Motivation
Analysis and design are understood as core tasks of structural engineering. In this field, nine areas of interest have been identified; hence, nine task groups form the basis of the new structure of Commission 2. Today, the analysis – i.e. the detailed investigation of the stress and strain state – has gained in importance, and consequently refined and physically based models and calculation procedures are required. On the other hand, the design of new structures (comprising conception, dimensioning and detailing) still is fundamental for practicing engineers. In general, the respective approaches should be one and the same for the two levels of detail, but more practical and easier to apply for the latter case. Commission 2 supports and follows this line of development of structural engineering.
Scope and objective of technical work
The scope of Commission 2 is to develop models and calculation procedures for the analysis and design of structures and structural members under short term and long term static loading as well as under fatigue, fire and extreme events. Serviceability limit states and ultimate limit states as well as their interaction are considered, and both research results and recommendations for the practical application shall be presented. In the near future the activity of COM2 will focus on new and also on existing structures in order to support the development of the new fib Model Code 2020.
Commission Chair
Deputy Chair| First name | Last name | Country | Affiliation |
|---|---|---|---|
| György L. | Balázs | Hungary | Budapest Univ. of Techn. & Economics |
| Oguzhan | Bayrak | United States | Univ. of Texas at Austin |
| Mikael | Braestrup | Denmark | Rambøll |
| John | Cairns | United Kingdom | Heriot-Watt University |
| Manfred | Curbach | Germany | Technische Univ. Dresden |
| David | Darwin | United States | University of Kansas |
| Rolf | Eligehausen | Germany | IWB, Universität Stuttgart |
| David | Fernández-Ordóñez | Switzerland | fib |
| Filip | Filippou | United States | Universtiy of California |
| Stephen | Foster | Australia | UNSW Australia |
| Mikael | Hallgren | Sweden | Tyréns AB |
| Niels | Høj | Switzerland | HOJ Consulting GmbH |
| Walter | Kaufmann | Switzerland | ETH Zürich |
| Johann | Kollegger | Austria | Vienna University of Technology |
| Koichi | Maekawa | Japan | University of Tokyo |
| Giuseppe | Mancini | Italy | Politecnico Torino |
| Giorgio | Monti | Italy | Sapienza Università di Roma |
| Aurelio | Muttoni | Switzerland | École polytechnique fédérale de Lausanne (EPF Lausanne) |
| Maria Rosaria | Pecce | Italy | Università del Sannio |
| Giovanni | Plizzari | Italy | University of Brescia |
| Viktor | Sigrist | Switzerland | Lucerne School of Engineering and Architecture |
| Frank | Vecchio | Canada | University of Toronto |
| Robert | Vollum | United Kingdom | Imperial College London |
| Jan | Vítek | Czech Republic | Metrostav a. s. |
| Joost | Walraven | Netherlands | Delft University of Technology |
| Güney | Özcebe | Turkey | TED University |
- TG2.1 - Serviceability models
- TG2.2 - Ultimate limit state models
- TG2.3 - Fire design of concrete structures
- TG2.4 - Computer-based modeling and design
- TG2.5 - Bond and material models
- TG2.6 - Composite steel-concrete construction
- TG2.7 - Seismic Design
- TG2.8 - Safety and performance concepts
- TG2.9 - Fastenings to structural concrete and masonry
- TG2.10 - Textile reinforced concrete construction and design
- TG2.11 - Structures made by digital fabrication
- TG2.12 - Protective Concrete Structures against Hazards
- TG2.13 - Design and assessment for tsunami loading
- TG2.14 - Open-source code development by the fib
- TG2.15 - Bridges with combined reinforcement
TG2.1 - Serviceability models
Serviceability limit states (SLS) determine the applicability of concrete structures. When these criteria are met, the concrete structure can function properly during its service life. Correct design according to serviceability limit states is therefore essential for the construction of durable, robust and valuable structures. Violation of the SLS criteria leads to structures that do not function properly and/or to reduced durability, the consequences of which can be recognised very quickly. Therefore, the models for verification of the expected criteria are of primary importance.
The activity of the group is focused on the development of models for analysis of cracks and deformations of concrete structures. Beside the sophisticated numerical models, engineering practice requires practical engineering approaches, which are applicable in codes and in preliminary design stages when important decisions on the conceptual design are accepted. The activity will be focused on new structures and also on existing structures for assessment, rehabilitation or strengthening.
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TG2.2 - Ultimate limit state models
Task Group 2.2 was established to evaluate and develop models for the conception, design and analysis of concrete structures. Topics within the scope of the work may include models that deal with the ultimate limit state and with ductility as to their affect on peak and post peak behaviours.
