Seit 2012 liegt Eurocode 2 zusammen mit dem nationalen Anhang in Deutschland vor. Die größtenteils aus dem Model Code 1990 übernommene Durchstanzbemessung regelt das Durchstanzen von Einzelfundamenten und Bodenplatten neu. Mit dem Model Code 2010 wurde das Bemessungskonzept zum Durchstanzen überarbeitet und in die zum 01.01.2013 eingeführte schweizerische Norm SIA 262:2013 übernommen. Im vorliegenden Beitrag werden die Bemessungsgleichungen zur Bestimmung der Durchstanztragfähigkeit nach Eurocode 2, dem deutschen Anhang zu Eurocode 2, Model Code 2010 und SIA 262 ausführlich vorgestellt. Durch Parameterrechnungen werden die Haupteinflüsse aus Schubschlankheit, statischer Nutzhöhe, Längsbewehrungsgrad und Betondruckfestigkeit auf die Durchstanztragfähigkeit von Einzelfundamenten näher untersucht und den rechnerischen Durchstanzwiderständen gegenübergestellt. Durch Vergleiche mit den Ergebnissen systematischer Versuchsserien werden das Sicherheitsniveau und die Wirtschaftlichkeit der Bemessungsgleichungen überprüft.

Punching shear design of footings - present code provisions: parametric study and comparison with test results
Since 2012, Eurocode 2 and the corresponding National Annex have been introduced in Germany. Most design provisions were adopted from Model Code 1990 and provide a new design approach for ground slabs and footings. For Model Code 2010, the design concept was again revised and introduced in the Swiss standard SIA262:2013. In this paper, the design equations for the determination of the punching capacity according to Eurocode 2, the German annex to Eurocode 2, Model Code 2010, and SIA 262:2013 are presented in detail.
Parameter studies are used to examine the influence of the main punching parameters (shear span depth-ratio, effective depth, longitudinal reinforcement ratio, and concrete compressive strength) on the punching shear resistance of footings. To quantify the safety level and the efficiency, the design provisions are compared to systematic test series.

Das ständig steigende Verkehrsaufkommen sowie die im Laufe der Jahre überarbeiteten Bemessungsnormen erfordern eine neue Beurteilung der angestrebten Nutzungsdauer bestehender Brücken. Die rechnerische Schubtragfähigkeit erweist sich hierbei in vielen Fällen als besonders problematisch. Im Zuge der Überarbeitung der österreichischen Nachrechnungsrichtlinie ONR 24008 “Bewertung der Tragfähigkeit bestehender Eisenbahn- und Straßenbrücken” wurden Vergleichsberechnungen bezüglich der rechnerischen Querkrafttragfähigkeit von Bestandsbrücken nach Eurocode 2 und fib Model Code 2010 durchgeführt. Der vorliegende Beitrag fasst die wesentlichen Ergebnisse aus dem Vergleich zwischen fib Model Code 2010 und dem Eurocode 2 zusammen und erläutert die Besonderheiten der Berechnung der rechnerischen Querkrafttragfähigkeit gemäß fib Model Code 2010.

Comparison of the calculative shear resistance of existing bridges according to Eurocode 2 and fib Model Code 2010
Due to the constantly increasing traffic loads and the revised design approaches it becomes necessary to reassess the expected service life of existing bridges. In many cases the calculative shear resistance turns out to be particularly problematic. In the course of the revision of the Austrian Assessment Technical Regulation ONR 24008 “Evaluation of load capacity of existing railway and highway bridges” comparative calculations according to the shear carrying capacity of existing bridges conforming to Eurocode 2 and fib Model Code 2010 were carried out. The present paper summarizes the main results of the comparison between the fib Model Code 2010 and Eurocode 2 and explains characteristics of the calculations of the shear resistance according to fib Model Code 2010.

