Many bridges built in the past 50 years are reinforced concrete. Because of their normal deterioration, the introduction of new safety standards, and the increasing traffic volume and loads, a high percentage of the older bridges require rehabilitation or expansion. Often, the choice between constructing a new bridge and rehabilitating the existing one must be made. An essential factor in making a sound decision is knowledge of the strength of the bridge in its existing form. Unfortunately, the inelastic response, load distribution characteristics, and ultimate strength of bridges can not be realistically assessed by use of simplified procedures currently used for design and evaluation. Prediction of this behavior ultimately requires extensive experimental tests or advanced analytical techniques. In many cases, analytical methods are more economical and expedient than laboratory or field testing, and a number of researchers have extolled the potential of using finite element analysis to predict bridge response.The primary objective of this study is to establish and demonstrate a convenient, reliable, and accurate methodology for analyzing reinforced concrete structures with particular emphasis on Reinforced Concrete Bridge and develop a capability for predicting stress and strain distribution through the thickness of bridge decks. A secondary objective of the analytical evaluation include the development of a finite element model that could correctly represent global bridge behavior and accUl1telypredict strains, stresses and displacements in the deck. A specific objective is to investigate the enhancing effects of compressive membrane action on the ultimate flexural strength of bridges.A nonlinear finite element program, NONLACS2, developed by Kheyroddin, was selected as the basic platform for this study. The next step was to demonstrate how reinforced concrete is modeled within NONLACS2 and to validate the results predicted by the NONLACS2 program by comparing them with relevant experimental data and accepted design calculations. The finite element model of a reinforced concrete beam, simply supported, and subjected to a uniformly distributed load, was initially investigated. Further verification of the validity of finite element models of reinforced concrete components were demonstrated by comparing the predicted response of the model with experimental results obtained from laboratory tests of a two-way reinforced, simply supported, concrete slab. Tests on existing slab and beam bridges around the world have shown that many of these structures possess a greater load capacity than current design codes predict they should have. Many researchers attribute the additional capacity to a phenomenon known as compressive membrane action. Compressive membrane action occurs as a result of in plane restraints that restrict the horizontal expansion of the bridge deck as it deflects vertically. For this purpose, finite element modeling of slabs with idealized end restraints has been carried out.With the information acquired through the research proposed in this paper, a more complete understanding of the nonlinear behavior of RC bridges was obtained. This would allow a more realistic assessment of the flexural strength of these bridge types to be made. Some important points can be noted. The type of end restraint imposed on a slab significantly affects its load deflection behavior. The ultimate load capacity of a slab with fully restrained ends is almost five times greater than that of a simply supported slab. The stiffness of the horizontally restrained slabs is also significantly greater. The behavior of slabs with pinned ends depends greatly on the height at which the horizontal support acts. T-shape beam have a high lateral strength rather than rectangular beam and cause decreasing of deflection of deck. The stiffness of the T-shaped beams was largely responsible for the mode of failure.

Plastic hinge properties play a crucial role in predicting the nonlinear response of structural elements. The plastic hinge region of reinforced concrete normal beams has been previously studied experimentally and analytically. The main objective of this research is to evaluate the behavior of the plastic hinge region of reinforced concrete deep beams and its comparison with normal beams through finite element simulation. To do so, ten beams contain six deep beams, and four normal beams, under concentrated and uniformly distributed loading, are investigated. Lengths in the plastic hinge region involving curvature localization, rebar yielding, and concrete crushing zones are studied. The results indicate that the curvature localization zone is not suitable for the prediction of plastic hinge length in reinforced concrete deep beams. Based on the results it can be stated that in simply supported normal beams the concrete crushing zone is focused on the middle span, but in simply supported deep beams by creating a compression strut between loading place and support, the concrete crushing zone spreads along the compression trajectory. The rebar yielding zone of simply supported beams increases as the loading type is changed from the concentrated load at the middle to the uniformly distributed load.

Composite Reinforced Concrete (RC) wall system refers to a cantilever composite wall, where steel or Fiber Reinforced Polymer (FRP) components are embedded in or attached to an RC wall. The results of an analytical and parametric study on the effectiveness of using externally bonded steel plates and FRP sheets on RC shear walls as a retrofit technique so as to improve their seismic behavior have been investigated in this paper. Calibration and verification of a base RC wall has been done by comparing the results of the finite element model and also the experimental model. Analytical results are used to evaluate the capacity curves (Load-Displacement relationships) of strengthened RC shear walls. Analysis results of a model with an optimized thickness of a steel jacket instead of an over-hanging part of the boundary element show the ductile behavior of a strengthened wall close to the behavior of the base RC wall with boundary elements; this achievement would lead to the theory that steel jacketing could be an alternative for the boundary elements of RC shear walls. The application of externally bonded Carbon Fiber Reinforced Polymer (CFRP) sheets is an effective seismic strengthening procedure in order to improve the behavior of reinforced concrete shear walls. In the retrofit method, using CFRP sheets, the flexural and shear strength would be increased by applying the CFRP sheets with the fibers oriented in the vertical or horizontal direction. The carbon fiber sheets are used to increase the precracked stiffness, the cracking load (up to 35%) and the ultimate flexural capacity (up to 18%) of the RC walls. Finally, a wrapped CFRP sheet around the plastic hinge area of the RC wall in parallel with boundary elements, provides not only enough shear strength, resulting in a ductile flexure failure mode, but also the confinement of concrete in the plastic hinge leads to an increase in the ductility of the RC wall.

