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Author: fib Fédération internationale du béton
Publisher: FIB - Féd. Int. du Béton
ISBN: 2883941254
Category : Technology & Engineering
Languages : en
Pages : 354
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Book Description
Reliable performance of beams and slabs in shear is essential for the safety and also for the serviceability of reinforced concrete structures. A possible failure in shear is usually a brittle failure, which underlines the importance of the correct specification of the load carrying capacity in shear. The knowledge of performance in shear is steadily developing and it is now obvious that older structures were not always designed in accordance with contemporary requirements. The increasing load – mainly on bridges – requires the assessment of existing structures, often followed by their strengthening. An appropriate understanding of actual performance of concrete structures in shear is therefore of primary interest. The workshop which was held in Zürich in 2016 brought together a significant number of outstanding specialists working in the field of shear design, who had a chance to exchange their opinions and proposals for improving the current knowledge of shear behaviour in beams and slabs. The specialists came from different parts of the world, which made the workshop general and representative. The workshop was organised by fib Working Party 2.2.1 “Shear in Beams” (convened by O. Bayrak), which is a part of fib Commission 2 "Analysis and Design". Individual contributions mainly address shear in beams with low transversal reinforcement. It is crucial because many existing structures lack such reinforcement. Different theories, e.g. Critical Shear Crack Theory (CSCT), Modified Compression Field Theory (MCFT), Multi-Action Shear Model (MASM), etc. were presented and compared with procedures used in selected national codes or in the fib Model Code 2010. The models for shear design were often based to a great extent on empirical experience. The refined presented models tend to take into account the physical mechanisms in structures more effectively. A brittle behaviour in shear requires not only to check the equilibrium and failure load, but also to follow the progress of failure, including the crack development and propagation, stress redistribution, etc. The significance of the size effect – which causes the nominal strength of a large structure to be smaller than that of a small structure – was pointed out. Nowadays, the fibre reinforcement is used more than before since it allows significant labour costs savings in the construction industry. The contribution of fibres is suitable for shear transfer. It is very convenient that not only ordinary fibre reinforced elements were addressed but also the UHPFRC beams. The production of this new material is indeed growing, while the development of design recommendations has not been sufficiently fast. Fatigue resistance of structures with low shear reinforcement is also an important issue, which was also addressed in this bulletin. It cannot be neglected in prestressed bridges, which are exposed to dynamic loads. A comprehensive understanding of the shear behaviour is necessary. Although many laboratory experiments are carried out, they are suitable only to a limited extent. New testing methods are being developed and show promising results, e.g. digital image correlation. An actual structure performance should rather be tested on a large scale, ideally on real structures under realistic loading conditions.ii The papers presented in the bulletin are a basis for the discussion in view of the development of updated design rules for the new fib Model Code (MC2020), which is currently under preparation. fib Bulletins like this one, dealing with shear, help to transfer knowledge from research to design practice. The authors are convinced that it will lead to better new structures design of as well as to savings and to a safety increase in older existing structures, whose future is often decided now.
