This paper investigates the strengthening techniques of lightweight concrete (LWC) flat slabs
vulnerable to punching shear failure. Thirteen reinforced LWC flat slab specimens were
experimentally tested. The main investigated parameters were the type of shear reinforcement
(steel bars, high strength bolts, or glass fiber reinforced polymers (GFRP) rods), spacing, shear
reinforcement configuration around the column and the fixation method of shear reinforcement.
The test results showed that using radial shear reinforcement with spacing of (d/2) resulted in the
most efficient strengthening technique. The punching shear capacities were improved by 77%,
61% and 54% by using steel bars, glass fiber rods and high strength bolts, respectively,
compared to the reference specimen. Moreover, using high strength steel bolts fixed to the slabs
with steel plates showed the highest ductility compared with the other strengthening techniques
Also, the failure mode converted from being brittle shear failure to flexural-shear mode. Nonlinear
finite element analysis (NLFEA) was carried out for the numerical verification. The
analysis adequately reflected the trend of experimental results. Finally, the experimental test
results were evaluated with the codes equations. The evaluation showed that ACI 318-2018 code
underestimated the punching shear capacity of the tested specimens. On the other hand, Euro
Code showed good prediction of the punching shear strength of the tested slabs. |
