Aufstellung und Anwendung einer Nachweiskonzeption zur realitätsnahen Ermittlung der Systemtraglast an Stahlbetonschleusen

Development and Application of an Analysis Conception for a Realistic Determination of the Structure's Load‐Bearing Capacity of Reinforced Concrete Navigation Locks Since 2004, the structural safety of the navigation locks, located at the Main‐Danube‐Waterway, is systematically analyzed by the Federal Waterways Engineering and Research Institute (Bundesanstalt für Wasserbau, BAW) in Karlsruhe. The reason for this analysis was a damage caused by material fatigue at the navigation lock at Bamberg. The use of common methods of structural analysis and conventional static models led to a significant lack of calculative safety margin. For a more realistic indication of the structural behaviour, an analysis of the load‐bearing capacity based on non‐linear material behaviour was necessary. Thus, an analysis‐concept has been developed that includes the semiprobabilistic safety format of the new engineering standard. This is subsequently presented and explicated on the basis of an example.     

Tragfähigkeit von Einzelstützen nach Eurocode 2 mit besonderem Bezug auf das Verfahren mit Nennsteifigkeiten

The Bearing Capacity of Single Columns according to Eurocode 2 with Regard to the Method based on Nominal Stiffness Within the context of European harmonization the general rules and execution for concrete constructions are documented in Eurocode 2. The calculation of structures with axial loads can be made either based on approximation procedures or based on the general method of non‐linear 2nd order analysis. A set of calculations of isolated members will demonstrate the influence of the material, of the slenderness and of the eccentricity of the axial force. The results are compared with one another in a critical discussion.     

Bauteile aus Stahlfaserbeton und stahlfaserverstärktem Stahlbeton

Mit der zu erwartenden Einführung der Richtlinie “Stahlfaserbeton” des Deutschen Ausschuss für Stahlbeton (DAfStb) entsteht für den Verbundwerkstoff Stahlfaserbeton ein neues, breites Spektrum an zusätzlichen Anwendungsmöglichkeiten. Durch die Wirkung der Fasern im Beton können nach Überschreitung der Betonzugfestigkeit nennenswerte Kräfte zwischen den Rissufern übertragen und bei der rechnerischen Erfassung des Tragverhaltens berücksichtigt werden. Im Aufsatz werden Vorgehensweisen, Hilfsmittel und ein auf Tabellenkalkulationen und Optimierungsmethoden basierendes Programm zur Biegebemessung und Verformungsabschätzung von Querschnitten und Systemen aus Stahlfaserbeton und stahlfaserverstärktem Stahlbeton entwickelt. Grundlage sind die bekannten Bemessungsansätze und ‐hilfsmittel für Stahlbetonquerschnitte. Die Anwendung der Hilfsmittel – auch für Verformungsabschätzungen auf Basis nichtlinearer Verfahren – zeigen zwei Beispiele. Structural Elements of Steel Fibre Reinforced Concrete with or without Bar Reinforcement Tools for Design and Deflection Estimations according to the Guideline “Stahlfaserbeton” by DAfStb The expected release of the guideline “Stahlfaserbeton” by ‘German Committee for Reinforced Concrete’ (DAfStb) offers a wide application range for the composite material steel fibre reinforced concrete (SFRC). Due to additional steel fibres in concrete considerable tension forces can be transferred between crack edges after reaching plain concrete's tensile strength. These forces can be accounted for in calculation of load bearing capacity. Adapted from common design methods and tools for plain reinforced concrete new procedures, tools and a computer application – based on spreadsheet analysis and optimisation methods – for SFRC are presented in this article. These allow for both bending design as well as deflection estimation of crosssections and structural systems made of SFRC with and without additional rebars. Their application – also in case of deflection estimation using non‐linear methods – is demonstrated in two elaborated examples.     

Stabwerke und Teilflächenbelastung nach DIN 1045‐1 und Eurocode 2 – Modelle und Anwendungen

Strut‐and‐Tie Models and Concentrated Loading according to DIN 1045‐1 and Eurocode 2 – Modelling and Application Strut‐and‐tie models are efficient tools for the demonstration of load‐bearing characteristics and for the design of reinforced and prestressed concrete structures. The illustration and determination of so called D‐regions is one of the most common areas of application. Another related problem is concentrated loading. In comparison to bending or shear design, the standards DIN 1045‐1 and Eurocode 2 (DIN EN 1992‐1‐1) provide only limited requirements and information for application of strut‐and‐tie models and concentrated loading problems. In praxis, the Engineer has to find possible solutions on basis of the principles given in the standards. The following paper compares the basic information of DIN 1045‐1 and Eurocodes 2 (DIN EN 1992‐1‐1) concerning strut‐and‐tie‐models and concentrated loading problems and gives additional proposals for certain application issues.     