The objective of TG2.2 is to synthesise available results from research, testing and design experience. Therefore, research and development in this field is monitored, documented and evaluated. For the time being, the work is focused on the behaviour of slabs and beams in shear, shear aspects in the design of members reinforced with steel bars, steel fibres or a combination of steel fibres and bars and the punching behaviour of slabs. Moreover, strut-and-tie modelling is treated as a specific method to capture ultimate limit states.
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ConvenerTG2.3 - Fire design of concrete structures
Task Group 2.3 welcomes active members with expertise in theory and practice in relation to fire design of concrete structures. The scope of TG2.3 comprises a discussion of theoretical and practical problems in relation to fire design and the development of the state-of-the-art and best practices for fire design of concrete structures. It is the goal that the results of the task group will not only serve as a reference for the experts within the topic of fire design, but also will be helpful for the members of the fib in general.
The scope of the work of TG2.3 is based on the previous achievements, which include Bulletins 38 and 46 on fire design of concrete structures: materials, modelling, structural behaviour and assessment, as well as contributions to the fib Model Code and various workshops and special sessions on these topics.
In the next phase, TG2.3 will concentrate on a number of topical issues within fire design, with the objective of providing general engineering guidance within these fields. The work is organised in three working parties, with the following titles and scope.
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The aim of WP2.3.1 is to prepare a technical report providing guidance on the structural fire engineering design for concrete structures with a high probability and/or sensitive to the occurrence of concrete spalling during or after a fire.
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TG2.4 - Computer-based modelling and design
Task Group 2.4 (TG2.4) aims to bridge the gap between complex and advanced analyses and practical design applications. The current state of knowledge on nonlinear methods, thermomechanical analyses as well as the application of holistic 3D building models will be prepared for practical use.
The scope and objectives of TG2.4 are to:
- survey the current state of knowledge on computer-based modelling and design;
- develop guidance documents related to the application of non-linear computer-based analysis methods for assessing performance and aiding the design of concrete members;
- develop guidance documents related to the application of thermomechanical computer-based analysis methods for assessing the cracking risk respectively the mode of cracking and the required minimum reinforcement due to imposed and restrained deformations;
- establish frameworks and methods to incorporate the application of holistic 3D building models in the static analysis and design in practice;
- provide guidance on the application of computational modelling procedures to post-construction assessments, forensic engineering, and rehabilitation work relating to existing concrete structures.
Moreover, the Task Group 2.4 shall become a platform for researchers and practical users to:
- propose criteria for calibrating or validating computer-based procedures employed for concrete structure design or assessment;
- discuss the extension of computer-based modelling procedures to structures employing high performance concretes, fibre-reinforced concretes, and composite concrete structures;
- work toward integrating computer-based analysis-related provisions within the Model Code.
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Discrete fibres are being added to cement based materials (Fibre reinforced concrete, FRC) in order to increase the post-cracking residual strength of concrete structures. The fibre reinforcement mechanisms are mainly activated after crack initiation of the binder paste, so modelling the behaviour of FRC requires numerical approaches able of simulating the crack initiation and crack propagation in cement based materials. However, the designers that have the responsibility to design FRC structures face several challenges for selecting the most appropriate constitutive model, such is the case when intended to use sophisticated computer programs based on the finite element method (FEM). The values of the parameters of the constitutive models, and how to assure that these values are representative of the behaviour of the real structure are key aspects that designers face.
The main aim of this WG is to propose reliable methodologies for the application of FEM-based computer models for the design of FRC structures by considering their serviceability and ultimate limit state exigencies.
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Accurate prediction of the durability and long-term performance of concrete structures is a challenging task due to numerous influencing factors involved and their complex combinations. Despite these complexities, the majority of current standard specifications deal with the durability of concrete on the basis of a rather simple, prescriptive approach, where a set of requirements are usually applied to at the design stage and serve mainly as the basis of quality control. The durability and long-term performance of concrete structures are also essential for evaluating sustainability aspects such as the life-cycle emissions of carbon dioxide (CO2). Therefore, we should be able to accurately predict the service life of a structure for given materials and processes. To improve our capability to predict the service life of concrete structures, we intend to use a multi-scale approach taking into account the time-dependent properties of concrete, externally applied loads and exposure environments in a holistic manner. To this end, such analysis models and simulation frameworks are still under development, and we aim to showcase its applicability, calculation procedures, required parameters, and appropriate ways of interpreting the simulation results.
The main scope of WP 2.4.2 is developing accurate and reliable models and simulation frameworks for life-span numerical simulation of concrete structures. The primary objective of the activity is to couple material and structural behaviors with their durability and sustainability. The developed numerical models should cover mechanical behaviors, durability issues, and sustainability aspects such as CO2 emissions.
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TG2.5 - Bond and material models
The overall motivation of TG2.5 is to advance theoretical and practical developments in topics related to bond and anchorage of reinforcing and prestressing materials, and to present these developments in an understandable and code-type formulated manner.
