• 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

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

In the fib Model Code for Concrete Structures 2010, fibre-reinforced concrete (FRC) is recognized as a new material for structures. This introduction will favour forthcoming structural applications because the need of adopting new design concepts and the lack of international building codes have significantly limited its use up to now. In the code, considerable effort has been devoted to introducing a material classification to standardize performance-based production and stimulate an open market for every kind of fibre, favouring the rise of a new technological player: the composite producer.
Starting from standard classification, the simple constitutive models introduced allow the designer to identify effective constitutive laws for design, trying to take into account the major contribution in terms of performance and providing good orientation for structural uses. Basic new concepts such as structural characteristic length and new factors related to fibre distribution and structural redistribution benefits are taken into account. A few examples of structural design starting from the constitutive laws identified are briefly shown.
FRC can be regarded as a special concrete characterized by a certain toughness after cracking. For this reason, the most important constitutive law introduced is the stress-crack opening response in uniaxial tension. A wide discussion of the constitutive models introduced to describe this behaviour, which controls all the main contributions of fibres for a prevailing mode I crack propagation, is proposed. The validity of the models is discussed with reference to ordinary cross-sections as well as thin-walled elements by adopting plane section or finite element models.

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.

This paper presents a five-spring model capable of predicting the complete pre- and post-peak shear behaviour of deep beams. The model stems from a two-parameter kinematic theory (2PKT) for the shear strength and displacement capacity of deep beams under single curvature. Four of the springs of the model represent the shear resistance mechanisms of the beam, while the fifth spring models the flexural behaviour. The model predicts not only the load-displacement response, but also the deformation patterns of the beam and how these patterns change with increasing load. Validation studies are performed by using 28 tests from the literature, showing excellent results. The model is used to interpret the tests and to draw conclusions about the behaviour of deep beams. It is shown that shear strength variations of up to 60 % between nominally identical specimens can be caused by variations in the path of the critical shear cracks. It is also demonstrated that loss of bond of large reinforcing bars increases the shear capacity of deep beams. Finally, the five-spring model is shown to predict the post-peak shear behaviour effectively, which is important for the analysis of structures under extreme loading.

Mit der Einführung des fib Model Code for Service Life Design werden dem bemessenden Ingenieur anerkannte und bewährte Vorhersagemodelle zur Verfügung gestellt, mit denen die Bestimmung der zeitabhängigen Carbonatisierungstiefe bzw. Chlorideindringtiefe bis zur Depassivierung des Betonstahls möglich ist. Unter Einbezug statistischer Kennwerte (z. B. Verteilungstyp, Mittelwert, Standardabweichung) lässt sich eine vollprobabilistische Dauerhaftigkeitsberechnung durchführen, mit der im Rahmen des leistungsbezogenen Entwurfsverfahren nach DIN EN 206-1, Anhang J, die zeitabhängige Zuverlässigkeit gegenüber Carbonatisierung bzw. Chlorideindringen bestimmbar ist. Rechnerische Untersuchungen zeigen jedoch, dass die vom Bindemittel abhängige, rechnerische Bandbreite der Zuverlässigkeit für jede Expositionsklasse variiert. Der DAfStb empfiehlt nun in einem in diesem Heft ebenfalls abgedruckten Positionspapier expositionsabhängige Mindestzuverlässigkeiten, die bei einer Anwendung von leistungsbezogenen Entwurfsverfahren nach DIN EN 206-1, Anhang J, nachzuweisen sind. In diesem Beitrag werden die wichtigsten Hintergrundinformationen zu verwendeten Modellen, Daten und Nachweiskonzepten geliefert.

This paper aims to put into perspective the influence of long-term effects, such as concrete creep and shrinkage, on concrete cracking. Long-term experimental results obtained at the Centre for Infrastructure Engineering & Safety (CIES) are reported and compared to design estimates made using the fib Model Code for Concrete Structures 2010. The influence of factors such as stirrup spacing and concrete cover are discussed. Results show that time-dependent shrinkage-induced cracking can considerably modify the cracking patterns obtained in short-term tests. For crack control in real structures and for the development of models for inclusion in codes of practice, it is strongly recommended that account be taken of time-dependent effects. Limiting observations to those made in short-term tests may lead to erroneous conclusions that are simply not applicable for structures that are more than a few weeks old.