Zur Ermittlung der Normalkraft‐Verlängerung und Moment‐Krümmung‐Beziehungen der Stahlbetonbauteile im Grenzzustand der Gebrauchstauglichkei

Die Nachweise zur Begrenzung der Verformungen von Stahlbetonbauteilen sind infolge der Verwendung von Baustoffen höherer Festigkeiten immer wichtiger geworden, oft sogar maßgebend. Eine Verdopplung der Betondruckfestigkeit eines normalen Betons ruft eine etwa 20%ige Erhöhung des E_c‐Moduls hervor aber keine des Betonstahls, da E_s konstant ist. Dies und die dementsprechend schlanker gewordenen Stahlbetonbauteile führen zu größeren Verformungen – Verlängerungen, Durchbiegungen und/oder Verdrehungen – die deren Verhalten beeinträchtigen können. Die für die Ermittlung der Verformungen benötigten “Normalkraft‐mittlere Dehnungslinien”, bzw. “Moment‐mittlere Krümmungslinien” werden erläutert. About the Calculation of Displacements of Reinforced Concrete Members in the Serviceability Limit State The verification of reinforced concrete elements for the purpose of limiting deformations has become increasingly important, often even decisive, as a result of the use of higher strength materials. A doubling of the compressive strength of a normal concrete causes an increase of about 20% in the E_c‐module, and none of reinforcing steel, because E_s is constant. This and, accordingly, the slender reinforced concrete elements lead to larger deformations – elongations, deflections and/or rotations – which may affect their behaviour. The determination of “axial tensile force – mean strain diagrams”, respectively “bending moment – mean curvature diagrams”, needed for the calculation of the displacements, is explained.     

Normen für den Konstruktiven Ingenieurbau

Codes in Structural Engineering In structural engineering codes are of essential importance. Codes have to represent accepted rules as well as the state of the art in science and technology and they provide a basis for the communication between all involved professionals. In codes of the future all procedural steps of planning have to be included – design, execution, service, conservation and dismantlement – and an integral approach to safety and quality has to be adopted. In comparison to present codes, the technical breadth and the level of detail will increase. Nonetheless, the overall aim of code writers shall be to come up with regulations that are easy to understand and to apply. Codes of the future have to (re‐)gain their significance and acceptance.     

Zur Ermittlung der Verformungen von Stahlbetonbauteilen im Grenzzustand der Gebrauchstauglichkeit

In Beton‐ und Stahlbetonbau 104, Heft 8, wurden die für die Ermittlung der Verformungen von Stahlbetonbauteilen benötigte Normalkraft‐mittlere Dehnungslinie, bzw. Biegemoment‐mittlere Krümmungslinie erläutert. Ein Rechenmodell und ein dazugehöriges Näherungsverfahren sowie deren praktische Anwendungen werden hier vorgestellt. Abschließend wird ein Vorgehen zur Vordimensionierung mit begleitenden Hilfsmitteln dargestellt. About the Calculation of Displacements of Reinforced Concrete Members in the Servicebility Limit State In Beton‐ und Stahlbetonbau 104, issue 8, the determination of axial tensile force – average strain, respectively bending moment – average curvature diagrams, in order to calculate the displacements of reinforced concrete members, were explained. A calculation model for the deformations, an approximation of it, and their practical applications are explained. Finally, a method for preliminary dimensioning with accompanying diagrams and tables is presented.     

Teilsicherheitsfaktoren für die Berechnung von Großkraftwerken

Die Baustrukturen von Großkraftwerken werden in Deutschland u. a. auf Basis der VGB‐Richtlinie R 602 U berechnet und bemessen. In dieser Richtlinie sind unter Berücksichtigung der Besonderheiten des Großkraftwerksbaus Einwirkungen und Teilsicherheitsfaktoren definiert. Während die Lasten auf diese Randbedingungen abgestimmt wurden, hat man die Teilsicherheitsfaktoren auf der Lastseite aus der DIN 1055‐100 entnommen und lediglich die Kombinationsbeiwerte angepasst. Diese Sicherheitsbeiwerte tragen jedoch den speziellen Randbedingungen eines Kraftwerks oder Schwerindustriebaus nur bedingt Rechnung. Im Rahmen des Beitrags werden die Teilsicherheitsbeiwerte auf der Einwirkungsseite – insbesondere für das Konstruktionseigengewicht – für die Bemessung von Stahlbetonteilen vor diesem Hintergrund kritisch diskutiert und ein optimierter, wissenschaftlich abgesicherter Vorschlag unterbreitet. Partial Safety Factors for the Design of Power Plants In Germany power plants are designed in accordance to VGB regulation R 602 U. In this code load actions and partial safety factors are applied taking the special characteristics of power plants into consideration. The actions are defined regarding these circumstances, however the safety coefficients are assumed according to DIN 1055‐100 and only the combination coefficients are adjusted. However it has to be recognized that the partial safety factors in DIN 1055‐100 are calibrated for building constructions and thus do not consider the specialities of power plants in an adequate manner. In this paper the partial safety factors for the design of power plants and other heavy industry buildings are discussed for structural concrete elements and a scientific based optimized approach for the safety factor for dead load is presented.     

Querschnittsberechnung von Stahlbetonstäben – Stand der Forschung

Cross‐Sectional Analysis of Reinforced Concrete Beams – State of the Art Many common structures consist of one‐dimensional members. For such structures beam theory is applicable. Within beam theory, the material behaviour can be captured on cross‐sectional level. Regarding reinforced‐concrete structures, material nonlinearity has generally to be considered. The present article provides an overview of the state of the art in cross‐sectional analysis of one‐dimensional reinforced‐concrete elements. A crosssectional analysis describes the relationship between the internal forces and the generalized strains. There is a large number of different models, for which a classification is suggested here. Existing models can be classified into resultant models, truss models, uniaxial models, wall models, and finite element models. For each class, the characteristics are outlined and the most important models are presented.