Author: fib Fédération internationale du béton
Publisher: FIB - Féd. Int. du Béton
ISBN: 2883941254
Category : Technology & Engineering
Languages : en
Pages : 354
Get Book Here
Book Description
Reliable performance of beams and slabs in shear is essential for the safety and also for the serviceability of reinforced concrete structures. A possible failure in shear is usually a brittle failure, which underlines the importance of the correct specification of the load carrying capacity in shear. The knowledge of performance in shear is steadily developing and it is now obvious that older structures were not always designed in accordance with contemporary requirements. The increasing load – mainly on bridges – requires the assessment of existing structures, often followed by their strengthening. An appropriate understanding of actual performance of concrete structures in shear is therefore of primary interest. The workshop which was held in Zürich in 2016 brought together a significant number of outstanding specialists working in the field of shear design, who had a chance to exchange their opinions and proposals for improving the current knowledge of shear behaviour in beams and slabs. The specialists came from different parts of the world, which made the workshop general and representative. The workshop was organised by fib Working Party 2.2.1 “Shear in Beams” (convened by O. Bayrak), which is a part of fib Commission 2 "Analysis and Design". Individual contributions mainly address shear in beams with low transversal reinforcement. It is crucial because many existing structures lack such reinforcement. Different theories, e.g. Critical Shear Crack Theory (CSCT), Modified Compression Field Theory (MCFT), Multi-Action Shear Model (MASM), etc. were presented and compared with procedures used in selected national codes or in the fib Model Code 2010. The models for shear design were often based to a great extent on empirical experience. The refined presented models tend to take into account the physical mechanisms in structures more effectively. A brittle behaviour in shear requires not only to check the equilibrium and failure load, but also to follow the progress of failure, including the crack development and propagation, stress redistribution, etc. The significance of the size effect – which causes the nominal strength of a large structure to be smaller than that of a small structure – was pointed out. Nowadays, the fibre reinforcement is used more than before since it allows significant labour costs savings in the construction industry. The contribution of fibres is suitable for shear transfer. It is very convenient that not only ordinary fibre reinforced elements were addressed but also the UHPFRC beams. The production of this new material is indeed growing, while the development of design recommendations has not been sufficiently fast. Fatigue resistance of structures with low shear reinforcement is also an important issue, which was also addressed in this bulletin. It cannot be neglected in prestressed bridges, which are exposed to dynamic loads. A comprehensive understanding of the shear behaviour is necessary. Although many laboratory experiments are carried out, they are suitable only to a limited extent. New testing methods are being developed and show promising results, e.g. digital image correlation. An actual structure performance should rather be tested on a large scale, ideally on real structures under realistic loading conditions.ii The papers presented in the bulletin are a basis for the discussion in view of the development of updated design rules for the new fib Model Code (MC2020), which is currently under preparation. fib Bulletins like this one, dealing with shear, help to transfer knowledge from research to design practice. The authors are convinced that it will lead to better new structures design of as well as to savings and to a safety increase in older existing structures, whose future is often decided now.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - Féd. Int. du Béton
ISBN: 2940643008
Category : Technology & Engineering
Languages : en
Pages : 2322
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Book Description
This Proceedings contains the papers of the fib Symposium “CONCRETE Innovations in Materials, Design and Structures”, which was held in May 2019 in Kraków, Poland. This annual symposium was co-organised by the Cracow University of Technology. The topics covered include Analysis and Design, Sustainability, Durability, Structures, Materials, and Prefabrication. The fib, Fédération internationale du béton, is a not-for-profit association formed by 45 national member groups and approximately 1000 corporate and individual members. The fib’s mission is to develop at an international level the study of scientific and practical matters capable of advancing the technical, economic, aesthetic and environmental performance of concrete construction. The fib, was formed in 1998 by the merger of the Euro-International Committee for Concrete (the CEB) and the International Federation for Prestressing (the FIP). These predecessor organizations existed independently since 1953 and 1952, respectively.
