A Strut-and-Tie Model for Predicting the Shear Strength of Exterior Beam–Column Joints Strengthened with Fiber-Reinforced Polymers

This paper presents a new strut-and-tie model (STM) based on provisions of ACI 318-19 and ACI 440.2R-17 for estimating the shear strength of fiber-reinforced polymer (FRP)-strengthened exterior joints. Beam–column joints are vulnerable elements in reinforced-concrete structures subjected to seismic loadings and similar extreme demands. The FRP strengthening technique offers numerous advantages for retrofitting joints in existing structures with inadequate reinforcement or confinement. The design of FRP-strengthened joints requires the development of reliable procedures, including equations to predict the shear strength of the joint. Existing literature and research on STM warrant the development of simple, reliable, and practical specifications applied to a wide range of design criteria. The proposed method involves an STM model containing horizontal and vertical mechanisms. The methodology compares predicted joint shear strength results with existing experimental results to obtain a reliable design approach. This comparison, along with verification of alternative analytical results, indicates the appropriateness of the presented model for predicting the shear strength of FRP-strengthened joints. Results contribute to the enhancement and efficiency of the practical design of these joints.