Der Ermüdungsnachweis nach CEB-FIP Model Code 90 ist auf Betone bis zu der Festigkeitsklasse C120 beschränkt. Gleichzeitig beinhaltet dieser Nachweis eine festigkeitsabhängige Reduktion der Druckfestigkeit unter Ermüdungsbeanspruchung, die bereits für hochfeste Betone zu einer unwirtschaftlichen Bemessung führt. In Anbetracht der mittlerweile vorliegenden umfangreichen Erkenntnisse zum Ermüdungsverhalten normalfester und hochfester Betone ist die Größe dieser Abminderung als nicht mehr gerechtfertigt einzustufen. Im vorliegenden Beitrag wird ein neu entwickeltes Ermüdungsbemessungsmodell vorgestellt, welches eine wirtschaftliche und sichere Bemessung von normalfesten, hochfesten und ultrahochfesten Betonen im Grenzzustand der Ermüdung ermöglicht. Der neue Bemessungsansatz wurde in das Bemessungskonzept des CEB-FIP Model Code 90 integriert, so dass eine einfache Anwendung möglich ist.

Design model for the fatigue behaviour of normal strength, high strength and ultra-high strength concrete
Fatigue design according to CEB-FIP Model Code 90 is limited to concrete grades of up to C120. In addition, the design rules include a strength dependent reduction of the fatigue reference strength, which leads to uneconomical design of high strength concretes. Considering today's existing comprehensive knowledge regarding the fatigue behaviour of normal strength and high strength concretes, the size of this reduction is no more justifiable. In this article, a newly developed design model for fatigue is presented, which enables an economic and safe design of normal strength, high strength and ultra-high strength concretes based on fatigue limit state. This new design approach is integrated into the design concept of the CEB-FIP Model Code 90, thereby guaranteeing a simpler application.

Die Regelungen zur Durchstanzbemessung im Eurocode 2 basieren im Wesentlichen auf den Modellvorstellungen in Model Code 90, der die Durchstanztragfähigkeit auf die Querkrafttragfähigkeit zurückführt. Nach Versuchsauswertungen ist diese Analogie für punktgestützte Platten jedoch nicht in jedem Fall zutreffend. Insbesondere für bügelbewehrte Platten ist bei der Bemessung nach Eurocode 2 ein Sicherheitsdefizit möglich, und es erscheint eine Anpassung der Bemessungsgleichungen zwingend erforderlich. Dieser Beitrag erläutert die Sicherheitsdefizite und schlägt verbesserte Bemessungsgleichungen vor.

Punching of Flat Slabs according to Eurocode 2
The punching shear provisions according to Eurocode 2 are based on the design recommendations in Model Code 90 where no differentiation between shear and punching shear design is made. This approach is not fully confirmed by test results for flat slabs. In particular for flat slabs with stirrups as shear reinforcement some design provisions according to Eurocode 2 do not achieve the required safety level. Therefore adjustments to the design equations seem to be necessary. In this paper the Eurocode 2 provisions are critically reviewed and improved design regulations are proposed.

Die Auswertung zahlreicher mehraxialer Versuche hat ergeben, dass die auftretenden Versagensmechanismen unter mehraxialer Beanspruchung für alle Betonarten prinzipiell gleich sind. Dies gilt sowohl für Normal- bis ultrahochfesten Beton, für Leichtbeton als auch für Faserbeton. Das vorgestellte Bruchkriterium orientiert sich an diesen Versagensarten und wird über eine entsprechende Kalibrierung an das Verhalten des jeweiligen Betons angepasst. Im Zuge der Aktualisierung des CEB-FIP Model Codes 90 wird es Einzug in die Bemessungsvorschriften finden.

A Unified Multiaxial Fracture Criterion for all Concretes
The evaluation of numerous multiaxial tests has shown that the occurring failure mechanisms under a multiaxial load are basically the same for all types of concrete. This is true for normal to ultra high performance concrete, lightweight concrete, as well as for fibre concrete. The presented fracture criterion is based on these failure types and is adjusted by a corresponding calibration to the behaviour of each concrete. In the course of the upgrade of the CEB-FIP Model Code 90, it will find entry into the dimensioning specification.

