Prestressing in flat slabs helps to control deformations and cracking under service loads and allows the required slab thickness to be reduced, thus leading to more slender structures and an economic solution for long spans. However, as a consequence of the limited thickness of these members, punching typically governs at the ultimate limit state. Studies of the punching shear strength have shown that the presence of prestressing in flat slabs has a number of potential beneficial effects, namely the vertical component (force) carried by inclined tendons, the in-plane compression stresses and the bending moments developed near the supported region. However, the approach provided by codes of practice for punching design in the presence of prestressing may differ significantly. Some codes neglect the influence of the bending moments introduced as a result of prestressing and the sections at which the deviation forces of the tendons are considered may be located at different distances from the edge of the supported region. The influence of prestressing on the punching shear strength of members without shear reinforcement is investigated in this paper by using the fundamentals of the critical shear crack theory. Using that as a basis, and also taking into account 65 tests available in the scientific literature, the suitability and accuracy of a number of design codes, e.g. Model Code 2010, Eurocode 2 and ACI 318-11, are investigated and compared.

This paper discusses the possibility of using precast tunnel segments in fibre-reinforced concrete without traditional reinforcement. The case study of a hydraulic tunnel in Monte Lirio, Panama, excavated with a tunnel boring machine (TBM) by SELI S.p.A., has been analysed.
The segments were designed according to the draft of Model Code 2010. In order to achieve the required performance and to optimize the structural behaviour, three different types of steel fibre were considered in the research.
The design was backed up by full-scale tests on precast segments. In particular, 18 full-scale tests were performed, including point load tests simulating the thrust of the TBM and bending tests. The results show the good behaviour of the elements and indicate the fibre-reinforced concrete suitable for the precast elements.

Fatigue design according to CEB-FIP Model Code 90 is limited to concrete grades up to C80. In addition, the design rules include a strength-dependent reduction in the fatigue reference strength, which leads to uneconomical design of high-strength concrete. Considering comprehensive knowledge now available concerning the fatigue behaviour of normal-strength and high-strength concretes, the amount of this reduction can no longer be justified. A new design model for compressive fatigue loading and its derivation is presented in this article. A comparison between the new design model and the current standard ones reveals that the new design model ensures safe and economical design of normal-strength, high-strength and ultra-high-strength concrete. This new design model is included in the new fib Model Code 2010.

This paper examines the evidence for the one-way shear model developed for the fib Model Code for Concrete Structures 2010 and provides examples of its application. For the design and analysis for shear, for members with and without shear reinforcement, the fib Model Code 2010 procedures have been developed from physical-mechanical models that are based on observed behaviour at the meso-scale level; they represent a significant advance over previous standardized empirical methods. In addition, an approach referred to as “level of approximation” (LoA) is incorporated where advanced models are simplified in a consistent and conservative way such that the designer can select the effort needed to justify their design. To illustrate the practical use of the models and the LoA approach, two examples are presented. The first is a deck slab of a cut-and-cover tunnel where design and possible refinements are discussed for a given configuration. The second is a prestressed concrete bridge girder, which is considered for the cases of design and for the analysis of an existing structure.

This paper outlines the theoretical background to the punching shear provisions implemented in the fib Model Code for Concrete Structures 2010 and presents a practical example of their application. The aim is to explain the mechanical model that forms the basis for the punching design equations, to justify the relevance of the provisions and to show their suitability for the design and assessment of structures.

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.

The scope of fib Model Code for Concrete Structures 2010 includes the fully fledged performance- and displacement-based seismic design of new structures and assessment of existing ones. This part of fib Model Code 2010 covers buildings, bridges or similar concrete structures and aims to provide well-defined performance levels for specific seismic hazard levels. Detailing of members for ductility is not based on opaque prescriptions, as in current codes, but on transparent, explicit verification of inelastic deformation demands against capacity limits. The reference analysis method is non-linear dynamic, but under certain conditions inelastic deformation demands may be estimated from linear analysis and the 5%-damped elastic response spectrum; in that case force demands on force-controlled, brittle failure modes are estimated from the plastic mechanism through equilibrium. In order to predict the seismic deformation demands with some confidence, the analysis should use realistic values for the member secant stiffness up to the yield point. The paper explains the background to the expressions given for this property in fib Model Code 2010 as well as of those for the deformation limits used when verifying seismic deformation demands. The modifications to the shear resistance approach of fib Model Code 2010, which takes cyclic loading into account, are also explained and justified.

