الفهرس 
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Abstract
This thesis presents an experimental study to investigate the effect of core drilling on the Reinforced Concrete (RC) column capacity, it also discusses how to restore the drilled RC column capacity. where the core drilling test is the most important and accurate test to measure concrete strength for existing buildings, but it is classified as destructive test and it has negative effect on column capacity.
The experimental work consists of sixteen rectangular concrete columns, the columns were divided into three groups. The first group consists of three column with cross section 160 x 300 mm and concrete strength was 26.5 MPa, the second group consists of seven rectangular columns with cross section 160 x 300 mm and concrete strength was 29 MPa, the third group consists of six rectangular columns, with cross section 230 x 300 mm and concrete strength was 49 MPa. All columns have the same column total and clear height which is equal to 1900 and 1300 mm, respectively.
For columns of first groups, core specimens were taken with diameters equal to 50 mm and 100 mm and the length of core specimens equals to 130 mm. For all columns of the second and third groups, core specimens were taken with diameter and length equal to 100 mm and 130 mm, respectively. On loading at 40% of column load capacity, the core has been taken to stimulate what happens in nature where core is drilled in buildings. The discussion presents the different strengthening techniques for the core drilling zone to restore the un-voided column capacity, strengthen techniques such as using Carbon Fiber Reinforcement Polymer (CFRP) and anchored steel plates.
The experimental results show that the common method which used for strengthening core void by filling the void with grout was not efficiency where this common method make losses in column capacity by 21% approximately. But the suggested technique with using CFRP is the best method for strengthening core void which make losses in column capacity less than 10%. By wrapping CFEP sheets around column at core location after filling it by grout make confinement for the concrete which restore the column capacity. This thesis uses different strengthen methods with CFRP, the case uses three anchored CFRP achieve the more restoration for column capacity.
The Finite Element Method (FEM) is used to model the columns specimens by using the ABAQUS Software program. The Numerical models present more parametric study to develop the suggested strengthening techniques by using CFRP. The factors which are studied by the program as width of CFRP, number of CFRP layers and width of column, then the numerical results achieve limits for CFRP sheets while are applied to strengthen core drilling location.
The experimental and numerical studies in this thesis show good agreement of the results, Also these results can be applied practically in the field of structural engineering. Finally, recommendations are given for the reduction in the RC column load carrying capacity under the effect of core hole.