Abstract:
he most accurate and reliable approach to investigating concrete
slabs structural behavior under impact loading is to conduct impact
experiments. This research has the aim of providing a better
understanding of the behavior of Hybrid Fiber Reinforced Concrete
(HFRC) slabs under impact loading. Experimental work was
conducted to study how to enhance the impact resistance of HFRC
slabs which are commonly encountered in modern buildings. The
focus is on preventing their collapse by increasing their ductility
and energy dissipation by strengthening them with steel and
Polypropylene (PP) fibers. In this research a study of the behavior
of hybrid fiber reinforced concrete slabs under impact loads was
carried out by casting and testing eight hybrid fiber reinforced
concrete slabs with dimensions of 1700x1700x100 mm and with
two fiber volume ratios of 0.5 % and 1.0 %. The tests were carried
out at Structural Laboratory of the University of Putra Malaysia.
The free-fall impact tests were conducted with a 200-kilogram
hammer and two different drop heights (1m and 2m). The
relationships between impact loads, displacements, and strains
were established from the recorded tests results. The dynamic
responses gained during tests, as well as the failure modes detected,
had been thoroughly analyzed. The tests findings show that, when
appropriately built, hybrid-fiber reinforcement can greatly improve
the overall impact resistance of concrete slabs, stop crack growth,
and thereby reduce the size of the damaged area. Under impact
force, the slab specimen with a mix of 1% steel fibers and 0.5% PP
fibers performed best improvement of integrity after failure and
impact resistance with an increase 30.79%.
The load tests showed that hybrid fiber reinforcement contributes
to increasing load capacity and ductility of the slab. In addition, the
dissipated energy of the reference slab was doubled in the hybrid
reinforced concrete slab. Also, applying the strengthening
technique led to a change in the crack pattern from one opened hair
crack to multiple cracks in the tension face. However, hybrid fiber
reinforcement results in a considerable reduction (by up to 68%) in
compressive strength.
