Effect of zinc on prestressing steel PDF Download
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Author: fib Fédération internationale du béton
Publisher: fib Fédération internationale du béton
ISBN: 2883941041
Category : Technology & Engineering
Languages : en
Pages : 28
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Book Description
Concerns have been raised regarding the durability of galvanized prestressing steels in contact with cementitious grout, and regarding the use of galvanized ducts for grouted tendons or galvanized inserts or components in contact with prestressing steel inside concrete. These concerns are mainly based on the assumption that the hydrogen formed on the zinc surface when exposed to the fresh cementitious grout for a short period of time represents a risk of hydrogen induced stress corrosion for the prestressing steel. Basic research has demonstrated that hydrogen induced stress corrosion may indeed occur with prestressing steels which are sensitive to hydrogen induced stress corrosion. The use of galvanizing for high strength steels exposed to atmosphere is less controversial. However, under certain conditions hydrogen may develop also and potentially damage the high strength steel. This report provides a summary and evaluation of the relevant parameters on the corrosion behaviour of high strength wires, strands and bars when in contact with zinc with and without the presence of fresh cementitious grout or concrete. Both, tendons made of prestressing steels used in structural concrete and cables under atmospheric conditions are considered. The main groups of applications discussed in the report are: A Zinc-coated high strength steel for applications in atmospheric corrosion conditions B Zinc-coated prestressing steel embedded in fresh cementitious grout or concrete C Bare prestressing steel (no zinc coating) embedded in fresh cementitious grout or concrete in direct contact with, or indirect contact in the immediate vicinity of galvanized components embedded in the grout or concrete (e.g. galvanized ducts, galvanized reinforcing steel, galvanized fastenings / dowels, etc).
Author: fib Fédération internationale du béton
Publisher: fib Fédération internationale du béton
ISBN: 2883941041
Category : Technology & Engineering
Languages : en
Pages : 28
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Book Description
Concerns have been raised regarding the durability of galvanized prestressing steels in contact with cementitious grout, and regarding the use of galvanized ducts for grouted tendons or galvanized inserts or components in contact with prestressing steel inside concrete. These concerns are mainly based on the assumption that the hydrogen formed on the zinc surface when exposed to the fresh cementitious grout for a short period of time represents a risk of hydrogen induced stress corrosion for the prestressing steel. Basic research has demonstrated that hydrogen induced stress corrosion may indeed occur with prestressing steels which are sensitive to hydrogen induced stress corrosion. The use of galvanizing for high strength steels exposed to atmosphere is less controversial. However, under certain conditions hydrogen may develop also and potentially damage the high strength steel. This report provides a summary and evaluation of the relevant parameters on the corrosion behaviour of high strength wires, strands and bars when in contact with zinc with and without the presence of fresh cementitious grout or concrete. Both, tendons made of prestressing steels used in structural concrete and cables under atmospheric conditions are considered. The main groups of applications discussed in the report are: A Zinc-coated high strength steel for applications in atmospheric corrosion conditions B Zinc-coated prestressing steel embedded in fresh cementitious grout or concrete C Bare prestressing steel (no zinc coating) embedded in fresh cementitious grout or concrete in direct contact with, or indirect contact in the immediate vicinity of galvanized components embedded in the grout or concrete (e.g. galvanized ducts, galvanized reinforcing steel, galvanized fastenings / dowels, etc).
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - International Federation for Structural Concrete
ISBN: 1874266263
Category : Technology & Engineering
Languages : en
Pages : 52
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Book Description
Author: fib Fédération internationale du béton
Publisher: fib Fédération internationale du béton
ISBN: 9782883940512
Category : Technology & Engineering
Languages : en
Pages : 24
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Book Description
Without doubt, active corrosion protection of prestressing steels by cement grout can be one of the most economic and durable solutions, if properly executed. Numerous other corrosion protection systems which fulfill requirements such as controllability and exchangeability are available. This state-of-the-art report, prepared by a task group and approved by fib Commission 9 Reinforcing and prestressing materials and systems, concentrates exclusively on factory applied corrosion protection that can be produced in controlled processes which should assure a better quality than corrosion protection applied on site. The report is addressed to designers and installers (executing persons) attempting to inform them about the various possibilities for industrially applied corrosion protection and to provide the necessary knowledge for their application.
