TG5.2 - Reinforcing steels and systems

fib TG5.2 will consider all aspects related to reinforcing steels and systems from design to manufacturing, testing and final installation, use and maintenance. It will initially focus on developing a new manual which provides guidance and rules for detailing reinforcing steel. This document is intended to provide the general principles of good detailing practice and not to act as a comprehensive detailing manual. In addition, TG5.2 will address other topics considered high priority, and will create sub-groups to work on particular subjects as needed.

Areas of interest:

• review of the reinforcing steel grades available on the market (strength, ductility, bond, fatigue, durability properties) and relevant concrete structure design codes;
• manual for reinforcing materials and systems;
• technical report on fabrication of reinforcement;
• state of the knowledge on the bond properties of reinforcing steels;
• state of the knowledge on the fatigue resistance properties of reinforcing steels.

Convener
Ladin Camci

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TG5.3 - Prestressing materials and systems

Since Eugène Freyssinet’s first of use high-strength steel wire for prestressing concrete in the late 1920s, there have been many changes in prestressing systems used around the world. Current systems bear little resemblance to many of the older methods used in the past. Designers and contractors need information regarding these historical practices and materials to evaluate existing prestressed concrete in need of repair and to determine effective strategies to extend service life and enhance performance. Further, as new technologies are developed, they are often used in some countries but not in others.

TG5.3 has established two goals:

• to develop a state-of-the-art report describing the evolution and development of prestressing systems and to identify recent innovations and advances,
• to develop a new bulletin that provides recommendations for the installation of post-tensioning systems.

Convener
Tommaso Ciccone

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TG5.4 - Recommendations for ground anchor systems

The overall motivation of TG5.4 is to establish a modern recommendation for the qualification of ground anchor systems.

The main objective of TG5.4 is to prepare a bulletin entitled “Recommendation for ground anchor systems” based on and updating earlier documents such as the “Recommendations for the design and construction of ground anchors”, 1996. The recommendations will include significant content for qualification of ground anchor systems covering prestressed permanent and temporary anchors.

Convener
Matthias Ryser

Co-Convener
Xiaomeng Wang

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TG5.5 - Cables for cable supported bridges

fib Bulletin 89, Acceptance of cable systems using prestressing steels, as an update of the previous fib Bulletin 30 was published in 2019.

The goal of TG5.5 is to work on selected individual topics related to cable systems for a further future update of Bulletin 89. The topics will be addressed one after the other and published in a few individual technical reports or recommendations before they will be included in a full revision of Bulletin 89.

Workflow and Timeline:

• Fire protection and fire testing of cables: 2020 - 2025
• Damper/damping requirements: 2022 - 2026
• Icing / ice mitigation of cables: 2026 - 2028
• Update on inspection technologies of cables
• SHMS for cable stayed bridges with post-data processing
• Illumination of stay cables
• Terrorism protection of cables

New recommendations on fire protection of stay cables is expected to be published in 2025.

Convener
Werner Brand

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TG5.10 - Inspection and monitoring of reinforced/prestressed concrete structures

Maintenance of aging infrastructure (buildings, bridges, tunnels, etc.) is a significant part of both public, and private-entities’ budgets. The worldwide infrastructure and property maintenance costs are estimated to be EUR 180 billion per year. These costs depend on industry sector, age of the assets and governmental regulations. They highly affect the financial situation of public bodies and the profitability of enterprises.

There is a need to develop a guideline document to cover state-of-the-art inspection method statements, available sensor technologies including emerging digital solutions and remote sensing (e.g. drone inspection).

The required time for the development of this guideline is estimated between two to three years. The rough and high-level schedule is suggested as follows:

• First 6 to 9 months focused on building up the team and finalize the definition of the scope and content. Both are interlinked;
• Next 12 to 18 months working on developing the content of the different chapters;
• Final 6 to 9 months to finalize the first draft, including editorial review, before its submission to the TG 5.10 and C5;
• Finally, some time is expected to engage the peer reviewers and answer questions/comments received from the TG 5.10 and C5.