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.

Im Zeitalter des Mobilfunks dienen viele turmartige Bauwerke als Antennenträger. Viele davon stellen die besonders dafür konzipierten Schleuderbetonmaste sowie alte, entsprechend nachgerüstete Schornsteine dar. Manche dieser Tragwerke weisen auffällige Vertikalrisse auf, deren Auswirkung auf die Tragfähigkeit begutachtet werden muß. Bei dieser Aufgabe muß in Betracht gezogen werden, daß das im Erfahrungsbereich liegende Rißverhalten normaler Betontragwerken nur bedingt auf Schleuderbetontragwerke übertragbar ist. In diesem Sinne befaßt sich der vorliegende Beitrag mit der Erforschung der Unterschiede im Rißverhalten der hochfesten Schleuderbetonmaste gegenüber dem der niederfesten Betonschornsteine. Die entsprechenden Untersuchungsergebnisse wurden mit der Rißnachweismethode der Normen DIN V 1056, DIN EN 13084 und CICIND Model Code gewonnen und stellen einen wichtigen Teil der Qualitätssicherung von turmartigen Tragwerken dar.

Um wirtschaftliche hochfeste Konstruktionsleichtbetone mit möglichst geringer Trockenrohdichte und guter Verarbeitbarkeit zu entwickeln und bestehende Forschungslücken zum Tragverhalten zu schließen, wurde ein mehrjähriges Verbund-Foschungsvorhaben aufgelegt, dessen Ergebnisse im Rahmen eines Pilotprojektes erstmals erfolgreich eingeflossen sind. Dieser Aufsatz widmet sich den durchgeführten Untersuchungen zum Tragverhalten. In mehreren Versuchsserien an Probebalken wurde für Konstruktionsleichtbetone unterschiedlicher Festigkeiten der Einfluß seiner Normaldruckkraft auf die Schub- und Biegetragwirkung untersucht mit dem Ziel, die Bemessungsansätze nach DIN 1045-1, Model Code MC 90 und ENV 1992-1-1 (EC 2) zu überprüfen bzw. ggf. zu modifizieren sowie konstruktive Details für Bauteile aus vorgespanntem Leichtbeton bereitzustellen. Die Untersuchungen stellen die Voraussetzungen für den sicheren Einsatz von hochfestem Konstruktionsleichtbeton im Spannbetonbau dar.

Die Bemessungsansätze und die Konstruktionsregeln für den Nachweis gegen Durchstanzen von Stahlbeton-Flachdecken unterscheiden sich deutlich voneinander. Die Querkrafttragfähigkeit, die gemeinsame Tragfähigkeit von Beton und Schubbewehrung und die daran geknüpfte baulilche Durchbildung werden für vier europäische und zwei nordamerikanische Normen sowie den CEB-FIP Model Code gegenübergestellt. Am Beispiel einer Flachdecke eines Bürogebäudes mit üblichen Abmessungen wird gezeigt, welche Möglichkeiten und Grenzen die Normen im einzelnen bieten und welche baupraktischen Konsequenzen die neue DIN 1045-1 und der EC 2 haben werden.

This article investigates the transferability of the Simplified Modified Compression Field Theory (SMCFT) [2], which is known in reinforced concrete design and included in the fib Model Code for Concrete Structures 2010 (Volume 3) [1], to reinforced or prestressed masonry beams (RM beams) with or without an additional layer of concrete. The investigation for this work is the obsolete shear design concept that has been used until now for reinforced masonry under shear loading, which does not adequately reflect the actual load-bearing behaviour of significant areas of masonry. The fundamentals of the SMCFT are explained and the transferability of the theory to RM beams is examined, taking into account in particular the different material properties of masonry compared to reinforced concrete. A first approach for future application is represented by the equations presented here for the determination of the shear force capacity of RM beams. The verification is performed through a comparison of the shear resistances determined experimentally (exp.) and by calculation (calc.).

