Study On Damage Assessment Of Corroded And Cracked R.C. Structures In Marine Environment

In this paper, the reason and rule of corrosion damage of R.C. balustrades of LianYun Harbor west dam are studied by on-site investigation and lab experiments. From microcosm, the damage of R.C. balustrades is caused by macro-cells causing pitting corrosion. From macrocosm, it is the synthetic effect of poor construction quality, improper design and environment. Maximum stress around reinforcement in concrete is analyzed by finite element method, so that four damage patterns obtained from on-site investigation are verified theoretically. Some measurements to ensure the durability of R.C. structures in marine environment are presented.Modal analysis technique is presented to locate and identify the damage of corroded and cracked R.C. structures. Frequency change square ratio is applied as a parameter to locate corrosion and cracking damage. A chart, which relates the loss in stiffness with changes in natural frequencies, is proposed to identify the degree of corrosion and cracking damage. On-site and lab testing results show modal analysis technique can be used to locate and identify corrosion and cracking damage. In order to locate damage exactly, testing error in the measurement of natural frequencies should be reduced.BP neural networks model for assessment of the degree of reinforcement corrosion is built in this paper. Many factors can be concluded in this model. Meanwhile the model is simple and feasible. The trial example shows the results of assessment of the degree of reinforcement corrosion coincide well with that of the experiment.In this paper, the failure mechanism and process of corroded R.C. flexural members are analyzed based on the modes of failure. The assessment models for the strength of crack and un-cracked R.C. flexural members are built. Experiment results show that the assessment models presented in this paper coincide well with reality. The models can be used to assess the strength of corroded R.C. flexural members.The stochastic models for the capacity of corroded R.C. flexural members are built based on the models for reinforcement corrosion in marine environment. The reliability analysis procedure for corroded R.C. structures is proposed by using the practical analysis method. The profiles, which relate reliability index decrease with time in the atmospheric and marine environment, are calculated by trial examples. They can be used to assess or predict the reliability of corroded and cracked R.C. structures in marine environment.The stochastic model for assessment of chloride concentration in concrete is built by analyzing the stochastic process of chloride diffusion in concrete and taking account of the time variation of the diffusion coefficient. The results of calculation using this model show better agreement with experimental data than that of traditional Pick' Second Law. This model can be used to predict chloride concentration in concrete. In this paper, theassessment procedure for service life of R.C. structures in the marine environment is presented, and this assessment procedure is used successfully in R.C. balustrades of LianYun Harbor west dam. The results of life assessment using routine inspection data show good agreement with that of on-site investigation, so that the correction and validity of the procedure are verified.