الفهرس 
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Abstract
The negative bending moment zone in continuous RC composite girders is exposed to the environmental effect. That could impair such zone especially these zones are hidden below the finishing such as asphalt layers. Therefore, it is necessary to find out appropriate improvement technique to enhance the cracking characteristics such as spacing and width, at the service conditions as well as to increase the ultimate capacity. The current thesis investigates experimental the behavior of strengthened continuous RC composite girders using different techniques the studied techniques used (HPC) at the flange in the negative moment zone by two grades and stirrups as shear connectors. (HSC) at precast prestressed slab by two levels with internal steel fasteners and (HSC) at precast slab strengthed by GFRP with different number of layers and connected with GFRP bands wrapping at the negative moment zone. This research consists of six chapters the first chapter presents the problem statements, methodology and the organization of the work within the thesis. Chapter (2) presents comprehensive over view on the conducted researches using different strengthening techniques. Chapter (3) presents detailed description of the characteristics of materials used for both monolithic and composite girders that have been used besides their dimension, reinforcement and form work. Chapter (4) describes the experimental results of the tested beams including deflections, strains, cracks width, cracks number, cracking load, yielding load, failure load, and mode of failure. Chapter (5) presents an analytical study of cracking and ultimate moment capacity of the proposed composite section. Also, a comparison between the proposed model and experimental values is presented. Chapter (6) summarizes the main conclusions extracted from the current research and recommendations set based on the experimental and analytical findings. In addition, scope for future work is highlighted.