Im Mittelpunkt des Beitrages stehen nichtlineare Materialmodelle, die das globale Tragverhalten von Stahlverbundstrukturen wiedergeben. Ein Vorteil ist dabei, daß die Anzahl der Materialparameter gering gehalten werden kann und diese zudem über Normen wie DIN 18800, EC2 und EC4 oder anhand des CEB-FIP Model Code bestimmt werden können. Die Materialmodelle der drei Querschnittskomponenten Stahlbeton, Stahl und der Verbundmittel berücksichtigen ein ver-/entfestigendes Materialverhalten. Eine erste Phase sieht die Anwendung dieser Materialmodelle innerhalb zweidimensionaler Finiter Elemente vor; typische Stahlverbundträger, bestehend aus Stahlbetonplatten als Gurtplatte auf Stahlträgern, verbunden durch Kopfbolzendübel, werden simuliert. In weiterführenden Arbeiten können diese Materialmodelle problemlos auf dreidimensionale Finite Elemente übertragen werden.

Results of the 2014 fib Awards for Outstanding Concrete Structures competition
Fourth International fib Congress and Exhibition, Mumbai, India
Recent fib-supported events in Asia
Model Code 2010 courses in Argentina and Austria
Report from the fib UK Member Group
3rd International Workshop on Concrete Spalling
Marseille, a UHPFRC world capital
fib Bulletins
A.S.G. Bruggeling's 90th birthday
Ralejs Tepfers' 80th birthday
Peter Schiessl's 70th birthday
Steen Rostam's 70th birthday
MC2010 book
Congresses and symposia

• fib General Assembly approves the Model Code 2010
• fib Symposium 2012
• Earthquake resistance short course, Athens
• fib Bulletins
• New fib website launched
• Elices receives Spanish prize
• Hans Wittfoht † 1924-2011
• Andrew Beeby † 1939-2011
• Congresses and symposia
• Acknowledgement
• 2011 reviewers

• fib short course in Nicosia, Cyprus: Durability and retrofitting of concrete structures
• 2011 Achievement Award for Young Engineers - Results
• Commission update: fib Commission 10, Construction
• 9th Symposium on HPC: change of venue
• Finalization of fib Model Code
• Pier Luigi Nervi workshop
• Honor to Prof. Ajdukiewicz
• HiPerMat symposium 2012
• Stockholm symposium 2012
• Short notes
• Congresses and symposia
• Acknowledgement

• Unter gutem Stern: Bestens aufgestellt für die zukünftigen Aufgaben - Neuausrichtung der FDB von der Mitgliederversammlung befürwortet und bestätigt
• Präsident Rainer Wulle wiedergewählt
• Hilfe bei der Strategieentwicklung
• Für eine bessere Normung: VBI, BVPI und Partner legen Forschungsbericht vor
• Die Qualität von Schutz- und Instandsetzungsleistungen sicherstellen
• 7. Hans Lorenz Symposium für Baugrunddynamik und Spezialtiefbau
• 1. Bayerischer Brandschutzkongress
• FDB aktualisiert Merkblatt Nr. 4 “über die Befestigung vorgefertigter Betonfassaden (11/2011)
• Approval of the fib Model Code 2010”

Eleven T-beams, reinforced with high strength steel, were tested to failure to investigate the effect of shear span to depth ratio, fibre ratio, fibre type, concrete strength and stirrup ratio on the shear behaviour, especially post-cracking shear strength and deformability, of ultra-high performance fibre reinforced concrete (UHPFRC) beams. Test results indicated that fibres were efficient not only in enhancing the post-cracking shear strength, but also in improving the post-cracking deformability of UHPFRC beams. In addition, fibres could bridge the cracks and help in redistributing and homogenizing the concrete stress beside the cracks, allowing more short fine diagonal shear cracks with small spacing to develop around the existing cracks. A moderate amount of stirrups can effectively restrain shear cracks and allow more parallel diagonal shear cracks to develop and propagate thoroughly within the shear span. The stiffness of the UHPFRC beams at ultimate state was about 50 % of initial beam stiffness, which was considerable in strength calculations and ductility analysis, especially in seismic performance evaluation. Lastly, the current shear provisions were evaluated using the experimental results.

