the target level of preloading, the length of thread engagement for components with internal threads, the single and multiple use of components, and the boundary criteria for determining the tightening parameters. Furthermore, the procedure is explained using practical examples.