Fibre-reinforced polymers (FRP) in the form of externally bonded reinforcement have been used successfully in the rehabilitation of concrete structures. Although considerable data has been produced on the performance of strengthened RC structures, the reliability of strengthened structures can be significantly reduced due to the variability in the FRP properties, especially when the wet layup technique is used. In addition to this, structural engineers are concerned about the durability of FRP-strengthened structures under extreme loading conditions. Nonetheless, knowledge of the behaviour of strengthened elements under fatigue loading may be important to raise confidence in the strengthening systems. This paper presents the results of an experimental programme developed to investigate the behaviour up to failure of RC beams strengthened with high-performance carbon and aramid fibre sheets and subjected to static and cyclic loadings in terms of ultimate loads, deflections, cracking behaviour, failure modes and fatigue life by means of loading, crack width and deflection monitoring. Experimental data on fatigue life were used to validate analytical models developed for strengthened and unstrengthened beams.

Interface shear transfer between differently aged concretes is a topic that crops up frequently and in different situations in structural design. In the fib Model Code for Concrete Structures 2010 the fundamental basics of concrete-to-concrete load transfer are given in section 6.3 and the corresponding design rules in 7.3.3.6. The different potential mechanisms contributing to the shear resistance along the interface, i.e. adhesive bond, aggregate interlock, friction and dowel action, are thus combined and their relationship taken into account by interaction factors. This article summarizes the most important results from past and ongoing studies and presents the background to the theory forming the design basis of fib Model Code 2010, the “extended shear friction theory” (ESF).

Mit der bauaufsichtlichen Einführung des Eurocode 2 in Deutschland wurde die Durchstanzbemessung von Fundamenten und Bodenplatten neu geregelt. Für die Bemessung der Durchstanzbewehrung wird im Eurocode 2 unabhängig vom Bauteil ein 33°-Fachwerk mit konstantem Betontraganteil vorgeschlagen. Aufgrund von Sicherheitsbedenken wurde im Deutschen Anhang zum Eurocode 2 (EC2+NA(D)) davon abweichend ein Aufhängefachwerk ohne Betontraganteil für die Bemessung der Durchstanzbewehrung in Fundamenten und Bodenplatten eingeführt. Während zur Bewertung der Bemessungsgleichungen für die Ermittlung der Durchstanztragfähigkeit von Fundamenten ohne Durchstanzbewehrung bzw. der maximalen Durchstanztragfähigkeit verschiedene Versuchsergebnisse vorliegen, fehlen bislang systematische Versuchsreihen an Fundamenten mit einem Durchstanzversagen innerhalb des durchstanzbewehrten Bereichs (Bemessung der Durchstanzbewehrung).
Zur systematischen Untersuchung des Durchstanztragverhaltens von Fundamenten mit Bügeln als Durchstanzbewehrung wurden insgesamt drei Versuchsserien (elf Versuche) mit variierendem Durchstanzbewehrungsgrad durchgeführt. Dabei erfolgte die Variation der Durchstanzbewehrungsmenge über den Bügeldurchmesser. Weitere untersuchte Einflussparameter waren die Schubschlankheit und die statische Nutzhöhe. Im vorliegenden Beitrag werden die durchgeführten Versuche vorgestellt und die Versuchsergebnisse diskutiert. Durch den Vergleich der experimentell ermittelten Bruchlasten mit den rechnerischen Durchstanztragfähigkeiten nach Eurocode 2 und EC2+NA(D) können die bestehenden normativen Regeln bewertet werden. Darüber hinaus werden die Bemessungsregeln nach Model Code 2010 in die Bewertung mit einbezogen.

