Abstract
Rehabilitation of weak and damaged structures has been considered widely during recent years. A relatively modern way of strengthening concrete components is to confine parts under tension and shear by means of carbon fiber reinforce polymer (CFRP). This way of strengthening due to the conditions of composite materials such as light weight, linear elastic behavior until failure point, high tensile strength, high elastic modulus, resistance against corrosion, and high fatigue resistance has become so common. During structural strengthening by means of not pre-stressed FRP materials, usually, it is not possible to benefit from the maximum capacity of FRP materials. In addition, sometimes, the expensive cost of such materials will not make a suitable balance between rates of strengthening and consuming spending. Thus, pre-stressing CFRP materials has an undeniable role in the effective use of materials. In the current research, general procedure of simulation using finite-element method (FEM) by means of the numerical package ABAQUS has been presented. In this article, 12 reinforced concrete (RC) models in two states (strengthened with simple and pre-stressed CFRP) under cycling loading have been considered. A parametric study has been carried out in this research on the effects of parameters such as CFRP surface area, percentage of tensile steel rebar and pre-stressing stress on ultimate load carrying capacity (ULCC), stiffness, and the ability of depreciation energy for the samples. In the current article also, for design parameters, percentages of tensile steel rebars, surface area of CFPR sheets, and the effective pre-stressing stress in RC beams retrofitted with pre-stressed CFPR sheets have investigated. In this paper, it was investigated that using different amount of parameters such as steel rebar percentage, CFRP surface area percentage, and CFRP pre-stressing, the resulted ULCC and energy depreciation of the specimens was observed to be increasing and decreasing. Results from examined specimens with optimum steel rebar percentage, CFRP surface area percentage, and CFRP pre-stressing which had the most enhancement on ULCC and energy depreciation are reported in the current article.
Highlights
FRP materials to the form of outer coverage have been used for enhancing the resistance and improvement of the existing concrete structures from 1980s so far
It can be mentioned that the main difference between reinforced concrete (RC) beams with pre-stressed steel cables and RC beams retrofitted with prestressed carbon fiber reinforce polymer (CFRP) sheets is at the range of yielding
For validation of FE simulation, experiments done by Xue et al (2010) have been referenced. With this series of examinations, researchers assessed the effects of CFRP sheets on the resistance of reinforced concrete beams with different proportions of steel rebars
Summary
FRP materials to the form of outer coverage have been used for enhancing the resistance and improvement of the existing concrete structures from 1980s so far. FRP composites have been topic of wide spread studies as alternatives of steel bars and pre-stressed cables. The connection of steel sheets to tensile part of concrete pieces by epoxy resins to enhance bending strength of such pieces is a normal and durable method. This method has been used for strengthening of many bridges and buildings around the world. Behavior of RC beams retrofitted with pre-stressed CFRP has been studied. It can be mentioned that the main difference between RC beams with pre-stressed steel cables and RC beams retrofitted with prestressed CFRP sheets is at the range of yielding. Carbon fibers have the best behavior in pre-stressing application rather than other types of fibers; the expense is considerable (El-Hacha et al 2001; Jonsson 2011)
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