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Cairns, JohnStaggered lap joints for tension reinforcementStructural Concrete1/201445-54Technical Papers

Kurzfassung

Staggering lapped joints increases the complexity of detailing and steel fixing, and may require additional resources and slow construction on site. Major design codes encourage staggering lapped joints in tension by imposing a penalty on lap length depending on the proportion of bars lapped at the same section. There are, however, inconsistencies in the value of the coefficients to be applied, and little evidence is available for validation. A programme of 17 physical tests found no evidence of an increase in strength when laps were staggered, and when allowance is made for increases in transverse spacing, staggering was found to reduce lap strength. Differences in the distribution of bond stress through a lap joint and in the share of the tension force taken by continuous and lapped bars are demonstrated to be responsible for the reduction.

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Magnusson, Johan; Hallgren, Mikael; Ansell, AndersShear in concrete structures subjected to dynamic loadsStructural Concrete1/201455-65Technical Papers

Kurzfassung

Shear failures in reinforced concrete structures under intense dynamic loads are brittle and limit the structure's energy-absorbing capabilities. This paper comprises a review of the literature dealing with the problem of dynamic shear of reinforced concrete elements, with a focus on parameters that control flexural shear and direct shear. In this context, dynamic loads refer to intense events due to explosions and impacts. For this reason, the initial response is also highlighted. Experimental investigations and calculations show that shear force and bending moment distributions in dynamic events are initially significantly different from the distributions under slowly applied loads. Therefore, structural wave propagation, geometrical properties of elements, strain rate effects and dynamic load characteristics need to be considered when analysing shear. The review also indicates that arch action in the shear span soon after the load has been applied has a large influence on the shear capacity of an element. This action is of particular importance in intense loading events. Finally, suggestions for further research are identified.

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Liu, Xian; Jiang, Wei; De Schutter, Geert; Yuan, Yong; Su, QuankeEarly-age behaviour of precast concrete immersed tunnel based on degree of hydration conceptStructural Concrete1/201466-80Technical Papers

Kurzfassung

Using the Hong Kong-Zhuhai-Macao Link project as an example, the focus of this research is to describe the early-age behaviour of a precast immersed tunnel using a constitutive model based on the degree of hydration concept. In this way, the effect of both age and temperature on the early-age behaviour can be taken into account simultaneously. Special attention is also paid to early-age creep under varying stress levels combined with the degree of hydration concept. Numerical procedures are proposed to predict the early-age behaviour of immersed tunnel segments during the entire fabrication process. The engineering factors related to early-age cracking are analysed and discussed. This in-depth study results in a better understanding, and further appropriate practical measures can be employed to control early-age cracking in the actual project.

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Aboutalebi, Morteza; Alani, Amir M.; Rizzuto, Joseph; Beckett, DerrickStructural behaviour and deformation patterns in loaded plain concrete ground-supported slabsStructural Concrete1/201481-93Technical Papers

Kurzfassung

The work presented in this paper is considered to be an attempt to contribute towards a better understanding of the structural behaviour of plain concrete slabs under step loading conditions. The Concrete Society Technical Report TR34 “Concrete Industrial Ground Floors” is in its 3rd edition (2003) and is currently under review. TR34 covers the design of concrete ground-supported slabs containing fibres, both steel and synthetic, as an alternative to mesh reinforcement. This work reports on tests carried out at different critical loading locations, including the centre, edges and corners of a 6.0 × 6.0 × 0.15 m deep plain concrete slab. The test results are compared with theoretical values derived using available design codes and other information sources. The results show a notable difference between the test results and the theoretical values.

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Abbas, Ali A.; Mohsin, Sharifah M. Syed; Cotsovos, Demetrios M.Non-linear analysis of statically indeterminate SFRC columnsStructural Concrete1/201494-105Technical Papers

Kurzfassung

The structural behaviour of steel fibre-reinforced concrete (SFRC) has been studied using non-linear finite element analysis (NLFEA) and ABAQUS software. An interesting feature of this work is the consideration of statically indeterminate SFRC columns. Most of the SFRC specimens studied in the literature are simply supported beams, and information on statically indeterminate columns is sparse. In addition, both axial and lateral loads were considered in order to allow for compression and flexural effects on the columns. The aim of the work was to examine the potential for using steel fibres to reduce the amount of conventional transverse steel reinforcement without compromising ductility and strength requirements. To achieve this, the spacing between shear links was increased while steel fibres were added as a substitute (spacing between shear links increased by 50 and 100 % with fibre volume fraction Vf increased to Vf = 1, 1.5, 2 and 2.5 %). The numerical model was carefully calibrated against existing experimental data to ensure the reliability of its predictions. Parametric studies were subsequently carried out, which provided insight into how the steel fibres can help reduce the number of conventional shear links.