Author: Jan Wastiels
Publisher: MDPI
ISBN: 3039283308
Category : Technology & Engineering
Languages : en
Pages : 284
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Book Description
This Special Issue presents the latest advances in the field of Textile-Reinforced Cement Composites, including Textile-Reinforced Concrete (TRC), Textile-Reinforced Mortar (TRM), Fabric-Reinforced Cementitious Matrix (FRCM), etc. These composite materials distinguish themselves from other fibre-reinforced concrete materials by their strain-hardening behaviour under tensile loading. This Special Issue is composed of 14 papers covering new insights in structural and material engineering. The papers include investigations on the level of the fibre reinforcement system as well as on the level of the composites, investigating their impact and fatigue behaviour, durability and fire behaviour. Both the strengthening of existing structures and the development of new structural systems such as lightweight sandwich systems are presented, and analysis and design methods are discussed. This Special Issue demonstrates the broadness and intensity of the ongoing advancements in the field of Textile-Reinforced Cement composites and the importance of several future research directions.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - International Federation for Structural Concrete
ISBN: 2883941459
Category : Technology & Engineering
Languages : en
Pages : 118
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Book Description
The concept of post-tensioning has been recognized for over a century. Interestingly, early developments started with external tendons, but failed to be recognized as a major construction technique for two main reasons: - Low tensile performance of early steels in combination with a poor knowledge of concrete creep and shrinkage properties, - Lack of a durable corrosion protection. With the technological progress, external tendons became increasingly popular in the 1980’s, as a post-tensioning method enabling inspection and, if necessary, replacement of tendons without demolition of structural members. Towards the end of the last century, more than 50 bridges have been built with external tendons, first in France and soon gaining traction in other countries. FIP published a state-of the-art report in May 1996 to provide a review of the application of external tendons, describing specific material problems and methods for dealing with them. 25 years have passed and, while the engineering principles covered by the FIP report remain unchanged, the context has evolved: - External tendons and construction methods have kept evolving with better materials, ever longer spans, and tighter schedules. - Normalization frame in Europe changed, Severe durability issues have occurred in some countries from which the industry can extract good knowledge of the causes and how to avoid similar problems in the future. This new fib bulletin has been prepared with the aim to reflect the current state of the art and encompass the knowledge amassed in the last quarter of century with chapters covering from the design and approval of systems and materials to installation, quality control and monitoring. The last chapter is a compilation of structures worldwide covering all sorts of materials, typologies and construction methods, which might be a source of inspiration for owners and designers alike.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - International Federation for Structural Concrete
ISBN: 2883941475
Category : Technology & Engineering
Languages : en
Pages : 116
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Book Description
Since the Second World War the demand of energy has undergone an exponential growth that has led to a sharp annual increase in the use of natural gas in both, cities and thermal power stations. Nowadays, the strategic relevance of natural gas as a main source of energy is evident with a contribution of more than 20% of the total world consumption. This development in increasing demand of natural gas has led for a need of suitable storage and transportation infrastructure. Various gases, especially hydrocarbons, are preferably stored in liquid form for transportation and storage since the phase transformation from gas to liquid comes with a significant reduction of the volume (e.g. up to 600 times). Gases can be liquefied by raising the pressure or by cooling to their boiling point, which for most gases is below 0°C. This is known as cryogenic storage. The term cryogenic is derived from two Greek words, namely kryos meaning icy-cold and genes which can be translated as shape. These fib recommendations are concerned about post-tensioning systems used in cryogenic tanks and have been formulated on the basis of actual available knowledge with the aim to reflect the current state of the art. Consequently, these recommendations have included a classification of the different cryogenic tanks typologies used in the past and nowadays, the associated different tendon types depending on their exposure to low temperature (e.g. never, only accidentally or during normal tank operation) and the testing regime required for acceptance of the materials and the post-tensioning system according to this document. An international working group comprising more than 20 experts from administrative authorities, universities, laboratories, owners, structural designers, suppliers of prestressing steels and post-tensioning systems suppliers have actively contributed in order to develop these recommendations. This text has been written to cover best construction practices around the world, and to provide material specifications which are considered to be the most advanced available at the time of preparing this text. For ease of use (for Owner, Designer and Post-tensioning System Supplier), the content has been arranged systematically according to the system components into chapters focusing on performance characteristics, requirements and acceptance criteria.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - International Federation for Structural Concrete
