Zur Torsionsbemessung von Stahlbeton‐ und Spannbetonbalken nach DIN 1045‐1

Torsion Design of reinforced and prestressed concrete Beams according to DIN 1045‐1 The DIN 1045‐1 provisions specify two different methods for torsion design regarding the concrete strut angle. The analysis of a database containing about 300 tests on reinforced and prestressed concrete beams under pure torsion or combined loading shows that under certain loading conditions the methods should not be used alternatively. In addition, the database also shows that the strength of the concrete strut according to DIN 1045‐1 overestimates the torsional capacity in general. On the basis of these results a suggestion for the definition of the concrete strut angle for torsion design in relation to DIN 1045‐1 is derived. Furthermore a design concept for the definition of the thickness of the shear flow zone is presented. Finally the database is analysed according to Eurocode 2 in its edition of April 2002.     

Berücksichtigung der Längsbewehrung beim Durchstanznachweis nach Eurocode 2 (DIN EN 1992‐1‐1/NA)

Consideration of flexural reinforcement in punching shear provisions according to Eurocode 2 (DIN EN 1992‐1‐1/NA) With introduction of Eurocode 2 in Germany in 2012, the pun ching shear design provisions of flat slabs and column bases were revised compared to DIN 1045‐1. Particularly the consi deration of flexural reinforcement caused some irritations for practical engineers. In this context, this paper presents recent recommendations of DIN technical committee ”NABau“ (DIN: German institute for standardization) for the distribution of minimum flexural reinforcement for wall corners and wall edges as well as for the width and anchorage of flexural reinforcement for the calculation of the flexural reinforcement ratio in flat slabs and column bases.     

Einheitliches Fachwerkmodell für Stahlbeton‐ und Spannbetonbauteile unter Querkraft‐ und Torsionsbeanspruchung

Uniform framework model for reinforced and prestressed concrete structural members under shear and torsion loading. Following the design provisions for shear and torsion according to DIN 1045‐1 the following two principle questions are raised: For a lot of situations in standard design praxis the allowable inclination of the concrete strut is determined to an angle as small as about 18° – while such a gentle strut angle in tests could only be proved in case of a high level additional compression force. Additionally, with the given two different design approaches a smooth transition between structures with and without required shear reinforcement is lacking. For the purpose of a general review experimental as well as theoretical investigations for beams under shear loading and torsion loading have been conducted. As consequence of the obtained results a uniform strut‐and‐tie model with simply application has been derived.     

Bemessung eines Stützbauwerks nach Eurocode — Teil 2: Erdbebenbemessung

Dieser Beitrag behandelt den Erdbebennachweis für die Bemessung von Gewichtsmauern aus Beton und Stahlbeton nach Eurocode 2 (EN 1992‐x), Eurocode 7 (EN 1997‐1) und Eurocode 8 (EN 1998‐x) anhand eines durchgerechneten Beispiels. Design of concrete retaining structures according to Eurocode standards — Part 2: Earth quake design. This contribution treats the design of concrete retaining structures under earth quake impact based on Eurocode 2 (EN 1992‐x), Eurocode 7 (EN 1997‐1) and Eurocode 8 (EN 1998‐x) by means of an application example.     

Bemessung eines Stützbauwerks nach Eurocode – Teil 1: Ständige Bemessungssituation

Dieser Beitrag zeigt das Zusammenwirken des Eurocode 2 (EN 1992‐x) und des Eurocode 7 (EN 1997‐1) bei der Bemessung von Gewichtsmauern aus Beton und Stahlbeton anhand eines durchgerechneten Beispiels. Design of concrete retaining structures basing on Eurocode standards – Part 1: persistent design situation. This contribution shows the use of Eurocode 2 (EN 1992‐x) and Eurocode 7 (EN 1997‐1) for designing of concrete retaining structures on an example.     

Zusammenführung von europäischen und deutschen Normen Eurocode 7, DIN 1054 und DIN 4020

Merging European and German standards – Eurocode 7, DIN 1054 and DIN 4020. The German version of Eurocode 7 Geotechnical design with its two parts DIN EN 1997‐1 General rules and DIN EN 1997‐2 Ground investigation and testing will shortly be available. The two parts of this Eurocode partly compete with two fundamental German geotechnical standards: DIN 1054:2005‐1 Ground – Verification of safety of earthworks and foundations and DIN 4020:2003‐09 Geotechnical investigations for civil engineering purposes. According to the regulations of the European Union standards which compete with European standards have to be withdrawn after a calibration period of two years and a coexistence period of another 3 years. That is why in three to five years DIN 1054 and DIN 4020 in their present form will have to be replaced by revised versions. The paper describes the necessary adaptations as far as the content is concerned and how the specific German geotechnical experience is preserved in the new system of European and German standards.     