The punching shear design provisions according to various codes have been derived from the results of tests conducted on centrically loaded flat slabs. The application of these provisions for footings and ground slabs might lead to inconsistent results since more compact dimensions and soil-structure interaction lead to higher punching shear capacities. In this context, Eurocode 2 introduced a new design equation for column bases, which was derived from the evaluation of test results from centrically loaded footings.
Since centrically loaded footings represent an exception in practice, Eurocode 2 and ACI 318-14 consider load eccentricities by increasing the applied load, while the fib Model Code 2010 proposes a reduced length of the control perimeter to determine the punching shear resistance. The different approaches were derived from the evaluation of tests on eccentrically loaded flat slabs and have not been verified for footings yet.
Theoretical and experimental investigations on the punching shear behaviour of eccentrically loaded footings indicate a reduction of the multi-axial stress state along the column face with increasing load eccentricity. Based on punching tests on eccentrically loaded footings described in literature, non-linear finite-element simulations were performed and subsequently the influence of load eccentricities on the punching shear behaviour was examined in parametric studies. In this article, the results of the numerical simulations are presented and compared to experimental results and various code provisions.

The paper discusses the effect of aging on steel fibre reinforced concrete (SFRC) after 10 years. The aim is to observe the change in mechanical properties, especially of the residual post-cracking tensile strength, due to long-term aging. For this purpose, a comparison between the results of four-point bending tests (4PB) at the age of 1 year and 10 years was carried out and it indicates that aging affects the serviceability post-cracking residual strength, increasing fibre interfacial bond strength. Material classification is performed according to fib Model Code 2010 for 1-year old and 10-year old specimens. The objective is to estimate possible changes in the material class through the years. Three- and four-point bending test results on 10-year old specimens are described, together with a comparison between those tests. Both tests showed very similar results; slightly higher values were obtained with the three-point bending (3PB) test. The tensile constitutive law is obtained according to fib Model Code 2010 and is compared with results of direct tensile tests on cylindrical specimens and Double Edge Wedge Splitting tests on prismatic specimens. A plane section (PS) approach adopting the tensile constitutive law is applied to predict the bending behaviour in terms of nominal stress against crack mouth opening displacement and it is compared with the bending test results.

The correlations among selected parameters of concrete were investigated for concrete mixes of the strength classes C20/25, C25/30, C30/37, C40/50 and C50/60. The focus was laid on correlations between basic mechanical parameters such as compressive strength, tensile strength and modulus of elasticity as well as parameters related to concrete fracture, represented here by specific fracture energy. Laboratory tests examining the fracture behaviour and mechanical properties were carried out in order to determine the fundamental concrete parameters. In particular, standard compression tests on test cubes and three-point bending tests on beams with central edge notch were performed. Additional material parameters were identified using the inverse analysis technique. Finally, correlation factors between different parameters of concrete were identified using the rank-order correlation method.

Concrete has become the most used material on Earth over the 200 years following the invention of modern cement. The design concept has undergone a transition from the allowable-stress design method, limit-state design method, to the performance-based design method, in response to the evolution of materials, sophistication of experimental facilities, and advancement of computation skills. From the issues on resources and energy depletion, global warming, and resilience etc., it is necessary to create a new design framework taking into consideration the required performance beyond the conventional concept, in order to construct infrastructure and buildings in a more rational way. In other words, we should construct a design system that sets the continued existence of the diverse and rich global environment as its most important criterion of value. In this paper, we review the design and technology system developed in the past and discuss it based on the above-mentioned new viewpoint, while constructing and presenting a new design system for concrete structures, focusing mainly on the concept of sustainability, which is regarded as the most important factor in achieving conservation of Earth's rich resources as well as sound socio-economic activities of humankind in the future, and we examine its feasibility.