Punching strength of footings with varying shear reinforcement ratios
With the introduction of Eurocode 2 in Germany, the punching shear design provisions of footings and ground slabs were revised. According to Eurocode 2, the design of the shear reinforcement is performed by means of a design model considering a strut inclination of 33° and a constant contribution of concrete. Due to safety related concerns, in German Annex to Eurocode 2 (EC2+NA(D)), a different concept was introduced. In this context, the design of the shear reinforcement in footings and ground slabs is conducted without consideration of a concrete contribution. Various test series on reinforced concrete footings without shear reinforcement and with high amounts of shear reinforcement are available and can be used for the evaluation of the current provisions. Nevertheless, the evaluation of the code equations for the design of the shear reinforcement (failure inside the shear-reinforced zone) is still not possible since systematic test series on footings with a varying amount of shear reinforcement have not yet been conducted.
To investigate the punching shear behavior of reinforced concrete footings with stirrups as shear reinforcement, three systematic test series (eleven specimens) with varying shear reinforcement ratios were performed. In the tests, the shear reinforcement ratio was varied by changing the stirrup diameter only. Further investigated influences were the shear span-depth ratio and the effective depth. In this paper, the results of the tests are discussed and compared to the predictions according to Eurocode 2 and EC2+NA(D). Moreover, the punching design provisions according to Model Code 2010 are evaluated.

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.

The design shear resistance of an existing structure can be evaluated with analytical design procedures and numerical procedures provided by non-linear finite element analyses. The new fib Model Code 2010 proposes different calculation methods that fall into four different levels of approximation. As the level of approximation rises, so the complexity and the accuracy of the calculated shear resistance increases. Non-linear finite element analyses belong to the highest level of approximation, but although they are more and more becoming a customary tool in the daily design process, building codes do not provide guidance on how to perform these analyses.
This paper describes non-linear finite element analyses performed on prestressed beams, which underwent shear failure during experimental loading, in order to assess and criticize the finite element approaches. The aim of this work is to propose guidelines for numerical simulations in order to reduce model and user factors. The results obtained from the non-linear finite element analyses have been compared with the analytical results using different levels of approximation. The design shear resistance obtained with the highest level of approximation, level IV, derived from non-linear finite element analyses, turned out to be higher than the design shear resistance obtained with analytical procedures (levels I/II/III).

Sowohl die zentrische Matrixzugfestigkeit als auch die zentrischen Nachrisszugfestigkeiten von faserbewehrten Betonen werden in der Regel indirekt über Biegezugversuche ermittelt. Dazu muss eine in Versuchen ermittelte Kraft-Verformungs-Kurve in eine Zugspannungs-Dehnungs-Beziehung überführt werden. Für ultrahochfesten Faserbeton (UHPFRC) gibt es in Deutschland zurzeit mangels gültiger Normen und Richtlinien kein geregeltes derartiges Umrechnungsverfahren. Zur Untersuchung des Zugspannungs-Dehnungs-Verhaltens von UHPFRC wurden am iBMB, Fachgebiet Massivbau der TU Braunschweig gekerbte 3-Punkt-Biegezugversuche nach DIN EN 14651 durchgeführt. Unter Berücksichtigung der Versuchsergebnisse und in Anlehnung an den Model Code 2010, der normal- und hochfesten Faserbeton regelt, wurde ein Umrechnungsverfahren für UHPFRC entwickelt. Zur Validierung des Verfahrens wurde die Finite-Elemente-Methode (FEM) hinzugezogen.

Tensile Stress-Strain Relationship for UHPFRC based on notched 3-point-bending tests
Both the tensile strength and the residual tensile strengths of fibre reinforced concrete are generally determined indirectly by flexural tests. For this purpose, a force-deformation curve has to be converted into a tensile stress-strain curve. For ultra-high performance fibre reinforced concrete (UHPFRC) there is currently no regulated conversion procedure due to the lack of valid standards and guidelines in Germany. To analyse the tensile stress-strain behaviour of UHPFRC, notched 3-point-bending tests according DIN EN 14651 were carried out at iBMB, Division of Concrete Construction of the TU Braunschweig. A conversion procedure for UHPFRC based on the Model Code 2010, which regulates normal- and high-strength fibre reinforced concrete, was developed taking into account the test results. The finite element method (FEM) was applied for validation.

