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Review of strengthening reinforced concrete beams using cfrp Laminate
DOI: http://dx.doi.org/10.20534/ESR-16-9.10-213-215
Sagatov Bahodir Uktamovich, Tashkent Institute of Architecture and Civil Engineering,
Senior Fellow Researcher, E-mail: sagatov-b88@mail.ru Shodmonov Anarqul Yuldashevich, Aliyev Mashrab Rahmonqulovich, Djurayev Uktam Uralbayevich, Jizzakh polytechnical Institute, Uzbekistan, Senior teachers, E-mail: a.mashrab@umail.uz
Review of strengthening reinforced concrete beams using cfrp Laminate
Abstract: This paper presents the Literature Review of carbon fiber reinforced polymer (CFRP) strips to reinforced concrete (RC) as a strengthening solution for T-beams. Although a great deal of research has been carried out on Rectangular beams strengthened with Fibre-Reinforced Polymer composites (FRP), Fiber reinforced polymer (FRP) composites have been increasingly studied for their application in the flexural or shear strengthening of reinforced concrete (RC) members. A detailed discussion of the shear strengthening repair with FRP is undertaken.
Keywords: Shear, Strengthening, Concrete, Flexural, carbon fiber reinforced polymer (CFRP), fiber reinforced polymer (FRP).
The growing interest in fiber-reinforced polymer (FRP) composite in strengthening and retrofit is becoming apparent in recent years because of the special properties of these composite materials.
The most efficient technique for improving the shear strength of deteriorated RC members is to externally bond fiber-reinforced polymer (FRP) plates or sheets [1]. FRP composite materials have experienced a continuous increase of use in structural strengthening and repair applications around the world in the last decade [2].In addition, the FRP when compared with steel materials found and provided unique opportunities to develop the shapes and forms to facilitate their use in construction.
In addition, the FRP when compared with steel materials found and provided unique opportunities to develop the shapes and forms to facilitate their use in construction.
Strengthening of beams and slabs in flexure and confinement of circular columns have been well documented. A review of research studies on shear strengthening, however, revealed that experimental investigations are still needed [3; 4].
There are many methods for shear strengthening option such as: Bonded surface configurations, end anchor, shear reinforcement spacing and fiber orientation. While many methods of strengthening structures are available, strengthening structures via external bonding of advanced fibre-reinforced polymer composite (FRP) has become very popular worldwide.
Although the materials used in FRP for example, fiber and resins are relatively expensive when compared with traditional materials, noting that the crises of equipment for the installation of FRP systems are lower in cost. FRP systems can also be used in areas with limited access where traditional techniques would be impractical. Commercially available FRP reinforcing materials are made of continuous aramid (AFRP), carbon (CFRP), and glass (GFRP) fibers. Possible failure modes of FRP strengthened beams are classified into two types:
The first type of failure includes the common failure modes such as concrete crushing and FRP rupture based on complete composite action. The second type of failure is a premature failure without reaching full composite action at failure. This type of failure includes: end cover separation, end interfacial delamination, flexural crack induced
debonding and shear crack induced debonding. Different failure mechanisms in experimental tests were reported by [5; 6].
For the first time great volume of work on research of possibilities FRP for strengthening of ferro-concrete designs has been spent in Switzerland with 1982 [7] (Meier, 2000). Sheet FRP wrapped up a design, pasting it epoxide pitch to a concrete surface, providing good coupling. Various experimental and theoretical researches according to strengthening of ferro-concrete beams FRP from glass — and carbon and their comparison with the identical beams strengthened by steel plates are reflected in [8, 9]. As a result of these researches questions of rigidity and durability of coupling of concrete with FRP, possible forms flacky have been studied, and also is shown that ferro-concrete beams with strengthening from FRP possessed considerably bigger bearing ability, than beams with steel strengthening. In work [9] simple analytical dependences for an estimation of limiting bearing ability of bent elements with strengthening from FRP, received of the equations of balance and compatibility of deformations, applicable to rectangular and t-beams are offered sections with single and double reinforcing. In overwhelming majority these researches are devoted strengthening of ferro-concrete beams in operative ranges of the bending moments, and only the few have concentrated on the sections testing action of cross-section forces [10].
