High strength concrete (HSC) is defined by American Concrete Institute (ACI
committee 363R, 1997) as "concrete that has a specified average compressive
strength of (41MPa) or more at 28 days". HSC has been widely used in the
construction industry due to the increasing requirements and economical
consideration for structures. The construction of multistoried buildings is increasing
day to day due to increase of land cost. In advent of construction technology the use
flat slabs are increasing in the building construction. Flat slabs are easy to build and
have through their smaller depth, economical and architectural advantages compared
to slab with beams. The undesirable suddenness and catastrophic nature of punching
failure are of concern to structural engineers(Yogendran et.al., 2007). Thus, it is
significant to investigate the efficiency of the use of highstrength concrete to improve
the punching shear strength of flat slabs under monotonic or repeated load. Severalresearch studies reported in the literature on improving the punching behavior of flat
slabs. Three studies are presented in this section.
(Osman et.al. 2000)analyzed six high strength light weight slabs under
concentrated loads. Four slabs were constructed of high strength lightweight concrete
of compressive strength higher than 70 MPa, with the steel ratio ranging from 0.5% to
2.0 %. the two references specimens were constructed with normal strength concrete
and light weight aggregates and had steel reinforcement ratios of 1% and 0.5 %. The
results included the ultimate loads, deflections, modes of failure, crack patterns,
ductility, concrete strain, and steel strains.