Fiber-reinforced polymer (FRP) composites do not only possess superior mechanical properties, but can also be easy to tailor, install, and maintain. As such, FRPs offer novel and attractive solutions to facilitate strengthening and/or retrofitting of aging, weakened, and upgraded structures. Despite the availability of general code provisions, the design and analysis of FRP-strengthened concrete structures is both tedious and complex—especially in scenarios associated with unique loading conditions. As such, designers often leverage advanced finite element (FE) simulation as a mean to understand and predict the performance of FRP-strengthened structures. In order to narrow this knowledge gap, this paper details suitable strategy for developing and carrying out advanced FE simulations on FRP-strengthened concrete structures. The paper also covers techniques related to simulating adhesives (bonding agents), material constitutive properties and plasticity (cracking/crushing of concrete, yielding of steel reinforcement, and delamination of FRP laminates), as well as different material types of FRP (CFRP, GFRP, and their hybrid combinations), and FRP strengthening systems (sheets, plates, NSM, and rods) under various loading conditions including ambient, earthquake, and fire. The principles, thumb rules, and findings of this work can be of interest to researchers, practitioners, and students.

The use of externally bonded carbon fiber-reinforced polymers (CFRPs) as strengthening systems to improve the condition and overall capacity of existing reinforced concrete structural members is found to be a promising scheme. This field has drawn the attention of many researchers in the past two decades through the implementation of much theoretical work as well as experimental studies. It was evident through many experimental investigations conducted by a number of researchers that the bond action between fiber-reinforced polymers and reinforced concrete members is considered one of the main factors affecting the performance and reliability of external strengthening systems and warrants further investigation. Debonding failure is a brittle mode of failure that may occur prematurely before strengthened members develop their full composite and expected capacities. This paper aims to investigate the bond behavior between the CFRP-concrete interface via experimental work and finite element (FE) simulations. The experimental study consisted in testing nine concrete prisms with different bonded lengths of the CFRP plates that vary between 25% (60 mm), 50% (120 mm), and 75% (180 mm) of the total length of the concrete prisms and instrumented with strain gauges. A FE simulation model was created and validated using the experimental results of the tested specimens, and a parametric study was carried out to investigate the effect of several parameters on the bond behavior between CFRP and concrete surfaces. The trend of the FE simulation results shows a good agreement with the experimental results and those available in the literature. It was observed that the optimum length of the CFRP plate is in the range between 150 mm and 160 mm when bonded to concrete surfaces. Other conclusions and observations were drawn based on the experimental and numerical results.

The main objective of this investigation is to assess the feasibility of using aluminum alloy (AA) plates as externally bonded strengthening material for reinforced concrete members. Consequently, the main aim of this paper is to experimentally investigate the bond stress-slip behavior of AA plates adhesively bonded to concrete surface. In addition, the effect of different AA surface roughness on the bond stress and bond behavior of AA-concrete interface was also investigated. Twelve specimens with six different surface roughnesses were instrumented and tested under single shear. The tested specimens have two bonded lengths – long bonded lengths (75% of prism length) and short bonded length (30% of prism length). It was observed that the bond shear stress, loading capacity, and failure modes vary with AA surface roughness and bonded length. The load capacity and maximum bond stress increased by 143.6 and 342.6%, respectively, for long bonded length (75%) of randomly grinded AA surface compared with those of normal AA surface. Such increase in load capacity and bond stress demonstrated the potential of using AA as externally bonded strengthening material. In addition, the bond-slip behavior of the AA plates was predicted, with reasonable level of accuracy, using existing bond-slip models that were originally developed for fiber-reinforced polymer materials. However, a more elaborate study is warranted to develop bond stress-slip models, specifically, for AA-concrete interface.

The fatigue life of steel reinforcing bars depends on the energy dissipated during cyclic loading. Steel bars play a major role in energy dissipation in reinforced concrete structures under low-cycle fatigue loading during earthquakes. In this study, seven artificial neural network (ANN) models were developed to predict the fatigue life of steel bars based on energy dissipated in the first cycle (W1), average cycles (WA), and total energy dissipated in all cycles (WT). The ANN-predicted number of reversals to fatigue failure (2Nf) were comparable to the experimentally measured values and also to the values predicted using nonlinear regression (NLR) models. The best overall ANN result was obtained when W1, WA, and WT were used together as input for the ANN with correlation coefficient r=0.985, normalized mean square error (NMSE)=0.0517, and mean absolute percent error (MAPE)=10.8%. When WA was used as a single input, the predicted 2Nf are also relatively accurate. In conclusion, the developed ANN m...