RETRACTED: Behaviour of RC flat slabs with openings strengthened with CFRP

Nine half-scale reinforced concrete continuous slabs with and without openings have been tested up to failure. The main objectives of this paper is to investigate the effect of the openings on the behavior of the flat slabs and study the effect of using Carbon Fiber Reinforced Polymer (CFRP) as a strengthening method to restore the load capacity of flat slabs after the introduction of the openings. The limit of the opening size according to two different international codes such as American Concrete Institute ACI 318-19 and Egyptian Code ECP 203-2007 have been examined. The Finite Element Method (FEM) is utilized via the software ANSYS12 to extend this study and the finite element results were compared with those experimentally obtained. The results show that strengthening flat slabs with openings by using CFRP could not restore behaviour to the slab without openings. The use of CFRP improves the ductility of the slab with openings by about 28 %. The opening located just at the column face makes the strains in the steel reinforcement larger; especially with the low deflections for this slab this ensures that this location is not preferable without strengthening. Although the ACI 318-19, limits the opening size to one-eighth of the column strip it has been noted that an opening size of one-fourth the width of the column strip is still safe in some cases. The numerical results obtained from the computer program ANSYS12 showed that, this software can be used successfully to simulate the behaviour of slabs with openings strengthened with CFRP.