A design procedure based on a simplified FE model for underground tunnels subjected to internal explosion and possibly preceded by fire accidents is proposed in this article. The procedure can provide a valuable tool for designers who have to check the structural safety of a tunnel for the case of an internal blast event. The tunnel geometry considered is the same adopted for the metro line in Brescia, Italy. It has an internal diameter of about 8.15 m, is about 13.7 km long and is located about 23.1 m below the surface. Six segments and a smaller key segment (6+1) make up the tunnel. The ring has an average width of about 1.5 m. The FE model is first tested under static serviceability loads. Dynamic analyses are carried out in order to reproduce the blast scenario. The aim of this work is to generate pressure-impulse (p-i) diagrams for underground tunnels for the case of internal explosion and pre-explosion fire actions. An ultimate limit state criterion based on the eccentric ultimate flexural capacity and capable of including fire-blast interaction is introduced. An innovative layered precast tunnel segment solution made of different fibre-reinforced cementitious composites is compared with a traditional solution with the lining section made of reinforced concrete. The potential applications of this new solution are also discussed in the paper.

• 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

Mit dem Ziel, einen Überblick über aktuelle normative Modelle zur Berechnung der Rissbreite im Stahlbetonbau zu erhalten, wurden diese am iBMB, Fachgebiet Massivbau der TU Braunschweig zusammengestellt und verglichen. Um einen unabhängigen Vergleich der Modelle sicherzustellen, wurde eine Datenbasis mit Versuchswerten zu Rissbreiten zusammengestellt. Der Modellvergleich wurde auf zentrische Zugversuche, bei denen charakteristische Werte der gemessenen Rissbreiten (95 %-Quantilwerte) angegeben waren bzw. ermittelt werden konnten, beschränkt. Durch die Vergleichsberechnungen konnte gezeigt werden, dass zwischen den unterschiedlichen Modellen signifikante Abweichungen auftreten. Während der Eurocode 2 die im Versuch gemessenen Rissbreiten tendenziell überschätzt, werden die Rissbreiten mit den Nationalen Anhängen für Deutschland bzw. Österreich überwiegend unterschätzt. Mit dem Modell nach Model Code 2010 werden die Versuchsergebnisse im Mittel ebenfalls überschätzt, die Ergebnisse liegen jedoch zwischen denen nach Eurocode 2 sowie den Nationalen Anhängen für Deutschland bzw. Österreich. Des Weiteren kann mit den Modellen der Nationalen Anhänge für Deutschland und Österreich sowie des Model Code 2010 eine, gegenüber dem Eurocode 2, erhöhte Vorhersagegenauigkeit erreicht werden.

Comparison of code provisions for the calculation of crack widths
In order to give an overview of current code provisions for the calculation of crack widths, these provisions were compiled and compared at the iBMB, Department of Concrete Construction of TU Braunschweig. In order to ensure an independent comparison, a database with test values for crack widths was compiled. The comparative calculations were limited to tensile tests in which characteristic values of the measured crack widths (95 %-quantile values) were or could be determined. As a result, it can be stated that significant deviations occurred for the different code provisions. While the provisions by Eurocode 2 tend to overestimate the test values, the National Annexes for Germany and Austria mainly underestimate the measured crack widths. Model Code 2010 also overestimates the test results on average, but the results are between those obtained with Eurocode 2 and the national annexes for Germany and Austria. Furthermore, the models in the national annexes for Germany and Austria as well as the Model Code 2010 achieve a higher prediction accuracy than Eurocode 2.

Considering the depletion of resources and energy and the risks of climate change on a global scale, a thoughtless increase in the use of resources and energy in the construction sector is obviously unacceptable. The sector has until now constructed a system of technology focused on safety and comfort, with priority given to economic and social benefits. Such demands remain extremely important; however, in the future we ought to give additional consideration to the depletion of resources, energy consumption and other, ensuing environmental issues. This means that the sector needs to incorporate sustainability - including the environmental, economic and social aspects - into its systems of design and technology. The fib decided to incorporate a “concrete sustainability” concept in its new fib Model Code for Concrete Structures 2010. This paper explains sustainability as expressed in this code together with the background to it. In addition, the essence of sustainability with respect to future Model Codes is discussed.

