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Research On Properties Of Corroded Reinforced Concrete Member

Posted on:2003-05-03Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y F FanFull Text:PDF
GTID:1102360092480357Subject:Structure engineering
Abstract/Summary:PDF Full Text Request
Due to various corrosive effects, reinforced concrete structures in corrosive environments had shown serious deterioration, which usually caused by concrete deterioration, rebar corrosion, degradation of bond strength between rebar and concrete. As a result, durability of many corroded reinforced concrete (CRC) structures usually degraded badly, and could not work normally much before their intended service lives. Presently, durability degradation of the CRC structures has led to the disastrous results in the civil engineering worldwide. Consequently, durability of CRC structures is becoming an important challenge to the engineering profession. Based on the systematic investigation of the literatures about mechanical properties of CRC member, research scheme, according to material property-*bond strength-rnechanical property of CRC member, was determined in this dissertation. The main contents are as follows:Firstly, mechanical properties of corroded concrete and rusty rebar were studied. Expansive corrosion mechanism of concrete corroded by Sulphate was analyzed; expansion stress in concrete was studied. Effect of steel pit on the mechanical property was discussed in succession. Numerical results show that exponential relation exists between the yield strength and depth of corrosion pit. The work in this part is the theoretical foundation on the study in modeling of constitutive behavior of the corroded concrete and rusty rebar.Secondly, Neural Network (NN) model was built up to predict ultimate bond strength between the rebar and corroded concrete. Deterioration mechanism of the bond property between rusty rebar and corroded concrete was discussed. Because that the bond strength between the corroded rebar and concrete is affected by many factors, and the relation between the factors and bond strength are highly nonlinear, to build the any calculation model will be very difficult. BP NN model was built up herein to predict the ultimate bond strength between the rebar and corroded concrete, good results are achieved. It is shown that NN method offers a fundamentally different approach in the research on the bond strength between corroded concrete and rusty rebar. Having the advantage of taking all the influential factors into account, this method is much .better than the conventional method.Thirdly, based on the test results of CRC members taken from the field structures, models were built up to predict the strength of CRC beam. Based on the test data of the CRC beams taken from some chemical plants, which were mainly corroded by Chloride, a calculation model was derived to calculate the ultimate load bearing capacity of such CRC beams. Then, BP NN model was built up to predict the ultimate load bearing capacity of CRC beams. Using such NN model to analyze many groups of test data (under various corrosion cases), satisfactory results are achieved. It is shown that the NN model in this paper is an effective and promising method for the prediction of the ultimate load bearing capacity of CRC members.IllFurther, corrosion level and mechanical properties of the CRC beams were studied based on the distribution character of the surface cracks. It is discovered that the cracks distribution on the CRC beams satisfies fractal behavior perfectly. Thereafter, the fractal dimension value of cracks distribution was presented as an effective index to appraise the corrosion level. Relations between fractal dimension and rebar corrosion ratio, concrete deterioration factor and strength of the member were studied respectively. Fractal NN model was also built up to predict the ultimate load bearing capacity of CRC members obtained from the field corroded structures, good results are achieved, which could provide an applicable method to evaluate the durability of CRC members. It is concluded that the use of fractal dimension explores an efficient way a new way to study the load bearing capacity of CRC members, and this method is convenient and applicable for the study of durability of CRC members in engineerin...
Keywords/Search Tags:corrosion, mechanism, reinforced concrete member, deterioration, rust, bond strength, BP neural network, crack, fractal dimension, ultimate load bearing capacity, ductility
PDF Full Text Request
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