This research presents an empirical study about the behavior of High Strength Concrete
beams under the static cyclic loading. It determines the influence of cyclic loading on the
moment capacity and deflection of HSC beams. A comparison of the mome
nt capacity and
deflection in both kinds of loading (monotonic and cyclic loading) were achieved.
High Strength Concrete mixture was designed, based on the specifications of the American
code ACI 211.4R-93. Thirty six concrete beams were prepared, nine of them were tested
under monotonic loading and the rest of beams were tested under cyclic loading. The
cyclic loading was performed for (5,10,15) cycles, at a range from zero to 65%, 75%, 85%
of the minimum expected monotonic load.
The results showed that the cyclic loading have positive effect on the flexural behavior of
HSC members, whereas the moment capacity increased and the deflection decreased,
especially at a range from zero to 75% of the minimum expected monotonic load, when
the number of cycles was 5,10,15.
Using high strength concrete made a big step in designing and
constructing reinforced concrete structures. In this research, shear
resistance of high strength concrete beams with average resistance
of (65Mpa) and without shear reinforcement was ca
lculated by
making Experimental tests, also we studied the effect of cross
section shape on shear resistance, and measured the deflection in the
middle of the beams then we compared these results with the
mathematical results and with results from other researchers, finally
we developed a relationship to determine shear capacity in high
strength concrete T beams.
This research presents an experimental study behaviour of high strength concrete, for
evaluation of stress - strain curve and derivation of factors of equivalent compressive
stress block, we depend it in design of high strength concrete elements.
For this purpose, number of cylinders specimens with strength 60 MPa were prepared
and tested in compression, then curve was obtained.
The results showed the possibility of producing high strength concrete from local
materials and with strengths are highest than those were obtained, the resulting diagrams of
curve are shown to be essentially linearly elastic up to failure with a steeper declining
portion of the stress - strain diagram, which agree with the results of global researches, the
failure was almost sudden and rapid with increasing strength which shows that the highstrength
concrete less ductile than normal concrete at the failure. Curve of high strength
concrete differs from that normal concrete, this affects on the properties of rectangular
equivalent stress block which requires modifications on the factors led to optimum represent
for it and with evaluation of curve of the tested specimens, the diagram takes a
trapezoidal shape ( ), its value at the top is and the depth of the compressive
block is and we found and ( is average compression/cylinder
compressive strength of concrete, is ratio of the active depth that defined location of
compression force center), when concrete strength increases up , the diagram
shape will be closer to triangular than trapezoidal and then curve takes the shape of triangle its
value at the top is and the depth is and with replacing triangular diagram to rectangle.
This research presents an experimental study about the effect of steel fibers on the
main variables of stress- strain curve for high strength concrete on simple compression,
which are: shape of stress- strain curve, ductility factor, energy absorpt
ion capacity. For
this purpose, series of cylinders concrete specimens were prepared in compressive strength
(70 MPa). the steel fiber with aspect ratio of L/D =70 were added at the volume fractions
of (0-1-1.5-2)%. The cylinders were tested under a monotonic loading at compression, and
as a result of the tests, the total curve of stress- strain was obtained. The experimental
results of research showed a positive effect of steel fibers on the behavior of high strength
concrete, this effect increased with increasing volume fraction of steel fibers. It can be seen
from stress-strain curve, whereas the slope of the ascending branch is not much affected.
The descending branch of the stress- strain curve decreases by the increase in the fiber
volume fraction. This means the ductility and toughness improve with the addition of steel
fibers and as a result the behavior of high strength concrete has gone far away from being
brittle as it is used to be.
Recently, the importance of high Strength concrete has appeared due to its
application in manufacturing most of the concrete structures and members, as well as to its
importance in the implementation of civilian facilities like bridge bases, skyscr
apers and in
implementing the columns and platforms which carry oil installations carried out in the
oceans and seas. The research aims to design concrete mixtures with cylindrical resistors
( 55- 65- 75 Mpa) according to the American code AcI-211-4R-93 by using local and
appropriate additions as well as explaining the method used in designing. Then, studying
the transformation in stress strain curve – deformation
(σ- ζ ) undergoing a simple pressure on the previous samples throughout the
available devices. Then, it was compared to the charts obtained mathematically .Law
behaviour of stress strain and deformation curve was rated, in addition to modulus of
elasticity taken from the chart.
Couple of results and recommendations related to the issue were concluded, those
which were applied in praxis.