Der Eurocode 2 für Deutschland – Erläuterungen und Hintergründe

Der neue Eurocode 2: “Bemessung und Konstruktion von Stahlbeton‐ und Spannbetontragwerken – Teil 1‐1: Allgemeine Bemessungsregeln und Regeln für den Hochbau” (EC2‐1‐1) mit seinem Nationalen Anhang ist nach einer ausführlichen Erprobungsphase bereit zur bauaufsichtlichen Einführung in Deutschland. In mehreren Beiträgen sollen Erläuterungen und Hintergründe zu einigen Regelungen im Eurocode 2 und zu den Entscheidungen für Regeln im Nationalen Anhang vorgestellt werden, die entweder zu Änderungen gegenüber DIN 1045‐1 oder zu Abweichungen vom Eurocode 2 führten. Der Teil 1 gibt zunächst eine Übersicht über die maßgeblichen europäischen Normen und führt in den Nationalen Anhang ein. The Eurocode 2 for Germany – Explanations and Backgrounds. Part 1: Introduction in the National Annex The new Eurocode 2 “Design of concrete structures – Part 1‐1: General rules and rules for buildings” (EC2‐1‐1) and its National Annex has undergone a phase of detailed testing and is now ready for the implementation in Germany. In some articles should be given explanations and backgrounds of some rules in Eurocode 2 and of decisions for rules in the National Annex, which have been taken either to changes compared with DIN 1045‐1 or to differences to Eurocode 2. Article 1 gives an overview about the important European standards and introduces in the National Annex.     

Einfluß der Deckenschlankheit auf den Durchstanzwiderstand nach DIN 1045‐1, SIA 262, Ö‐Norm B 4700(01) und Eurocode prEN 1992‐1‐1

Influence of the Slab Slenderness on the Punching Resistance according to DIN 1045‐1, SIA 262, Ö‐Norm B 4700(01) and Eurocode prEN 1992‐1‐1 In the last three years the new design codes [1] — [4] were established. The punching resistance of each code was developed on the state of the art. But the formulas show significant differences. Parametric studies documented, that the punching resistance of less slender flat slabs ( λ = length between the supports / effective depth = l/d = 20) is increased according to SIA 262 and Ö‐Norm B 4700(01) in comparison to DIN 1045‐1. EC prEN 1992‐1‐1 neglects the influence of the flat slenderness, however the maximum punching capacity of stirrups is on the design level of double headed studs or stud‐rails. This is contradictory to the current design experience and punching test results [5]. In this contribution the influence of the slab slenderness on the punching resistance with and without shear reinforcement is discussed. In addition, the extremely high maximum punching shear capacity according prEN 1992‐1‐1 is judged by the codes DIN 1045‐1, SIA 262 and Ö‐Norm B 4700(01).     

Hinweise für den Ansatz der Betonzugfestigkeit beim Nachweis der Mindestbewehrung für frühen Zwang gemäß Eurocode 2‐2 (DIN EN 1992‐2/NA)

Guideline for the assumption of the effective concrete tensile strength within the minimum reinforcement check due to early cracking according to Eurocode 2‐2 (DIN EN 1992‐2/NA) In December 2015, the A1‐amendment [1] for the German National Annex [2] of DIN EN 1992‐1‐1 was published. The amendment affects among others the assumption of the effective concrete tensile strength within the minimum reinforcement check due to early cracking. The following contribution elucidates the background, why a respective A1‐amendment for DIN EN 1992‐2/NA has not been provided. Furthermore, the main differences between building‐ and bridge constructions are outlined in order to constitute the different approach.     