The paper reports on a benchmark of European deemed-to-satisfy rules for exposure class XC (carbonation exposed structural members). The benchmark of the descriptive rules was carried out following the probabilistic design approach for carbonation-induced corrosion developed in [1] and adopted in fib bulletin 34: Model Code for Service Life Design (2006) [2] and fib Model Code for Concrete Structures 2010 [3], respectively. To perform a representative study, three groups of European countries were selected, representing different parts of Europe, south (Spain, Portugal), middle (Netherlands, Great Britain and Germany) and northern Europe (Denmark, Norway). Reliability ranges for carbonation-induced depassivation of rebar were calculated for “favourable” and “unfavourable” design situations in exposure classes XC2, XC3 and XC4 [4]. In each design situation the deemed-to-satisfy rules of selected countries were followed. The probabilistic calculations were mainly based on short-term carbonation data. However, some calculations were also based on long-term observation. The latter was implemented for independent validation purposes. The calculated reliability ranges are very broad and in some “unfavourable” situations, the deemed-to satisfy requirements do not guarantee the required limit state (LS) arget reliabilities for the particular exposure. In “favourable” situations less stringent demands would have been sufficient.

The design philosophy of the new fib Model Code for Concrete Structures 2010 represents the state of the art with regard to performance-based approach to the design and assessment of concrete structures. Given the random nature of quantities determining structural behaviour, the assessment of structural performance cannot be well established by deterministic methods, instead requires a probabilistic approach. The performance-based approach is introduced in Part I of fib Model Code 2010 by applying the concept of performance requirements and reliability management during service life. Correct understanding of the reliability concept of fib Model Code 2010 is a basic prerequisite for applying its design philosophy in an appropriate manner. Therefore, the main objective of this paper is to explain some decidedly non-trivial issues related to safety and reliability management aspects. In this context, this paper indicates how this general philosophy in fib Model Code 2010 is further developed into a set of operational rules for the design and assessment of concrete structures.

The aim of this research is to compare the predictions of the design load-carrying capacity of slabs obtained with simplified analytical and numerical procedures which can be readily used by analysts in the current design process. The research fits into a research programme initiated by the Dutch Ministry of Infrastructure and the Environment for the re-examination of the load-carrying capacity of existing bridges and viaducts, and the beams and slabs they include, through the use of non-linear finite-element analyses. The behaviour of reinforced concrete slabs subjected to concentrated loads close to their supports is investigated in this contribution. Three tests from a series of 18 slabs with a total of 108 tests, tested at Delft University of Technology, were selected as case studies and analysed with non-linear finite-element analyses and analytical models either proposed by design codes or available in the literature. The research agrees well with the philosophy of the fib Model Code for Concrete Structures 2010, which offers different analytical and numerical calculation methods for evaluating the design shear resistance of reinforced concrete members according to different levels of approximation. For the three slabs investigated in this study, it indeed pays to use higher levels of approximation. The highest level (level IV) based on non-linear finite element analysis gives the highest design load resistance, but still well below the resistance obtained experimentally.

Section 5.1 “Concrete” of the fib Model Code for Concrete Structures 2010 contains basic definitions and well-established constitutive relations for structural concrete. However, it also presents various new approaches and updated models compared with the earlier CEB-FIP Model Code 1990. This is particularly true for the strength, stress and strain characteristics of structural concrete, for creep and shrinkage and for sophisticated durability-related processes. The validity of the models has been extended to several types of concrete such as high strength concrete, self-compacting concrete and lightweight aggregate concrete. The durability-related models are either suitable for facilitating a full probabilistic service life design or for applying simpler code-type approaches.
This article provides a concise and selective overview of some of those models. Background information is summarized and there is a focus on improvements achieved by the updated models. In addition, some simple design aids are given to allow pre-design, for example