A performance-based safety factor durability design format is proposed and developed with respect to carbonation of concrete. Deemed-to-satisfy rules based on a partial safety factor design approach are developed for the carbonation of concrete. This design format follows the design procedure proposed in EN 1990 [1]. For the design format, the limit state equation for the carbonation is introduced in its probabilistic and safety factor format. The PSF approach has been used to derive design charts. Values for minimum concrete cover depending on material resistance and exposure class are proposed for critical environmental conditions and a design service life of 50 years.

This paper presents a procedure for designing precast tunnel segments for mechanically excavated tunnel linings in fibre-reinforced concrete, without any traditional steel reinforcement. Both ultimate and serviceability limit states are considered as well as structural checks at different construction stages of the segment, including demoulding, positioning on floor, storage, transportation, handling and the final stage concerning the loads due to the ground pressure.
The structural checks are performed by means of bending moment-axial force interaction envelopes for both the considered limit states, once the constitutive relationship of the material is defined for each stage. Traditional interaction envelopes are drawn for the ultimate limit state check, whereas for the serviceability limit state check, envelopes obtained by limiting the maximum crack opening and maximum concrete compressive stress are proposed. The shear action is also accounted for by reducing the bending moment-axial force envelope. The possibility of having the assistance of a test procedure for particular loading situations is also proposed. Finally, a case study related to a precast steel fibre-reinforced concrete segment is analysed in order to clarify the procedure and show, practically, how to define the actions and evaluate the interaction envelopes.

This paper presents a critical comparison of the existing code provisions for the shear strength of concrete beams. The comparison is based on the computerized filtering-out of the inevitable statistical bias from the available multivariate database on shear strength, on an examination of the predicted size effects on shear strength and their underlying hypotheses and on the results of recent high-fidelity numerical simulations of shear failure. In addition to examining the existing models, the present comparison also provides several key considerations for testing the scientific soundness of any model of shear failure in concrete beams, which is necessary for future revisions to the design code provisions.

This paper presents a new theory for the shear capacity of reinforced concrete members without shear reinforcement. While recognizing that there are multiple failure mechanisms, the theory attributes the opening of a critical flexural shear crack as the lower bound of the shear capacity. It proposes that the shear displacement of an existing flexural crack can be used as the criterion for the unstable opening of the critical flexural shear crack. Based on the theory, the paper presents a simplified shear evaluation model. Compared with the current shear provisions in the design codes, the model is characterized by good accuracy and a solid physical background. It demonstrates a great flexibility for dealing with complex design conditions. As an example, the paper discusses the possibility of extending the theory to the shear resistance of higher-strength concrete. The suggested method provides a more logical and fluent transition from normal- to high-strength concrete and shows good agreement with experimental observations.

A concrete interface is a material discontinuity that requires special care with respect to structural design and assessment. Therefore, the definition of design expressions based on experimental testing data must ensure the necessary reliability depending on the type of structure and its use. The present work describes a new proposal for the design of concrete interfaces subjected to shear loading for different roughness profile types. The proposal is characterized by three linear branches (for monotonic loading) and an S-N curve (for cyclic loading) and is the result of a parametric analysis of existing experimental data (obtained by the authors and also from an extensive literature search) based on statistical and probabilistic methods. Design expressions were defined in order to minimize the dispersion and variability of the safety factor values for each experimental test considered and also to assure that those values are within a target range (defined according to reliability considerations). These improvements became clearer when the new proposal was compared with the most common design code recommendations.