الفهرس 
Chapter 1 INTRODUCTION.Only 14 pages are availabe for public view
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Abstract
The current study focused on studying the behaviour of strengthened Reinforced Concrete (RC) Closed Circular Beams (CCBs) subjected to simulated tensile force. This study aimed to generate a better strengthening technique can be applied on RC curved beams using sustainable materials in order to enhance the major structural behaviour. Twelve RC CCBs were experimented up to failure. The main studied variables were concrete type, strengthening techniques and over lapping length for the reinforced material used for strengthening. The first group aimed to study the impact of concrete type. Four concrete types were introduced. There were Normal Concrete (NC), Engineered Cementitious Composite (ECC), High Strength Concrete (HSC) and High Strength Fiber Reinforced Concrete (HSFRC). The second group was designed to study the External Bond Reinforcement (EBR) Stainless Steel Plates (SSPs). In the third group, the post-tensioning system as a strengthening technique was studied. The last group studded strengthening technique using Near Surface Mounted (NSM) deformed steel bars. The study included a comparison between ultimate loads, elastic index, energy absorption, service load, horizontal displacement and cracking patterns of the all-tested beams. A validated modes for the RC CCBs were built-up using Finite Element Analysis (FEA) software package, ABAQUS. A parametric study was performed to evaluate the effects of SSPs and ECC. The use of HPCs could significantly improve the failure mode and cracking behavior of RCRBs. The cracking loads (Pcr) of RC CCBs made with HSC and HSFRC were 27% and 41% higher than that of the NC beam, respectively; the ultimate loads (Pu) were enhanced by about 54% and 57%, respectively. The use of ECC in RC CCBs could improve the absorbed energy by145% compared to the beam made with NC.