Beams are considered as one of the most loaded concrete elements, which needs to
be strengthened either as a result of insufficient of concrete section, or insufficient rebar or
increased loads, or the result of a superficial steel or corrosion of
internal steel
reinforcement, and other reasons that we will mention them what we need to study this.
The damaged structural elements and their inability to function fully as a result of exposure
to different environmental factors damage materials and lead to lower resistance, or
because of the existence of of an executive defects or inappropriate investment for its,
leads to the need to rehabilitate maintenance and repair or reinforcement. So it was
resorting to strengthen either magnify sections or supply necessary reinforcement or steel
platelets linking external supported well to concrete section, and because of the difficulty
of execution the recent studies has been implemented on the use of more efficient material
which is concentrated fiber reinforced polymers.
We will present here to methods of strengthening the shear up to the global studies
conducted using these materials from polymers, which are characterized by high resistance
to tensile and large resistance to environmental factors and weather conditions and ease of
application in the specified permissible sites.
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.
Analysis of The results for one of the most important
experimental tests on masonry arches strengthened at their
extrados or at their intrados by fiber reinforced polymer
(FRP)strips;shows that the presence of the fibers prevents the
brittle coll
apse that occur in plain arch because of formation of
four hinges, therefore (depending on position and amount of
reinforcement) in strengthened arches, there are three possible
mechanisms : 1- masonry crushing , 2- detachment of fibers, and
3- sliding along a mortar joint due to the shear stresses. Some
analytical approaches describing these mechanisms are discussed
and a comparison between the theoretical values that give and
the experimental results was performed to show the agreements ,
according to analytical study of the experimental results
strengthening by fibers enhances the strength and ductility of
strengthened arches, the width of strips and the bond between
them and masonry are so important to perform optimum
strengthening.
Fiber reinforced polymer (FRP) plates have gained popularity in the strengthening of reinforced concrete (RC) members due to the high strength to weight ratio, the ease of installation and low maintenance costs compared to other systems such as steel
plates. Also, external bonding of fiber reinforced polymer (FRP) plate has been proven to be an effective method to strengthen and damage RC structures. However, not much attention has been given to the long-term behavioral aspects of FRP-strengthened RC members. It is difficult to accurately predict the long-term deflection, crack width and behavior of FRP-strengthened RC members.
This study presents a method for predicting the deflections at any time of the service life of normal and high strength concrete structures, loaded at any age, creep coefficient and shrinkage strain and the participation of the compressive steel for RC beams, and for RC beams strengthened with FRP plates.
The accurate prediction of deflections is a complex problem which requires the use of non-linear and time-dependent analytical methods. These methods are, in general, time consuming and require great effort[6-13]. However, at the design stage, simple but reliable methods which take into account the most important parameters influencing the long-term deflections may be very useful to adequately design the structure. For that purpose, many simplified methods have been developed [1-2-3-4-14]. Equations have been programmed to access the method combines the simplicity and accuracy and provides valuable information about the influence of each parameter on the increasing deflections with time.
The analytical values are compared to the experimental results from some existing papers [8-9], and to the results obtained from ACI code [1]. It is found that the analytical method is in a good agreement with the experimental results from some existing papers
[8-9].
The mixed use of steel bars and carbon rods in concrete beams can offer beams with different behaviour from that of steel reinforcement only. This paper studies the case of reinforcing concrete beams with two layers of bars, and the main parameters
investigated are the proportion and the distribution of carbon rods in the cross-section. Four groups containing 12 beams are tested, and each is reinforced with 4 bars located in two layers. The first group includes three control beams reinforced with steel bars, while the second includes three beams reinforced with carbon bars. Each of the third and fourth groups includes three beams reinforced with two steel bars and two carbon bars, whereas in the third group, steel bars are located above carbon ones, but in the fourth group, steel bars are located under carbon ones. Concrete beams reinforced with carbon rods in the second group exhibit a higher load carrying capacity and deflections, compared with other beams. However, the beams in the third and fourth groups have approximately the same load carrying capacity and the same behaviour up to the load level equal to 75% of their load carrying capacity. But after that, the beams in the fourth group become more deformed, compared with those of the third group.
It is well known that arch is a main part of the historical structures. Therefore, many techniques are used to strengthen these arches. In this paper, Fiber Reinforced Polymer (FRP) is used to reinforce the arch under vertical loads. Materially Non-L
inear Analysis (MNLA) is performed to demonstrate the behavior of the arch with and without the FRP.
On the other hand, the effect of FRP lamina thickness and length is undertaken in this research. This paper shows that a small amount of the FRP to some local areas can enhance the ultimate strength of the arch significantly.