ISBN: 2883941637
Category : Technology & Engineering
Languages : en
Pages : 326
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Book Description
Structural behavior of reinforced concrete elements strongly depends on the interaction between the reinforcing bars and the surrounding concrete, which is generally referred as “bond in concrete”. In service conditions, the reinforcement-to-concrete bond governs deformability through the tension stiffening of concrete surrounding the bar as well the crack development and crack width. At Ultimate Limit State, bond governs anchorage and lap splices behavior as well as structural ductility. When plain (smooth) bars were used, the steel-to-concrete bond was mainly associated with “chemical adhesion/friction” that is related to the surface roughness of the rebar. As steel strengths increased the need to enhance interaction between steel and the surrounding concrete was recognized, and square twisted rebars, indented rebars or, later on, ribbed rebars came into the market, the latter being the type of deformed bar most commonly adopted since the 1960/70s. When ribbed rebars became widely used, several research studies started worldwide for better understanding the interaction between ribs and the surrounding concrete. Researchers evidenced the development of micro-cracks (due to the wedge action of the ribs) towards the external face of the structural element. If confinement is provided by the concrete cover, by transverse reinforcement or by an external transverse pressure, the full-anchorage capacity is guaranteed and a pull-out failure occurs, with crushing of concrete between the ribs. On the contrary, with lesser confining action, a splitting failure of bond occurs; the latter may provoke a brittle failure of the lap splice or, in some cases, of anchorages. However, after many years of research studies on bond-related topics, there are still several open issues. In fact, new materials entered into the market, as concrete with recycled aggregates or fibre reinforced concrete; the latter, having a kind of distributed reinforcement into the matrix (the fibres), provides a better confinement to the wedge action of the ribs. In addition, concrete and steel strength continuously increased over the years, causing changes in the bond behavior due to differences in mechanical properties of materials but also to the different concrete composition at the interface with the steel rebar causing a different bond behavior. Moreover, the lower water/cement ratio of these high-strength concrete makes the bleeding phenomena less evident, changing the concrete porosity in the upper layers of the structural element and thus making the current casting position parameters no-longer reliable. Finally, concrete with recycled aggregates are becoming more important in a market that is looking forward to a circular economy. As such, all the experimental results and database that allowed the calibration of bond rules now present in building codes for conventional concrete, may be not be representative of these new types of materials nowadays adopted in practice. Furthermore, after more than 50 years of service life, structural elements may not satisfy the current safety requirements for several reasons, including material degradation (with particular reference to steel corrosion) or increased loads, by also considering the seismic actions that were non considered by building codes at the time of the original design. The structural assessment of existing structures requires proper conceptual models and new approaches for evaluating the reliability of existing structures by also considering the remaining expected service life. In addition, specific rules for older materials, as plain smooth bars, should be revised for a better assessment of old structures. Last, but not least, interventions in existing structures may require new technologies now available such as post-installed rebars. While many advances have been achieved, there remain areas where a better understanding of bond and its mechanisms are required, and where further work is required to incorporate this understanding into safe and economic rules to guide construction and maintenance of existing infrastructures. These aspects were widely discussed within the technical community, particularly in the fib Task Group 2.5 and in the ACI 408 Committee dealing with bond and anchorage issues. Furthermore, special opportunities for discussing bond developments were represented by the International Conferences on ‘Bond in Concrete’ held each decade since 1982 as well as by joint workshops organized by fib TG2.5 and ACI 408. Within this technical collaboration, this Bulletin was conceived, and, thus, it collects selected papers presented at the joint fib-ACI Convention Session on Bond in Concrete held in Detroit (USA) in 2017. The bulletin is based on four main Sections concerning: - General aspects of bond - Anchorages and laps of bars and prestressing tendons - Bond under severe conditions - Degradation of bond for corrosion - Bond in new types of concrete The main aim of the Bulletin is to shed some new lights on the advances in understanding and application of bond related issues achieved over the last few years, and identify the challenges and priorities to be addressed in the next years. Another important aspect of the bulletin is to provide practical information from research findings.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - International Federation for Structural Concrete
