الفهرس 
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Abstract
This thesis discusses an experimental study on strengthening reinforced concrete (RC) halfscale columns with short lap splices using externally bonded Carbon Fiber Reinforced Polymer (CFRP) wrapping to improve the behavior and strength of these columns. Eleven reinforced concrete columns of dimensions 250 mm x 300 mm x 1300 mm: Eight columns were tested under eccentric axial load (two columns without lap splice, two columns with various lengths of tension lap splice, three columns with tension lap splice strengthened via various heights of carbon fiber reinforced polymer sheets (CFRP), and one column with tension lap splice strengthened via laminate strips on the tension side only), and three columns were tested under concentric axial load (one column without lap splice, one column with short lap splice, and one column with short lap splice strengthened via carbon fiber reinforced polymer sheets (CFRP)). The values of concrete strength, bar diameter, clear concrete cover, and reinforcement percentage were kept constant as 35 N/mm2 , 12 mm, 25 mm, and 0.904% respectively. The clear distance between spliced bars was equal to zero. The main studied variables were: 1- Lap splice length, 2- Height of strengthening in the lap spice zone. 3- Strengthening methods by wrapping two layers of carbon fiber reinforced polymer sheets (CFRP), or by using two vertical 100 mm laminate strips on the tension side only, in addition to wrapping one horizontal layer of carbon fiber-reinforced polymer sheets (CFRP) 70 mm wide at the top and bottom of the laminate strips. 4- Load eccentricity. Test results were illustrated and discussed in detail. Some of the outcome conclusions may be summarized as follows for the dimensions and reinforcement used in the present study: 1- The type of loading did not affect the behavior of columns without lap splices in this research. Repeated gradually increasing cyclic loading has been chosen to study the stability of the lap splice joint under different loading & unloading cycles rather than monotonic loading. 2- Using a lap splice length equal to 15 db is sufficient for developing the axial forces in the bars for the testing eccentricity value. 3- Using a lap splice length equal to 10 db is not sufficient for developing the axial forces in the bars compared to a lap splice length equal to 15 db. 4- Strengthening the defected column with a short lap splice equal to 10 db by using CFRP sheets with different jacket heights of 1.25 times, 2.00 times, and 3.00 times the lap splice length increased the stiffness of the columns become close to the column without lap splices. 5- Strengthening the defected column with a short lap splice equal to 10 db by using CFRP sheets with a jacket height equal to 3.00 times the lap splice length is close to the column without lap splices in terms of shortening, elongation, and ultimate load. 6- The column strengthened with carbon fiber reinforced polymer sheets, presented higher strength and better behavior compared to the one strengthened with laminate strips on the tension side only.