Research On Fuzzy Reliability Of Crack Control In Concrete Structure Under Chloride Erosion

Concrete is one of the most important civil engineering materials at present.With the rapid development of concrete structure,its durability problem is also growing.Under the influence of chlorine salt erosion environment,the problem of structural failure caused by insufficient durability of concrete structures in coastal or offshore areas is more serious.Therefore,reliability analysis and durability assessment of concrete structures in Marine environment are increasingly paid attention by scholars at home and abroad.In normal use,concrete structure is often accompanied by cracks,and the existence of structural cracks generally is uncertain,which include the randomness and fuzziness.Based on the sub-project of the national natural science foundation of China(No.51508171),the reliability analysis of durability of concrete structures in different Marine environments is carried out based on Monte-Carlo method which introduces fuzzy representation function.The specific research works are as follows:(1)A theoretical study on the modified model of chloride ion diffusion in concrete structures.The transport mechanism of chloride ions in concrete structures under the erosion of chloride salt is studied.Considering the influence of time,temperature,humidity,load and the binding effect of chloride ions on the diffusion performance of chloride ions in concrete,the theoretical modification model of chloride ions diffusion in concrete with cracks is preliminary established based on the dual-porosity model.(2)Experimental study on chloride diffusion model of concrete structure with cracks.Test blocks with different crack widths are fabricated by prefabricated crack method and four rounds of soaking and dry-wet cycle tests are carried out respectively.Based on the regression analysis of the measured data,the functional relationship between crack width and chloride ion diffusion coefficient is established.Based on the modified complete concrete chloride ion diffusion model,the related parameters in the chloride ion diffusion model of concrete with cracks are supplemented and improved by considering the influence of crack effect.(3)Study on durability reliability of concrete structure crack control under chloride erosion.According to the revised complete with cracks in concrete structures under different saturation state of chloride ion diffusion model,the structure of the limit state equation,combined with practical engineering examples,consider the randomness and fuzziness,and with the introduction of fuzzy sexual function in fuzzy reliability analysis,and fracture under the chloride ion erosion to evaluate the durability of concrete structure crack control.With crack width and the exposure time of the chlorine salt erosion environment as the main influencing factors,and consider the concrete cover thickness,concrete structure surface chloride ion concentration and other factors,to analyze the sensitivity of the reliability index and the cracks in the concrete structure durability life prediction.The results of this research can provide reference for the durability optimization design and service life evaluation of concrete structures in coastal and surrounding areas.