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].
This research includes an experimental study and a nonlinear
analysis using the finite element method of reinforced concrete
beams with large opening in body that exist in shear zone . The
tested beams are simply supported with rectangular section
and
without additional reinforcement in opening region. The opening is
square in shape with variable dimensions and constant distance
from the support . Studying the effect of changing length of the
opening on the behavior of the reinforced concrete beams was
already completed. The modes of cracks , (load-deflection )
relationship, ultimate load and the mode of failure for all beams
were determinate . The study showed that existence an opening in
shear region of beams reduce the strength of beams and affect on
the mode of shear failure , and any addition in the depth of the
opening lead to early cracks , more deflections and less ultimate
failure load .
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.
This research aims to study the efficiency of flexural strengthening of RC beams with different lengths of CFRP strips by using (NSM) technique. The study is carried out experimentally on (14) concrete beams; the variables considered are (the length
and number of CFRP strips). This is established by dividing the work into two groups: the first one includes (6) beams strengthened by variable carbon fiber strip lengths and one strip, The second group includes (6) beams strengthened by variable carbon fiber strip lengths and two strips, as well as two control beams. The results indicate that carbon fibers have a noticeable effect on increasing the bearing capacity of (NSM) strengthened beams. The results also show that strengthening the beams by CFRP and not along the length of the beam and in one layer does not contribute to increasing beam strength, but when the number of layers increases, an increase in beam strength is noticed at a rate range (40%-72%).
