Experimental Study of Flexural Behavior of Prestressed Concrete Beams Under the Influence of Corrosion and the Role of Fiber Reinforced Concrete in Bearing Capacity

نوع: Type: thesis

مقطع: Segment: PHD

عنوان: Title: Experimental Study of Flexural Behavior of Prestressed Concrete Beams Under the Influence of Corrosion and the Role of Fiber Reinforced Concrete in Bearing Capacity

ارائه دهنده: Provider: Pouya Hassanvand

اساتید راهنما: Supervisors: Dr. Fereydoun Rezaei

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr. Morteza Madh Khan, Dr. Mojtabi Hosseini, Dr. Mohammad Shooshtari

زمان و تاریخ ارائه: Time and date of presentation: 2023

مکان ارائه: Place of presentation: Amphitheater

چکیده: Abstract: One of the factors of premature failure of reinforced concrete structures is the corrosion of buried steels in it, and this issue is one of the most important problems faced by the construction industry in terms of durability. Usually, the corrosion of reinforcements is caused by the loss of the protective layer on the reinforcements due to the penetration of chloride ions or carbonation and the formation of corrosion micro-piles. This issue becomes more important especially in structures with higher sensitivity such as prestressed structures where steel elements such as prestressed cables play a much more important role in carrying the structure. One of the ways to improve mechanical properties against structural damage is the use of fibers, especially in increasing bending strength and controlling crack width in concrete structures. In this research, in order to experimentally evaluate the flexural behavior of prestressed concrete beams under the influence of corrosion and the role of reinforcing concrete with fibers in its bearing capacity, 20 samples of prestressed concrete beams with a rectangular cross section of width 150 mm, height 300 mm and length 2 meters were made. Two types of macro polymer and steel fibers with a corrugated and hooked-end with different volume percentages of 0.5% and 1% were used in the studied prestressed concrete beams. The method of causing corrosion in prestressed concrete beams was accelerated by applying constant electric current to the prestressing cables and in a pool containing 5% salt water electrolyte solution. Five prestressed concrete beams without corrosion were considered as control samples and fifteen other studied beams were classified into three groups and subjected to corrosion at three levels of 5, 10 and 15%. In order to investigate the structural behavior, the samples were subjected to four-point bending loading test. The parameters for investigating the structural behavior of beams include bearing capacity, mid-span displacement, energy absorption rate, effective stiffness, and ductility. The results showed that corrosion reduces the bearing capacity and other behavioral characteristics of the studied samples, such as energy absorption, effective hardness, and mid-span spring, and with the increase in the level of corrosion, the decreasing trend of the studied parameters increases. The use of fibers in the design of the concrete mixture had a positive effect on the recovery of the lost capacity due to corrosion in the studied samples. The positive effect of macro polymer fibers in restoring the reduction of the displacement parameters in the middle of the opening, the ductility and the energy absorption rate of the beam due to corrosion was much higher than that of steel fibers. Also, the positive effect of steel fibers in recovering the reduction of load capacity and effective hardness parameters was much higher than that of macro polymer fibers. The investigations also showed that the distribution of corrosion caused by the accelerated method along the length of the prestressing cables is non-uniform and there is a difference between the actual and calculated corrosion rates based on Faraday's law

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