The durability of post-tensioning tendons depends undoubtedly on the durability of the materials used, but there are design concept specifics which are also of major importance: the post-tensioning layout and layers of protection such as concrete cover and selected materials in view of the aggressivity of the environment for instance. It is well known that sustainability principles guide the Engineer from the very beginning, at the project conception, during construction and the service life of a structure. Decisions made during conceptual and design stage have the largest influence on the durability and sustainability of post-tensioning tendons. fibBulletin 33 addresses the specifics for prestressed concrete structures: the durability of post-tensioning tendons. It should be noted that it does not repeat topics that have been addressed in other fib bulletins and which is common for both reinforced concrete and prestressed concrete structures. Pre-tensioning, which is used extensively in the precast industry, is not considered here, although conclusions and recommendations herein may, in many cases, also be applicable. This recommendation was prepared by Working Party 5.4.2, Durability specifics for prestressed concrete structures, in cooperation with fib Commission 9,Reinforcing and prestressing materials and systems. A preliminary version of this recommendation served as the basic document for the second workshop on "Durability of post-tensioning tendons", held on 11-12 October 2004 in Zurich. This workshop was a follow-up to the first workshop held in Ghent in 2001. Bulletin 33 includes revisions corresponding to the agreed results of the Zurich workshop.

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.

This book provides an overview of post-tensioning (PT) in reinforced concrete bridge structures. It specifically addresses corrosion issues that were initially unforeseen but subsequently occurred, raised concerns regarding structural integrity and long-term viability. It begins by exploring the introduction and background of PT bridge development, addressing post-tensioning systems and the various types of PT bridge construction methods. It also covers corrosion issues and failures that have previously occurred, and other designs for durability. Further, it goes into the details of experimental investigations of corrosion-caused bridge PT tendon failures, and the modeling efforts of wire and strand fractures. Lastly, it provides an assessment of the path forward, suggesting alternatives for current inspection and condition assessment. This book is highly recommended for graduate and postgraduate students of civil, structural, and mechanical engineering. It will also be an interesting read for structural and civil engineers, and researchers involved with integrity assurance of PT structures.

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.

Optimum corrosion protection of post-tensioning tendons has been a priority since the beginning of this technology. The temporary ban of grouted post-tensioning tendons in the United Kingdom, from 1992-1996, has initiated a review of all aspects related to durability of post-tensioning tendons. One of the UK conclusions of this review was to require encapsulation of the post-tensioning tendons into wear-resistant and leak-tight plastic ducts to serve as an additional corrosion protection barrier. Since that time, other countries have at least partially adopted similar approaches. Designs of these plastic ducts may vary significantly between different suppliers. In addition, experience with these systems is still relatively limited. Hence, these plastic ducts cannot be standardised at this time. Therefore, the former FIP Commission 2, and now fib Commission 9 Reinforcing and Prestressing Materials and Systems, has set-up a task group to prepare a fib report on corrugated plastic ducts for internal, bonded post-tensioning. This report is written as a guide for an approval process for such plastic ducts. It shall serve readers such as authorities, and engineers as a guide on how to set-up a formal state approval process for these ducts, or at least allow them to properly assess systems offered for a specific project.