Study On Performance Degradation Of High-piled Wharf Structure In Port Engineering

Port engineering structures are usually in the harsh marine environment such as directly or indirectly loaded by waves, wind, and water flow and, corroded by chloride salt, causing serious degeneration of the structural performance. Therefore, it is highly required to carry out researches on structural performance degradation, to obtain knowledge of degradation rules and to conduct qualitative and quantitative analyses of structural performance, which are not only relevant to structure safety but also helpful for the performance evaluation of existing structures. Selecting the correct structure repairing method and maintenance plan has practical significance and economical value for ensuring the structural working safety and functions.Firstly, influencing factors of structural performance degradation are summarized and analyzed through investigations on concrete structures in typical ports, while major factors for affecting the performance degradation of the high-piled wharf structure in the marine environment are identified. High-pile beam slab wharf is selected as the object in structural form, while component safety and applicability degradation caused by steel corrosion, durability degradation caused by chloride ion erosion, and performance degradation of the overall structure caused by pile horizontal bearing capacity decrease are the main approaches in degradation forms. These findings provide basis and direction for further study on the regularity of performance degradation of high-piled wharf structures.Secondly, electrolyte accelerated corrosion tests are conducted on reinforced concrete beams with varying degrees of corrosion and under different stress states, and the influences of sustained stress on corrosion of reinforced concrete members are investigated. Structural mechanical tests are carried out on corroded reinforced concrete members, in which failure modes for different corrosion rate of the test beam and the crack developments, sectional strain are tested and analyzed. A calculation model about reinforced maximum corrosion rate is set up which is based on corrosive crack width under uneven corrosion, and is considering interaction of adjacent measured points.This model considers visible and easily measured corrosive crack width with reinforcement corrosion rate, and is able to quantitatively predict the structural performance degradation from the structural appearance. A reinforcement corrosion rate based method is provided which can calculate the bending bearing capacity, flexural rigidity, and ductility of the degraded reinforced concrete beam. Prediction processes of the position of dangerous section and evaluation of structural performance degradation are proposed. These methods provide better scientific and more reasonable basis for the design and maintenance of port engineering structures.Thirdly, the degradation rule of durability parameters is studied by selecting large diameter post tensioned pre-stress concrete cylinder pile and pre-tensioned spun high-strength concrete pile as representative forms of the substructure. Initial boundary conditions are obtained by indoor test:Through the service from 1 to 17 years of large pile and PHC piles and pile drilling site survey sampling, and combined with laboratory chemical testing, the chloride content of the concrete pile at different sampling depth are measured and analyzed, while the influences of the different environments and service time on the durability parameters such as chloride diffusion index and corrosion coefficients of the pile are obtained. Durability degradation model for large pipe pile and PHC pipe pile is set up based on the basis of statistical analysis of large numbers of investigation data.Finally, rules of stiffness degradation of pile body and soil resistance degradation around piles are analyzed on the basis of large numbers of data of test piles when pile foundation is horizontally loaded with a large displacement. Relationships between soil resistance coefficients for different soil conditions and index degradation of horizontal displacement at the soil surface are defined by fitting methods. The results provide reliable theoretical basis for correctly selection of soil resistance coefficients under different levels of horizontal load.The methods and results in this work enrich and perfect the content and approaches of structural performance degradation in port engineering structures. They also provide basis for whole-life designs of port engineering structures with both theoretical and practical methods. Further, they can also be regarded as instructions for the design, construction, testing and maintenance methods of port engineering structures.