Erhöhung der Ermüdungsfestigkeit von geschweißten höherfesten Baustählen durch Anwendung von Nachbehandlungsverfahren

Enhancement of the fatigue strength of welded high strength steels by application of post‐weld treatment methods. According to the present state of the art welded high strength steels have the same fatigue strength as welded standard steels. For an effective application of high strength steels in constructions subjected to fatigue are therefore additional efforts necessary in order to improve the fatigue strength, for example by the application of post‐weld treatment methods. However up to the present it is not possible to apply the positive effects of these methods in the fatigue design of steel structures. This paper shows first results of a research project, that examines the effectiveness of the post‐weld treatment method TIG‐dressing and the relatively new method “Ultrasonic Impact Treatment” (UIT) for the improvement of fatigue strength of welded high strength steels.     

Tragverhalten von horizontal belasteten Flügelpfählen

Zur Verbesserung des horizontalen Last‐Verformungsverhaltens von Pfählen ist der Einsatz von Flügeln zur Aufweitung des Pfahlschafts im Pfahlkopfbereich eine sinnvolle Maßnahme. Der Bettungswiderstand wird im aufgeweiteten Bereich erhöht und die Verformung reduziert. In diesem Beitrag werden numerische Untersuchungen zur Verbesserung der Tragwirkung vorgestellt und ein Berechnungskonzept abgeleitet. Des Weiteren werden Feldversuche in Sand und Klei beschrieben, bei denen die Tragwirkung des Flügelpfahls messtechnisch dokumentiert wird. Es werden zudem Bemessungsdiagramme für Flügelpfähle in Sand vorgelegt. On the response of laterally loaded piles with wings. The use of wings attached to the pile shaft near ground surface is a simple but effective way to improve the lateral pile response. The mobilised soil resistance in this section is significantly higher and the lateral deformation decreases. This paper presents numerical analysis of winged piles and a design method is outlined. Small‐scale field trials in sand and organic clay clearly point out the benefit of winged piles and proved the validity of the design method. Furthermore, design charts for a pre‐design of winged piles in sand are included.     

Zur Bemessung von Lochleisten als duktile Verbundmittel in Verbundträgern aus höherfesten Materialien

Im Rahmen eines gemeinsamen FuE‐Projekts der HOCHTIEF Construction AG und ArcelorMittal Belval & Differdange S. A. wurden umfangreiche experimentelle und theoretische Untersuchungen an Lochleisten als duktiles Verbundmittel durchgeführt. Ziel der Untersuchung ist die Entwicklung technisch hochwertiger und wirtschaftlicher Verbundbauteile aus höherfesten Werkstoffen (z. B. Beton C50/60 und Stahl S460), [1] bis [4]. Hierbei wurden insbesondere das Tragverhalten, die Traglast, die Duktilität und die Dauerfestigkeit von unterschiedlichen Lochleistenformen sowie das Gesamttragverhalten von Verbundbauteilen mit Lochleisten untersucht. Aufbauend auf den in Versuchen gewonnenen Erkenntnisse wurden Bemessungskonzepte für Lochleisten als Verbundmittel in Verbundträgern aus höherfesten Materialien entwickelt. Design of aperture plates as ductile shear connectors for composite beams with high strength materials. Within a joint research project of HOCHTIEF Construction AG and ArcelorMittal Belval & Differdange S. A. various experimental and theoretical investigations in aperture plates, as ductile shear connector for composite members have been carried out. The aim of the research has been to develop technically advanced and economic composite members with the application of high strength materials (e.g. steel S460 and concrete C50/60). The main focus of the research has been put on the load bearing behaviour, ultimate bearing capacity, ductility and fatigue resistance of different types of aperture plates geometries as well as the related overall bearing performance of the composite members with the application of these plates as shear connectors. Based on the conclusions from the experimental test results, design concepts for aperture plates as shear connectors for composite beams with the application of high strength materials have been developed.     

