The Comparative Analysis Of Concrete Structural Durability At Home And Abroad

With the rapid development of the global urbanization and infrastructure construction,the stock of concrete structure is more and more big,and their durability problem has become increasingly serious both at home and abroad.Not only increased the cost of structural maintenance,but also make the structural life lower than expected.Which has been increasing the environmental pressure and going against sustainable development.To this end,Industrialized countries such as Europe,America earlier carried out targeted scientific research and developed related technology,and then put it into the engineering application.In recent years,a series of research projects have been carried out on the basis of drawing on the achievements and experience of other countries,and then our country constitute the ?the code for durability design of concrete structures?(GB/T 50476).Because of the complexity of the durability of concrete structures: The environmental factors are complex and changeable.the interaction of different factors,the deterioration process,deterioration mechanism and degradation effect of structural materials are difficult to track,measure and quantify accurately and so on.So the existing codes of concrete structure durability in various countries has more or less problems,such as the content is not comprehensive,the research support is not enough,the technical provisions are not fine enough,the maturity and operability need to be improved.It is necessary to find out the similarities and differences of different specifications and their respective technical characteristics through comparative study,and put forward constructive suggestions and suggestions to promote the durability of concrete structures from the perspective of research and application.Therefore,this article takes 5 domestic and overseas mainstream concrete structure durability specification as the object,carries on the comparative research: ?the code for durability design of concrete structures?(GB/T 50476),?Eurocode 2:Design of concrete structures-Part 1-1:General rules and rules for buildings?(EN1992-1-1:2004),? EN 206-1:Concrete:Spectification,performance,production and conformity ?,?Control of Cracking in Concrete Structures?(ACI224R-01),?Guide to Durable Concrete?(ACI201.2R-08)and?Building Code Requirements for Structural Concrete and Commentary?(ACI318-05).The main tasks are as follows:(1)This paper compared The concrete strength values of three specifications in China,America and Europe.Discussed the direct relationship between structural damage degree and concrete strength grade under severe environment and The influence of the concrete strength standard value and design value on the durability of the structure.A comparison is made on the classification of environmental effects,categories and grades,and the similarities and differences between them in terms of classification criteria,classification thickness,coverage factors and so on.(2)On the corrosion of reinforcing steel bar,This paper compared the concrete crack width and comparison of the norms in the different environmental conditions,the minimum limit of protection layer thickness of concrete materials and the performance rules and regulations,The factors influencing the deterioration of reinforcing steel bars and the similarities and differences between them are also discussed.And then some suggestions for further theoretical and technical research are put forward.(3)This paper compared the control measures for the alkali aggregate reaction in the codes.The engineering application and feasibility of the relevant provisions are discussed.Some measures such as adding additive and active mixture to control alkali aggregate reaction are put forward.The influence of air entraining agent and water reducing agent on the durability of concrete is summarized.Finally,It is suggested that the influence of admixture should be taken into account in determining the maximum water cement ratio of concrete.(4)In the general atmosphere,This paper summarized the basic methods and mathematical models of predicting the service life of the structure.Niu Ditao's and Zhang Weiping's model has been computed to compare the carbonized service life and corrosion cracking span-life of the structure in the medium and high humidity environment.The influence of relative humidity,partial carbonization zone and carbonization residue on the service life of the structure is analyzed.At last,this paper compared the gap between the service life of the structure obtained from the norms of China,America and Europe.(5)The influence of concrete strength and protective layer thickness on the service life of structures is studied by using the control variable method.It is found that the concrete strength grade in certain environment has more obvious life prolonging effect than the thickness of protective layer.Thus the suggestion of the concrete strength and the limit of the thickness of the protective layer under the condition of medium and high humidity is put forward.(6)Based on the dynamic reliability theory,Considering the initial investment and maintenance cost,the remaining life expectancy model of the active concrete structure under the ideal condition is established according to the structural reliability,economic index and state index control principle.In this paper,the comparative study on the durability of mainstream concrete structures at home and abroad is carried out to find out the similarities and differences between the environmental effects,structural materials and tectonics,and to summarize their technical characteristics and explore the technical roots behind the differences and characteristics.Which can provide reference for the future research and compilation and development of concrete structure durability in China,and provide guidance and reference for the durability design,construction and maintenance of concrete structure in practical engineering.