Der Eurocode 2 für Deutschland – Erläuterungen und Hintergründe

Der neue Eurocode 2: “Bemessung und Konstruktion von Stahlbeton‐ und Spannbetontragwerken – Teil 1‐1: Allgemeine Bemessungsregeln und Regeln für den Hochbau” (EC2‐1‐1) mit seinem Nationalen Anhang ist nach einer ausführlichen Erprobungsphase bereit zur bauaufsichtlichen Einführung in Deutschland. In mehreren Beiträgen sollen Erläuterungen und Hintergründe zu einigen Regelungen im Eurocode 2 und zu den Entscheidungen für Regeln im Nationalen Anhang vorgestellt werden, die entweder zu Änderungen gegenüber DIN 1045‐1 oder zu Abweichungen vom Eurocode 2 führten. Der Teil 3 enthält Erläuterungen zur Begrenzung der Spannungen, Rissbreiten und Verformungen. The Eurocode 2 for Germany – Explanations and Backgrounds Part 3: Limitation of Stresses, Cracks and Deformations The new Eurocode 2 “Design of concrete structures – Part 1‐1: General rules and rules for buildings” (EC2‐1‐1) and its National Annex has undergone a phase of detailed testing and is now ready for the implementation in Germany. In some articles should be given explanations and backgrounds of some rules in Eurocode 2 and of decisions for rules in the National Annex, which have been taken either to changes compared with DIN 1045‐1 or to differences to Eurocode 2. Article 3 contains explanations for the limitation of stresses, cracks and deformations.     

Der Eurocode 2 für Deutschland – Erläuterungen und Hintergründe

Der neue Eurocode 2: “Bemessung und Konstruktion von Stahlbeton‐ und Spannbetontragwerken – Teil 1‐1: Allgemeine Bemessungsregeln und Regeln für den Hochbau” (EC2‐1‐1) mit seinem Nationalen Anhang ist nach einer ausführlichen Erprobungsphase bereit zur bauaufsichtlichen Einführung in Deutschland. In mehreren Beiträgen sollen Erläuterungen und Hintergründe zu einigen Regelungen im Eurocode 2 und zu den Entscheidungen für Regeln im Nationalen Anhang vorgestellt werden, die entweder zu Änderungen gegenüber DIN 1045‐1 oder zu Abweichungen vom Eurocode 2 führten. Teil 2 enthält Erläuterungen zu den Grundlagen der Tragwerksplanung, zur Sicherstellung der Dauerhaftigkeit, zu den Baustoffeigenschaften und zu den Spannungs‐ Dehnungslinien. The Eurocode 2 for Germany – Explanations and Backgrounds Part 2: Basics, Durability, Materials, Stress‐Strain‐Relationships The new Eurocode 2 “Design of concrete structures – Part 1‐1: General rules and rules for buildings” (EC2‐1‐1) and its National Annex has undergone a phase of detailed testing and is now ready for the implementation in Germany. In some articles should be given explanations and backgrounds of some rules in Eurocode 2 and of decisions for rules in the National Annex, which have been taken either to changes compared with DIN 1045‐1 or to differences to Eurocode 2. Article 2 contains explanations for the basis of design, for the durability, for the material properties and for the stress‐strain‐relationships.     

Bemessungshilfen und Konstruktion bei geneigten Querkräften

Design Methods and Detailing for RC Beams with Inclined Shear Forces The shear‐resistant design of reinforced concrete (RC) beams with rectangular cross sections and inclined shear forces (biaxial shear) is presented. Equations for the shear resistances provided by the tensile strut and by the compressive strut are derived according to the design concepts of DIN 1045‐1 and EC 2. They are verified to experimental data and elaborated to gain design charts. Examples show the practical applications. Existing detailing provisions for the anchorage of stirrups and the horizontal displacement in the tensile force of the bending reinforcement can directly be applied to cases of biaxial shear, if the rotations of the neutral axis and of the resultant strut‐and‐tie system are taken into account.     

Druckbeanspruchte Winkelprofile mit Ein‐Schrauben‐Anschluß – Bemessung nach den Normen DIN 18800‐2 und EC 1993‐3‐1 (Türme und Maste)

Dimensioning of pressed angle steel with one screw joint based on the standards DIN 18800 vol. 2 and EC 1993‐3‐1 (towers and masts). There are different kinds of methods for the structural analysis of the stability of angle steel in mast constructions in DIN 18800 vol. 2 and Eurocode 1993‐3‐1. It depends on the kind of joint with one or two screws. The calculated loading capacities for a one screw joint based on Eurocode are significant higher than the results based on DIN . Comparing calculating with the Finite Element Method as well as experiments with equal‐leg angles show the simplified method of the EC 1993‐3‐1 for the one screw joint in the existing form is not wise to be used in practice.     