Convener
Antonio Caballero

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TG5.12 - Ultra-high strength prestressing steels for post-tensioning kits and stay systems

The goal of sustainability involves a consensus among economic, environmental and social factors. Due to climate change, environmental concerns have increased in society. The construction sector is among the most active high environmental impact sectors. Emissions from building and infrastructure construction are expected to form the single largest category of consumption-based emissions for C40 cities between 2017 and 2050, producing 21% of consumption emissions. As this period is critical for reducing greenhouse gas (GHG) emissions in line with keeping global temperature rise to within 1.5ºC above pre-industrial averages, serious action is needed in this area.

According to the report Building and Infrastructure Consumption Emissions prepared by C40, Arup and the University of Leeds , material efficiency stands out as having the highest potential emission reduction impact, offering savings of 18% in cumulative emissions between 2017 and 2050. Ultra-High Strength Prestressing (UHSP) strands, namely strands with tensile strength of 2060 to 2360 MPa, has the potential to greatly reduce the quantity of steel necessary in concrete structures.

The goal of new proposed Task Group is the development of a guideline where the key aspects of introducing ultra-high strength strands at different prestressing applications (along with post-tensioning and stay cable systems) i.e. crucial material properties and risk of hydrogen induced stress corrosion failure, design recommendation, system and material testing, quality control, etc. are covered.

Convener
TBD

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TG5.13 - Grouting of tendons in prestressed concrete

Prestressed Concrete is a very efficient, reliable and durable form of construction. However, in the 1990’s it was discovered that grout was, in some cases, inadequate.

Major investigations followed, and new regulations and recommendations (The Concrete Society TR47, PTI, fib bulletin 20, EN 445-447) were published, representing major steps forward in materials and testing requirements.

Since then, the Concrete Society has released the technical report TR72, making the TR47 obsolete. PTI has published new issue of the M50.3 specification in 2012 and again in 2019.

In 2022, time came to re-read and review the fib bulletin 20 and to collect the current state-of-the-art on grouting of multistrand tendons. The goal of Task Group was the development of a Guide to good practice, covering the same topics as the original bulletin 20.

A first draft should be presented to Commision 5 in December 2025.

Convener
Guillermo Ramírez

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TG5.14 - Durability of post-tensioning tendons

fib Commission 5 has recently initiated a new Task group TG 5.14 to cover the Durability of Post-tensioning Tendons. The task group worked jointly with fib Commission 8 and in collaboration with the Federal Highway Administration (FHWA). The document is co-published with National Member Group partner, the Post-tensioning Institute (PTI). This effort established the initial goal to update and build upon the past work of fib Bulletin 33 Durability of Posttensioning Tendons which was published in 2005. The document has been widely referenced and valuable in establishing recommendations for durable post-tensioning systems with consideration of the application and aggressivity of the environment. This guidance included the use of the Protection Level (PL) concept and information on durable post-tensioning materials and their installation. There have been continued advances since the publication of the document, and therefore the need for an update.

The scope of work for TG 5.14 focuses on providing strategies for durable post-tensioning tendons in new structures. It includes guidance on determination of appropriate protection levels, detailing for durability, guidance on specifying components of post-tensioning systems, guidance on the installation of post-tensioning systems, and information on available monitoring methods to confirm the intended durability performance. The task group collected and reviewed international experience and examined the current guidance and specifications throughout the industry. While not a fully comprehensive list, some of the documents considered include: fib Bulletin 33 Durability of Post-tensioning Tendons, TR72 Durable bonded post-tensioned Concrete Bridge, PTI/ASBI M50.3-19 Specification for Multistrand and Grouted Post-tensioning, PTI M55.1-19 Specification for Grouting of Post-tensioned Structures, and FHWA-HIF- 20-041 Methodology for Risk Assessment of Post-Tensioning Tendons, and several current fib documents related to post-tensioning. This task group under fib Commission 5 and worked jointly with fib Commission 8. There are several related efforts, within fib and other organizations. Specifically, the significant work of WP 1.1.5 Management of Post-tensioned Bridges within fib TG 1.1 is recognized and recommended for further information relating to in-service bridges.

TG 5.14 comprised a cross-section of experts representing various roles (owners, designers, suppliers, government agencies, academics, contractors, and testing laboratories) and also representing different international perspectives. The contributions of the task group led to the updates and documentation of the state of practice. This guidance provides strategies toward ensuring durable post-tensioned concrete structures.

Convener
Gregory Hunsicker

Co-Convener
Hans-Rudolf Ganz

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