At the same time the wide inspections of ferro-concrete designs spent in the various countries, speak about extensive damages to operative ranges of cross-section forces which can lead to destruction [11; 15] because of inefficient cross-section reinforcing, corrosion of armature, excess of design loadings while in service and many other factors which are not considered at designing under operating standard documents. Almost all ferro-concrete designs of buildings and constructions to some extent work on perception the cross-section forces. For example, the basic and most dangerous defects in most flying structures of maintained ferro-concrete bridges and overpasses are the inclined cracks arising and developing in at the basic to a zone of flight. Their uncontrolled development can lead to sharp decrease in bearing ability of designs and terms of their service, and sometimes and to destruction even in the absence of normal cracks. For the majority of ferro-concrete designs calculation on cross-section force is
Section 10. Technical sciences
defining at appointment of the sizes of section and the cross-section reinforcing which, for example, in beams of flying structures of bridges and overpasses sometimes makes over 50% from the general expense of armature on an element. The considerable share (to 20%) reinforc-ings ofsuch beams can be replaced by effective external reinforcing in the form of high-strength fabric polymeric materials from carbon, widespread abroad (in the USA, Europe, Japan and Russia).
For the first time questions of designing and an estimation of bearing ability of the ferro-concrete elements strengthened FRP have appeared for last decade in standard documents of the USA, Switzerland, Japan, Germany and Australia. They reflect sufficient understanding of a problem with reference to normal sections of bent ferro-concrete elements though some questions connected with infringements of anchoring and flacky coverings from FRP are still studied insufficiently. However questions of development of methods of calculation of the strengthened ferro-concrete beams on inclined sections in many respects still are insufficiently clear. It first of all is connected by that used in national and foreign standard documents methods of calculation of durability on cross-section force are far from perfect on a level of development, to accuracy and reliability and considerably concede to methods of calculation of durability at action of the bending moments and longitudinal forces.
It is quite obvious that for the ferro-concrete beams strengthened FRP, the mechanism of resistance to action of cross-section forces even more becomes complicated and demands additional experimental and theoretical studying [12]. In works [8, 16] resistance researches to a cross-section bend ferro-concrete t-beams strengthened by fibres from glass and aramid which were pasted to an edge ofbeams by two-componental mastic from epoxide pitches are executed. Thus, their shift resistance raised by wrap up the beams fibres focused under corners 0 °/90 ° and 45 °/135 Tests have shown that orientation at an angle 0 °/90 ° increased durability of beams by shift much more, than orientation at an angle 45 °/135
Influence of orientation of a fibre (0 90 ° and 45 °) on behaviour damaged rectangular and t-beams strengthened unidirectional continuous fabric and sheet FRP on the basis of thin carbon of fibres has been investigated in [12; 13; 16] where it has been noticed that increase in shift durability of beams and the form of their destruction are essentially connected with orientation offibres. Also it was noticed that the strengthened beams collapsed basically because of flacky FRP from a concrete surface.
Extensive researches to strengthening of ferro-concrete beams in a cut zone have spent [8; 13; 16; 11; 18] having used unidirectional sheets CFRP. Influence of the relation of flight of a cut to working height of section, quantity of layers CFRP, U-shaped fixing CFRP in the form of sheets and strips on lateral surfaces of edges of beams was investigated. Results show that infringement of coupling of layers FRP with a concrete surface was a principal view of destruction of beams. If to prevent coupling infringement the strengthening material is used more effectively and, hence, it is
possible to increase even more bearing ability of a ferro-concrete beam in a cut zone. In 2003 Imran and others also have conducted tests for studying of bearing ability at a cut of the small-scale rectangular beams strengthened by gluing of external reinforcing from aramide FRP. The thickness and width of strip AFRP (20 мм and 40 мм) were the basic variables. For revealing of influence of type of fixing AFRP two schemes — U-shaped strip and full обертывание were used by sheets. The reached increase in durability at a cut was within 7-19%. In works [10; 11; 18] it is noticed that the further experimental work is necessary for revealing of influence of orientation of fibres, quantity of longitudinal working armature and the relation of flight of a cut to working height of section.
