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.
In the last two decades, the use of advanced composite materials such
as Fiber Reinforced Polymers (FRP) in strengthening reinforced
concrete (RC) structural elements has been increasing. Research and
design guidelines concluded that externally bo
nded FRP could increase
the capacity of RC elements efficiently. However, the linear stressstrain
characteristics of FRP up to failure and lack of yield plateau have
a negative impact on the overall ductility of the strengthened RC
elements. Use of hybrid FRP laminates, which consist of a
combination of either carbon and glass fibers, or glass and aramid
fibers, changes the behavior of the material to a non-linear behavior.
This paper aims to study the performance of reinforced concrete beams
strengthened by hybrid FRP laminates.
In this research, we discussed an analytical
study of the seismic behavior of an internal joint, and we improved
the plastic response of the joint after observing the effect of the
concrete encasement to the column’s steel section along the
connection area.
The study
will examine the effect of changing the diameter of the longitudinal
and lateral reinforcement on the carrying capacity of the concrete
columns and compare the value of the compressive strength of
concrete, which is associated with the theoretical relations provided
by (Mander), (Park et all) by building an analytical model using
finite element Program ANSYS.
