There is a shortage of studies related to the effects of fiber anchorage on the behavior of strengthened frame members undergoing seismicity. This study models experimental data of four frame specimens having seismic code-compliant joints with CFRP-strengthened members secured with different fiber anchorage systems. Analytical formulation using a trilinear moment-curvature response is extended to accurately model the envelope curves of the vertical frame member by including the nonlinear interaction from the horizontal member, which presents a new solution. Furthermore, the experimental hysteresis data provides a basis to formulate an analytical model based on phenomenological observations to capture the cyclic load-drift curves. When modelling the drift-based hysteresis loops, each cycle is divided into three linear regions in the unloading and reloading paths, respectively. These are named push-bound, inflection range, and pull-bound regions. Curves correlating the ratio of unloading and reloading slopes of these regions to the initial backbone curve slope as a function of the drift ratio to yielding drift ratio are generated. These curves define the rules that the hysteresis loops behave according to. The hysteresis rules are calibrated against two different RC frame assemblies and used to predict the cyclic response of two other frame assemblies with similar features.

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.

Unreinforced masonry buildings (URM) are particularly vulnerable to local out-of-plane failure mechanisms of the walls during earthquakes. This study investigates the effectiveness of a relatively novel class of inorganic composite materials, namely Fibre Reinforced Mortars (FRM), for the out-of-plane strengthening of masonry walls. Experimental tests by using a setup to perform out-of-plane tests on masonry panels, part of an enlarged ongoing testing campaign, are presented herein. Two types of masonry walls are investigated: solid clay brick masonry walls and tuff masonry walls. The specimens are subjected to compressive axial load and out-of-plane horizontal actions according to a “four-point bending test” scheme. Two specimens are reinforced before testing with FRM in double-side configuration, while other two specimens are tested in their bare configuration. Experimental results in terms of capacity curves and deformed shapes are reported and discussed. The preliminary results attest that FRMs are effective in increasing the out-of-plane capacity of masonry walls and in postponing the activation of the out-of-plane failure mechanism.

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.