Quantitative Model Of Climate Load And Its Applications In Life Predictions Of Concrete Structures

Actions of climate environment are important factors influencing durability design and prediction of service life of reinforced concrete structures. To make the actions of climate environment, with the similar to load, being used for durability design and prediction of service life by quantitative methods, this dissertation attempts to link the actions of climate environment and the responses of concrete's micro-environment together, and establish the durability degradation model related to concrete's micro-environment.In artificially controlled constant climate environment, based on the experimental studies of the internal temperature response of concrete and corresponding basic physical parameters, the temperature response laws of concrete's micro-environment were analyzed, and combined with the basic theory of heat transfer process, the prediction model of concrete's micro-environmental temperature response under artificial climate environment is established.In the artificially controlled constant climate environment, based on the researches of the response laws of relative humidity inner concrete and the concrete's humidity diffusion coefficients, and combined with the basic theory of mass transfer, the prediction model of concrete's micro-environmental relative humidity response under artificial climate environment is established; at the same time, the relationship of relative humidity, temperature and moisture content in concrete's micro-environment was studied.The long-term experimental study of concrete's micro-environmental responses under natural climate was carried out, based on testing results, then the hysteretic laws of concrete's micro-environmental response under natural environment were analyzed; at the same time, considering the difference of concrete's micro-environmental responses under between shelter and open-air conditions of natural environment, the effects of sunlight and rainfall on the concrete's micro-environment were studied.The methods for building climatic action spectra of temperature and relative humidity are proposed using certain mathematical treatment, based on the natural climate environmental changes in temperature and relative humidity; based on the climatic action spectra, the theoretical values of concrete's micro-environmental response under natural climate were calculated using the prediction models of concrete's micro-environmental responses under artificial climate environment; based on the analysis of the changes of concrete's micro-environmental responses and their effects on durability degradation, the concepts and building methods of response spectra in concrete's micro-environment also are proposed.Through the control factors of steel corrosion rate in concrete being analyzed, a basic electrochemical model of steel corrosion rate in concrete is founded using the kinetics equations of metal corrosion and the electrochemical principles of steel corrosion; with the basic model, and based on a series of experiments and theoretical derivation, the prediction model of time-variation corrosion rate of reinforced bars in concrete is established ultimately considering the impacts of concrete's micro-environment.The real development of steel corrosion rate in concrete under natural climate environment was obtained by the long-term test, and its mechanism analysis also was carried out; based on the research results of climatic action spectra, concrete's micro-environmental response spectra and prediction model of steel corrosion rate, the prediction method of corrosion rate of reinforced bars in concrete under natural climate is presented.The whole process of service life of reinforced concrete structure is expounded, and the relevant calculation models of service life in different stages are proposed. Finally, combining the above results, the strategies for predicting the service life of concrete materials and structures are presented, including the prediction of service life in the durability design of new concrete structures and the design of durability testing based on the life prediction.