Most industrial-practical projects deal with nonlinearity phenomena. Therefore, it is vital to implement a nonlinear method to analyze their behavior. The Finite Element Method (FEM) is one of the most powerful and popular numerical methods for either linear or nonlinear analysis. Although this method is absolutely robust, it suffers from some drawbacks. One of them is convergency issues, especially in large deformation problems. Prevalent iterative methods such as the Newton-Raphson algorithm and its various modified versions cannot converge in certain problems including some cases such as snap-back or through-back. There are some appropriate methods to overcome this issue such as the arc-length method. However, these methods are difficult to implement. In this paper, a computational framework is presented based on meta-heuristic algorithms to improve nonlinear finite element analysis, especially in large deformation problems. The proposed method is verified via different benchmark problems solved by commercial software. Finally, the robustness of the proposed algorithm is discussed compared to the classic methods.

In this paper, dynamic modeling of flexible links manipulators is discussed. The modeling approach is based on the Lagrange equations and finite element discretization method. In order to obtain the closed form of dynamic equations for flexible links manipulators, symbolic calculation in MATLAB's symbolic mathematics toolbox is utilized, then the non-linear dynamic equations of a single-link manipulator have been obtained and compared with the results presented in other references. In this study, the nonlinear effects of centrifugal, Coriolis and gravity are Also considered which is rarely studied in other contributions. Then the equations of motion are solved by the Runge-Kutta method for different levels of excitation torque. The simulation results show that at low levels of excitation torque, the linear and non-linear models have the same results, while with the increase of the excitation level, the difference between the linear and non-linear models is considerable and the size of the elastic components in the non-linear model becomes smaller.

Changes of up to 80°C has been reported for oral cavity temperature. This could well effecti on the nature of restorations for example failure of bonding of adhesive restorations. It is advocated that using opaque layer in porcelane to restorations could reduce this problem. This experimental study was designed to evaluate the effect mentioned using finitelement analysis method.Results showed that cooling has a more destructive effect than warming process restorations with the presence of opaque having a finitelement analysis effect on restorations.

This article demonstrates a new approach for nonlinear finite element analysis. The methodology is very suitable and gives very accurate results in linear as well as in nonlinear range of the material behavior. Proposed methodology can be regarded as stress based finite element analysis as it is required to define the stress distribution within the structural body with structural idealization and modelling assumptions. The methodology eliminates the lengthy and tedious procedure of step by step and then iterative procedure adopted classically for nonlinear analysis problems. One dimensional problem of a simple bar loaded axially is solved to formulate the basic principles. Two dimensional problem of a cantilever beam bending and a torsional problem are solved for further demonstrating and strengthening the method. Results of torsional problem are verified with experimental results. The method is applicable for material nonlinear analysis only.

Most industrial-practical projects deal with nonlinearity phenomena. Therefore, it is vital to implement a nonlinear method to analyze their behavior. The Finite Element Method (FEM) is one of the most powerful and popular numerical methods for either linear or nonlinear analysis. Although this method is absolutely robust, it suffers from some drawbacks. One of them is convergency issues, especially in large deformation problems. Prevalent iterative methods such as the Newton-Raphson algorithm and its various modified versions cannot converge in certain problems including some cases such as snap-back or through-back. There are some appropriate methods to overcome this issue such as the arc-length method. However, these methods are difficult to implement. In this paper, a computational framework is presented based on meta-heuristic algorithms to improve nonlinear finite element analysis, especially in large deformation problems. The proposed method is verified via different benchmark problems solved by commercial software. Finally, the robustness of the proposed algorithm is discussed compared to the classic methods.

Throughout the present study, a simulation of tire–soil interaction model was considered with special view at the two-Dimensional (2-D) Finite Element Method (FEM) model of carcass. In contrast with the existing 2-D tire models, in the new model it was not tried to find a mathematical description for the global reaction of tires, but was based on a mechanical structure of the basic components of a tire. Here, the reproduction of the carcass as the most challenging part for a 2-D model was described in details. Also, the reproductions of tire wall model as a hyperelastic material and soil model as an elastopelastic one were investigated. Coefficients of mechanical behavior of silty-loam soil were accurately assessed to obtain an effective simulation. The results of simulation implemented in MATLAB7 Software, showed that the radial-ply tire benefitted from a greater tractive efficiency than the bias one within the same conditions on silty-loam soil. Bias-ply tires suffered from a greater motion reduction (slip) and while their gross traction was slightly greater than that of radial-ply tire. The net traction force was estimated as the same for both tires. Also, the results of simulation and tests revealed that the radial-ply tire bore lower rolling resistance than bias-ply tire on silty-loam soil in similar conditions. Based upon the simulation results, the effects of slip, inflation pressure and mechanical stiffness of soil on tractive efficiency were satisfactorily predicted.