Author: fib Fédération internationale du béton
Publisher: fib Fédération internationale du béton
ISBN: 2883941157
Category : Technology & Engineering
Languages : en
Pages : 183
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Book Description
The purpose of this recommendation - fib Bulletin 75: Polymer-duct systems for internal bonded post-tensioning - is to update and amend fib Bulletin 7:Corrugated plastic ducts for internal bonded post-tensioning, a technical report published in 2000. fib Bulletin 75 is meant as a cornerstone for the technical approval of polymer (plastic) ducts for internal bonded post-tensioning and possibly for the test procedures of a future testing standard. The updated bulletin includes new information on the design and detailing of concrete structures containing tendons with polymer ducts. The recommendation provides detailed test specifications for polymer materials, duct components and duct systems. In addition, the report contains recommendations for approval testing and attestations of conformity for polymer-duct systems. Although the new generation of corrugated polymer ducts for bonded post-tensioning have now been around for approximately twenty years, products still differ in material properties, geometrical detail, installation procedures and on-site use. Unlike corrugated steel ducts or smooth polyethylene (PE) pipes, they have not yet become standardized. It is the opinion of fib Task Group 9.16 and Commission 9 that these plastic ducts should, therefore, still be subjected to a systems approval process. This recommendation offers information acquired from twenty years of experience as well as new specifications that will, hopefully, lead to the standardization of polymer-duct systems.
Author: fib Fédération internationale du béton
Publisher: fib Fédération internationale du béton
ISBN: 288394055X
Category : Technology & Engineering
Languages : en
Pages : 279
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Book Description
In some countries durability problems with post-tensioning tendons have in the past led to fairly restrictive regulations. Improvements to execution procedures have been developed since, and new or improved prestressing systems have been proposed, too. This development was, of course, subject of discussions in fib Commission 9 Reinforcing and Prestressing Materials and Sytems and in IABSE Working Commission 3 Concrete Structures. It was decided to organise a workshop with the aim to review the different aspects of the problems encountered and to discuss solutions available today. Keynote speakers from various countries were invited to contribute. Their papers are published in this bulletin, grouped together under the following themes: Inventory and condition (6 papers) Investigation and repair (5 papers) Technical progress (4 papers) Strategies for improvement (6 papers) Supported by the international federation for structural concrete fib, and the international association for bridge and structural engineering IABSE, the workshop took place on 15-16 November 2001 at Ghent University, celebrating the 75th anniversary of the Magnel Laboratory for Concrete Research, whose director also chaired the Scientific Committee and edited the bulletin. It needs to be emphasised that in the bulletin invited experts present their individual views. Although not yet discussed in any of the association's working bodies, the highly topical contents of the bulletin is believed to be of general interest to fib's members and to document a starting point for future work in this field. Therefore, the Council of fib agreed to exceptionally publish these papers within fib's series of Bulletins.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - International Federation for Structural Concrete
ISBN: 0721012205
Category : Technology & Engineering
Languages : en
Pages : 35
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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 Fédération internationale du béton
ISBN: 2883941165
Category : Technology & Engineering
Languages : en
Pages : 205
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Book Description
Standards for specifying and ensuring the durability of new concrete structures are commonly of the prescriptive kind. fib Bulletin 76: Benchmarking of deemed-to-satisfy provisions in standards - Durability of reinforced concrete structures exposed to chlorides presents the benchmarking of a number of rules for chloride-induced corrosion as given in national codes such as European, US and Australian standards. This new benchmark determines the reliability ranges in the chloride-induced depassivation of rebar if the deemed-to-satisfy rules of different countries are taken into consideration. It does not only involve (probabilistic) calculations using input mainly based on short-term and rapid laboratory-test data but also involves input based on an independent assessment of existing structures. The reliability analyses are carried out using the probabilistic design approach for chloride-induced corrosion presented in fib Bulletin 34: Model Code for Service Life Design (2006), fib Model Code for Concrete Structures 2010 and ISO 16204:2012. The work compares the calculated reliability ranges thus determined with the target reliabilities proposed by current specifications and, based on the comparison, offers a proposal for the improvement of deemed-to-satisfy rules and specifications. fib Bulletin 76 presents and discusses in detail the input data for the examined model parameters and offers an extensive annexe documenting the values of the individual parameters used in the analyses. It thus provides a reliable database for the performance-based probabilistic service-life design of concrete structures exposed to chlorides, be they in the form of salt fog, sea water or de-icing salts.