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fib-news: Structural Concrete 1/2014Structural Concrete1/2014106-113fib-news

Kurzfassung

2014 fib Congress, Mumbai; 2014 Freyssinet Medals; ConLife and 70th anniversary of NIISK ; fibUK seminar report; 20th anniversary of CBS; Report from the Spanish NMG; 2015 fib Symposium; fib Bulletins; Congresses and symposia.

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Contents: Structural Concrete 4/2013Structural Concrete4/2013Contents

Kurzfassung

Keine Kurzfassung verfügbar.

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Müller, Harald S.Sustainable structural concrete - from today's approach to future challengeStructural Concrete4/2013299-300Editorial

Kurzfassung

Keine Kurzfassung verfügbar.

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Sakai, KojiSustainability in fib Model Code 2010 and its future perspectiveStructural Concrete4/2013301-308Technical Papers

Kurzfassung

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.

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Bigaj-van Vliet, Agnieszka; Vrouwenvelder, TonReliability in the performance-based concept of fib Model Code 2010Structural Concrete4/2013309-319Technical Papers

Kurzfassung

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.

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Müller, Harald S.; Anders, Isabel; Breiner, Raphael; Vogel, MichaelConcrete: treatment of types and properties in fib Model Code 2010Structural Concrete4/2013320-334Technical Papers

Kurzfassung

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

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Triantafillou, Thanasis; Matthys, StijnFibre-reinforced polymer reinforcement enters fib Model Code 2010Structural Concrete4/2013335-341Technical Papers

Kurzfassung

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.

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di Prisco, Marco; Colombo, Matteo; Dozio, DanieleFibre-reinforced concrete in fib Model Code 2010: principles, models and test validationStructural Concrete4/2013342-361Technical Papers

Kurzfassung

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.

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Matthews, Stuart; Bigaj-van Vliet, AgnieszkaConservation of concrete structures according to fib Model Code 2010Structural Concrete4/2013362-377Technical Papers

Kurzfassung

Conservation of concrete structures forms an essential part of the fib Model Code for Concrete Structures 2010 (fib Model Code 2010). In particular, Chapter 9 of fib Model Code 2010 addresses issues concerning conservation strategies and tactics, conservation management, condition surveys, condition assessment, condition evaluation and decision-making, making interventions and the recording of information for through-life management.
Chapter 9 incorporates the overall philosophy adopted in the development of fib Model Code 2010, which introduces a new integrated life cycle perspective into the design of concrete structures. Accordingly, Chapter 9 provides a response to concepts introduced earlier within fib Model Code 2010 relating to the service life design process, which requires the structure and its component parts to be allocated to a condition control category at the time of design. Different condition control categories are defined depending on factors such as the importance of the structure, its function, design service life, impact on third parties, environmental conditions, ease of maintenance and cost. The condition control levels and inspection regimes are defined in conjunction with these requirements. A through-life management process, outlined in Chapter 9, provides feedback for service life design and allows the associated theoretical model employed to be updated, in turn facilitating the assessment of compliance with the original design objectives.
An example of concrete structure conservation according to the fib Model Code 2010 concept is also presented.

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Phan, Thanh Song; Tailhan, Jean-Louis; Rossi, Pierre3D numerical modelling of concrete structural element reinforced with ribbed flat steel rebarsStructural Concrete4/2013378-388Technical Papers

Kurzfassung

Construction company MATIERE has developed a new type of reinforcement based on ribbed flat steel in recent years. The objective of the present work is to obtain information about the bending behaviour of RC structural elements reinforced with these ribbed flat steel bars and also about the cracking process they induce (number of cracks and crack opening), especially at the serviceability limit state. The structural element chosen for this work is a small slab-beam (330 × 15 × 80 cm) subjected to three-point central bending. Concurrent with this experimental study, a 3D finite element model was developed at IFSTTAR to consolidate the experimental results. It appears that the numerical modelling strategy chosen in this work is relevant for analysing both the bending behaviour of an RC structural element and its cracking process.