ISBN: 2883941416
Category : Technology & Engineering
Languages : en
Pages : 555
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Book Description
The first international FRC workshop supported by RILEM and ACI was held in Bergamo (Italy) in 2004. At that time, a lack of specific building codes and standards was identified as the main inhibitor to the application of this technology in engineering practice. The workshop aim was placed on the identification of applications, guidelines, and research needs in order for this advanced technology to be transferred to professional practice. The second international FRC workshop, held in Montreal (Canada) in 2014, was the first ACI-fib joint technical event. Many of the objectives identified in 2004 had been achieved by various groups of researchers who shared a common interest in extending the application of FRC materials into the realm of structural engineering and design. The aim of the workshop was to provide the State-of-the-Art on the recent progress that had been made in term of specifications and actual applications for buildings, underground structures, and bridge projects worldwide. The rapid development of codes, the introduction of new materials and the growing interest of the construction industry suggested presenting this forum at closer intervals. In this context, the third international FRC workshop was held in Desenzano (Italy), four years after Montreal. In this first ACI-fib-RILEM joint technical event, the maturity gained through the recent technological developments and large-scale applications were used to show the acceptability of the concrete design using various fibre compositions. The growing interests of civil infrastructure owners in ultra-high-performance fibre-reinforced concrete (UHPFRC) and synthetic fibres in structural applications bring new challenges in terms of concrete technology and design recommendations. In such a short period of time, we have witnessed the proliferation of the use of fibres as structural reinforcement in various applications such as industrial floors, elevated slabs, precast tunnel lining sections, foundations, as well as bridge decks. We are now moving towards addressing many durability-based design requirements by the use of fibres, as well as the general serviceability-based design. However, the possibility of having a residual tensile strength after cracking of the concrete matrix requires a new conceptual approach for a proper design of FRC structural elements. With such a perspective in mind, the aim of FRC2018 workshop was to provide the State-of-the-Art on the recent progress in terms of specifications development, actual applications, and to expose users and researchers to the challenges in the design and construction of a wide variety of structural applications. Considering that at the time of the first workshop, in 2004, no structural codes were available on FRC, we have to recognize the enormous work done by researchers all over the world, who have presented at many FRC events, and convinced code bodies to include FRC among the reliable alternatives for structural applications. This will allow engineers to increasingly utilize FRC with confidence for designing safe and durable structures. Many presentations also clearly showed that FRC is a promising material for efficient rehabilitation of existing infrastructure in a broad spectrum of repair applications. These cases range from sustained gravity loads to harsh environmental conditions and seismic applications, which are some of the broadest ranges of applications in Civil Engineering. The workshop was attended by researchers, designers, owner and government representatives as well as participants from the construction and fibre industries. The presence of people with different expertise provided a unique opportunity to share knowledge and promote collaborative efforts. These interactions are essential for the common goal of making better and sustainable constructions in the near future. The workshop was attended by about 150 participants coming from 30 countries. Researchers from all the continents participated in the workshop, including 24 Ph.D. students, who brought their enthusiasm in FRC structural applications. For this reason, the workshop Co-chairs sincerely thank all the enterprises that sponsored this event. They also extend their appreciation for the support provided by the industry over the last 30 years which allowed research centers to study FRC materials and their properties, and develop applications to making its use more routine and accepted throughout the world. Their important contribution has been essential for moving the knowledge base forward. Finally, we appreciate the enormous support received from all three sponsoring organizations of ACI, fib and Rilem and look forward to paving the path for future collaborations in various areas of common interest so that the developmental work and implementation of new specifications and design procedures can be expedited internationally.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - International Federation for Structural Concrete
ISBN: 2883941572
Category : Technology & Engineering
Languages : en
Pages : 338
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Book Description
