الفهرس 
St. Venant Theory for Elastic Noncircular SectionsOnly 14 pages are availabe for public view
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Abstract
Torsional effects dominate the structural behavior in many structures such as helical stairways, curved beams, and eccentrically loaded box beam. Retrofitting or strengthening of concrete structures by wrapping FRP sheets provides a more economical and technically superior alternative to the traditional techniques in many situations because it offers high strength, low weight, corrosion resistance, high fatigue resistance, easy and rapid installation and minimal change in structural geometry. An experimental test program of fourteen reinforced concrete beams of identical dimensions and reinforcement is carried out to study the effect of using different methods and materials in the repair and strengthening of RC beams subjected to pure torsion. Two major techniques of repair and strengthening were applied. The first method was applying additional layers on the external surfaces subjected to torsional moment, while the second was inserting embedded bars or intertwined rods as stirrups inside manufactured grooves cut around the perimeter of the specimen at the part subjected to torsion. The behaviors of the tested specimens were investigated and compared to illustrate the effectiveness of each method and material of strengthening. A computer program based on nonlinear finite element analysis of isoparametric layered elements is developed and a new specified compound element is used to simulate the confined concrete members by external layers of GFRP or CFRP as well as to simulate the effect of near surface mounted techniques using steel stirrups or intertwined GFRP or CFRP rods. The nonlinear analysis includes the stress strain relationships for the different materials, crushing, propagation of cracks, tension stiffening effects. The finite element results are also compared and verified with the experimental results. The main conclusions and recommendations were drawn from the study, discussed and summarized. The research shows that the methods of repair or strengthening using CFRP wraps was the better than the traditional method using steel stirrups.