The majority of the spent researches on strengthening of a zone of a cut of ferro-concrete beams have been made with use unidirectional carbonaceous sheet AFRP. Strengthening two-forked carbonaceous sheet AFRP practically has not been considered [14]. In particular all researches have concentrated on systems with external reinforcing in the form of continuous wrap up though the method of strip reinforcing FRP is more economic. Some works by a technique of external strengthening are spent by separate strips FRP in [11; 18]. In works [15] it is specified in obvious insufficiency of researches of behaviour of partially damaged beams strengthened FRP.
In work [13] the simple equation for definition of bearing ability of the strengthened beams is offered at a cut taking into account rupture of fibres FRP. In work [16] it is offered two equations for orientation of fibres at an angle 0/90 and 45/135 of degrees with restriction of deformations. In works [17; 19] the equations for calculation of bearing ability of the strengthened samples are presented at a cut in the assumption that paste on layers of external strengthening from FRP work the same as also internal steel armature. This model has been developed for external strengthening of sides of edges by a strip and U-shaped covering from FRP and can be applicable and for cases of rupture or infringement of coupling FRP with a concrete surface. In works [18] three lowering factors, based on character of destruction and connected with rupture FRP, infringement of its coupling with concrete and the crack disclosing, leading to decrease in it of forces of gearing are entered. The models describing possible forms of destruction of beams, resulted in works [18; 19], will well be coordinated with experimental results.
Conclusion: This paper reviewed the research works on shear of RC beams strengthening by CFRP. The review given in this research is based on CFRP composite and has been covered extensively but not exhaustively. The importance to study the strengthening of the T-beams is due more practical in the site compare with rectangular beams. A working knowledge of how material properties change as a function of climate, time and loading will also be of great value to the engineering and design communities. In addition FRP in concrete and allows engineers to increase or decrease margins of safety depending on environmental and stress conditions, generic FRP type and required design life.
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Study of energy indicators of power-consuming equipmentat in-plant procurement centers of cotton-cleaning plants
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DOI: http://dx.doi.org/10.20534/ESR-16-9.10-215-217
Tukhtamishev Botir Kunishevich, Institute of Power Engineering and Automation of the Academy of Sciences, Uzbekistan, Tashkent, Isakov Abdusaid Jalilovich, Tashkent Institute of Irrigation and Melioration, Uzbekistan, Tashkent, E-mail: lider_1987@mail.ru
Study of energy indicators of power-consuming equipmentat inplant procurement centers of cotton-cleaning plants
Abstract: The problems of formation of energy indicators of power-consuming equipment at in-plant procuring centers are considered in the paper, as well asthe method of calculation of electrical loads, which improves the accuracy of planning and the prediction of electricity consumption.
Keywords: cotton, energy, electric power, equipment, consumption, increase, design.
The mode so drive gear operation and other energy-consuming devices of the enterprises are the bases for formation of electric-power indicators in industrial production, consumption levels and the character of electric loads change. The study and exact assessment of the indicators of power-consumption of these units with consideration of their technical state, physical-chemical and physical- technological features of the technological process allow us to correctly analyze the dynamics of electrical loads of an enterprise, to reveal the reserves of electric energy, to increase the accuracy of planning and prediction of energy-consumption.
Knowing that the mode so electrical loads in individual machines determine the level of energy indicators, we have studied
the principal regularities of the change in electrical loads, specific electric power consumption of these machines. Calculations are carried out and energy characteristics of machines and mechanisms are built.
To build energy characteristics of consumed power and specific electrical consumption depending on productivity and other indicators, experiments on currently operating equipment have been carried out. Data processing was conducted with the use of mathematical statictics and probability theory.
Since the machines have different shut-off capacity due to different regulation and lubrication, the studies have been conducted on machines with average values of shut-off capacity.
