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In this research, steel plate-fiber concrete composite jackets (SPFCJ) was used to strengthen the RC beams. The accuracy of the analysis method was evaluated by modeling RC beams fabricated in the laboratory, and a good agreement was observed. Variables in the finite element method (FEM) analysis include the strength class of concrete used in the main beam (15,20, and 25 MPa), the beam length (1.4 and 2.8 m), the type of jackets (RC jacket, SPFCJ, and CFRP sheet), and jacket thickness (40, 60 and 80 mm). SPFCJ is effective for all three concrete grades and increased the energy absorption capacity by 1.88, 2.07, and 2.25 times, respectively. The bearing capacity of the strengthened beam with 60 mm composite jackets increased by 79 and 20% more than the values corresponding to jackets with 40 and 80 mm thickness. The jacket thickness parameter significantly influences the response of strengthened beams with the proposed composite jackets. Depending on the dimensions and geometric characteristics of the beam, the appropriate thickness for the jacket should be considered, and increasing the thickness can not always improve the beam bearing capacity.

Reinforced concrete shear walls with features such as high stiffness, good performance in earthquakes, ductility, and high bearing capacity in earthquake-prone regions are widely used as convenient and reliable structural systems in medium-and high-rise reinforced concrete buildings. However, due to architectural limitations, the use of opening in shear walls is unavoidable. Fiber-reinforced polymer sheets with unique structural characteristics and easy implementation have been used in recent years for rehabilitating concrete structures, especially shear walls. In this study, using the finite element method, the effect of openings with different sizes and locations in reinforced concrete shear walls was studied. The effect of retrofitting specimens with openings by carbon fiber-reinforced polymer sheets with different patterns and thicknesses on the structural behavior of shear walls was also investigated. According to the results, opening reduced the bearing capacity, energy absorption capacity, and stiffness but increased wall displacement. Different reinforcement patterns and different thicknesses of carbon fiber-reinforced polymer sheets had different effects on improved structural behavior of shear walls. Reinforcement with carbon fiber-reinforced polymer sheets is one of the effective ways to rehabilitate concrete shear walls with opening.

Abstract. This study describes the implementation of a 2-D finite element model of an integral abutment bridge (IAB) system which explicitly incorporates the nonlinear soil response. The superstructure members have been represented by means of three-node isoparametric beam elements with three degrees of freedom per node. The soil mass is idealized by eight node isoperimetric quadrilateral element at near field and five node isoparametric infinite element to simulate the far field behavior of the soil media. The non-linearity of the soil mass has been represented by using the Duncan and Chang hyperbolic model. The applicability of this model was demonstrated by analyzing a single span IAB. This study has shown that the soil nonlinearity has significant effect on the response of the structure, where the displacement that have been obtained on basis of nonlinear analysis is 1.5-2.0 times higher than that obtained from linear analysis. The stress magnitudes in the nonlinear analysis are also higher where in some point the difference reached almost 3 times.

The current investigation focused on the development of effective and suitable modelling of reinforced concrete component with and without strengthening. The modelling includes physical and constitutive models. New interface elements have been developed, while modified constitutive law have been applied and new computational algorithm is utilised. The new elements are the Trusslink element to model the interaction between concrete and reinforcement bars, the interface element between two plate bending elements and the interface element to represent the interfacial behaviour between FRP, steel plates and concrete. Nonlinear finite-element (FE) codes were developed with pre-processing. The programme was written using FORTRAN language. The accuracy and efficiency of the finite element programme were achieved by analyzing several examples from the literature. The application of the 3D FE code was further enhanced by carrying out the numerical analysis of the three dimensional finite element analysis of FRP strengthened RC beams, as well as the 3D non-linear finite element analysis of girder bridge. Acceptable distributions of slip, deflection, stresses in the concrete and FRP plate have also been found. These results show that the new elements are effective and appropriate to be used for structural component modelling.