Engineering and Technology Journal

In this research, the results of experimental test of seven reinforced SCC continuous deep beams after being retrofitting by CFRP with different techniques. The main objective of the current research is to investigate the structural behavior in the shear performance and failure modes. The first beam tested up to failure and assumed as reference beam, while remaining six beams firstly loaded with 65% of ultimate load capacity then retrofitted by three systems namely: externally bonded reinforcing (EBR) by CFRP strips, near surface mounted technique (NSM) CFRP rods and the third system was hybrid technique by composite between EBR CFRP strips and NSM CFRP rods. The experimental results show that applying the EBR CFRP strips in a vertical direction improved the loading capacity in comparison with the horizontal direction. On the other hand, the NSM CFRP rods applied in horizontal direction presented higher values in both ultimate loading capacity and final deflection, where the increasing in ultimate load capacity about 43.48%, and the increasing in deflection about 33.5% compared with control beam. Therefore, it can be concluded that applying the hybrid technique is more efficient when the EBR strips and NSM bars applied in the vertical, and the horizontal directions, respectively.

The main objectives of this study are: encouraging the production and use of  self-compacting  concrete,  use  of  materials  which  are  lightweight,  easy to  use,  and  highly  efficient  in  the  retrofitting  of  reinforced  concrete buildings. Six deep beams specimens (L= length of 1400mm, h= height of 400mm,   and   b=   width   of   150mm)   were   cast   using   self-compacting concrete.  The  location  of  the  openings  is  in  the  middle  of  assumed  load path.  Five  patterns  were  adopted  to  arrange  carbon  fiber  reinforced polymer (CFRP) strips. The cylinder compressive strength of the concrete was  approximately  equal  for  all  beams  and  was  about  (44  MPa)  at  28 days  age.  All  the  beams  have  the  same  steel  reinforcement  for  shear  and flexure. There have been many tests for fresh and hardened concrete. The reinforced  concrete  deep  beams  were  tested  up  to  (60%)  of  the  ultimate load of control beams to simulate degree of damage, and then released the load. After that,the beams were retrofitted using (CFRP) strips, and then the beams were tested to failure. The study was focused on determining the vertical mid-span deflection, ultimate load, the load that causes first shear and flexural cracks, and mode of failure. Theresults showed that, the best increase in the ultimate failure load was (27.27%) and achieved using the inclined  strips  pattern  and  the  pattern  of  vertical  and  horizontal  strips together.  Reduction  in  the  deflection  values  for  the  retrofitted  beams compared  to  the  control  beam  by  about  (12-13%)  due  to  restrictions imposed by CFRP strips and the epoxy.

In this literature review, steel fibers reinforced self-compacting concrete properties in fresh and hardened states and factors affecting them were reviewed. In spite of the high workability of self- compacting concrete, using steel fibers depending on their length, aspect ratio, shapes and volume fraction can cause detrimental effects on it. Using steel fibers improves hardened properties especially flexural and post-peak performance, and this improvement depends on how fibers can distribute and orientate in the fresh state. The better hardened properties can be obtained when fibres aligned and orientated in the direction parallel to tensile stress.

Torsion of structural members and the behavior of steel fiber self- compacting reinforced concrete became the area of interest for many researchers nowadays. The experimental program of the present work consists of casting nine reinforced self-compacting concrete beams in three groups. Each group consists of three beams with the dimensions of 200×300×1500 mm. The first beam has a solid cross-section, the second beam has a hollow core with the dimensions of 60×120×1500mm and the last beam has a hollow core with the dimensions of 80×180×1500mm. The steel fiber contents were 0, 0.5 and 1.0 % by volume for first, second and third groups respectively. The torsional angle of twist versus torsional moment (torque) of each beam was found during the experiments, and the effect of variables, fibers volume fraction and section geometry, on this relationship was investigated. Moreover, the fresh and hardened properties of concrete were carried out using several tests, which included slump flow, L-Box, compressive strength, tensile strength, and finally the torsion test. The current results showed that the addition of steel fibers has improved the torsional strength for all beams and the fibers were more effective in hollow core sections than in the solid ones.