The idea of preparing a technical document for the repairs and interventions upon concrete structures goes back to the former fib COM 5: Structural Service Life Aspects, being the goal of the then TG 5.9. After a long period of reduced activity, and taking into account the reorganization of fib commissions that meanwhile took place, on June 2017 a different approach was proposed to push forward the task of TG 8.1 (formerly TG 5.9). The (new) goal of TG 8.1 was to deliver a ‘how-to-do’ guide, gathering together protection, repair, and strengthening techniques for concrete structures. Chapters are intended to provide both guidelines and case-studies, serving as support to the application of fib MC 2020 pre-normative specifications. Each chapter was written by an editorial team comprising desirably at least a researcher, a designer and a contractor. Templates have been prepared in order to harmonize the contents and the presentation of the different methods. Following the writing process, chapters were reviewed by experts and, after amendments by the authors, they underwent a second review process by COM 8 and TG 3.4 members, as well as by different practitioners. For each protection, repair and strengthening method addressed in this guide, readers have a description of when to adopt it, which materials and systems are required, which techniques are available, and what kind of equipment is needed. It then presents a summary of stakeholders’ roles and qualifications, design guidelines referring to most relevant codes and references, the intervention procedure, quality control measures and monitoring and maintenance activities. Due to the extent of the guide, it was decided to publish it as bulletin 102, addressing protection and repair methods, and bulletin 103, addressing strengthening methods. We would like to thank the authors, reviewers and members of COM 8 and TG 3.4 for their work in developing this fib Bulletin, which we hope will be useful for professionals working in the field of existing concrete structures, especially those concerned with life-cycle management and conservation activities. As noted above, this Bulletin is also intended to act as a background and supporting document to the next edition of the fib Model Code for Concrete Structures, which is currently under development under the auspices of TG10.1 with the working title of ‘fib Model Code 2020’.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - International Federation for Structural Concrete
ISBN: 2883941610
Category : Technology & Engineering
Languages : en
Pages : 461
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Book Description
Fibre Reinforced Concrete (FRC) is a composite material characterized by an enhanced post-cracking tensile residual strength, due to the capacity of fibres to bridge the crack faces by means of pull-out mechanism. Due to a better knowledge of FRC and the recent developments worldwide of guidelines for structural design, the fib Special Activity Group 5, who prepared the new fib Model Code, decided to introduce some sections on new materials and in particular on FRC structural design. At that time, working Groups TG 8.3 (“Fibre reinforced concrete”) and TG 8.6 (“Ultra high performance fibre reinforced concrete”) of fib prepared these sections of the new fib Model Code concerning FRC design rules for providing a guidance to engineers to properly and safely design FRC structural elements, both at serviceability and at ultimate limit states, based on the state-of-the-art knowledge. This bulletin was written with the aim to share the main framework used by the two groups to introduce these two sections and to describe the many aspects already known, but not yet introduced in the Model Code. Even though the basic principles introduced in the two sections are mainly obtained from research on steel fibre reinforced concrete, the Model Code is open to every type of fibres, following a performance-based design approach. The bulletin represents a wide effort made by the people of the Task Group 4.1 and 4.2 to trace the knowledge on FRC and aims to be helpful for structural designers when using this new material in the practice.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - International Federation for Structural Concrete
ISBN: 2883941351
Category : Technology & Engineering
Languages : en
Pages : 219
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Book Description
Serviceability limit states are essential for appropriate function and durability of concrete structures. The attention is paid especially to the stress limitation, crack width analysis and deflection analysis. The document provides supplementary information to the fib Model Code 2010 (MC2010), where a limited space did not allow for a detailed description of individual procedures. The principles used in MC2010 in chapter 7.6 are explained in detail within this document. The stress analysis is focused on stresses in concrete and steel including the stress redistribution due to the long-term load and cracking of reinforced concrete and prestressed concrete elements. Crack width analysis explains the mechanism of cracking under mechanical loading and due to deformation restraint. Cracks in prestressed concrete elements are also discussed. Deflection analyses with different levels of accuracy are described including the shear effects. Examples illustrate the practical application of rules defined in the MC2010 of individual serviceability limit states. Simplified and more general methods are used. An important part of the bulletin shows the development and extension of the serviceability limit states after publishing of the MC2010 and alternative approaches. Special attention is paid to deflections of prestressed concrete beams, shear effects on deflection, slenderness limits and influence of the concrete cover. The final part deals with an application of numerical simulations.
