There are various types of industrial fibers such as: (polypropylene fiber, fiberglass, silica fume powder, etc..). These fibers are used widely as additives for improving concrete strength. We study in our research the effect of each of polypropylen
e fibers, steel fibers, and silica fume powder, on two kinds of concrete mix the first ordinary mix and the second is mix other with Mazar sand. We found after the studying of mechanical properties for those mixes that a slight improvement on tensile strength of concrete has
occurred, an increasing of compression strength of concrete has happened, and the failure style has changed according to the type of additive compared with concrete without additive.
Cracks are considered important defects in concrete elements, it was noticed after constructing the reinforced concrete walls related to the Foundation, that after a short time after the hardening of concrete and without any overloading on the wall,
there have been vertical cracks of regular distances along each wall we noticed this phenomenon it had happened in many construction projects. We have described the situation, we have also explained, analyzed it by examining its reasons. By a thorough study of three projects carried out in lattakia including scale decanter, building of a tourist hotel and a trade centre, which crack width ranging from 1.25 mm to 3 mm, the height differed in each case studied. Ultimately we have found the practical solutions to avoid this phenomenon including adoption of longitudinal joints for reinforced concrete walls, spacing is about thirty times the wall thickness in order to avoid cracks caused by shrinkage and thermal stress where the depth of joint about 20 mm and the width ranging between 15 mm to 20 mm implemented on both sides of the wall internal and external. After hardening of concrete and lifting the wooden template fill the joints with filler flexible materials.
The extended crack resistance of concrete is necessary in the desisn of nonlinear behavior of structural It can be described through the intensity stress factor and the critical crack opening under maximum
force. The length of the crack is necessary
for calculating intensity stress factor and the critical crack opening under maximum force.
The aim of this work is to conehede the relations between intensity stress factor and the critical crack opening under maximum force with the material properties of concrete such as paste volume, compressive strength and maximum aggregate diameter. The length of crack is calculated using the analytical model of Olesen that depends on bilinear softening, and the parameters of the softening curve were found using inverse analysis. The experimental results of three point bending test for beams with different sizes which are made from concretes with different compressive strengths are used in the inverse analysis.
It is found that intensity stress factor and the critical crack opening under maximum force depend on paste volume and they increase when F'c increases, while they are independent from maximum
aggregate size.
Slabs are considered one of the most exposed elements to disasters and deformities
that can be clear to the viewer. These deformities are reflected as sign of defects that
appear clearly on big slabs. So, here comes the importance of applying and d
esigning
accurate slabs.
The purpose of this research is stating the need for persistent efforts to get a better
form of the slabs in order to increase their ability to be able to carry any outside extra
weights without the appearance of any deformities that might take place during the period
of investing the building. When deformities happen, they have bad effect on the beauty
and main function (purpose) of the building.
This research includes an experimental study for the real applicable slabs under our
supervision, in addition to a theoretical study about the deflection appearing on the slabs
by taking into consideration the plastic specifications of the concrete and the formation of
cracks.
This research aims at constructing reflexive deflections in the slabs during the
construction period and measuring the actual deformities and watching them through a
period of time, then comparing them with the theoretical expected deformities.
The findings that we could get at the end of our research are supposed to play a main
role in choosing the best design for the mandate slabs and at the same time getting the best
value for the reflexive deflection that can be used in the slab to make it better functionally
and to increase its ability to resist the outside applied weights. We hope this is just a start
for more research in this field.
Recently, the methods and theories of the structural and technicalevaluation for
cracked buildings have been developed because of different reasons (Natural disasters,
wars, the oldness… etc.) That was due to urgent need for right evaluation proces
s,
understand the structural and function status of the building and make the right decision.
The research includes the clarification of the importance of building structural
evaluation in addition to the basis and criteria of cracked buildings classification regarding
their structural and technical status.
The structural and technical evaluation for concrete building is considered as nonrepetitive
unique process, which has its particularity due to its link with large group of
indicators ( concrete natural and structure- structural system - the natural and intensity of
failures and cracks …etc.) Therefore, the evaluation process based on groups of
measurements, tests and views. The personal experience of the engineer has an important
role at evaluation process.
The research includes the preparation of scientific methodology to evolution process
and designing structural and technical evaluation software to evaluate cracked buildings
and limit the personal and mood role of the engineer during evaluation process. In addition
to that, the software will include applications from the real situations.
the purpose of this research was to concentrate on this subject, where
four types of concrete mixes of the same shape were prepared (Abrams
settlement about 20 cm), but the cement content and compression strength
in each mixture were different, al
l samples were exposed to destructive acid
effect (nitric acid, sulphuric acid ) of a ratio 3% and PH ≤ 4.
The physical properties of gravel play an important role on the
quality of concrete industry in local workshops. Because they
constitute a main role in various concrete mix design. It's
necessary to understand the importance of the physical proper
ties
of gravel and It's improving role in the concrete mixes.
This research aimed to study the role of the properties of gravel
on the concrete mixes manufacture.
This paper presents structural
analysis in using ANSYS programme for modeling of heat load then
comparison between the analytical results and experimental results is
performed .
This article, will look at the structural development of the high
rise buildings and the factors that led to these developments, and so out
of the basic structural systems, even new classifications for
constructional systems (internal systems external systems), as well as
most construction systems deployed use.