Bemessung von Stützmauern aus Stahlbeton nach Eurocode

Design of Concrete Retaining Structures basing on Eurocode Standards Design of retaining structures bases on current concrete and geotechnical design standards. At this time the basis of the Austrian state of the art is changing from a national system to the System of European standards (EUROCODES). This contribution shows the actual situation of the Austrian standardisation and the use of the Eurocode 2 (EN 1992‐x) and the Eurocode 7 (EN 1997‐1) for designing of concrete retaining structures. For this the essential design approaches and there standardised regulations are shown.     

Der Eurocode 2 für Deutschland – Erläuterungen und Hintergründe

Der neue Eurocode 2: “Bemessung und Konstruktion von Stahlbeton‐ und Spannbetontragwerken – Teil 1‐1: Allgemeine Bemessungsregeln und Regeln für den Hochbau” (EC2‐1‐1) mit seinem Nationalen Anhang ist nach einer ausführlichen Erprobungsphase bereit zur bauaufsichtlichen Einführung in Deutschland. In mehreren Beiträgen sollen Erläuterungen und Hintergründe zu einigen Regelungen im Eurocode 2 und zu den Entscheidungen für Regeln im Nationalen Anhang vorgestellt werden, die entweder zu Änderungen gegenüber DIN 1045‐1 oder zu Abweichungen vom Eurocode 2 führten. Der Teil 4 enthält einige Erläuterungen zu den Bewehrungs‐ und Konstruktionsregeln. The Eurocode 2 for Germany – Explanations and Backgrounds Part 4: Detailing of Reinforcement and Members The new Eurocode 2 “Design of concrete structures – Part 1‐1: General rules and rules for buildings” (EC2‐1‐1) and its National Annex has undergone a phase of detailed testing and is now ready for the implementation in Germany. In some articles should be given explanations and backgrounds of some rules in Eurocode 2 and of decisions for rules in the National Annex, which have been taken either to changes compared with DIN 1045‐1 or to differences to Eurocode 2. Article 4 contains some explanations to detailing of reinforcement and members.     

Vergleich des ETV Beton und DIN 1045‐1

Comparison of the ETV Beton and DIN 1045‐1 The paper compares the safety elements of the ETV Beton and the valid German reinforced concrete code DIN 1045‐1. The comparison is carried out in general for the characteristic values of the actions, for the partial safety factors of the actions and the resistance and for the action combination factors as well. Additionally the comparison has been done in terms of calculation of the required amount of reinforcement in an example. The comparison yields to the result that especially the partial safety factor for dead load is substantially lower in the ETV Beton compared to DIN 1045‐1. Newer developments in the Eurocode suggesting a lower partial safety factor for dead load are therefore backed by the presented investigation.     

Die VGB‐Richtlinie “Bautechnik bei Kühltürmen” und ihre Anpassung an die neue DIN 1045 / DIN 1055

The VGB Guideline “Structural Design of Cooling Towers” and its adjustment to the new DIN 1045 The current VGB guideline for the structural design of cooling towers is based on obsolete versions of the German design standards DIN 1045 and DIN 1055. Corresponding to the new generation of German standards DIN 1045 and DIN 1055 a revision of the VGB guideline has become necessary. Regarding the revision essential topics are given by the consideration of the partial safety concept, the possible application of non‐linear design analyses and the increased requirements with respect to durability. The revised VGB guideline is intended to be published at the beginning of 2005.     

Korrelation von Betondruck‐ und Zugfestigkeit historischer Betone

Correlation between the compressive and tensile strength of old concretes – Applicability of the relationship described by DIN EN 1992‐1‐1 In the design of a new structure, DIN EN 1992‐1‐1 [1] normatively regulates the correlation between the compressive strength and tensile strength of concrete, produced according to DIN EN 206‐1 [2]. However, as there are many different time‐ and load‐dependent impacts on existing structures, the relationship described by DIN EN 1992‐1‐1 [1] can't be assumed without any further observations for existing structures. At the moment, there is no comprehensive investigation on the influences of e.g. subsequent hardening and carbonation on the concrete compressive or tensile strength. The tensile strength of concrete defined in DIN EN 1992‐1‐1 [1] is based on a water storage and a testing age of 28 days. Furthermore, the in‐situ tensile strength is affected by micro‐crack formation cause of internal stresses due to outflow of hydration heat. Generally, there is a different influence of micro‐crack formation on the tensile strength of concrete than on the compressive strength of concrete. The real value of the in‐situ tensile strength of concrete affects the shear force resistance and the load‐bearing capacity of anchors with concrete cone failure as decisive failure mode. Within the framework of a research project, financed by ”Forschungsinitiative Zukunft Bau“, an initiative of the Federal Institute for Research on Building, Urban Affairs and Spatial Development (BBR) structural investigations on the correlation between the compressive and tensile strength of old concretes have been performed. Below, the results of the research project are presented.     