TG2.5 undertakes activities which stimulate and advance modelling of the influence of bond and anchorage of reinforcement on structural performance, as well as the development of design provisions related to bond behaviour and detailing of laps and anchorages.
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TG2.6 - Composite steel-concrete construction
Steel-concrete composite construction allows various structural solutions that optimize the performances of the two-component materials through a well-assessed design that takes into account all the particularities of steel and RC constructions as well as interaction problems.
The use of composite construction is widely spread all around the world, and its use for the construction of medium-sized bridges is a very frequent technical choice. In this historical period, the concrete industry must take this into account.
The motivation of the fib TG2.6 is to identify the meaningful characteristics of composite steel- concrete structures with respect to typical aspects of RC structures in order to provide technical knowledge and design provisions.
The activity of the group is focused on the analyses of the structural behaviour of RC parts constituting steel-concrete composite members and the modeling of their interaction with the steel parts.
Convener
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TG2.7 - Seismic Design
The motivation for the work of Task Group 2.7 (TG2.7) is the promotion of the use and improvement in safety of concrete structures under accidental (e.g. seismic) actions and/or in exposed regions worldwide.
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TG2.8 - Safety and performance concepts
The overall motivation of Task Group 2.8 (TG2.8) is based on the fact that structural systems are typically designed to stay in service for at least several decades. This implies that proper attention must be given to structural performance under various actions, both man-made and environmental, to the methodology of structural analysis and assessment, to material properties, to the inverse identification and monitoring of structural resistance among others. The main focus is the development of a holistic performance based design approach for new and existing structures and infrastructures.
The objective of TG2.8 is to promote and to provide on the basis of the guide to good practice “safety and performance concepts – reliability assessment of concrete structures” the theoretical and practical developments for the performance based design. This includes structural safety, serviceability and reliability, advanced methodology including probabilistic methods, inverse analyses techniques, monitoring methods, and performance and optimised life-cycle cost based design concepts.
Convener
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TG2.9 - Fastenings to structural concrete and masonry
The modern fastening technique is employed extensively for the transfer of concentrated loads into concrete and masonry structures. Cast-in-place anchors, placed in the formwork before casting of the concrete, as well as post-installed anchors and reinforcing bars, which are installed in hardened structural concrete or masonry, are equally common. Loads are transferred into the concrete or masonry by mechanical interlock, friction, bond or a combination of these mechanisms. However, independently of the load-transfer mechanism, all anchorages rely on the tensile strength of the concrete or masonry, a fact which must be taken into account in both assessment and design. Despite the widespread use of cast-in-place as well as post-installed anchors and reinforcing bars in construction, the overall level of understanding in the engineering community regarding their behaviour remains quite limited.
In order to improve the general state of knowledge in this field, Task Group 2.9 “Fastenings to Structural Concrete and Masonry” (former Special Activity Group 4) was formed.
The aim of TG2.9 is to collect and discuss the latest research results in the field of fastening technology, to identify new areas of research and to synthesise the research results in harmonised provisions for the design of fastenings.
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ConvenerTG2.10 - Textile reinforced concrete construction and design
New material composites such as concrete with non-metallic reinforcement have been intensively developed during the past 25 years. Usually, the composite material consists of concrete with a reduced maximum grain size and endless fiber-based textile or bar-shaped reinforcementstructures instead of classical steel reinforcement. Fibers made of carbon, alkali-resistant glass, or basalt (and similar) are currently the most suitable for use in structural concrete. Their resistance to corrosion and their high tensile bearing behavior and stiffness allows a clear reduction of concrete cover thickness and freedom of form in comparison to classical steel-reinforced concrete.
These developments offer new ways in concrete construction due to the possibility for curved, thinner and more filigree construction components. This might be a starting point for several new research works. And there is a need for recommendations or guidelines that secure and facilitate the use of the new material. Therefore, the work of a task group is considered meaningful.
The task group may contribute to working out rules and compiling guidelines for the design of(a) new constructions and (b) of strengthening, retrofitting and repair measures made of concrete with non-metallic reinforcement. The focus will be on grid-like (textile) endless-fiberbased reinforcement materials, as this is where the greatest differences lie compared to construction using reinforcing steel. Rod-shaped reinforcements are not considered for now. Due to the wide range of possible fiber materials, focusing is necessary. In any case, carbon and AR glass fibers will be a key focus. However, which types of fibers are particularly relevant depends heavily on local conditions and will be discussed in the group of experts. Basic principles can usually be applied to other fiber types as well.
