Aims: Study the strengthening of reinforced concrete slabs at tension side using lower concrete
layer reinforced by FRP bars. The proposed layer improves strongly the flexural strength and the
rigidity of R.C slabs, moreover, FRP elements are noncorrosive in contrast with the traditional
strengthening layers reinforced by steel bars.
Study Design: Parametric study is carried out by varying the material type, thickness of
strengthening layer, spacing between strengthening layer reinforcement bars, cross sectional area
of this reinforcement and the type of the strengthening reinforcement.
Methodology: This study presents the efficiency of adding lower concrete layer reinforced by
different materials to increase the flexural strength for two-way R.C slabs. Eleven half-scale two-way
R.C slab specimens were prepared and tested under four point bending. One of these slabs was
unstrengthened and considered as a control specimen. The other specimens were strengthened by
using different lower concrete layers reinforced mainly by fiber reinforced polymer (FRP) bars. The
parameters of this study included the material type (reinforcement steel, glass fiber and carbon
fiber), the thickness of strengthening layer (30 & 50 mm), spacing between strengthening layer reinforcement bars (100 & 200 mm), cross sectional area of this reinforcement (A & 2A) and the
type of the strengthening reinforcement (FRP bars & FRP strips).
Results: The experimental results included cracking load, ultimate load, load-deflection
relationships, relative ductility, and flexural stiffness.
Conclusion: The experimental results showed an improvement in the flexural behavior of the
strengthened specimens compared to control specimen. The flexural strength of the different
strengthened specimens increased by 37% to 112% compared to the control specimen. Moreover, a
finite element models were developed by ANSYS (version 15) to simulate all the tested specimens.
The results calculated based on FEM models were in good agreement with the corresponding
experimental ones. However, the calculated ultimate loads were slightly higher than the
experimental ultimate loads up to 12%.