A Review of ACI 544 Publications on FRC Design and Applications
Presented By: Amir Bonakdar
Affiliation: FYFE
Description: ACI 544 is the committee on fiber-reinforced concrete (FRC) and has developed 12 publications since its formation. These include several guides, reports, technotes and more recently a specification. The intent of this presentation is to provide a summary of the committee publications related to the structural design and applications of FRC with the purpose of familiarizing other ACI committee members on the available information.
The Use of Fiber Reinforcement for ICF Commercial and Residential Wall Construction
Presented By: Michael Mahoney
Affiliation: Euclid Chemical
Description: Insulated Concrete Formwork (ICF) for commercial and residential wall construction has been readily available on the market for many years. These structures have traditionally been reinforced with distributed steel rebar reinforcement. Challenges with this type of construction include that concrete must flow around bars during placement, consolidation must be achieved to ensure design strengths and spacing of rebar is not supportive for controlling temperature induced cracking. Time, labor and storage of materials on site can also pose operational difficulties. The use of synthetic macrofibers are used under the same design considerations as rebar with engineering tables and documentation demonstrating successful use and adherence to engineering requirements. Speed of construction, on-site labor challenges and cost are all improved in both complete replacement and conditions where fiber can be used to significantly reduce the amount of traditional steel required.
Design and Application of Precast Fiber-Reinforced Concrete Segments in Mechanized Tunneling
Presented By: Mehdi Bakhshi
Affiliation: AECOM
Description: Fiber-reinforced concrete (FRC) has become increasingly prevalent in precast tunnel segments across North America due to its benefits in cost savings, crack control, durability, accelerated production, and reduced carbon footprint. The development and implementation of ACI 544.7R (2016) and ACI 533.5R (2020) have provided essential guidance for the structural design and application of FRC in segmental linings. This presentation highlights key case studies from North American tunnels constructed under diverse geological conditions, illustrating how FRC has consistently achieved strength requirements while enabling efficient and sustainable construction. Emphasis will be placed on detailed design practices, material performance, and the role of FRC in delivering long-term serviceability. Practical insights will be shared for engineers, contractors, and owners involved in mechanized tunneling. The presentation aims to demonstrate how FRC is reshaping modern tunnel design and construction.
Large Scale Testing and Applications of Fiber-Reinforced Concrete Slabs, Walls and Beams
Presented By: Barzin Mobasher
Affiliation: Arizona State University
Description: This research has incorporated full-scale structural testing, digital image correlation, closed-loop control, and evaluations of fracture, fatigue, and creep to establish performance-based design criteria. Case studies involving projects with the City of Phoenix, Maricopa County, Salt River Project, and Valley Metro in Arizona demonstrate FRC applications in bridges, tunnels, canal linings, track slabs, and precast systems. Notable findings include the successful use of synthetic fibers in corrosive environments for tunnels, fatigue resistance in light rail slabs after 2 million load cycles saving millions, and reduced reinforcement in precast elements while meeting service load and crack-width requirements enhancing infrastructure durability. The study also presents analytical models for beams, slabs, retaining walls, and underground structures, demonstrating their suitability for simplified design and structural analysis with FRC. These findings support faster construction, reduced material consumption, and significant long-term cost savings compared to conventional concrete.
Structural Design Principles and Applications of Steel Fiber Reinforced Concrete
Presented By: Hendrik Thooft
Affiliation: Bekaert
Description: Steel fibers and steel fiber reinforced concrete have been in the market for over 50 years. During these years the knowledge on this innovative building material has drastically evolved and is coming to maturity. The design principles are adopted by the new Eurocode 2 in the informative Annex L. Expected publication date is 2027. This normative framework opens the way for using steel fibers in a wide range of structural applications. This presentation will focus on some practical use cases. The first application will be floors on foundation piles. Based on large scale experiments done at international leading universities we will validate the design models applied for these applications. We will show real-world examples of this system where rebar was replaced in these structured slab systems. A second application is the use of SFRC in combination with post tensioning for elevated slabs. In 2017 – 2019 we conducted a series of large-scale tests at Virginia Tech University. These tests clearly demonstrated that SFRC could effectively replace most if not all of the passive reinforcement in post-tensioned flat slabs. All design criteria in relation to ultimate and serviceability limit states were met. The presentation will highlight the findings of the research and the basic design principles used in developing the test slabs. The presentation will show case studies to demonstrate where this application has been utilized and the benefits of doing so. Lastly, we will give a summery overview of a couple of other structural applications with references built specifically in the U.S. and abroad such as ASRS mat slabs and shear wall link beams.
Full Scale Structural Testing to Validate Design of Slip-Formed Fiber Reinforced Concrete Tunnel Segments
Presented By: Liberato Ferrara
Affiliation: Politecnico di Milano
Description: Automation in construction industry has been gaining great potential and momentum due to the necessity of enhancing the productivity and innovation uptake of the sector and making it more and more aligned with the evolving needs of the society. In this frame-work, this paper presents the validation through full scale tests, of a slip-forming methodology for the refurbishment of existing tunnels which employs extrudable steel fiber reinforced concrete (SFRC). This method provides an innovative framework for the maintenance interventions of highways and railways tunnels. In order to validate the design methodology four real scale mock-ups replicating a motorway tunnel lining have been produced employing the aforesaid technology and tested in load configurations mimicking the relevant combination of actions for tunnel linings in the intended scenarios. Both a symmetric and a skew symmetric load combinations have been tested, in one case also in sequence to assess of accumulated damage on the residual bearing capacity. The structural tests have been performed at the ELSA laboratory of the European Commission Joint Re-search Centre in Ispra in the framework of the OPENLAB ETRL project and are meant as a preliminary validation of the employed design criteria as well as of the effectiveness and structural soundness of the proposed technology. A design-wise assessment of the full-scale test results has been also performed using as input design parameters those fed by material testing, performed in the framework of the fib Model Code 2010 design approach for FRC structures..