Joshi, Suhas S and S, Suriya Prakash
(2019)
BEHAVIOR OF HYBRID FIBER REINFORCED
PRESTRESSED CONCRETE BEAMS UNDER
FLEXURE-SHEA.
Masters thesis, Indian institute of technology Hyderabad.
Abstract
The present study aims at understanding the effect of hybridization of the steel and synthetic
fibers on the flexure-shear behavior of prestressed concrete (PSC) beams. The first phase of
the test program consists of evaluating the efficiency of individual fibers viz. steel and
structural synthetic fibers on the performance of prestressed concrete (PSC) beams. Later, a
hybrid fiber combination consisting of steel and synthetic fibers are introduced to understand
the behavior. The effect of different fiber reinforcement on the behavior of prestressed concrete
beams are evaluated in two stages. First, fracture tests are conducted to understand the
influence of fibers at the material level. Secondly, full-scale prestressed concrete beams are
tested for evaluating the effect of fiber addition on the flexure-shear behavior. The test matrix
consists of seventeen beams with fiber reinforced concrete, having fiber dosages of 0.35%,
0.70% and 1.0% by volume of concrete. All the beam specimens are tested at a shear span (a)
to depth ratio (d) of five under four-point bending configuration. Effect of hybrid fiber addition
on the overall load-displacement, load-strain, and strain energy absorption capacity of PSC
beams are analyzed. Other parameters such as shear span to depth ratio (a/d), the compressive
strength of concrete, prestressing reinforcement ratio are kept constant. Results of hybrid fiber
reinforced specimens is compared with the results of steel and Synthetic (polyolefin) fiber
reinforced beams. The test results portray that the addition of fibers stiffen the post-cracking
response and increases the energy absorption capacity. Additionally, failure mode changed
from flexure-shear (brittle) to flexure (ductile) mode with the addition of fibers. Change of
failure mode occurred at dosages of 0.35% for steel and hybrid fibers and 0.70% for synthetic
(Polyolefin) fibers. The strain energy absorption capacity increased by more than 100% at 1.0%
fiber addition for both steel and macro-synthetic fibers. Flexural capacity of the tested
vi
specimens is verified with the RILEM recommendation for fiber reinforced concrete
specimens. RILEM recommendations always underpredicted the actual value, indicating the
conservative estimates of design guidelines. Cracking behavior of PSC beams are analyzed viz.
crack width and crack spacing parameters using Eurocode, CEB-FIP modal code and Moffatt’s
modified formulation. It is observed that, as the fiber dosage is increased, corresponding crack
widths are reduced in the post-cracking regime.
Actions (login required)
 |
View Item |
Altmetric
Altmetric