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TG2.11 - Structures made by digital fabrication
Digital fabrication processes for fabricating concrete-like products, objects and/or structures are typically grouped into three main categories: (i) Layered Extrusion (e.g. contour crafting, concrete printing etc.), (ii) Binder Jetting (e.g. D-shape), (iii) Slip-forming (e.g. smart dynamic casting). However, to date, many important developments have been accomplished for layered extrusion technology, consisting of a digitally controlled moving printing head (or nozzle) that precisely lays down the concrete or mortar material layer-by-layer.
It is clear that the full understanding of the structural performances of digitally fabricated elements represents noteworthy progress in supporting the design of such innovative structures. In this way, reliable structural concepts and assessment methodologies could be integrated within existing international building codes/standards and adapted to the particularities of DFC, providing effective recommendations to the construction industry stakeholders.
The primary objective of the task group is to identify limiting aspects of the current design practice for the implementation of novel, digitally-fabricated concrete structures. Based on that, the task group will address fundamental structural issues related to the particularities of DFC with the final aim of providing effective guidelines for code-compliant applications.
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TG2.12 - Protective Concrete Structures against Hazards
Concrete structures are suitable for the development and construction of protective structures against several kinds of hazards, like a blast, missiles, impact or thermal loads. The reasons for such extreme loadings may be different, but the structures under consideration have to provide conditions for safe and relatively comfortable survival of people inside. The TG2.12 will develop documents which specify the conditions of performance of protective structures and conditions for their design.
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TG2.13 - Design and assessment for tsunami loading
The primary objective of the task group (TG) is to identify methodologies for: (i) the design of tsunami resistant structures/infrastructure, (ii) the assessment of existing assets against tsunami-induced loads and (iii) the design/assessment of existing assets towards the sequential hazards such as earthquakes and tsunami, or other triggering hazards. Assets under investigation include RC, masonry, steel and composite structures and infrastructure.
The TG plans to face structural issues by focusing on the structural response of reinforced concrete structures and infrastructure under tsunami loading, with main focus on:
- The definition and estimation of loads (i.e., hydrostatic and hydrodynamic horizontal and vertical loads induced by a tsunami, such as buoyancy) acting on structural members for design/assessment of structures and infrastructure;
- The behaviour of non-structural components, such as infill walls;
- The structural analysis methodology for design/assessment;
- Performance levels and safety checks at local and global levels.
The fundamental knowledge produced in this framework will support the introduction of reliable design/assessment criteria in the field of tsunami engineering. This will provide an improvement with respect to existing international codes and will represent the first guideline for Europe.
The TG will also address aspects related to the harmonization of tsunami design provisions with existing design provisions for other kind of hazards.
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TG2.14 - Open-source code development by the fib
The fib has started developing an open-source Python package containing models from the fib Model Code. Github is used as a platform for version control and code collaboration. On the long-term, this package should contain all models in the fib Model Code. When sufficiently mature, the package should be published on PyPI.org to arrange for easy distribution. The package should be published with a license that grants the user flexible rights to use, study, edit and publish the source code, without warranty of any kind.
Primary objective of the TG: serve as a team of core developers or maintainers of the Python package. This includes, but is not limited to:
- Contribute code to the package.
- Respond to issues that are reported and initiate relevant actions.
- Maintain a CI/CD, continuous integration and continuous delivery, pipeline.
- Review contributions from the community, and merge these when properly matured.
The fib seeks contributions from the fib and the engineering community as a whole.
Convener
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TG2.15 - Bridges with combined reinforcement
Unbonded – external post-tensioning (PT) tendons are gaining interest world-wide within the concrete bridge community. The ability to address unforeseen issues has always been valued by bridge engineers and unbonded external PT tendons provide bridge designers and owners the flexibility to address these issues through their ability to be replaced while the bridge is in-service. Four countries, France, Germany, Japan, and United States are using this technology to provide tendon replaceability.
The use of unbonded tendons has led to components with both bonded and unbonded prestressing and/or mild reinforcement. Research has shown that the use of mixed reinforcement conditions (i.e. bonded and unbonded PT with and without mild reinforcement) in concrete members has structural implications (UF Report). Most current specifications consider their design approach as conservative for the design of components with mixed reinforcement conditions. However, research has shown that the performance and appropriate design of these members is complex and comprehensive guidance is needed to educate engineers on the design of these unique components. Therefore, there is a great need for clear design guidance to bridge designers on this unique and increasingly popular posttensioned component.
This guidance can have at least four purposes: i) provide background information on the performance of mixed reinforced elements with varying amounts of unbonded to bonded PT ratios, ii) synthesize current codified design methods for members with mixed reinforcement, iii) develop guidance on appropriate analysis methods, and iv) develop design approach for flexural capacity, including resistance factors & associated ductility requirements.
The primary objective of the task group (TG) is to serve as a team of core technical reviewers for the development of this technical report. Expertise in the design of complex concrete elements and experience with design methods for mixed reinforced members is desired.
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