In the last decades, the devastating effects of earthquake events in seismic prone regions increased the attention on the vulnerability of existing constructions. Masonry walls especially experienced severe damage, both considering out-of-plane and in-plane mechanisms. To increase their resistance to horizontal forces, different strengthening systems can be applied. The objective of the present work is to study the efficiency of an innovative strengthening solution, involving the use of fiber reinforced polymer (FRP) pultruded bars. An experimental campaign is presented, in which clay-brick single-leaf masonry panels are retrofitted by carbon FRP rebars, inserted into grooves cut within the masonry panel with a cementitious mortar, and CFRP sheets applied on the panel external surfaces. A total of seven direct shear tests (ST) and four diagonal compression tests (DC) were performed on unreinforced and strengthened samples. The results of the tests showed that the strengthening technique can be effective for the improvement of the shear sliding and diagonal cracking resistances, also allowing to deepen the knowledge of the principal failure mechanisms characterizing the FRP-retrofitted masonry elements.

Fiber reinforced polymers (FRP) are commonly used to seismically retrofit concrete structural walls. Limited design guidance for the seismic application of FRP strengthening is currently available to designers in guidelines such as ACI PRC-440.2-17 or standards like ASCE/SEI 41-17. This paper presents the description and results of an experimental effort to investigate the effectiveness of FRP retrofitted concrete walls. The specimen wall thickness was either 6 in or 12 in, which represents a typical range of wall thickness seen in older buildings. To better reflect the most common applications seen in the industry, the walls were retrofitted with FRP, and anchored with fiber anchors only on one side of the wall. The study demonstrates that the effectiveness of FRP is reduced as the wall thickness increases and that the FRP must be anchored to the wall for any tangible benefit. The results are used to assess the current provisions in ACI PRC-440.2-17 and ASCE/SEI 41-17. It is apparent that additional testing is required to better understand the complexities involved in the FRP strengthening of shear walls and such testing is scheduled for the near future.

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.

Recent seismic events demonstrated the high vulnerability of existing reinforced concrete (RC) buildings. Lack of proper seismic details resulted in significant damage to structural components with many collapses and number of fatalities. The destruction of entire cities shield lights on the need of effective strengthening solutions that can be applicable at metropolitan/regional scale. They should be effective increasing significantly the seismic performance, affordable in the cost, fast to apply and with a low level of disruption to the occupants. This research work presents and discusses the preliminary results of an experimental programme on full-scale RC beam-column joints with reinforcement details typical of the existing buildings in the Mediterranean area. After assessing the response of the as-built specimen under a constant axial load and increasing cyclic displacement, a novel FRP-based strengthening system is presented. It combines the use of a quadriaxial CFRP fabric applied on the joint panel with CFRP spikes installed at the end of the beam and columns to improve the bond. The preliminary results pointed out the effectives of this strengthening solution in avoiding the joint panel shear failure and promoting a more ductile failure mode.

The seismic performance of reinforced concrete (RC) bridge columns subjected to multidirectional ground motions is a critical issue, as these columns can experience axial compression, bending, and torsional loading. Moreover, steel corrosion is a significant concern in existing bridges, leading to deficiencies in steel-RC structural members. The use of glass fiber-reinforced polymer (GFRP) reinforcement has been established as a practical and effective solution to mitigate the corrosion-related issues associated with traditional steel reinforcement in concrete structures. However, the dissimilar mechanical properties of GFRP and steel have raised apprehensions regarding its feasibility in seismic-resistant structures. The current study involves conducting an experimental investigation to assess the feasibility of utilizing GFRP reinforcement as a substitute for conventional steel reinforcement in circular RC bridge columns subjected to cyclic lateral loading, which induces shear, bending, and torsion. One column was reinforced with GFRP bars and stirrups, while the other column, served as a control and was reinforced with conventional steel reinforcement. The aim of this investigation was to analyze the lateral displacement deformability and energy dissipation characteristics of the GFRP-RC column. The results showed that GFRP-RC column exhibited stable post-peak behavior and high levels of deformability under the applied combined loading. Additionally, with a torsion-to-bending moment ratio of 0.2, both columns reached similar lateral load and torsional moment capacities and were able to attain lateral-drift capacities exceeding the minimum requirements of North American design codes and guidelines.