Many national codes in Asia are heavily influenced by those from either Europe or the USA. The climatic, technological and economic conditions together with the material properties in Asia are, however, quite different from those in Europe and the USA, and even different among Asian countries. Thus, many Asian countries need their own national codes with suitable concepts and technologies. At the same time, many construction projects in Asia are carried out in multi-national environments in which various national codes are applied, meaning that international code harmonization is necessary. In order to work for the global issue, such as the construction of a sustainable world, Asia, as the largest economic zone in the 21st century, should take on a leading role. For this purpose, international code harmonization with the new direction of life cycle management (LCM) would provide an efficient way.
The International Committee on Concrete Model Code for Asia (ICCMC) was established in 1994 as the first international body in Asia. The ICCMC issued the Asian Concrete Model Code (ACMC) in 2001, the first international structural code in Asia. The ACMC is an umbrella code with a performance-based concept and a multi-level document structure, which makes it suitable for the considerable diversity in Asia. It is also the first international code covering maintenance and repair, which makes the ACMC ready to adopt the LCM concept. The ACMC has been a model for various national codes. The main features of the ACMC, i.e. the performance-based concept, durability design concept, seismic design concept and the inclusion of maintenance/repair, are shared with JSCE Standard Specifications in Japan. The ICCMC has been working together with ISO/TC71 towards international code harmonization.

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 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.

Nach den heutigen aktuell gültigen Normen und Vorschriften (z. B. CEB-FIP-Model Code 2010 [1]) werden für den Ermüdungsnachweis und auch für die Bestimmung des Schädigungsgrades von Betonbauteilen Lastzyklen gezählt und lineare Schadens-Akkumulations-Hypothesen angewandt. Die so gewonnenen Ergebnisse entsprechen nicht der Realität, da Beton ein sehr stark nicht lineares Verhalten aufweist. Ein Weg, diese Ergebnisse zu verbessern, ist die Anwendung von Monitoring, um die Veränderung in der inneren Struktur des Betons mittels eines lastunabhängigen Messverfahrens überwachen zu können. In diesem Artikel wird ein Monitoring-Konzept vorgestellt, mit welchem es möglich ist, diese Ziele zu verwirklichen. Die zugehörigen Laborversuche wurden bereits in [2] beschrieben. Nun folgt deren tiefergehende Auswertung. Am Ende dieses Artikels werden dynamische Tests an vorgespannten Monoblockschwellen gezeigt. Diese wurden mithilfe des im Rahmen dieser Veröffentlichung beschriebenen Monitoring-Konzepts überwacht. Die dadurch erhaltenen Sensormesswerte wurden mit einer numerisch nichtlinearen Simulation der Schwelle korreliert.

Monitoring of the real degree of Fatigue deterioration within concrete structures - Research Project MOSES
According to actual codes and regulations (e.g. CEB-FIP-Model Code 2010 [1]) the verification concept for fatigue and the determination of the real degree of deterioration of Concrete structures is based on counted load cycles and the linear Palmgren-Miner summation. The results gained in this manner will never depict the reality because of the not considered heavily non-linear behavior of concrete. A way to improve the results is the application of monitoring sensors, which are able to image the changes in the inner part of the concrete matrix independently from applied loads. In this article a monitoring concept will be proposed which can achieve these objectives. The laboratory tests are already described in [2] and now a deeper assessment of the measured results will be made. At the end of this article dynamic tests with prestressed railway sleepers and mounted monitoring system are presented. The measurement data of the sensors will be correlated with results of a numerical nonlinear simulation of the sleeper.

Um Bauwerke bis zu ihrem wirklichen Lebensende zu nutzen, ist es von großer Bedeutung, den aktuellen Grad der Schädigung einer Struktur bestimmen zu können. Mithilfe der zurzeit gültigen Nachweis- und Bemessungskonzepte (z.B. CEB-FIP Model Code 2010) ist dies nicht möglich. Ein gangbarer Weg, den Schädigungsgrad einer Betonstruktur vor Ort zu bestimmen, ist der Einsatz von zerstörungsfreien Prüfmethoden (Monitoring). Dieser Bereich ist allerdings noch nicht zur Gänze erforscht. Das konstante Monitoring von der Entstehung eines Bauwerks bis hin zu dessen Lebensende wird als eine vielversprechende Möglichkeit der Lebenszeitabschätzung gesehen. In diesem Beitrag werden Ermüdungsversuche an Betonprüfkörpern, begleitet mit konstantem Monitoring durch Ultraschall- und Körperschall-Sensoren, näher betrachtet und ein möglicher Weg zur Bestimmung des Schädigungsgrades und der Lebenszeitabschätzung aufgezeigt.

Monitoring based lifetime assessment of concrete structures - Research Project MOSES
In order to use structures up to their real end of lifetime it is of great importance to know the degree of damage of the structure. By using the actual Codes and Specifications (e.g. CEB-FIP Model Code 2010) it is not possible to define the real degree of deterioration. A practicable way of determining the degree on-site is the employment of non-destructive testing methods (monitoring). This field until now is not finally explored. The constant monitoring from the erection of a structure up to the end of its lifetime is seen as a very promising possibility to assess the residual lifetime. In this article fatigue tests on concrete specimens, accompanied with ultrasonic and acoustic emission measurements will be investigated closer and a possible way for the determination of the degree of damage and lifetime assessment will be proposed.