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Silva, Ricardo; Faria, Duarte M. Viúla; Ramos, A. Pinho; Inácio, MicaelA physical approach for considering how anchorage head size influences the punching capacity of slabs strengthened with vertical steel boltsStructural Concrete4/2013389-400Technical Papers

Kurzfassung

The introduction of new vertical steel bolts is an easy, practical and common solution for retrofitting and strengthening slabs for punching. Although a common option where punching strengthening is concerned, few studies exist regarding how the bolt's anchorage dimensions and its embedment in the concrete slab affect the strengthening efficiency. This work presents an analytical approach that is able to predict the punching capacity of slabs strengthened with post-installed vertical steel bolts, taking into account the anchorage dimensions and positioning plus the material properties. This approach results from the combination of two physical models: one provided in the fib Model Code for Concrete Structures 2010 regarding the punching capacity estimation, and another that allows the deformation (crushing) of the concrete beneath the head of the anchorage to be taken into account. The predicted values are compared with experimental results, showing that the analytical approach is able to simulate correctly the anchorage behaviour and its influence regarding a slab's loadbearing capacity. A parametrical analysis is carried out in order to study the importance of different factors such as concrete compressive strength, longitudinal reinforcement ratio and steel bolt length, always accompanied by the effect of anchorage head size and embedment.

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Sagaseta, JuanThe influence of aggregate fracture on the shear strength of reinforced concrete beams: an experimental and analytical research projectStructural Concrete4/2013401-414Technical Papers

Kurzfassung

High-performance concretes such as high-strength concrete (HSC) or lightweight aggregate concrete (LWAC) are generally used to reduce member sizes and self-weight, and to optimize the construction of reinforced concrete structures. The bond between the aggregate particles and the cement paste can be strong enough in HSC and LWAC to cause the aggregate to fracture at cracks, which in turn reduces the shear stress that can be transferred across cracks by means of aggregate interlock. Relatively smooth cracks can also develop in self-compacting concrete due to the low coarse aggregate content. The contribution of aggregate interlock to the shear strength of RC beams is uncertain and depends on parameters such as the amount of shear reinforcement or the contribution of arching action for loads applied close to the support. Existing tests on slender RC beams without shear reinforcement have shown that shear strength is reduced by aggregate fracture. However, there is a lack of similar test data for members with stirrups and for members with varying shear span/effective depth ratios. This paper reviews the findings and contributions in this area from the experimental and analytical research of the author's PhD thesis, which was awarded the fib Achievement Award for Young Engineers in 2011.

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Lu, Xilin; Yin, Xiaowei; Jiang, HuanjunRestoring force model for steel reinforced concrete columns with high steel ratioStructural Concrete4/2013415-422Technical Papers

Kurzfassung

Key points on the load-displacement skeleton curves of steel reinforced concrete (SRC) composite cantilever columns are established based on the experimental results in the literature. Influencing parameters such as the ratio of encased steel, the transverse reinforcement characteristic value, the size of the cross-section, etc. are considered in the study. A degrading trilinear restoring force model applicable to SRC columns with an encased steel ratio of 10-20% is suggested. The main results show that the influencing parameters have different effects on the values of key points. The proposed restoring force model, which considers various influencing parameters, can predict the test results more accurately and can be applied to the non-linear dynamic analysis of structures with such SRC column types.

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2013 reviewersStructural Concrete4/2013423Reviewers

Kurzfassung

A list of referees who have reviewed papers for Structural Concrete in 2013. Ernst & Sohn and fib are very grateful for their assistance.

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fib-news: Structural Concrete 4/2013Structural Concrete4/2013424-433fib-news

Kurzfassung

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

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Contents: Structural Concrete 3/2013Structural Concrete3/2013Contents

Kurzfassung

Keine Kurzfassung verfügbar.

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Foster, StephenPhysical understandings and development of mechanical models for the design of concrete structuresStructural Concrete3/2013193-194Editorial

Kurzfassung

Keine Kurzfassung verfügbar.

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Sigrist, Viktor; Bentz, Evan; Ruiz, Miguel Fernández; Foster, Stephen; Muttoni, AurelioBackground to the fib Model Code 2010 shear provisions - part I: beams and slabsStructural Concrete3/2013195-203Technical Papers

Kurzfassung

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.

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Muttoni, Aurelio; Ruiz, Miguel Fernández; Bentz, Evan; Foster, Stephen; Sigrist, ViktorBackground to fib Model Code 2010 shear provisions - part II: punching shearStructural Concrete3/2013204-214Technical Papers

Kurzfassung

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.

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Fardis, Michael N.Performance- and displacement-based seismic design and assessment of concrete structures in fib Model Code 2010Structural Concrete3/2013215-229Technical Papers

Kurzfassung

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.

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