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Register a new userDUCTILITY ENHANCEMENT OF RC BEAMS STRENGTHENED BY FIBER REINFORCED POLYMERS
تحسين مطاوعة الجوائز المسلحة المدعمة خارجيا بألياف البوليمرات المسلحة
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عبد الرحمن عيسى( باحث )
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تزايد في العقدين الماضيين استخدام المواد المركبة المستحدثة كألياف البوليمرات المسلحة بالألياف (FRP) لتقوية العناصر البيتونية و توصلت الأبحاث و كودات التصميم لاستخدام البوليمرات المسلحة بالألياف الملصقة خارجيا على العناصر البيتونية لتزيد كفاءة قدرتها الإنشائية. و أظهرت العلاقة الخطية للإجهاد و الانفعال للألياف انعكاسا سلبياً على المطاوعة الكلية دون ظهور منطقة خضوع للعناصر المدعمة المقواة حتى الانهيار. فاستخدام الشرائح المؤلفة من الألياف المكونة من استخدام الألياف الكربونية مع الألياف الزجاجية تغير من تصرف المواد المرنة للتصرف غير المرن. و يهدف البحث لدراسة تصرف الجوائز البيتونية المدعمة بمزيح من البوليمرات المسلحة الألياف.
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 bonded 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.
References used
Belarbi A., Chandrashekhara K. and Watkins S. 1999, “Performance Evaluation of Fiber Reinforced Polymer Reinforcing Bar Featuring Ductility and Health Monitoring Capability”, Fourth International Symposium on Fiber Reinforced Polymers (FRP) for Reinforced Concrete Structures, Baltimore, Maryland, U.S.A., ACI SP 188-29, pp. 1-12
Collins M., and Mitchell D. 1997, “Prestressed Concrete Structures”, Response Publications, Canada, pp. 168-250
El-Afandy T., “Applications of Hybrid Fiber Reinforced Polymers in Strengthening RC Elements”, PhD Dissertation, Ain Shams University, Cairo, Egypt, 2006, 238 p
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This paper makes an experimental and analytical investigation of cracks characteristics in Fiber Reinforced Polymer strengthened RC beams under different levels of sustained load and Reinforced ratio.
As the equations available for conventional RC b
eams are inappropriate for the calculation of the short-term crack width in FRP-strengthened RC beams[8], a statistical analysis is carried out on available test data from international sources [6-9-10] and from the test results obtained in the current study (Concrete Labor- Civil engineering Department- Damascus University-2014) to establish a new equation that considers the effect of the FRP laminates. This equation is a correlation of stress in steel bars, concrete surface tension , and effective side cover.
The long-term crack width is then related to the instantaneous crack width by empirical equations which are derived from the test results obtained in the current study.
Insuring structural system ductility is a main factor justifying the reduction made on design
earthquake forces. Reinforced concrete shear wall is one of the most important systems used for
earthquake resistance of buildings. In this research, many
factors affecting curvature ductility of
shear wall sections are studied. These factors are reinforcement ratio, reinforcement
distribution (uniform and concentrated), axial force level, section length, and material
properties. Results show that increasing reinforcement ratio, will reduce ductility in case of
uniform reinforced shear walls, but it stays stable in case of concentrated reinforcement. As for
axial force level, curvature ductility becomes lower as axial force increases and almost
diminishes when it becomes more than half ultimate axial force bearing capacity.
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].
In this research a study was carried out to evaluate the effect of
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Many techniques have been used in repair and strengthening of
reinforced beam, among which are external steel beams, external
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steel plates, additional longitudinal and transver
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Fifteen R.C. beams were tested until failure and the deflection,
surface strains, internal steel strains, external steel strains and crack
patterns were measured, the results were analyzed and conclusions
were summarized. Finally, the recommendations were stated with
the needed future work.
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