PSI - Issue 54

Ahmed Selim et al. / Procedia Structural Integrity 54 (2024) 601–608 Selim et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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Finite element modeling (FEM) is a very powerful tool for structural analysis applications. It can accurately simulate the behavior of structural elements by developing a model composed of fine-sized elements. Structural engineering researchers have been using finite elements to perform analytical predictions for various applications. To illustrate, a study by Abuodeh et al. (2019) developed finite element models to simulate the behavior of RC beams with different anchorage systems. The study was composed of a reference beam, a beam externally strengthened with aluminum alloy plate, and a beam externally strengthened with aluminum alloy plate and anchored with CFRP U-wraps. Comparison between FE results and experimental results has shown great agreement, which indicates the effectiveness of the FEM. Another structural application of FEM showing its effectiveness in structural simulation was done by Selim et al. (2022) and Mahmoudi et al. (2022). In these two studies, FEM was developed to evaluate the behavior of engineered cementitious composite (ECC) prisms, beams, and dogbone specimens. The beams and prisms were tested in a four-point load bending test, while the dogbone specimens were tested in a uniaxial tensile test. The authors observed that the FE showed reasonable predictions for experimental results with high accuracy for the prisms and dogbone specimens compared to the beams. A 3D nonlinear finite element model that takes into account the orthotropic nature of the polymer's fibers and uses a layer of adhesive epoxy resin as an interface element was used to model beams externally strengthened using carbon fiber reinforced polymers (Hawileh et al. 2011). It was observed that the responses of the finite element beam model were in good agreement with those of the experimental tests. Similarly, 3D nonlinear finite element models of reinforced concrete (RC) beams externally strengthened in flexure with mechanically fastened and externally bonded aluminum alloy plates were developed (Abuodeh et al. 2021). From the result of the simulation, it was concluded that the finite element models can serve as a valid predictive platform for simulating the flexural behavior of RC beams externally strengthened with aluminum plates. Panahi et al. (2021) conducted a study to analytically investigate the effectiveness of flexural strengthening in reinforced concrete beams using a combination of externally bonded FRP sheets and near-surface mounted FRP rods. The numerical analyses were performed using the finite element software ABAQUS, known for its accurate simulation capabilities in studying the flexural behavior of reinforced concrete beams strengthened with FRP composites. The validation of the finite element simulation began with a comparison to experimental studies found in the literature, covering both un-strengthened and FRP-strengthened beams. The validated model of the un strengthened beam, employed as a control beam, was then used to simulate reinforced concrete beams strengthened through externally bonded FRP sheets and a combined approach involving externally bonded and near-surface mounted techniques. The numerical results encompassed mid-span bending moment deflection, ultimate bending moment, failure deflection, and ductility index. Based on the findings of this study, it is concluded that the developed finite element models for externally bonded, near-surface mounted, and combined externally bonded near-surface techniques can serve as alternative solutions for structural engineers in design-oriented parametric studies of reinforced concrete elements undergoing strengthening. 2. Finite element modeling (FEM) In this study, two 3-D non-linear finite element models were developed to study the effect of grooving the FRP laminate inside the concrete prism. The results of this model were compared with another FEM of a typical externally strengthened concrete prism, where FRP is externally bonded to the surface of the substrate of a simply supported prism. Modeling was done using the commercial multipurpose software package ABAQUS. 2.1. Elements & geometry The two models have a total length of 330 mm, a thickness of 70 mm, and a height of 35 mm as shown in Fig. 1 and 2. The first model (reference specimen) was modeled using an 8-node linear brick C3D8R element with reduced integration and hourglass control. However, the second model (with grooved FRP) was modeled using a 10-node quadratic tetrahedron C3D10. C3D10 was used rather than C3D8R because the grooving makes a typical brick element not applicable for this model. The roller supports and plates applying the two-point loads were modeled as a 4-node 3-D bilinear rigid quadrilateral R3D4 element. In addition, FRP was modeled using an 8-node linear brick C3D8R similar to concrete. The FRP was modeled as a single composite material since modelling different materials