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.
The research aimed to recognize the level of psychological pressures and its -sources
amongst students at the college of education –University of Damascus and itsrelationship
with students level of psychological stiffness amongst themthe research s
ample has
consisted of (843) male and female students which represent about (17%) of the study
population, a total of the study has attained a set of findings, the most important of which
are as follows:
The level of psychological pressure amongst students of the college of education-was
(79.85) and their average psychological stiffness was (81.41).
The study has shown that there are significant statistical differences amongststudents
of the college of education regarding the level of psychological pressureand
psychological stiffness ascribed to the sex variable and in favor of malestudents. In other
words, psychological pressures and psychological stiffness arehigher amongst male
students compared to female students..
-The study has recommended many results.
Recently worldwide researches have been devoted to the use of steel fibers recovered from used tires in concrete. In Syria the amount of recovered steel from used tires is estimated about 6000 tons/year.
For this purpose a bead wire having a diamete
r of 0.8 mm from burnt tires was extracted and used. Three mixes with cement content 300- 350 -400kg/m3 were produced incorporating three different volumes of fiber 0.5%, 1.0%, and 1.5% and three different length 30-40-60 mm. The concrete obtained by adding these fibers evidenced a satisfactory improvement of the fragile matrix mostly in terms of toughness and post cracking behavior On the other hand it was improvements in compressive strength by steel fiber inclusion the interesting results confirm the promising application of concrete reinforced with steel fibers extracted from used tires in aircraft pavement hydraulic structures and ground slab in fabrics.
The objective of this research is to find out the relationship between psychological pressure and mental toughness, and to find out the differences in these variables regarding the income and academic qualification of people who suffer from diabetes
(A) in Lattakia Province. The study sample consisted of (750) diabetics, (416) males and (334) females. The ages ranged between 15 and 60 years with an average of 35 years. For this purpose, the researcher used psychological pressures scale and mental toughness scale, where their psychometric characteristics were identified through an empirical sample.
The research yielded the following results:
There is a statistically significant positive relationship between psychological pressure and mental toughness in the research sample.
There are statistically significant differences at the indication level (0.05) between the average scores of the answers of the members of the research sample on the psychological pressure scale and mental toughness scale depending on the research's two variables: (level of income, academic qualification).