Author: FIB – International Federation for Structural Concrete
Publisher: FIB - Féd. Int. du Béton
ISBN: 2883941297
Category : Technology & Engineering
Languages : en
Pages : 126
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Book Description
Cable-stayed structures have become increasingly popular over the last 30 years and have been used in all parts of the world. Modern cable-stayed bridges have a history of over 50-years and have been constructed with span lengths ranging from 15 m to over 1000 m. Many long span cable-stayed bridges have been built for railway and highway traffic applications. Stay cables have also been used on pedestrian structures, many of which are architecturally striking and have become landmark structures. There is growing use in building structures, particularly for cable-supported roofs. Most of the cable supported structures have been in the form of cable-stayed bridges; but in recent years, extradosed bridges have seen increased popularity among the designers. Led by the experience in Japan, more than 200 extradosed bridges have been constructed worldwide in the past 15 years. The first edition of these fib recommendations was published as fib Bulletin 30 in 2005 and was the first specification published by fib for stay cable systems. This new bulletin has been updated based on Bulletin 30 with the aim to reflect the current state of the art and encompass the latest knowledge in cable systems. In addition, it has been the aspiration of Commission 5 and Task Group 5.5 to harmonize the guidance in this updated bulletin with other stay cable recommendations from around the world, including those from Europe, Japan and the USA. This new bulletin is intended to supersede and replace fib Bulletin 30. It is recommended that it be used in lieu of fib Bulletin 30 for all future cable supported applications. The updated bulletin introduces several significant enhancements to the specifications: These recommendations are applicable to both stay cable and extradosed cable applications. In the past, there has been some debate over the boundary between cable-stayed and extradosed bridges. This bulletin presents a new continuous approach valid for both. A completely new testing requirement to assess the performance of cable systems under bending fatigue, including both anchorages and saddles, if applicable, has been added. Testing requirements for saddle systems have been reformulated. In addition to the bending fatigue test noted above, new testing procedures for stay cable saddles with isolated tensile elements are introduced. This includes tests for saddle axial fatigue, friction and tensile testing, and determination of the effective saddle friction coefficient. Expanded system qualification, including requirements for both stay cable and extradosed applications. Includes new provisions for MTE qualification and additional load transferring connection devices. Minimum number of tests is specified for each. A new in-situ damping measurement test has been added to verify the actual damping ratio of the damping devices installed. By testing on site, selected cables may be excited to vibrate without and with the damping devices so that the observed v vibration behaviour can be compared to the specified value. Other revisions have been made to reflect the current state of practice: Expanded quality control testing requirements Inclusion of epoxy-coated prestressing steel as a protection layer. Previous recommendations only considered zinc coatings. Specifications for epoxy coating material are given. Requirements for stainless steel components such as pipes, caps and plates Updated guidance for designing lightning protection systems Detailed recommendations for different levels of inspection of cable systems, including: initial, routine, detailed and exceptional inspections An updated list of references, relevant standards, and extended literature
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.
