الفهرس 
CHAPTER(1) introductionOnly 14 pages are availabe for public view
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Abstract
Finally, the theoretical work was done using the nonlinear finite element programme based on the isoparamteric Timoskenko beam element. In order to allow the development of cracks through the thickness and to represent the properties of different material through the thickness a ”layer approach” was adopted. Nonlinear effects due to the yielding of steel, cracking and crushing of concrete were included. this programme were used to carry out the theoretical analysis of the experimental ductile models.
5-2 Conclusions
Based on the obtained experimental and theoretical results, the following conclusions can be drown
(A)T-Beams with ended column
1- The ultimate strengthen of reinforced concrete T-beam subjected to negative moment could be increased by the addition of externally bonded steel plates. This increase depends on the cross-sectional dimensions of the steel plate added i. e. depends on the plate width to thickness
ratio (bit). For T-beams strengthened with steel plate of ~
similar areas, increasing the bit ratio from 33.75 to 58.33, 132.5 and 500 increased the gain in the ultimate capacity from 71\ to 100\, 157\ and 157\ over that of unplated beam respectively.
2- For the same dimensions of the steel plate added, using one plate glued at the middle of the tension surface of the flange is better in increasing the ultimate strength 186
by an average of 14.58 \ than using two plate glued at the sides of the tension surface of the flange. Also using one plate only showed a slight reduction in both the plate strains and the central deflection than using two plates.
3- For a given steel plate area, increasing the bit ratio from 33.75 to 58.33 changed the mode of failure from shear Ibond to a combination of flexure and shear Ibond, while the mode of failure was flexure for bit ratio equal to or greater than 132.5.
4- Beams which 62\ of their conventional reinforcement were replaced by glued steel plates of (bit) ratio equal or greater than 132.5 showed a significant increase in their ultimate load of 40\ over the 90ntrol beams BC2. i. e. up to 62\ of the conventional reinforcement of the beam can be replaced by external glued steel plate and the composite section still achieve its theoretical ultimate capacity.
5- As the shear span to effective depth (aid) ratio decreased the effect of the glued steel plate in improving the ultimate load of the strengthen beams decreased.
6- The addition of glued steel plate to the reinforced concrete T-beams can substantially increased their flexural stiffness, delayed the appearance of the first visible crack loads, reduced the crack widths and improved and the structural deformations at all load level.
7- For the same area of the steel plate added, increasing the width to thickness ratio (bit) up to 132.5 increase both the ultimate strength and the plate strains, decrease the
bending stiffness and had no clear effect in the cracking load.
8- The CP110 method for evaluating the ultimate load underestimated the value of the ultimate load of beams strengthened with steel plate of (bIt) ratio more than 132.5 and failed by flexure while overestimated those of plated beams with (bIt) ratio less than 132.5 and failed by shear bond or shear only.
9- from the experimental results obtained, a steel plate of bIt ratio equals to 130 is recommended to strengthen a reinforced concrete T-beam, with ended column subjected to negative moment or strengthen an inverted T-beam.
(B)T-beams with continuous columns
lO-AII the methods which were used in strengthening the beams with continuous column except method B which used 1n strengthening beam B3 introduced the same improvement 1n increasing the ultimate load. The maximum percentage increase obtained was 42.8\ over that of unplated beam
11-Method A of strengthening introduced the highest value of cracking load and flexural stiffness, and consequently the lowest value of deflection and crack width.
12-Either method A or 0 used in strengthening B2 and B5 15 recommended to strengthen a beam- column connect1on (joint) because they are simple in application and economical. Method A is preferable this depends on the column dimensions.