Tragverhalten von Einfeldverbundträgern mit Stegöffnungen

Structural behaviour of single‐span composite beams with openings. In the view of few of the available analytical researches on single‐span composite beam with web openings the non‐linear computed results for a test beam with web opening are hire presented. From them some of interest findings can be viewed.     

Das große Viadukt von Millau – Stahlbau und Montage mit hochfesten Feinkornbaustählen

The Millau Viaduct – Steel construction, fabrication and erection with high‐strength fine grain steel. 16^th of December 2004 the Millau Viaduct, a 2460 m long multi cable‐stayed bridge, was opened of traffic in the Southern part of the French Massif Centrale mountains. This bridge comprises 6 main spans of 342 m length respectively and two side spans of 204 m length respectively. The steel superstructure consists of an orthotropic box deck of 27.75 m width and a maximum height of 4.20 m aerodynamically optimised due to the enormous wind loads in the valley. The deck is fixed to the 7 steel pylons via 22 stay cables per pylon in a height of up to 270 m above the river Tarn. Thus this viaduct represents the highest bridge in world with a total height of 343 m, even more than the Eiffel Tower in Paris.     

Neuste Entwicklungen von thermomechanisch gewalzten Feinkornbaustählen – Erfahrungen aus Offshore‐Industrie und Stahlwasserbau

Newest development for thermomecanically rolled steels plates – experiences with offshore constructions and hydropower plants. This article reports about the newest development for thermomechanically rolled steels plates. Steel products with a minimum yield strength of 500 MPa can today be produced by thermomechanical rolling in a thickness range up to 100 mm. The first‐mentioned steel plates are especially characterized by very good fabrication properties, in particular an excellent weldabilty. The article will also describe the first experiences gained with these steel grades in the fields of offshore construction and hydro power plants.     

Knicken von schlanken Pfählen in weichen Böden

Buckling of slender piles in soft soils. Buckling of piles is resisted by the surrounding soil. Therefore, in sufficiently stiff soils there is no risk of buckling of piles with conventional geometry (L/D ratio). National and international design codes require checks of the safety against buckling for slender piles in soils with an undrained shear strength of c_u < 15 kPa or c_u < 10 kPa, respectively. In practice, the codes are taken to imply that buckling failure does not occur at higher undrained shear strengths. However, using simple calculations this assumption has been proven to be invalid for slender piles in very soft soils. Therefore, buckling tests on piles up to 4 m long were carried out at the Zentrum Geotechnik of the Technical University of Munich. Based on these results a concept for calculating buckling loads was derived, which covers all essential aspects observed in the tests. The proposed model accounts for material non‐linearity as well as second order effects.     

Untersuchungen zum vertikalen Tragverhalten von Spundwänden

Spundwände werden im Wesentlichen auf Biegung infolge einer Belastung durch Erd‐ und Wasserdrücke beansprucht. Sie können aber auch zum Abtrag von Vertikallasten dienen. Das Tragverhalten von Spundwänden ist bei genauer Betrachtung äußerst komplex, da diesem eine räumlich und zeitlich gekoppelte Boden‐Bauwerk‐Interaktion zugrunde liegt. Für die praktische Bemessung muss das Tragverhalten daher stark idealisiert werden. Die Rechtfertigung der dafür notwendigen Modellvorstellungen sowie deren Vereinfachungen und Annnahmen sind, wie häufig in der Geotechnik, hauptsächlich durch Erfahrung begründet. Researching the vertical load bearing behaviour of sheet piles. Sheet pile walls are mainly used to carry loads caused by earth and water pressure via bending. In special cases these walls can be used to transfer vertical loads to the subsoil. The complex load bearing behaviour of sheet pile walls is caused by the sterical and temporal coupled soil structure interaction. For practical design the load bearing behaviour needs to be idealised. The apologies used to explain the model conceptions as well as their simplifications are, as usual in geotechnics, mainly motivated by operating experience.