International Concrete Abstracts Portal

After a brief reminder of the main characteristics of UHPFRC and of the history of their development, this paper presents the 2013 AFGC recommendations on UHPFRC, with emphasis on developments based on practical experience and on research carried out during the last decade. The paper then presents the progress of French standardization on UHPFRC and a summary of the similarities and main differences between normal fibre-reinforced concrete and UHPFRC. It presents specific topics which have to be examined in order to formulate intermediate fibre-resistant concrete (between HPFRC and UHPFRC) and/or to formulate UHPFRC with a lower fibre content combined with traditional reinforcement. The paper ends with a summary of the technological breakthroughs brought about by UHPFRC with respect to both design methods and implementation processes.

After several decades of research work and some years of pioneer applications, fibrereinforced concrete (FRC) is nowadays a material ready for the world community, also considering that design rules are already available in several countries and the fib Model Code 2010 includes specific sections for design of FRC elements. FRC can be a suitable solution, especially for statically indeterminate structures, where stress redistribution occurs. In addition to the structural bearing capacity, FRC is particularly useful for better controlling crack opening in service conditions, which has a particular influence on structural durability, especially in aggressive environments. Furthermore, structural robustness is nowadays a major concern among structural engineers. Also in this perspective, FRC could improve structural behaviour since it provides structural resistance both in compression and in tension in all the regions of the structural element. In the present paper, the design procedure is applied to some structural elements where FRC may represent a suitable material for structural behaviour. Beside structural strength, crack opening in service conditions is determined and comparison in terms of total amount of reinforcement (fibres + rebars) is presented.

The ACI Committee 544 on fibre-reinforced concrete (FRC) has been involved in development and dissemination of technical information for nearly a half century. A key advantage in using FRC is the reduction in construction time compared to the traditional reinforcing bars or welded wire mesh. Application areas for FRC have extended to areas where high early strength and ductility are important and include pavement, shotcrete and structures such as bridge deck slabs, or rock slide stabilization. In these cases, the material properties must be measured using experimental test data obtained from an experimental program. Test results must be analysed in order to obtain effective stress strain responses that can be incorporated in analytical, or computer simulation. A list of examples including wall panels, hydraulic structures, airport pavements, and industrial floor overlays are described. To maintain integrity without collapse, such structural elements need to be designed with proper material models and analysis tools discussed.

In January 2014 the Draft for Public Comment Australian Standard for the design of concrete bridges was released (DR AS5100.5); this is the first standard in Australia, and one of the few national standards in the world, to include design procedures for steel-fibrereinforced concrete in a comprehensive way. This presentation provides the background for the development of the design rules, including on determination of the mechanical properties of the materials, design models for strength and serviceability, considerations with regards to durability and on quality control measures. Validation of the mechanical models adopted for design is also presented.

In tunnels built by means of a tunnel boring machine, the use of fibre-reinforced concrete (FRC) in the precast segmental linings lead to several advantages. On one hand, FRC improves the mechanical behaviour of the segments during construction, reducing the incidence of damages. On the other hand, it contributes to a decrease of the global costs by reducing the amount of conventional passive reinforcement required. The objective of this paper is to present a real experience regarding the use of fibres as the main reinforcement in precast segmental linings in the metropolitan area of Barcelona. First, the design approach presented in the fib Model Code for Concrete Structures 2010 for fibre-reinforced concrete is adapted taking into account the mechanical requirements of the precast segments. Then, this methodology is used to assess the minimum fibre content for this application, estimated in 60 kg/m³. These results are compared with the obtained in an experimental program performed with real-scale segments simulating the critical load condition found during the most critical transient stage (stocking). The study shows an example of optimized design of FRC tunnel segments that might be useful for future tunnels.