الفهرس 
LITERATURE REVIEWOnly 14 pages are availabe for public view
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Abstract
Torsion has been considered with an increasingly greater importance by engineers. Some of the typical cases are space frames, spandrel beams, beams supporting balconies, eccentrically loaded beams, spiral staircases, horizontally curved beams, skew bridges…. etc. Transverse openings, in concrete beams may be essential required for accommodating utility services in a building structure. Provision of openings through a beam, however, changes its simple mode of behavior to a more complex one. Therefore, the design of such beams needs special treatment. Strengthening or retrofitting of concrete structures to compensate the presence of opening not only depends on the applied material but also depends on the used technique. Carbon Fiber Reinforced Polymer (CFRP) plates provides a more technically alternative to the traditional methods of strengthening in many cases as it gives high strength, low weight, corrosion resistance, easy and quick installation and less changes in structural geometry. An experimental test program of twenty-one reinforced concrete beams with central large openings strengthened by using additional layers of externally bonded steel plates or Fiber Reinforced Polymer (FRP) woven wraps with different techniques and subjected to pure torsion is prepared. The behaviors of the tested specimens were investigated and compared to identify the effectiveness of each method and material of strengthening to increase the torsional strength of beam with opening. A computer program based on the two dimensional nonlinear finite isoparametric degenerated layered shell elements is developed to simulate the different specimens and a new specified compound element is used to represent the reinforced concrete beam with opening by adding external bonded layers of steel or CFRP plates around the opening in the space. The nonlinear analysis includes the stress strain relationships for the concrete, steel reinforcement and different strengthening materials, propagation of cracks, tension stiffening effects and crushing of concrete. The finite element results are also compared and verified with the experimental test results. The main conclusions and recommendations drawn from the study were discussed and summarized. The research shows that the methods of strengthening by using steel strips fixed by eboxy and steel dowels and CFRP plates gave best results.