الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 270 |  |  |
| | | from | 270 | | |
Abstract
During the past period, the number of buildings with structural defects that affect the appearance and behavior of these buildings and their performance has increased and, in some cases, may lead to the complete collapse of some buildings. Attention has already been paid to study the causes of defects, collapses, and ways to avoid them and it was found that one of the reasons leading to this is weak resistance. The concrete is used for designing strength, thus reducing the flexural and shear strength of the used beams. The aim of the study is to find the best method for strengthening and repairing the continuous n shaped concrete beams made of weak concrete in order to raise their efficiency in resisting the flexural and shear strength. The section which is at the inner substrate of the continuous beam is the exposed section to the maximum negative bending moments and the maximum shear force. Several methods have been used to strengthen the beams of two-span at the intermediate substrate using various methods such as the use of Carbon Fiber Reinforced Polymer sheets, Engineering Cementitious Composite , plates ,and stirps steel. Therefore, the tested samples were divided into three main groups:The first group includes three beams reinforced externally using Carbon Fiber reinforced Polymer sheets, a thin layer of Engineering Cementitious Composite and steel plate The second group includes three beams reinforced internally using Carbon Fiber reinforced Polymer sheets, a thin layer of Engineering Cementitious Composite, and steel plate.The third group contains iii three beams that were strengthened externally and internally with steel stirps. The research is divided into six main sections: Chapter (1) This chapter includes a general introduction to presenting the main problem of the study, the desired goals, and the ways to carry out the study to reach its goals. Chapter (2) includes a review of what has been done in previous research, either for shear or for various strengthening methods, in addition to related research on redistribution moment for continuous beams. Chapter (3) includes the experimental program and the study of the behavior of used materials such as cement, sand, gravel, steel, epoxy material and used concrete mixture; Carbon Fiber reinforced Polymer sheets, Engineering Cementitious Composite, steel plate ,and stirps. Chapter (4) includes studying the results, analyzing them for all the beams with respect to the external deformation whether they are strains or deflection, studying the maximum loads of the collapses of the beams, and comparing them with the main ones that are not reinforced and moment redistribution for specimens and comparison between them. Chapter (5) includes an analytical study to calculate the maximum loads of collapse in shear and flexural and to calculate the values of the redistribution moment ratios. iii Chapter (6) shows the results extracted from the laboratory and analytical study that have been exposed, it olso contains some recommendations for future studies.