ملخص الدراسة:

The aim of this research is to achieve the best thin concrete jacketing and bonding between column cores and their jackets among two used jacketing styles for repairing and strengthening damaged RC columns. The experimental work included casting of three identical unjacketed reference column specimens having similar cross sections of 100×100 mm and 300 mm high, Six monolithically cast reference column specimens were cast having two cross sections of 150×150 mm and 170×170 mm and 300 mm high and also a total of 36 identical column cores were cast having similar cross sections of 100×100 mm and 300 mm high. The 36 column cores were damaged by loading them to about 90% of their ultimate actual axial capacities under monotonic uniaxial compression then its four sides were repaired and strengthened by applying two jacketing styles with two jacket thicknesses namely; 25 and 35 mm. The two applied jacketing styles in this study were; Group1 consisted of 18 column cores jacketed by Normal Strength Concrete with maximum aggregate size of 4.75mm (NSC-4.75) with steel reinforcement and Group2 consisted of 18 column cores jacketed using Ultra High Performance Fiber Reinforced Self Compacting Concrete (UHPFRSCC) with steel reinforcement, the surfaces of all column cores also were prepared to bond the new and old concretes by three methods; roughening by mechanical wire brushing, scarification and using shear studs. The experimental results revealed that Group1 jacketed column specimens showed that the ultimate load capacity is about 2.13 times that of the unjacketed reference column, and about 1.16 times the monolithically reference columns respectively. Group2 jacketed column specimens showed a significant increase in the ultimate load capacity (about 3.4 times the unjacketed reference column), and about 1.86 times the monolithically reference columns respectively. The measured axial displacement of Group1 jacketed column specimens was almost the same of unjacketed and monolithically reference columns. Whereas the axial displacement of Group2 jacketed column specimens was about 2.0 and 2.10 times that of unjacketed and monolithically reference columns respectively. The results also showed that the failure patterns and crack formation were significantly influenced by the jacketing thickness and the surface roughening method. Applying the three methods of surface roughening which aimed at bonding the column cores and their jackets namely; roughened by mechanical wire brushing, mechanical scarification and using shear studs, revealed that using shear studs is the best among the three methods.

توثيق المرجعي (APA)