الفهرس 
CHAPTER (1): INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The Strengthening processes of existing structures have recently become taking a different curve than before, due to the rapid development of construction and building operations. As a reason, there was no option for the science of repair
and strengthening facilities except to keep pace with that development. In the last decade, a lot of new and effective repair and strengthening techniques came to light and became available to keep pace with the rapid development of construction processes. One of those techniques was strengthening by using
external prestressing. This technique was very useful for rehabilitating existing beams. External prestressing was an effective strengthening technique because of the reduction of deflections, stresses, and cracks in structural members. In this research, the strengthening of reinforced concrete beams by using external prestressing was studied. The experimental program was divided into two parts. The first considers the main mechanical properties of concrete as well as reinforced concrete beams used. The fresh properties were discussed in terms
of slump values. The hardened concrete properties were discussed in terms of
compressive strength, splitting tensile strength, flexural strength, and bond
strength. The second part was conducted to study the feasibility of strengthening the RC beams with external prestressed tendons. Two prestressing profiles were used, straight and trapezoidal. The differences between the two methods were studied. Based on this study, the strengthening of reinforced concrete beams by using external prestressing increased the load-carrying capacity and decreased the deflection and crack width. The external prestressing process was a very effective, useful, and relatively cheap technique compared to the cost of reconstructing a new structure.