Hinweise und Erläuterungen zur Anwendung der neuen Windlastnorm DIN 1055‐4:2005‐03

Notes and Comments on the Application of the New Wind Loading Standard DIN 1055‐4.2005‐03 The final draft of the German Wind loading code DIN 1055‐4 has been published in March 2005. It is scheduled for implementation as a design rule in 2007. The code is basically new in several aspects: the development of a new wind map, the introduction of two wind profiles accounting for changes of surface roughness and the application of the gust response factor to determine equivalent static wind loads for structures and structural elements prone to wind induced vibration. The development of the DIN 1055‐4 has been harmonized during the final drafting process with the Eurocode Draft prEN 1991‐1‐4.6:2002: Actions on Structures – Wind Actions. The following contribution presents a survey of the main features and illustrates the application referring to some typical cases.     

Zur Druck‐Zug‐Festigkeit von Stahlbeton und stahlfaserverstärktem Stahlbeton

Während die Druckfestigkeit des Betons durch gleichzeitig wirkenden Querdruck gegenüber der einaxialen Druckfestigkeit erheblich gesteigert werden kann, führen Querzugbeanspruchung und Rissbildung zu einer Abminderung der Tragfähigkeit. Dies gilt für unbewehrten Beton und Stahlbeton gleichermaßen. In den einschlägigen Regelwerken finden sich hierzu international sehr unterschiedliche Bemessungsansätze, wobei die vorgesehenen Abminderungsbeiwerte für denselben Anwendungsfall um das bis zu Zweifache differieren. Die Frage der Druck‐Zug‐Festigkeit von Stahlbeton wurde in den vergangenen 40 Jahren von zahlreichen Wissenschaftlern untersucht. Ihre Ergebnisse sind allerdings zum Teil ebenso widersprüchlich wie die aktuelle Normensituation. Basierend auf eigenen experimentellen Untersuchungen sowie einer kritischen Auswertung und Einordnung als richtungweisend angesehener, früherer Versuchsreihen wird ein Vorschlag zur Abminderung der Druckfestigkeit des gerissenen Stahlbetons entwickelt. Erstmals wird dabei auch der Einfluss einer Faserzugabe in Kombination mit Stabstahlbewehrung berücksichtigt. Ein Vergleich mit den in DIN 1045‐1, CEB‐FIP Model Code 1990, Eurocode 2 und ACI Standard 318‐05 angegebenen Bemessungsregeln zeigt, dass allein DIN 1045‐1 die in den Versuchen beobachtete maximale Abminderung der Druckfestigkeit durch Querzug und Rissbildung zum Teil erheblich unterschätzt, so dass eine konservative Auslegung der Tragwerke nicht immer sichergestellt ist. Biaxial Compression‐Tension‐Strength of Reinforced Concrete and Reinforced Steel Fibre Concrete The compressive strength of concrete can be substantially increased in relation to uni‐axial compressive strength by transverse compression acting at the same time. In contrast, transverse tension and cracking lead to a reduction of the load‐carrying capacity. This holds true for plain concrete as well as for reinforced concrete. In international standards very different calculation rules can be found on this subject, whereby the provided reductions differ up to a factor of two for the same application. The question of biaxial compression‐tension‐strength of reinforced concrete was examined in the past 40 years by numerous scientists. Their results are, however, partially contradictory in the same way as the current standard situation. Based on own experimental investigations as well as on a critical review and classification of former test series regarded as trend‐setting, a proposal for the reduction of the compressive strength of cracked reinforced concrete is developed. For the first time, also the influence of fibres in addition to bar reinforcement is considered thereby. A comparison with the calculation rules in DIN 1045‐1, CEB‐FIP Model Code 1990, Eurocode 2, and ACI Standard 318‐05 shows, that exclusively DIN 1045‐1 underestimates sometimes substantially the maximum reduction of the compressive strength by transverse tension and cracking observed in the tests, so that a conservative design of structures cannot always be ensured.