الفهرس 
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Abstract
This investigation is concerned with the development of a static material nonlinear finite element computer program for the analysis of reinforced concrete (R.C.) slabs and deep beams retrofitted with fiber reinforced plastics (FRP) . The proposed model for analyzing reinforced concret section attached with FRP is based on an isoparametric 4-nodes layerd finite element approach. Using this approach, the composite section model of R.C and FRP is divided up through the thickness into anumber of concre , steel and FRP layers.
Each layer is assumed to be in a state of plane stress and then one of the material models (concrete, steel or FRP) is applied to each layer individually. The Concrete model takes The elastolastic behavior in compression domain, and the elastic brittle fracture behavior in tension domain, into consideration, as well as compression softening. Crack tension stiffening, and rotating crack concept. The steel is modeled by an idealized bilinear curve identical in both tension and compression whil the FRP is treated as an orthotropic layer with eelastic brittle fracture behavior. The constitutive laws are incorporated into the proposed finite element computer program and an incremental-iterative solution technique combines with Newton-Raphson strategy is used for solving the governing nonlinear equations. Several structures such as tow-way slabs, flat plates and deep beams were modeled by the developed program. A. very good agreement between the numerical prediction and available theoretical and experimental results in the literature was found.
Within the scope of the current investigation, it was found that the moste effective parameter in retrofitting R.C element with FRP sheets was the hibier orientation angle. The deflection was mininum where the angle of orientation was perpendicular to the major crack directions.
It was also found that studying the cracks propagation and failure mechanism of the structure under consideration is very helpful to choose the approoriate location and direction of fiber orientation for the FRP used in the stregthening process.