• 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”

Fibre-reinforced concrete (FRC) without any traditional reinforcement is used particularly extensively in structures such as pavements and tunnels. The fib Model Code for Concrete Structures 2010 introduced the possibility of using FRC for structural design and it is becoming a reference document for such structures. The application of fib Model Code 2010 suggestions for flexural and axial forces, once the constitutive relationships of the material are defined, allows for safe design. However, shear verification is often a cause of discussion in the design community. The aim of this paper is to clarify this aspect and provide a procedure that can be followed in the design process. A case study is also presented.

This paper focuses on the reliability of the design approach proposed in the fib Model Code for Concrete Structures 2010 for estimating the ultimate capacity of fibre-reinforced concrete (FRC) elevated slabs on the basis of different tests for material characterization. The fracture properties of the material are determined through three-point bending tests on notched beams and through double edge wedge splitting (DEWS) tests carried out on cylinders cored in the full-size test structure. As a case study, an FRC elevated flat slab 0.2 m thick is considered which consists of nine bays (panels) measuring 6 × 6 m (overall size 18.3 × 18.3 m) and is supported by 16 circular concrete columns. The ultimate bearing capacity of the slab determined experimentally is compared with the design value predicted by means of a procedure based on limit analysis following fib Model Code 2010. The results show that the method proposed in fib Model Code 2010 using the characteristic values and the classification is reliable. Even if the tests are affected by a significant standard deviation and the two experimental campaigns with three-point bending tests give a significant difference between class “5c” and class “3e”, the structural test results in a loadbearing capacity that is always larger than the predicted one, which considers a safety coefficient for the material &ggr;F = 1.5.

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 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.

At present, prescriptive regulations with regard to concrete cover and composition are applied to provide sufficient durability of reinforced concrete members under exposure conditions with different degrees of severity. In view of current knowledge on deterioration mechanisms and their modelling, it is planned to change from these deemed-to-satisfy specifications to a performance-based design approach in future standards. In such specifications, concrete durability design is based on the statistically characterized performance of concrete, determined in standardized tests with respect to defined classes of concretes with similar performance.
This paper presents the results of a study in which concrete mixes were tested and analysed with respect to their carbonation resistance. Compositions with similar performance are grouped into carbonation resistance classes. These classes are described statistically and requirements for performance testing are given. In addition, composition requirements are introduced in order to determine concrete performance depending on mix composition prescriptively. Finally, an example is given for the assessment of concrete performance with regard to carbonation.
This work was carried out at the request of JWG under CEN TC 250/SC2 and CEN TC 104/SC1 as an input and starting point for the ongoing committee work to implement the methodology from the fib Model Code for Concrete Structures 2010 in the next generation (2021) of European concrete standards.

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.

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.

When reinforcing bars are post-installed in holes drilled in cured concrete, adhesive mortars are used to create a bond between concrete and bars. Appropriate adhesives can develop higher bond strengths than standard ribbed bars cast into concrete. A detailed design concept for the anchorage length of reinforcing bars has been developed by taking into account splitting/spalling of the concrete and pullout. Pullout and splitting tests on reinforcing bars set in concrete were carried out with different adhesive mortars and with varying concrete strengths and concrete covers. When higher bond strengths than those recommended for cast-in reinforcement are taken into account, it is important to check deformations and crack widths at the serviceability limit state (SLS) separately. For this reason, structural tests on slabs and corbels were carried out. Moreover, pullout tests on post-installed reinforcing bars were performed in order to measure displacements at service load level.

Eurocode 2 and the corresponding National Annex were introduced in Germany in 2012. Most of the design provisions for these new standards were adopted from Model Code 1990 and provide a new design approach for ground slabs and footings. For the fib Model Code for Concrete Structures 2010, the punching shear design concept has been revised and introduced in Swiss standard SIA262:2013. This paper presents in detail the design equations for determining the punching capacity according to Eurocode 2, the German National Annex to Eurocode 2, fib Model Code 2010 and SIA 262:2013.
Parametric studies have been used to examine the influence of the main parameters (shear span-depth ratio, effective depth, longitudinal reinforcement ratio and concrete compressive strength) on the punching shear resistance of footings. To quantify the level of safety and the efficiency, the design provisions are compared with systematic test series.

The fib Model Code for Concrete Structures 2010 introduces a new design concept for punching shear based on critical shear crack theory. This paper presents and provides the background to the design provisions for punching shear according to fib Model Code 2010, Eurocode 2 and the corresponding German National Annex to Eurocode 2. The different punching shear design provisions are critically reviewed by means of parameter studies and a comparison of the calculated resistances and test results. The safety levels of the code provisions are verified and the influence of the different punching parameters on the calculated resistances is examined in detail.

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.