The 16th International Symposium on Fiber-Reinforced Polymer (FRP) Reinforcement for Concrete Structures (FRPRCS-16) was organized by ACI Committee 440 (Fiber-Reinforced Polymer Reinforcement) and held on March 23 and 24, 2024, at the ACI Spring 2024 Convention in New Orleans, LA. FRPRCS-16 gathers researchers, practitioners, owners, and manufacturers from the United States and abroad, involved in the use of FRPs as reinforcement for concrete and masonry structures, both for new construction and for strengthening and rehabilitation of existing structures. FRPRCS is the longest running conference series on the application of FRP in civil construction, commencing in Vancouver, BC, in 1993. FRPRCS has been one of the two official conference series of the International Institute for FRP in Construction (IIFC) since 2018 (the other is the CICE series). These conference series rotate between Europe, Asia, and the Americas, with alternating years between CICE and FRPRCS. The ACI convention has previously cosponsored the FRPRCS symposium in Anaheim (2017), Tampa (2011), Kansas City (2005), and Baltimore (1999). This Special Publication contains a total of 52 peer-reviewed technical manuscripts from 20 different countries from around the world. Papers are organized in the following topics: (1) FRP Bond and Anchorage in Concrete Structures; (2) Strengthening of Concrete Structures using FRP Systems; (3) FRP Materials, Properties, Tests and Standards; (4) Emerging FRP Systems and Successful Project Applications; (5) FRP-Reinforced Concrete Structures; (6) Advances in FRP Applications in Masonry Structures; (7) Seismic Resistance of FRP-Reinforced/Strengthened Concrete Structures; (8) Behavior of Prestressed Concrete Structures; (9) FRP Use in column Applications; (10) Effect of Extreme Events on FRP-Reinforced/Strengthened Structures; (11) Durability of FRP Systems; and (12) Advanced Analysis of FRP Reinforced Concrete Structures. The breadth and depth of the knowledge presented in these papers is clear evidence of the maturity of the field of composite materials in civil infrastructure. The ACI Committee 440 is witness to this evolution, with its first published ACI CODE-440.11, “Building Code Requirements for Structural Concrete with Glass Fiber Reinforced Polymer (CFRP) Bars,” published in 2022. A second code document on fiber reinforced polymer for repair and rehabilitation of concrete is under development. The publication of the sixteenth volume in the symposium series could not have occurred without the support and dedication of many individuals. The editors would like to recognize the authors who diligently submitted their original papers; the reviewers, many of them members of ACI Committee 440, who provided critical review and direction to improve these papers; ACI editorial staff who guided the publication process; and the support of the American Concrete Institute (ACI) and the International Institute for FRP in Construction (IIFC) during the many months of preparation for the Symposium.

The use of FRP tendons has become an attractive alternative to steel tendons in prestressed concrete structures to avoid strength and serviceability problems related to corrosion of steel. There is however a lack of knowledge in serviceability behavior related to deflection after cracking for beams prestressed with FRP tendons. Conventional approaches used to compute deflection of cracked members prestressed with steel is problematic at best, and the situation is exacerbated further with the use of FRP tendons having a lower modulus of elasticity than steel. Deflection of FRP reinforced (nonprestressed) concrete flexural members computed with Branson’s effective moment of inertia 𝐼􀀁 requires a correction factor (called a softening factor) that reduces the member stiffness sufficiently to provide reasonable estimates of post-cracking deflection. For FRP prestressed concrete however, this approach does not always work as expected and deflection can be either underestimated or overestimated significantly.

This study investigates the accuracy of different models proposed for estimating deflection of cracked FRP prestressed members using a database of 38 beams collected from the literature. All beams are fully prestressed. Results indicate that using Branson’s effective moment of inertia 𝐼􀀁 with a generic softening factor can produce reasonable estimates of deflection provided the 𝐼􀀁 response is shifted up to the decompression moment or adjusted with an effective prestress moment defined by an effective eccentricity of the prestress force. The former approach overpredicts deflection by 20% on average while the latter overpredicts deflection by not more than 5% based on the beams available for comparison. Assuming a bilinear moment deflection response overpredicts deflection by 12%, while an approach proposed by Bischoff (which also shifts the 𝐼􀀁 response upwards) overpredicts deflection by 23%. These last two approaches work reasonably well without the need for a correction factor.

Deterioration of concrete bridges has resulted in reduction of their service lives and increase in required maintenance which is associated with cost and inconvenience to the public. A prevalent cause of concrete bridge deterioration is corrosion which initiates by chloride ions penetration past the protecting layers and by corroding the steel reinforcement. Because corrosion in prestressed concrete members has more serious consequences than in non-prestressed reinforced concrete, it is important that bridge designers and inspectors be aware of the potential problems and environments that may cause the issue and address them as soon as they are detected. This paper discusses a case study of a highway bridge (Hyndman Bridge, Ontario) including its deterioration, causes, mitigation measures, structural evaluation and the selected repair method. The rehabilitation design is based on guidelines of the latest editions of the CHDBC and ACI 440.2R. CFRP strengthening techniques have been proposed to address the flexure and shear deficient capacity of deteriorated girders. It is concluded that by using a suitable repair methodology employing CFRP, it is possible to upgrade the bridge to comply with the latest requirements of the code and increase the service life of the structure which otherwise would have needed imminent replacement.

Developments in the prestressed concrete industry evolved to incorporate innovative design materials and strategies driven towards a more sustainable and durable infrastructure. With steel corrosion being the biggest durability issue for concrete bridges, FRP tendons have been gaining acceptance in modern prestressed technologies, as bonded or unbonded reinforcement, or as part of a “hybrid” system that combines unbonded CFRP tendons and bonded steel strands. Assessments of the efficacy of hybrid-steel beams, combining bonded and unbonded steel tendons. in the construction of segmental bridges and in retrofitting damaged members has been established by several researchers. However, limited research has been conducted on comparable hybrid prestressed beams combining CFRP and steel tendons (hybrid steel-cfrp beams). This paper provides an insight on the flexural behaviour of eighteen prestressed beams tested under third-point loading until failure with the emphasis on the tendon materials (i.e., CFRP and steel) and bonding condition (i.e., bonded, unbonded). In addition, a comprehensive finite element analysis of the beams’ overall behaviour following the trussed-beam methodology is conducted and compared with the experimental results. Results show that hybrid beams, utilizing CFRP as the unbonded element maintained comparable performance when compared to hybrid steel beams. The results presented in this paper aim to expand the use of hybrid tendons and facilitate their incorporation into standard design provisions and guidelines.

A large number of bridges in the Netherlands have transversely post tensioned deck slabs cast in-situ between flanges of precast girders and were found to be critical in shear when evaluated by Eurocode 2. To investigate the bearing (punching shear) capacity of such bridges, a 1:2 scale bridge model was constructed in the laboratory and static tests were performed by varying the transverse prestressing level (TPL). A 3D solid, 1:2 scale model of the real bridge, similar to the experimental model, was developed in the finite element software DIANA and several nonlinear analyses were carried out. It was observed that the experimental and numerical ultimate load carrying capacity was much higher than predicted by the governing codes due to lack of consideration of compressive membrane action (CMA). In order to incorporate CMA in the Model Code 2010 (fib 2012) punching shear provisions for prestressed slabs, numerical and theoretical approaches were combined. As a result, sufficient factor of safety was observed when the real bridge design capacity was compared with the design wheel load of Eurocode 1. It was concluded that the existing bridges still had sufficient residual bearing capacity with no problems of serviceability and structural safety.