Objective
Comprehensive State-of-the-Art reports on testing of SFRC and design of SFRC have been finished (task 1). They establish a clear and common starting point for all partners in the project. The round robin study (task 2) has been focused on both the bending test geometry (on notched beams, 5 labs involved) and the tensile test geometry (on notched cylinders, 3 labs involved) proposed by RILEM TC162-TDF. The round robin study is now finished and analysed. It has made a significant contribution to the development of these two tests, since it provided invaluable information regarding the robustness and sensitivity of the tests. The main conclusions of the work related to the bending test are the following: the test has been shown to be very robust; there is a good direct relationship between deflection and CMOD measurements, and also between CMOD measurements at different positions (heights) from the bottom of the beam. The beam study clearly showed that 1 CMOD measurement alone can thus be used to obtain all necessary design parameters, at least in an industrial type of test. This will save cost and time. A proposition has been made for the procedures to extract design parameters from the test results; some parameters that need further research (subtask 2.3) have been identified. The work related to the tensile test revealed similar results and conclusions, but this test required some more "fine tuning". The tensile test is more sophisticated to run, and therefore more appropriate for research needs than to become a standard industrial test. Besides the two basic tests (bending test and tensile test), also application specific tests have been developed to characterize material behaviour that is impossible to estimate from a bending or tensile test.All the work on the development of tests for SFRC has resulted in a document with firm recommendations on testing of SFRC (subtask 7.1).
The work on the development of design methods for sections subjected to bending moments, shear (subtasks 3.1 and 3.2) as well as the work on design methods for structural applications (subtask 3.3 and 3.4) has resulted in a document containing clear guidelines for the design of SFRC (subtask 7.2). Basically two design methods have been investigated, the s-e design method and the s-w design method. In the document also a section is included with considerations on the use of finite element programs for the design of SFRC. The development of all design guidelines was based on the recommendations of Rilem TC162-TDF. These recommendations have been checked with laboratory tests and if necessary adapted. The laboratory tests concentrated on beams in bending and bending with additional compression, beams in shear, splitting induced by local forces and members subjected to imposed or restrained deformations.
Long-term test programs have been executed for durability (subtask 5.1) and for creep/relaxation (subtask 5.2). The relaxation tests have shown that under long-term loading the post-peak stresses can be reduced by about 40% indicating a possible increase in the structural deformations but there is no loss in the ultimate load-carrying capacity of the SFRC. For dynamic effects and fatigue (subtask 5.3) a comprehensive literature survey has been done as well as a few fatigue tests on arch shaped ribs (in co-operation with subtask 6.3).
A complete list of innovative SFRC applications (defined as either completely new applications, or as applications that could now be 'engineered' on the basis of the present research project) has been compiled by the consortium. The industrial partners have chosen from this list which would be the most strategic application(s) for further developments in design, prototype fabrication, testing, full-scale demonstration, (task 6). These applications have been investigated with full-scale experiments.
Finally, based on the experience acquired in the project, recommendations are made for the quality assurance of SFRC. This should enable future users to obtain good results with the material, without having to go through a lot of trial and error mixes.
Since the early seventies, steel fibres are used in concrete to improve its per formances. Steel fibres have been proven, mainly by empirical observations, to improve significantly the behaviour of concrete beams and slabs in the Servicea bility Limit State (SLS) by limiting the crack widths and by assuring a more fa vourable crack distribution. Promising research results allow the consideration of using SFRC in structural - bearing - applications (ULS - Ultimate Limit Sta te). However, the utilisation of steel fibres in reinforced concrete for struct ural purposes is still quite limited in European building and bridge constructi on, mainly because the use of these fibres for structural purposes has not yet been recognised in National and European Building Code requirements for structu ral concrete. Indeed, structural uses of fibre concrete have primarily develope d in specific applications (such as pavements) which, at present, are not gover ned by structural design codes. It is very important to envisage the establishm ent of a theoretical basis, both for SLS and ULS, in order to allow the design of SFRC-materials for optimum performance. Empirical and semi-empirical design methods bind the designer to certain fibre types and impede a rational optimisa tion process. In this context, it is important to realise that current design a nd test methods for (conventionally reinforced) concrete structures do not prov ide such opportunities. This is due to the fact that the post-peak behaviour (' toughness') is primarily affected by the presence of fibres, whilst most design tools used by the structural concrete designer only take pre-peak behaviour (t ypically Young's modulus and compressive strength) into account. A key requirem ent for the inclusion of SFRC in future design codes is consequently a well-fou nded and reliable way to measure and introduce toughness properties of SFRC in the design approach. It is the objective of this project to plan and collect ba sic research efforts to facilitate the proper recognition of the role of fibres in concrete, through: developing design methods aiming at accurately evaluat ing the structural behaviour of SFRC in structural applications (both in SLS an d ULS) defining appropriate test methods to characterise the toughness proper ties of SFRC materials validating the developed combined test and design appr oach through testing of large-scale SFRC specEmens representing existing and pr omising applications, such as slabs-on-grade, permanent shotcrete, pavements fo r road/rail, bridge girders ...
Fields of science (EuroSciVoc)
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CORDIS classifies projects with EuroSciVoc, a multilingual taxonomy of fields of science, through a semi-automatic process based on NLP techniques.
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Call for proposal
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CSC - Cost-sharing contractsCoordinator
8550 Zwevegem
Belgium