Das tatsächliche Sicherheitsniveau bei der Ermüdungsbemessung von druckschwellbeanspruchtem Beton ist derzeit unbekannt. Für die Ermüdungsnachweise werden Sicherheitsbeiwerte verwendet, die aus der statischen Bemessung übernommen wurden, und weitere, teilweise nicht wissenschaftlich begründete Sicherheitselemente implementiert. In diesem Beitrag werden Sicherheiten in aktuellen Nachweiskonzepten nach DIN EN 1992-1-1(/NA), DIN EN 1992-2(/NA) und fib Model Code 2010 diskutiert und Entwicklungspotenziale aufgezeigt. Außerdem werden Ergebnisse bestehender Ermüdungsuntersuchungen stochastisch ausgewertet und mit Wöhlerlinien nach fib Model Code 2010 verglichen. Die vergleichenden Untersuchungen deuten auf ein höheres Sicherheitsniveau des Ermüdungswiderstands im Vergleich zur statischen Bemessung hin.

Concrete fatigue - safety and development potential of current design concepts
The safety level for the fatigue design of concrete under compression is currently unknown. This is the result of safety factors taken from the static design and other safety elements, which are in some cases not scientifically justified. In this paper, the safety aspects of current fatigue design concepts according to DIN EN 1992-1-1(/NA), DIN EN 1992-2(/NA) and fib Model Code 2010 are discussed and potentials for further developments are shown. In addition, results of existing fatigue tests are evaluated stochastically and compared with S-N curves according to fib Model Code 2010. The comparative investigations indicate a higher safety level of the fatigue resistance compared to the static design.

Punching tests on 13 specimens under uniform soil pressure were conducted to evaluate the punching shear behaviour of footings with practical dimensions. The test series included square footings with and without punching shear reinforcement. The dimensions of the footings varied between 1.20 × 1.20 m and 2.70 × 2.70 m and the slab thickness varied between 0.45 and 0.65 m, resulting in shear span-depth ratios a&lgr;/d between approx. 1.25 and 2.00.
In addition to the measured steel strains in the flexural reinforcement and the stirrups, the increase in the slab thickness as well as the saw-cuts were examined to investigate the internal cracking and failure characteristic. In combination with previous tests conducted at RWTH Aachen University, this test series permits a description of the effect of the main parameters on the punching shear strength of footings. These parameters are the size effect of the effective depth, the concrete compressive strength, the flexural reinforcement ratio and the punching shear reinforcement.

The probabilistic assessment of structures damaged by corrosion calls for deterministic models of the degradation of the structural performance and probabilistic models accounting for the uncertainties in material properties, geometry and models used in the reliability analysis. This paper describes the development of a probabilistic model of the uncertainties that arise from the prediction of the loadbearing capacity of reinforced concrete structures damaged by corrosion of the reinforcement. The investigation focuses on the flexural failure of simply supported beams suffering from chloride-induced corrosion. The loss of steel cross-sectional area, the reduction in strength and ductility of the corroded bars, the loss of bond between reinforcement and concrete and the cracking of the concrete cover are taken into account in a non-linear finite element analysis. The comparison between experimental results and numerical predictions of the failure load allows the quantification of the model uncertainty according to the framework proposed by the Joint Committee on Structural Safety. A Bayesian updating methodology is proposed to account for prior knowledge and experimental results.

Most applications of fibre-reinforced polymers (FRP) deal with externally bonded reinforcement as a means of repairing and strengthening reinforced concrete (RC) structures or retrofitting RC structures in seismic regions. As internal reinforcement, FRP rebars or (more rarely) prestressing elements are used in special projects, combining material strength and durability characteristics. Over the last years, several national and international design guidelines have become available specifically for the design and application of FRP-strengthened or FRP-reinforced concrete structures. These efforts clearly demonstrate the interest in FRP as a novel reinforcing material for concrete construction. Hence, the time had come to introduce FRP reinforcement into the new fib Model Code for Concrete Structures 2010 as well. The main contributions to the fib Model Code 2010 relate to sections 5.5 “Non-metallic reinforcement” and 6.2 “Bond of non-metallic reinforcement”. The material presented in those two sections is further elaborated in this article.