الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Introducing openings in existing reinforced concrete slabs can severely weaken the slabs due to the cut out of both concrete and reinforcing steel which affects the overall behaviour of the slab. This research includes both experimental and numerical investigations for the use of Carbon Fiber Reinforced Polymers (CFRP) as a strengthening method to restore the capacity of continuous flat plates with openings in the column/field and column/column strips. A total of five medium scale reinforced concrete slabs (S1, S2, S3, S4 and S5) were tested in the laboratory up to failure. The specimens had dimensions of 3000x3000x60mm and divided to four square panels. Slab S1 served as the control specimen without openings while slab S2 had two openings in the intersections of field and column strips. On the other hand, slab S4 had one opening adjacent to central column. Slabs S3 and S5 were identical to slabs S2 and S4, respectively, but strengthened using CFRP. In order to simulate a distributed load, sixteen concentrated equal loads were applied at the top surface of the slabs. For the tested specimens, it was shown that the presence of openings decreased the capacity of studied flat plates by about 25% compared with the control slab. On the other hand, CFRP strengthening enabled the slabs to approximately restore the full load capacity of the control slab. The commercial Finite Element (FE) program ANSYS was used to perform a parametric study on twenty three models to investigate the effect of opening flat plates at different locations with different sizes and numbers and to examine CFRP strengthening of such slabs using the proposed techniques. Studied flat slabs had dimensions of 12m×12m supported by nine columns (400×400×4200 mm) and divided into four square panels (6000×6000 mm) and loaded uniformly at the top surface of the slabs. Adding to the control model, fifteen models with openings at the intersections of field/field, column/field and column/column strips were studied. Seven CFRP strengthened models at openings locations were also investigated. It was found that the presence of openings at field/field intersections has slight effect upon the overall behaviour. However, the presence of openings in other locations affected the behavior; deflections, ductility, toughness, stresses, strains and ultimate loads of slabs depending on the locations and sizes of the openings. Generally, as expected, increasing opening size has a negative effect upon the behavior. For the studied models, CFRP strengthening enhanced the behavior including ultimate strength of all slabs with openings except for slabs with opening adjacent to edge column in the column/column intersection. CFRP strengthening restored the ultimate strength of flat plates with openings that are up to twice as large as the opening size allowed by Egyptian Code of Practice; ECP-203. Also, it was suggested that adding two beams at both sides of edge column adjacent to opening may be useful as an additional strengthening technique. Other recommendations are given for shear strengthening.